Copernicus: Sentinel-1 — The SAR Imaging Constellation for Land and Ocean Services
Sentinel-1 is the European Radar Observatory, representing the first new space component of the GMES (Global Monitoring for Environment and Security) satellite family, designed and developed by ESA and funded by the EC (European Commission). The Copernicus missions (Sentinel-1, -2, and -3) represent the EU contribution to GEOSS (Global Earth Observation System of Systems). Sentinel-1 is composed of a constellation of two satellites, Sentinel-1A and Sentinel-1B, sharing the same orbital plane with a 180° orbital phasing difference. The mission provides an independent operational capability for continuous radar mapping of the Earth with enhanced revisit frequency, coverage, timeliness and reliability for operational services and applications requiring long time series.
Table 1: Copernicus is the new name of the former GMES program 1)
The overall objective of the Sentinel-1 mission is to provide continuity of C-band SAR operational applications and services in Europe. Special emphasis is placed on services identified in ESA's GSE (GMES Service Element) program. Additional inputs come from on-going GMES projects funded by ESA, the EU, and ESA/EU member states. The Sentinel-1 mission is expected to enable the development of new applications and meet the evolving needs of GMES, such as in the area of climate change and associated monitoring. 2) 3) 4)
The Sentinel-1 mission represents a completely new approach to SAR mission design by ESA in direct response to the operational needs for SAR data expressed under the EU-ESA GMES (Global Monitoring for Environment and Security) program. The mission ensures continuity of C-band SAR data to applications and builds on ESA's heritage and experience with the ERS and Envisat SAR instruments, notably in maintaining key instrument characteristics such as stability and accurate well-calibrated data products.
The key mission parameters are revisit time, coverage, timeliness combined with frequency band, polarization, resolution and other image quality parameters. Short revisit time demands for an appropriate orbit selection and large swath widths.
The baseline mission concept under development is a two-satellite constellation, with four nominal operational modes on each spacecraft designed for maximum compliance with user requirements. 5) 6) 7) 8) 9) 10)
• Orbit: Sun-synchronous near-polar orbit, repeat cycle of 12 days, cycle length of 175 days
• Operational modes:
- Stripmap mode (SM): 80 km swath, 5 m x 5 m resolution, single-look
- Interferometric Wide Swath mode (IWS): 240 km swath, 5 m x 20 m resolution, single-look
- Extra Wide Swath mode (EWS): 400 km swath, single-look
- Interferometric Wide Swath mode (IWS): 240 km swath, 25 m x 80 m resolution, 3-looks
- Wave mode (WM): 20 km x 20 km, 20 m x 5 m resolution, single-look
• Polarization: Dual polarization for all modes VV+VH or HH+HV
- Consistent, reliable and conflict free mission operations
- Near real-time delivery of data within 3 hours (worst case) with 1 hour as goal
- Data delivery from archive within 24 hours
• Sensitivity: NESZ (Noise Equivalent Sigma Zero), σo = -25 dB
- Stability = 0.5 dB
- Accuracy = 1.0 dB
• Ambiguity ratio: DTAR (Distributed Target Ambiguity Ratio) = -25 dB
In April 2007, ESA selected TAS-I (Thales Alenia Space Italia) as prime contractor for the Sentinel-1 spacecraft (overall satellite design & integration at system and subsystem level, including the design of the SAR antenna's transmit/receive modules). ESA awarded the contract to TAS-I on June 18, 2007 at the Paris International Air Show. EADS Astrium GmbH of Friedrichshafen, was in turn awarded a contract by TAS-I to build the radar imaging payload for Sentinel-1, including the central radar electronics subsystem developed by Astrium UK. The objective of Sentinel-1 is to assure C-band SAR data continuity for the user community currently provided by Envisat and ERS-2. 11)
Three priorities (fast-track services) for the mission have been identified by user consultation working groups of the European Union: Marine Core Services, Land Monitoring and Emergency Services. These cover applications such as: 12)
• Monitoring sea ice zones and the arctic environment
• Surveillance of marine environment
• Monitoring land surface motion risks
• Mapping of land surfaces: forest, water and soil, agriculture
• Mapping in support of humanitarian aid in crisis situations.
Unlike its more experimental predecessors ERS-1, ERS-2 and Envisat that supply data on a best effort basis, operational satellites like Sentinel-1 are required to satisfy user requirements and to supply information in a reliable fashion with the data provider accepting legal responsibility for the delivery of information.
In March 2010, ESA and TAS-I signed a contract to build the second Sentinel-1 (Sentinel-1B) and Sentinel-3 (Sentinel-3B) satellites, marking another significant step in the Copernicus program. 13)
As part of the Copernicus space component, the Sentinel-1 (S1) mission is implemented through a constellation of two satellites (A and B units) each carrying an imaging C-band SAR instrument (5.405 GHz) providing data continuity of ERS and Envisat SAR types of mission. Each Sentinel-1 satellite is designed for an operations lifetime of 7 years with consumables for 12 years. The S-1 satellites will fly in a near polar, sun-synchronized (dawn-dusk) orbit at 693 km altitude. 14)
The Sentinel-1 mission, including both S-1A and S-1B satellites, is specifically designed to acquire systematically and provide routinely data and information products to Copernicus Ocean, Land and Emergency as well as to national user services. These services focus on operational applications such as the observation of the marine environment, including oil spill detection and Arctic/Antarctic sea-ice monitoring, the surveillance of maritime transport zones (e.g. European and North Atlantic zones), as well as the mapping of land surfaces including vegetation cover (e.g. forest), and mapping in support of crisis situations such as natural disasters (e.g. flooding and earthquakes) and humanitarian aid.
In addition, the 12-day repeat orbit cycle of each Sentinel-1 satellite along with small orbital baselines will enable SAR interferometry (InSAR) coherent change detection applications such as the monitoring of surface deformations (e.g. subsidence due to permafrost melt) and cryosphere dynamics (e.g. glacier flow).
Figure 1: Artist's view of the deployed Sentinel-1 spacecraft (image credit: ESA, TAS-I)
The spacecraft is based on the PRIMA (Piattaforma Italiana Multi Applicativa) bus of TAS-I, of COSMO-SkyMed and RADARSAT-2 heritage, with a mission-specific payload module. Attitude stabilization: 3-axis, attitude accuracy = 0.01º (each axis), orbital knowledge = 10 m (each axis, 3σ using GPS).
The spacecraft structure provides the accommodation for all platform and payload units. A box type structure has been adopted using external aluminum sandwich material, with a central structure in CFRP (Carbon Fiber Reinforced Plastic). A modular approach has been taken whereby the payload is mounted to a dedicated part of the structure, allowing separate integration & test of the payload before integration to the main part of the structure carrying the platform units. This has many advantages for the overall AIT (Assembly, Integration and Test) process. 15) 16) 17) 18) 19) 20)
The PRIMA platform comprises three main modules, which are structurally and functionally decoupled to allow for a parallel module integration and testing up to the satellite final integration. The modules are: 21)
1) SVM (Service Module), carrying all the bus units apart from the propulsion ones
2) PPM (Propulsion Module), carrying all the propulsion items connected by tubing and connectors
3) PLM (Payload Module), carrying all the payload equipment including the SAR Instrument antenna.
Figure 2: 3D exploded view of the Sentinel-1 platform (image credit: TAS-I)
TCS (Thermal Control Subsystem): The TCS provides control of the thermal characteristics and environment of the Satellite units throughout all phases of the mission. In general the TCS is passive, with the control provided by means of standard techniques such as heat pipes, radiators and MLI (Multi-Layered Insulation). Survival heaters are provided to prevent units becoming too cold during non-operative phases.
EPS (Electric Power Subsystem): The EPS uses two solar array wings for power generation. Each wing consists of 5 sandwich panels using GaAs triple junction solar cells. The average onboard power is 4.8 kW (EOL), the Li-ion battery has a capacity of 324 Ah. The PCDU (Power Control and Distribution Unit) is designed to provide adequate grounding, bonding & protection for the overall electrical system (e.g. by use of fuses) and must also be integrated into the satellite FDIR concept to ensure that adequate power resources and management are available in the event of on-board failures. Li-Ion battery technology has been selected for the batteries in view of the large benefits offered in terms of mass and energy efficiency.
The spacecraft dimensions in stowed configuration are: 3.4m x 1.3 m x 1.3 m. The Sentinel-1 spacecraft has a launch mass of ~2,200 kg, the design life is 7.25 years (consumables for up to 12 years). 22) 23)
Since the B2 Phase of Sentinel-1, a commonality approach with Sentinel-2 and Sentinel-3 was introduced and deeply investigated, to optimize and minimize as much as possible new developments, HW procurement and operations costs. Besides the differences among payload instruments and their relative required performances, each of these three satellites have its own orbital parameters, as well its own specific requirements. 24) 25)
Table 2: List of some Sentinel-1, -2, -3 characteristics and key requirements impacting on end-to-end performance 26)
The Sentinel-1 spacecraft design is characterized by a single C-band SAR (Synthetic Aperture Radar) instrument with selectable dual polarization, a deployable solar array, large on-board science data storage, a very high X-band downlink rate, and stringent requirements on attitude accuracy and data-take timing. In addition, the spacecraft will embark the LCT (Laser Communication Terminal) unit allowing downlink of recorded data via the EDRS (European Data Relay Satellite). 27) 28)
Table 3: Main parameters of the Sentinel-1 spacecraft
AVS (Avionics Subsystem): The AVS performs both Data Handling & Attitude/Orbit Control functions. This is realized through the concept of an integrated control system that performs the control of the platform and payload. The AVS performs all data management & storage functions for the satellite, including TM/TC reception and generation, subsystem & unit monitoring, autonomous switching actions and synchronization. The AVS includes the AOCS processing and the interfaces to the AOCS sensors Star trackers, fine sun sensors, and fine gyroscope and actuators, 4 reaction wheels, 3 torque rods, 14 thrusters, 2 solar array drive mechanism. 29)
The AOCS comprises all means to perform transfer- and on-orbit control maneuvers and to control all necessary satellite attitude and antenna pointing states during all mission phases, starting at separation from the launcher until de-orbiting of the satellite at end of life. This includes the attitude steering of the LEO satellite to provide both yaw and roll steering capability. At present, a dedicated precise orbit predictor is implemented within the AOCS, in addition to making use of the data uploaded to the payload by the GPS constellation. The AOCS (Attitude and Orbit Control Subsystem) is able to perform some functions autonomously and it is supported by a very reliable FDIR scheme (Ref. 15). Telecommand data will be received from the TT&C subsystem and will be decoded and deformatted in the AVS.
AOCS consists of the following sensors and actuators: fine sun sensors, magnetometers, gyroscopes, star trackers, GPS receivers, magnetic torquers, a reaction wheels assembly and a monopropellant (hydrazine) propulsion system. The propulsion system has 3 pairs of 1 N orbit control thrusters and 4 pairs of reaction control thrusters for attitude correction. Every pair is made up of a prime and a redundant component. The attitude control thrusters are fired when the spacecraft enters RDM (Rate Damping Mode) after separation, damping any residual rotation left by the launcher upper stage and achieving a spacecraft pitch rotation of -8 times the orbital period. In the subsequent AOCS mode, called SHM (Safe Hold Mode), magnetotorquers and reaction wheels maintain the attitude and reduce the pitch rotation rate to twice the orbital period.
The periodic behavior of the Earth's magnetic field in a polar orbit and the polarization of the angular momentum with the loading of the reaction wheels allow the magnetotorquers to maintain this pitch rate while aligning the spacecraft –Y axis with the orbit normal, which in a dusk-dawn orbit coincides with the direction to the Sun (Figure 3). When the appendages deployment commences, the effect of the gravity gradient torque dominates over the magnetic torque, resulting in the alignment of the S/C X axis (appendages axis) with the nadir direction, maintaining thus a pitch rate equal to the orbital period. Upon ground telecommand, a transition into the NPM (Normal Pointing Mode) occurs, where the spacecraft performs a fine attitude control based on the use of reaction wheels in close loop with star trackers, gyroscopes and GPS, and magnetotorquers for wheel unloading (Ref. 20).
Figure 3: Sentinel-1A stowed representation (in RDM and SHM). +X S/C axis points towards the flight direction. S/C Y axis is aligned with the Sun direction. Solar Array –Y illuminated when stowed (image credit: ESA, Ref. 20)
Figure 4: Architecture of the avionics subsystem (image credit: TAS-I)
Table 4: Sentinel-1 attitude steering modes (Ref. 226)
Figure 5: Spacecraft power generation and distribution (image credit: TAS-I)
PDHT (Payload Data Handling & Transmission) subsystem (Ref. 24):
The commonality process is driving the spacecraft design with the objective to satisfy the needs of three different missions within the same product. This involves several Sentinels subsystems: in particular, TAS-I was selected to coordinate the common design of two assemblies: 30)
• TXA (Telemetry X-band transmission Assembly) 31)
• XBAA (X-Band Antenna Assembly)
The objective of the PDHT subsystem is to provide the services of data acquisition, storage and transmission to the ground in X-band. After having acquired observation data from the DSHA (Data Storage and Handling Assembly), the TXA executes encoding, modulation, up-conversion, amplification and filtering; the X-band signal provided at the TXA output is then transmitted by an isoflux, wide coverage antenna, included in the XBAA.
To summarize, the performance requirements on TXA specification took into account the different needs of the Sentinels, allowing a fully recurrent units approach: beside a specific TXA layout due to accommodation needs, the modulator, TWTA, and RF filter are exactly the same for the three Sentinels.
After the selection of the TXA & XBAA suppliers (TAS-España and TAS-I IUEL respectively), an agreement was reached between ESA and the Sentinel prime contractors on the way to handle the common design and procurement for TXA and XBAA.
Besides strong efforts to manage different needs coming from different missions, the commonality activities performed in the frame of Copernicus Sentinels enable an effective optimization of costs and development time for those subsystems selected for a common design.
To provide flexibility in the downlink operation, the PDHT is designed with two X-band independent links. The PDHT provides an overall input/output throughput of about 1950 Mbit/s, with a payload input data rate of 2 x 640 Mbit/s (multi-polarization acquisition) or 1 x 1280 Mbit/s (single-polarization acquisition) and a transmitted symbol rate of 2 x 112 Msample/s. The data storage capacity is > 1410 Gbit at EOL.
The provided antenna isoflux coverage zone is about ±64º with respect to nadir to allow link establishment with the ground starting from the ground antenna elevation angle of 5º above the horizon.
Figure 6: The PDHT (Payload Data Handling & Transmission) subsystem (image credit: TAS-I)
Legend of Figure 6:
• DSHA (Data Storage & Handling Assembly)
• TXA (Telemetry X-band transmission Assembly)
• XBAA (X-band Antenna Assembly)
Table 5: Main performance characteristics of the PDHT
The TXA architecture provides two redundant X-band channels with the same output power (16 dBW) and useful data rate (260 Mbit/s). Cold redundancy is implemented at channel level. The main elements of the assembly are:
- X-band modulators, developed by TAS-F, are fully compliant with ECSS and modulation standard
- TWTA (Traveling Wave Tube Amplifiers), provided by TAS-B (ETCA), deliver up to 60 W RF power
- OMUX (Optical Multiplexer), developed by TAS-F, filters and combines both channels and provides out of band rejection.
To achieve good spectral confinement and especially to ensure that the emission levels in the adjacent deep space band (8400 to 8450 MHz) are respected, both baseband filtering with a roll-off of 0.35 (0.35-SRRC) and filtering techniques have been applied. In addition, 6-pole channel band pass filters have been implemented in the OMUX. The 6-pole solution provides two main advantages in front of other less selective solutions, such as 4-pole:
- It filters our more efficiently the regrowth of baseband filtered 8PSK carrier due to the gain nonlinearity of the TWTA, thus allowing for a better overall DC efficiency
- It is compatible with data rates up to 300 Mbit/s per channel by adjusting the frequency plan (increase of frequency spacing between channels).
Figure 7: Architecture of the TXA (image credit: TAS)
Table 6: Summary of the key performances of the Sentinel TXA
PRP (Propulsion Subsystem): The PRP is based on 14 RCTs (Reaction Control Thrusters) located in 4 different sides of the spacecraft, provides the means to make orbit corrections to maintain the requested tight orbit control throughout the mission. Initially, corrections are required to reach the final orbit position after separation from the launcher. During the mission, some infrequent corrections to the orbit are necessary to maintain the requirements upon the relative and absolute positioning of individual satellite. The thrusters located on the –Z side of the satellite are specifically dedicated to attitude control during the safe mode.
Figure 8: Sentinel-1 satellite block diagram (TAS-I, ESA, Ref. 15)
Figure 9: Stowed satellite views (image credit: TAS-I)
RF communications: Onboard source data storage volume of 900 Gbit (EOL). TT&C communications in S-band at 4 kbit/s in uplink and 16, 128, or 512 kbit/s in downlink (programmable). Payload downlink in X-band at a data rate of 2 x 260 Mbit/s.
The Copernicus Sentinel spacecraft are the first ESA Earth Observation spacecraft to implement communications security on the command link. It has been decided to secure the spacecraft from unauthorised command access by adding a security trailer to the command segments which are sent to the spacecraft. The trailer is composed of a Logical Authentication Counter and a Message Authentication Code. The latter is obtained by performing cryptographic encryption of the hash value of the command segment and the Logical Authentication Counter. Only parties in possession of the right key can perform this operation in a way that the command segment is accepted by the spacecraft. The concept applies to all Copernicus Sentinel spacecraft. 32)
Science data compression: Currently, the most promising solution seems to be the FDBAQ (Flexible Dynamic Block Adaptive Quantization) approach as proposed by ESA; 3 output bits would be sufficient for most of "typical" acquisitions over various targets, while few high reflectivity scenes would need 4 bits, making the expected average output bit rate little higher then 3 bits, thus lower then the estimated 3.7 bits for the ECBAQ (Entropy-Constrained Block Adaptive Quantization) compression. 33) 34) 35) 36)
Data delivery: Sentinel-1 will provide a high level of service reliability with near-realtime delivery of data within 1 hour after reception by the ground station, and with data delivery from archive within 24 hours.
OCP (Optical Communication Payload): In parallel to the RF communications, an optical LEO-GEO communications link using the LCT (Laser Communication Terminal) of Tesat-Spacecom (Backnang, Germany) will be provided on the Sentinel spacecraft. The LCT is based on a heritage design (TerraSAR-X) with a transmit power of 2.2 W and a telescope of 135 mm aperture to meet the requirement of the larger link distance. The GEO LCT will be accommodated on AlphaSat of ESA/industry (launch 2012) and later on the EDRS (European Data Relay Satellite) system of ESA. The GEO relay consists of an optical 2.8 Gbit/s (1.8 Gbit/s user data) communication link from the LEO to the GEO satellite and of a 600 Mbit/s Ka-band communication link from the GEO satellite to the ground. 37)
Since the Ka-band downlink is the bottleneck for the whole GEO relay system, an optical ground station for a 5.625 Gbit/s LEO-to-ground and a 2.8 Gbit/s GEO-to-ground communication link is under development.
Table 7: Technical data of the LCT generations 38)
Ground segment: Spacecraft operations is provided by ESOC, Darmstadt, while the payload data processing and archiving functions (including the planning for SAR data acquisitions) are provided by ESRIN, Frascati. Options are being provided to permit some functions to be outscored to other operating entities.
Figure 10: Isometric views of the deployed satellite (image credit: TAS-I)
Figure 11: SAR antenna deployment test supported by zero gravity deployment device (solar array in stowed position), image credit: TAS-I, (Ref. 21)
Figure 12 shows the fully integrated Sentinel-1A spacecraft with the SAR antenna and the solar array wings in stowed position. The figure shows the Sentinel-1 spacecraft already mounted on the shaker and ready for sine vibration testing after it has successfully passed the Mass Properties measurements (namely center of mass and inertia moments). Successful completion of vibration and acoustic testing has been followed by the deployment tests of both the SAR antenna and the solar array. Each solar array is tied down on four hold down points by dedicated Kevlar cables. Wing deployment is purely passive, driven by springs, and actuated upon activation of specific thermal knives devices. The time to complete deployment of one wing lasts about 3.5 minutes since the last cable cut. In the end position, the solar array panels are mechanically latched.
• Prior to shipment to the launch site in late February 2014, the Sentinel-1 spacecraft has spent the last couple of months at Thales Alenia Space in Cannes, France, being put through a last set of stringent tests. This included suspending the satellite from a structure to simulate weightlessness and carefully unfolding the two 10 m-long solar wings and the 12 m-long radar antenna. 40)
• The first satellite dedicated to Europe's Copernicus environmental monitoring program arrived at Cayenne in French Guiana on 24 February 2014. Sentinel-1A is scheduled to be launched from Europe's spaceport in Kourou on 3 April. By delivering timely information for numerous operational services, from monitoring ice in polar oceans to tracking land subsidence, Sentinel-1 is set to play a vital role in the largest civil Earth observation programme ever conceived.41)
Figure 13: The Sentinel-1A radar satellite has arrived at Europe's Spaceport in French Guiana to be prepared over the coming weeks for launch in April (image credit: ESA,M. Shafiq) 42)
Launch of S-1A: The Sentinel-1A spacecraft was launched on April 3, 2014 (21:02 UTC) on a Soyuz-STB Fregat vehicle from Kourou, French Guiana (the launch is designated as VS07 by the launch provider Arianespace). After a 617 second burn, the Fregat upper stage delivered Sentinel-1A into a Sun-synchronous orbit at 693 km altitude. The satellite separated from the upper stage 23 min 24 sec after liftoff. 43)
Launch of S-1B: The Sentinel-1B spacecraft, a twin sister of Sentinel-1A, was launched on April 25, 2016 (21:02:13 GMT) into the same orbital plane of Sentinel-1A (phased by 180º). The launcher was a Soyuz-STA/Fregat vehicle (VS 14) of Arianespace and the launch site was Kourou. 44) 45)
The contract between ESA and Arianespace to launch the Sentinel-1B satellite was signed on July 17, 2014 by ESA's Director of Earth Observation Programs, Volker Liebig, and CEO of Arianespace, Stéphane Israël, at ESA headquarters in Paris, France. As part of the Copernicus program, Sentinel-1B will round out the initial capacity offered by Sentinel-1A to offer a comprehensive response to the need for environmental and security monitoring via spaceborne radar systems. 46) 47) 48)
On March 22, 2016, the Sentinel-1B satellite has arrived in French Guiana to be prepared for liftoff on 22 April. 49)
Secondary payloads of Sentinel-1B: 50)
• MicroSCOPE, a minisatellite (303 kg) of CNES (French Space Agency) which will test the universality of free fall (equivalence principle for inertial and gravitational mass as stated by Albert Einstein).
• AAUSAT4, a 1U CubeSat of the University of Aalborg, Denmark to demonstrate an AIS (Automatic Identification System), identifying and locating ships sailing offshore in coastal regions.
• e-st@r-II (Educational SaTellite @ politecnico di toRino-II), a 1U CubeSat from the Polytechnic of Turin, Italy.
• OUFTI-1 (Orbital Utility for Telecommunication Innovation), a 1U CubeSat of the University of Liège, Belgium, a demonstrator for the D-STAR communications protocol.
Tyvak International installed the three CubeSats in the orbital deployer. The three CubeSats are part of ESA's FYS (Fly Your Satellite) student program.
Orbit: Sun-synchronous near-circular dawn-dusk orbit, altitude = 693 km, inclination = 98.18º, orbital period = 98.6 minutes, ground track repeat cycle = 12 days (175 orbits/cycle). An exact repeat cycle is needed for InSAR (Interferometric Synthetic Aperture Radar) support. LTAN (Local Time on Ascending Node) = 18:00 hours.
Orbital tube: A stringent orbit control is required to the Sentinel-1 system. Satellites' position along the orbit needs to be very accurate, in terms of both accuracy and knowledge, together with pointing and timing/synchronization between interferometric pairs. Orbit positioning control for Sentinel-1 is defined by way of an orbital Earth fixed "tube" 50 m (rms) wide in radius around a nominal operational path (Figure 14). The satellite is kept inside such a tube for most of its operational lifetime Ref. 15). 51)
One of the challenges of the Sentinel-1 orbit control strategy is the translation of a statistical tube definition in a deterministic control strategy practically functional to the ESOC (European Space Operations Center) operations.
The second obvious challenge is the very stringent tube diameter which forces the application of frequent and intense maneuvers nevertheless still compatible with S/C request for consumables of up to a 12 years lifetime.
A satellite control strategy has been specifically developed and consists in applying a strict cross-track dead-band control in the most Northern Point and in the ascending node crossing. Controlling the orbit at these 2 latitudes, the satellite is shown to remain in the tube, within the rms (root mean square) criteria, for all other latitudes.
Figure 15: Orbital tube section (image credit: ESA, TAS, Ref. 15)
Orbit knowledge accuracy (< 3 m rms in each axis) in realtime for autonomous operations is not considered as demanding as the on-ground postprocessing requirements (< 5 cm 3D rms) for the detection of (slow) land movements and deformations through the differential interferometry technique. The latter is almost as demanding as for Sentinel-3 and requires dual-frequency receivers. 53)
As both satellites, Sentinel-1A and Sentinel-1B, will fly in the in the same orbital plane with 180º phased in orbit, and each having a 12-day repeat orbit cycle, it will facilitate the formation of SAR interferometry (InSAR) image pairs (i.e., interferograms) having time intervals of 6 days. This, along with the fact that the orbital deviation of each Sentinel-1 satellite will be maintained within a tube of ±50 m radius (rms) will enable the generation of geographically comprehensive maps of surface change such as for measuring ice velocity in the Polar regions, as well as monitoring geohazard related surface deformation caused by tectonic processes, volcanic activities, landslides, and subsidence (Ref. 248).
Figure 16: The main Sentinel-1 mode will allow complete coverage of Earth in six days when operational with the two Sentinel-1 satellites are in orbit simultaneously (image credit: ESA/ATG medialab) 54)
• June 21, 2019: The Copernicus Sentinel-1 mission takes us over the Lena River Delta, the largest delta in the Arctic. At nearly 4500 km long, the Lena River is one of the longest rivers in the world. The river stems from a small mountain lake in southern Russia, and flows northwards before emptying into the Arctic Ocean, via the Laptev Sea. 55)
- The river is visible in bright yellow, as it splits and divides into many different channels before meandering towards the sea. Sediments carried by the waters flow through a flat plain, creating the Lena River Delta. Hundreds of small lakes and ponds are visible dotted around the tundra.
- The delta's snow-covered tundra is frozen for most of the year, before thawing and blossoming into a fertile wetland during the brief polar summer – a 32,000 km2 haven for Arctic wildlife. Swans, geese and ducks are some of the migratory birds that breed in the productive wetland, which also supports fish and marine mammals.
- In 1995, the Lena Delta Reserve was expanded, making it the largest protected area in Russia.
Figure 17: This false-color image was captured on 14 January 2019, the peak of the Arctic winter, and shows a large amount of ice in the waters surrounding the delta. Cracks can be seen in the turquoise-colored ice at the top of the image, and several icebergs can also be seen floating in the Arctic waters to the right. Snow can also be seen in yellow on the mountains at the bottom of the image. This image is also featured in this week's edition of the Earth from Space program (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
• April 12, 2019: The Copernicus Sentinel-1 mission takes us over the busy maritime traffic passing through the English Channel. 56)
- Many vessels crossing at the narrowest part of the English Channel can be seen in the far right of the image. Connecting Dover in England to Calais in northern France, the Strait of Dover is another major route, with over 400 vessels crossing every day. The shortest distance across the Channel is just 33 km, making it possible to see the opposite coastline on a clear day.
- The cities of London and Paris, other towns and buildings and even wind turbines in the English Channel are visible in white owing to the strong reflection of the radar signal.
Figure 18: The two identical Copernicus Sentinel-1 satellites carry radar instruments, which can see through clouds and rain, and in the dark, to image Earth's surface below. Here, hundreds of radar images spanning 2016 to 2018 over the same area have been, compressed into a single image. The sea surface reflects the radar signal away from the satellite, making water appear dark in the image. This contrasts metal objects, in this case ships, which appear as bright dots in the dark water. Boats that passed the English Channel in 2016 appear in blue, those from 2017 appear in green, and those from 2018 appear in red. Owing to its narrowness, as well as its strategic connection of the Atlantic Ocean and the North Sea, the Channel is very busy with east-west ship traffic. Because of the volume of vessels passing through daily, a two-lane scheme is used, in order to avoid collisions. The two lanes can easily be detected in the image. This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2016-18), processed by ESA, CC BY-SA 3.0 IGO)
• March 29, 2019: Separating the Black Sea and the Sea of Marmara, the strait is one of the busiest maritime passages in the world, with around 48,000 ships passing through every year. Daily traffic includes international commercial shipping vessels and oil tankers, as well as local fishing and ferries. Ships in the strait can be seen in the image as multi-colored dots. Three bridges are also visible spanning the strait and connecting the two continents. 57)
- The two identical Copernicus Sentinel-1 satellites carry radar instruments, which can see through clouds and rain, and in the dark, to image Earth's surface below. The multi-temporal remote sensing technique combines two or more radar images over the same area to detect changes occurring between acquisitions.
- In the far-left of the image of Figure 19, the aqua-green patches of land show the changes in the fields between the three satellite acquisitions.
- Turkey's most populous city, Istanbul (population of around 15 million residents in its metropolitan area) , can be seen on both sides of the Bosphorus (mostly spelled as Bosporus). The city appears in shades of white owing to the stronger reflection of the radar signal from buildings, which contrasts with the dark black color of the inland lakes and surrounding waters.
Figure 19: Captured by the Copernicus Sentinel-1 mission, this image shows the narrow strait that connects eastern Europe to western Asia: the Bosphorus in northwest Turkey. The image contains satellite data stitched together from three radar scans acquired on 2 June, 8 July and 13 August 2018. This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• March 27, 2019: It is thought that well over a million people have been affected by what is probably the worst storm on record to hit the southern hemisphere. Making landfall on 15 March 2019, Cyclone Idai ripped through Mozambique, Malawi and Zimbabwe, razing buildings to the ground, destroying roads and inundating entire towns, villages and swathes of farmland. The human death toll is still unknown. While humanitarian efforts continue, people are now also facing the mammoth task of picking up the pieces and cleaning up after this devastating storm. 58)
- Images from Copernicus Sentinel-1 contributed to activations triggered in the Copernicus Emergency Management Service and the International Charter Space and Major Disasters. Both services take advantage of observations from several satellites and provide on-demand mapping to help civil protection authorities and the international humanitarian community in the face of major emergencies.
Figure 20: This Copernicus Sentinel-1 image indicates where the flood waters are finally beginning to recede west of the port city of Beira in Mozambique. The image merges three separate satellite radar images from before the storm on 13 March, from one of the days when the floods were at their worst on 19 March, and as the waters are beginning to drain away on 25 March. The blue-purple color indicates where floodwater is receding, while areas shown in red are still underwater (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
• March 20, 2019: Copernicus Sentinel-1 acquired this radar image of the oil slick, the large, dark patch visible in the center of the image, stretching about 50 km. Marine vessels are identifiable as smaller white points, which could be those assisting in the clean-up process. 59)
- Oil is still emerging from the ship now lying at a depth of around 4500 meters. French authorities trying to reduce the impact of pollution along the coast.
- Satellite radar is particularly useful for monitoring the progression of oil spills because the presence of oil on the sea surface dampens down wave motion. Since radar basically measures surface texture, oil slicks show up well – as black smears on a grey background.
Figure 21: Captured on 19 March at 17:11 GMT (18:11 CET) by the Copernicus Sentinel-1 mission, this image shows the oil spill from the Grande America vessel. The Italian container ship, carrying 2200 tons of heavy fuel, caught fire and sank in the Atlantic, about 300 km off the French coast on 12 March (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• March 20, 2019: As millions of people in Mozambique, Malawi and Zimbabwe struggle to cope with the aftermath of what could be the southern hemisphere's worst storm, Copernicus Sentinel-1 is one of the satellite missions being used to map flooded areas to help relief efforts. 60)
Figure 22: Millions of people in Mozambique, Malawi and Zimbabwe are struggling to cope with the aftermath of what could be the southern hemisphere's worst storm: Cyclone Idai. This image is from Copernicus Sentinel-1 and shows the extent of flooding, depicted in red, around the port town of Beira in Mozambique on 19 March. This mission is also supplying imagery through the Copernicus Emergency Mapping Service to aid relief efforts (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
- Cyclone Idai swept through this part of southeast Africa over the last few days, leaving devastation in its wake. Thousands of people have died and houses, roads and croplands are under water.
- It is currently thought that well over two million people in the three countries have been affected, but the extent of destruction is still unfolding.
- It is currently thought that well over two million people in the three countries have been affected, but the extent of destruction is still unfolding.
Figure 23: Captured by the Copernicus Sentinel-3 mission, this image shows Cyclone Idai on 13 March 2019 west of Madagascar and heading for Mozambique. Here, the width of the storm is around 800–1000 km, but does not include the whole extent of Idai. The storm went on to cause widespread destruction in Mozambique, Malawi and Zimbabwe. With thousands of people losing their lives, and houses, roads and croplands submerged, the International Charter Space and Major Disasters and the Copernicus Emergency Mapping Service were triggered to supply maps of flooded areas based on satellite data to help emergency response efforts (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA)
- In order to plan and execute this kind of emergency response it is vital to understand exactly which areas have been affected – especially as accessing people cut off is extremely challenging.
- Satellites orbiting Earth can provide indispensable up-to-date information to observe such events, as shown here on the right from the Copernicus Sentinel-3 mission, and, importantly, to map flooded areas for response teams facing these dire situations.
- The disaster triggered activations in both the Copernicus Emergency Mapping Service and the International Charter Space and Major Disasters.
- Both services take advantage of observations from several satellites and provide on-demand mapping to help civil protection authorities and the international humanitarian community in the face of major emergencies.
- The image of Figure 22 is from Copernicus Sentinel-1 and shows the extent of flooding, depicted in red, around the port town of Beira in Mozambique on 19 March. The image of Figure 24 uses the mission to map the flood for relief response through the Copernicus Emergency Mapping Service.
- Sentinel-1's radar ability to ‘see' through clouds and rain, and in darkness, makes it particularly useful for monitoring floods.
- Images acquired before and after flooding offer immediate information on the extent of inundation and support assessments of property and environmental damage.
Figure 24: Tropical Cyclone Idai made landfall on 14 March 2019 close to the port city of Beira in Mozambique. This map, which was generated through the Copernicus Emergency Management Service, uses information from the EC's Copernicus Sentinel-1 mission on 19 March (bright blue), and Italy's Cosmo-SkyMed satellite on 16 March (light blue) to map the floods to aid relief efforts. More maps of floods caused by Cyclone Idai are available at the Copernicus Emergency Management Service website (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), Cosmo-SkyMed, processed by GAF AG/e-GEOS/CMEMS)
• March 14, 2019: The Bering Strait is a sea passage that separates Russia and Alaska. It is usually covered with sea ice at this time of year – but as this image captured by the Copernicus Sentinel-1 mission on 7 March 2019 shows, it is virtually ice-free. 61)
- The extent of sea ice in the Bering Sea has dropped lower than it has been since written records began in 1850, and is most likely because of warm air and water temperatures. On average, the fluctuating sea ice in this region increases until early April, depending on wind and wave movement.
- To travel between Arctic and Pacific, marine traffic passes through the Bering Strait. Owing to the reduction of ice in the region, traffic has increased significantly.
- The Copernicus Sentinel-1 satellites provide images to generate maps of sea-ice conditions for safe passage in the busy Arctic waters, as well as distinguish between thinner, more navigable first-year ice and thicker, more hazardous ice. Each satellite carries an advanced radar instrument to image Earth's surface through cloud and rain, regardless of whether it is day or night.
Figure 25: The Bering Strait is a narrow passage - around 80 km wide - connecting the Pacific and Arctic Oceans. The few patches of sea ice are shown in light-blue colors. According to the National Snow & Ice Data Center in Boulder, CO, between 27 January to 3 March 2019, sea-ice extent decreased from 566,000 km2 to 193,000 km2. Sea ice was also exceptionally low last year, but it has been reported that this March the extent of sea ice is the lowest in the 40-year satellite record (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
• March 14, 2019: The Copernicus Sentinel-1 radar mission shows how cracks cutting across Antarctica's Brunt ice shelf are on course to truncate the shelf and release an iceberg about the size of Greater London – it's just a matter of time. 62)
- The Brunt ice shelf is an area of floating ice bordering the Coats Land coast in the Weddell Sea sector of Antarctica.
Figure 26: Using radar images from the Copernicus Sentinel-1 mission the animation shows two lengthening fractures: a large chasm running northwards and a split, dubbed Halloween Crack, that has been extending eastwards since October 2016. They are now only separated by a few kilometers. The image show two lengthening fractures: a large chasm, Chasm 1, running northwards and a split, dubbed Halloween Crack, that has been extending eastwards since October 2016. They are now only separated by a few kilometers. Halloween Crack runs from an area known as McDonald Ice Rumples, which is where the underside of the otherwise floating ice sheet is grounded on the shallow seabed. This pinning point slows the flow of ice and crumples the ice surface into waves. The Copernicus Sentinel-1 mission carries radar, which can return images regardless of day or night and this allows us year-round viewing, which is especially important through the long, dark, austral winter months (video credit: ESA, the video contains modified Copernicus Sentinel data (2016–19), processed by ESA)
- The Brunt ice shelf is at its maximum extent during the satellite era and compared to images collected by Argon declassified intelligence satellite photographs in 1963 and maps made by Frank Worsley during the Endurance expedition into the Weddell Sea in 1915.
Figure 27: Changing locations of Brunt calving. A comparison of the Brunt ice shelf calving front locations over the last 100 years, based on 1915 and 1958 historical survey data from the Endurance expedition (Worsley 1921) and the International Geophysical Year, respectively, followed by the location in satellite images from Landsat in 1973 and 1978, ESA's, Envisat in 2011, and Copernicus Sentinel-1 in 2019. A comparison of the images indicates that the Brunt ice shelf is at its maximum 20th Century extent (image credit: ESA, the image contains modified Copernicus Sentinel-2 data (2019), courtesy Stef l'Hermitte TU Delft)
- History shows that the last event was in 1971 when a portion of ice calved north of the Ice Rumples and in what appears to have been a previous iteration of today's Halloween Crack which is separating along lines of weakness.
- Mark Drinkwater, Head of ESA's Earth and Mission Science Division, says, "Importantly, tracking the entire ice shelf movement reveals a lot going on north of the Halloween Crack, where the shelf flows in a more northerly direction. Meanwhile, this divergence is splitting the northern and southern parts of the shelf along the Halloween Crack. Interestingly, the animation also reveals a widening split right across the Ice Rumples, which may also put the structural integrity of this northern outer segment into question. We have been observing the Brunt ice shelf for decades and it is constantly changing. Early maps made in the 1970s indicate that the ice shelf was more like a mass of small icebergs welded together by sea ice."
Figure 28: Cracks cutting across Antarctica's Brunt ice shelf are on course to truncate the shelf and release an iceberg about the size of Greater London. The Brunt ice shelf is an area of floating ice bordering the Coats Land coast in the Weddell Sea sector of Antarctica (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
Legend to Figure 28: This Copernicus Sentinel-2 image from 7 February 2019 shows two lengthening fractures: a large chasm running northwards and a split, dubbed Halloween Crack, that has been extending eastwards since October 2016. They are now only separated by a few kilometers. The Halloween Crack runs from an area known as McDonald Ice Rumples, which is where the underside of the otherwise floating ice sheet is grounded on the shallow seabed. This pinning point slows the flow of ice and crumples the ice surface into waves. Routine monitoring by satellites with different observing capabilities offer unprecedented views of events happening in remote regions like Antarctica, and how ice shelves manage to retain their structural integrity in response to changes in ice dynamics, air and ocean temperatures.
- As the ice flows down the steep coastal area and across the grounding line into the floating ice shelf, it fractures into a series of regular blocks. The structural integrity of the shelf relies on the fractures being filled over decades by marine ice and snow. Since Copernicus Sentinel-1 radar penetrates through the surface snow, this pattern of fractures is revealed to give Brunt its skeletal-like appearance.
- When the chasm and cracks around McDonald ice rumples finally intersect, it is likely that the northern end of the calved iceberg remains pinned by its grounding point, leaving the southern end of the berg to swing out into the ocean.
- Although it may be the biggest berg observed to break off Brunt, compared to the recent Larsen ice shelf iceberg A68, for example, it won't be a particularly large one. However, the concern is that this calving could allow the ice left behind to flow more freely towards the ocean.
- "We are now poised for this eventual calving, which could have consequences for the ice shelf as a whole. After the 1971 calving, ice shelf velocities are reported to have doubled from 1 to 2 m/day. So we will be carefully monitoring the ice shelf with the combination of both Copernicus Sentinel-1 and Copernicus Sentinel-2, which carries an optical instrument, to see how the dynamics influence the integrity of the remaining ice sheet," continues Dr Drinkwater.
- With the ice shelf currently deemed unsafe, the British Antarctic Survey (BAS) has closed up their Halley VI research station, which was repositioned south of Halloween Crack and east of the chasm in 2017.
- The station used to be operational all year round, but this is the third winter running that it has had to close because of potential danger.
- There has been a permanent research station on Brunt since the late 1950s, but in 2016–17 the base was dragged 23 km to its current, more secure location. If it had not been moved, it would now be on the seaward side of the chasm.
- Routine monitoring by satellites with different observing capabilities offer unprecedented views of events happening in remote regions like Antarctica, and how ice shelves manage to retain their structural integrity in response to changes in ice dynamics, air and ocean temperatures.
- The Copernicus Sentinel-1 mission carries radar, which can return images regardless of day or night and this allows us year-round viewing, which is especially important through the long, dark, austral winter months. A recent image from the Copernicus Sentinel-2 mission provides complementary information.
• February 22, 2019: When Mount Agung, a volcano on the island of Bali in Indonesia erupted in November 2017, the search was on to find out why it had stirred. Thanks to information on ground deformation from the Copernicus Sentinel-1 mission, scientists now have more insight into the volcano's hidden secrets that caused it to reawaken. 63)
Figure 29: Copernicus Sentinel-1 InSAR data shows ground uplift on the flank of Mount Agung, which is on the island of Bali in Indonesia. The data show uplift between August and November 2017, prior to the eruption of Mount Agung on 27 November. The eruption was preceded by a wave of small earthquakes. A team led by Bristol University's School of Earth Sciences in the UK used radar data from the Copernicus Sentinel-1 radar mission and the technique of InSAR to map ground motion, which may indicate that fresh magma is moving beneath the volcano. Their research provides the first geophysical evidence that Agung and the neighboring Batur volcano may have a connected plumbing system (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by University of Bristol/COMET)
- After lying dormant for more than 50 years, Mount Agung on the Indonesian holiday island of Bali rumbled back to life in November 2017, with smoke and ash causing airport closures and stranding thousands of visitors.
- Fortunately, it was preceded by a wave of small earthquakes, signalling the imminent eruption and giving the authorities time to evacuate around 100,000 people to safety.
- The prior event in 1963, however, claimed almost 2000 lives and was one of the deadliest volcanic eruptions of the 20th century. Knowing Agung's potential for devastation, scientists have gone to great lengths to understand this volcano's reawakening.
- And, Agung has remained active, slowly erupting on and off since 2017.
- Bali is home to two active stratovolcanoes, Agung and Batur, but relatively little is known of their underlying magma plumbing systems. A clue came from the fact that Agung's 1963 eruption was followed by a small eruption at its neighboring volcano, Batur, 16 km away.
- A paper published recently in Nature Communications describes how a team of scientists, led by the University of Bristol in the UK, used radar data from the Copernicus Sentinel-1 mission to monitor the ground deformation around Agung. 64)
- Their findings may have important implications for forecasting future eruptions in the area, and indeed further afield.
Figure 30: As an advanced radar mission, Sentinel-1 satellites can image the surface of Earth through cloud and rain and regardless of whether it is day or night. This makes it an ideal mission, for example, for monitoring the polar regions, which are in darkness during the winter months and for monitoring tropical forests, which are typically shrouded by cloud. Over oceans, the mission will provide imagery to generate timely maps of sea-ice conditions for safe passage, to detect and track oil spills and to provide information on wind and waves, for example. Over land, Sentinel-1's systematic observations will be used, for example, to track changes in the way the land is used and to monitor ground movement. Moreover, this new mission is designed specifically for fast response to aid emergencies and disasters such as flooding and earthquakes (video credit: ESA/ATG medialab)
- They used the remote sensing technique of InSAR (Interferometric Synthetic Aperture Radar), where two or more radar images over the same area are combined to detect slight surface changes.
- Tiny changes on the ground cause differences in the radar signal and lead to rainbow-colored interference patterns in the combined image, known as a SAR interferogram. These interferograms can show how land is uplifting or subsiding.
- Juliet Biggs from Bristol University's School of Earth Sciences, said, "Using radar data from the Copernicus Sentinel-1 radar mission and the technique of InSAR, we are able to map any ground motion, which may indicate that fresh magma is moving beneath the volcano."
- In the study, which was carried out in collaboration with the Center for Volcanology and Geological Hazard Mitigation in Indonesia, the team detected uplift of about 8–10 cm on Agung's northern flank during the period of intense earthquake activity prior to the eruption.
- Fabien Albino, also from Bristol's School of Earth Sciences and who led the research, added, "Surprisingly, we noticed that both the earthquake activity and the ground deformation signal were five kilometers away from the summit, which means that magma must be moving sideways as well as vertically upwards. - Our study provides the first geophysical evidence that Agung and Batur volcanoes may have a connected plumbing system. This has important implications for eruption forecasting and could explain the occurrence of simultaneous eruptions such as in 1963."
- Part of European Union's fleet of Copernicus missions, Sentinel-1 is a two-satellite constellation that can provide interferometric information every six days – important for monitoring rapid change. Each satellite carries an advanced radar instrument that can image Earth's surface through cloud and rain and regardless of whether it is day or night.
- ESA's Copernicus Sentinel-1 mission manager, Pierre Potin, noted, "We see the mission is being used for a multitude of practical applications, from mapping floods to charting changes in ice. Understanding processes that are going on below the ground's surface – as demonstrated by this new research – is clearly important, especially when these natural processes can put people's lives and property at risk."
- While the European Union is at the helm of Copernicus, ESA develops, builds and launches the dedicated Sentinel satellites. It also operates some of the missions and ensures the availability of data from third party missions contributing to the Copernicus program.
Figure 31: This image of Mount Agung on the Indonesian island of Bali was captured on 2 July 2018 by the Copernicus Sentinel-2 mission (the image was released on 22 February 2019, offering a ‘camera-like' view of the Agung and Batur volcanoes). After being dormant for 50 years, Mount Agung erupted in November 2017. It has continued to erupt on and off since then – a bright orange spot can be seen in the volcano's crater. Recent research provides evidence that Agung and the neighboring Batur volcano, visible northwest of Agung, may have a connected magma plumbing system (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• February 1, 2019: This week's edition of the Earth from Space program features a Copernicus Sentinel-1 image over one of the areas in Iraq that suffered flooding recently. 65)
- The town of Kut is in the lower-center of the image. It lies within a sharp ‘U-bend' of the Tigris River, which can be seen meandering across the full width of the image. The image has been processed to show floods in red, and it is clear to see that much of the area was affected including agricultural fields around the town. Dark patches in the image, including the large patch in the center , however, indicate that there was no or little change between the satellite acquisitions.
- After the searing dry heat of summer, November typically signals the start of Iraq's ‘rainy season' –but November 2018 brought heavier rainstorms than usual. Many parts of the country were flooded as a result. Thousands of people had to be evacuated, and infrastructure, agricultural fields and other livelihoods were destroyed, and tragically the floods also claimed lives. Declared an emergency, the International Charter Space and Major Disasters was activated. The Charter takes advantage of observations from a multitude of satellites to aid emergency relief. Images from Copernicus Sentinel-1 contributed to this particular effort.
- The two identical Copernicus Sentinel-1 satellites carry radar instruments, which can see through clouds and rain, and in the dark, to image Earth's surface below. This capability is particularly useful for monitoring and mapping floods, as the image shows. Satellite images play an increasingly important role in responding to disaster situations, especially when lives are at risk. Also, after an event, when damage assessments are needed and plans are being made to rebuild, images from satellites are a valuable resource.
Figure 32: This Copernicus Sentinel-1 image combines two acquisitions over the same area of eastern Iraq, one from 14 November 2018 before heavy rains fell and one from 26 November 2018 after the storms. The image reveals the extent of flash flooding in red, near the town of Kut. This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• January 10, 2019: Images acquired every six days by the European Union's Copernicus Sentinel-1 satellites are being used to map ground movement across two billion measurement sites in Norway, revealing shifts as small as one millimeter a year. 66)
- Thanks to this information, the Geological Survey of Norway, the Norwegian Water Resources and Energy Directorate, and the Norwegian Space Center have recently launched the Norwegian Ground Motion Service – InSAR Norway.
- This new service will provide the basis for strategic governmental use of interferometry in Norway. Interferometry is a technique involving multiple repeat satellite radar images over the same scene that are combined to identify slight alterations between acquisitions, thus 'spotting the difference'.
- The service will map ground deformation caused by, for example, subsidence. It will also assess the risk of landslides and monitor changes in infrastructure in urban areas. Furthermore, the service will lead to downstream commercial and public use – for instance in sectors such as big data analysis, insurance, real estate, structural engineering and transport infrastructure.
- The service will also benefit road and rail authorities, municipalities and city planners, as well as citizens.
Figure 33: On 29 November 2018, the Geological Survey of Norway (NGU), the Norwegian Water Resources and Energy Directorate (NVE) and the Norwegian Space Center launched the Norwegian Ground Motion Service, InSAR Norway, to help monitor and measure all of Norway's ground movements, using Copernicus Sentinel-1 data. InSAR data is given at full resolution, freely and openly available to everyone from the InSAR Norway portal (image credit: ESA, the image contains modified Copernicus Sentinel data (2018)/processed by InSAR Norway and powered by KSAT-GMS)
- InSAR Norway aims to find all unstable rock slopes in Norway that could collapse catastrophically, and understand the geologic conditions of each unstable slope and rank them based upon their hazard and risk, and establishing a 24/7 early-warning system where necessary.
- John Dehls, from the Geological Survey of Norway, stated, "Setting-up such an operational ground motion service has had significant technical challenges. However, we are already seeing the first benefits. New critical areas prone to large landslides were discovered within days of the first dataset being produced. These will be followed up with fieldwork next summer. - We consider that the information provided by the InSAR Norway service will be of interest not only for public and commercial entities, but also for citizens. We have decided to provide the related data at full resolution, freely and openly to everyone. Furthermore, InSAR Norway data will be maintained and updated at regular intervals, thus creating predictability for long-term operational users".
Figure 34: The service uses images acquired every six days by the Sentinel-1 satellites of the European Union's Copernicus Program. Over 4000 images a year, in two different geometries (so-called ascending and descending orbit passes) are used, ensuring that more than two billion locations in Norway can now be measured and continuously monitored to within1mm/year. This represents an average of more than 6,000 measurement locations/km2. 67)
Legend to Figure 34: On 29 November 2018, NGU, NVE and the NSC (Norwegian Space Center) launched the operational Norwegian Ground Motion Service with InSAR subsidence data at full resolution, free and open to everyone on the InSAR Norway portal. More than 25,000 users accessed the service in the first week of operation.
Figure 35: This 3D image map covered with InSAR measurement points showing a mountain on the move in Osmundneset, Gloppen, Norway. The dark red points correspond to subsidence of up to 2 cm/year, while green ones correspond to negligible movement. The inlet figure shows the average subsidence of 2236 points for the light grey marked polygon in the map. The average velocity of the subsidence is calculated at some 4-5 mm/year for the period 2015-2018 Image credit: ESA, the image contains modified Copernicus Sentinel data (2018)/processed by InSAR Norway and powered by KSAT-GMS)
- The Norwegian research institute, Norut, and the Dutch company PPO.Labs, have been the research and development partners for InSAR Norway, through the KSAT-GMS partnership with the Norwegian Kongsberg Satellite Services (KSAT). The official unveiling was the result of several years of intensive research and development activities, from the design phase of innovative algorithms to implementation and operationalization of the service.
- The main goal of this free service is to produce operational Interferometric Synthetic Aperture Radar (InSAR) ground deformation measurements over Norway and improve accessibility of InSAR results for public and commercial users.
- InSAR Norway will provide the basis for strategic governmental use of interferometry in Norway, by mapping ground deformation such as subsidence, assessing rock-slide risks and by monitoring infrastructure in cities. Furthermore, the service will be a tool for creating downstream commercial and public use, for instance in geotechnical, climate, big data analysis, insurance, real estate, structural engineering and transport infrastructure applications. The service will also benefit users such as road authorities, railroad authorities, municipalities and city planners, as well as citizens.
Beyond Norway: towards a European ground motion service (Ref. 67)
- "We are very proud of the state-of-the-art tools and methods our team from NGU, NSC, NVE, Norut, PPO.Labs and KSAT-GMS have been able to develop for the InSAR Norway operational ground motion service. Personally, I think this is a breakthrough for applied operational nation-wide large-scale use of InSAR."
- A European–wide Copernicus ground motion service based on Sentinel-1 data is under planning by the European Commission in partnership with the European Environment Agency and the states participating in the Copernicus Earth Observation program.
- "This is a very important and valuable development also for Europe, which we look forward to supporting, as well as collaborating with the European Commission and nations in Europe to make it happen successfully", concluded Dag Anders Moldestad and John Dehls.
• November 30, 2018: The Copernicus Sentinel-1 mission takes us over Mexico City. This huge, densely-populated capital can be seen in the top right of the image. It is home to almost nine million people, with the Greater Mexico City area recording a population of over 21 million. This makes it the largest Spanish-speaking city in the world. 68)
Figure 36: Mexico City is located in the top right of the SAR image. This striking image has been created using three Copernicus Sentinel-1 acquisitions from 28 July, 27 August and 26 September 2018, overlaid in red, green and blue, respectively. Where we see explosions of color, changes have occurred between the different acquisitions. This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
- In the left of the image, three bodies of water are shown in black: Villa Victoria, Valle de Bravo, and Tepetitlán. Water is significant to the development of Mexico City, which is thought to have been built over a lake by the Aztecs around 1325.
- Today, the city finds itself in a precarious situation in terms of water supply in spite of the regular flash floods and heavy rainfall it experiences during the wet season from June and September.
- In the top right, we can see the round structure of El Caracol meaning ‘the snail' in Spanish. Currently used as a reservoir for industrial facilities within Mexico City, there are plans for this to become a wastewater treatment plant. A 62 km-long sewer tunnel is also due to begin operating this year.
- The Cumbres del Ajusco national park is shown to the southwest of the capital, in an area of the image that shows colorful dots forming a circle. Famous for being up to almost 4000 m above sea level at its highest elevation, it is one of many national parks surrounding the capital.
- Volcanoes are also dotted around this area. Popocatépetl, to the south east of Mexico City, last erupted in September 2018.
• On 8 October 2018 at 05:28 GMT (07:28 CEST), the Copernicus Sentinel-1 mission captured its first images of the oil spill from a collision between two ships that had occurred the day before in the Mediterranean Sea, north of the French island of Corsica. This first image shows that the oil slick was about 20 km long. By the evening at 19:21 CEST, however, imagery shows that the slick had lengthened to about 35 km. And 24 hours later, on 9 October at 19:14 CEST, the slick had grown to about 60 km long. 69)
Figure 37: The Copernicus Sentinel-1 mission returns images showing how oil is spreading in the Mediterranean Sea following a collision between two ships (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO
Legend to Figure 37: The image from 9 October also shows a large black patch southeast of the oil slick – this is a result of low reflectivity of the radar signal and therefore depicts calm waters.
• October 8, 2018: The Copernicus Sentinel-1 mission has imaged the oil spill in the Mediterranean following a collision between two merchant ships on Sunday 7 October 2018. A Tunisian cargo ship is reported to have struck the hull of a Cypriot container ship in waters north of the French island of Corsica. There were no casualties, but the collision caused a fuel leak – which has resulted in an oil slick about 20 km long. Although the collision occurred in French waters, the cleanup operation is part of a joint pact between France, Italy and Monaco to address pollution accidents in the Mediterranean. 70)
Figure 38: This image of the slick, which can be seen as a dark patch north of the tip of Corsica, was captured by the Sentinel-1A satellite on 8 October at 05:28 GMT (07:28 CEST). Sentinel-1 is a two-satellite constellation built for the European Commission's Copernicus environmental monitoring program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• September 28, 2018: The Copernicus Sentinel-1B satellite takes us over central Italy. From the Apennine Mountains in the top right, to the fertile, former lakebed of the Avezzano plain in the center right, this bright, false-color image (Figure 39) captures the diversity and beauty of the region's landscapes. 71)
- Dual-polarization radar technology has been used, resulting in vibrant shades of green for most of the land surface shown. Built-up areas, such as Italy's capital city of Rome, appear in shades of red and pink. Meanwhile, the structure of the agricultural fields of Altopiano in the Abruzzo region is clearly reflected in a combination of blue and violet hues.
- This radar technology allows us to see the crater lake structures of the volcanic lakes of Nemi and Albano in the bottom left clearly. The same is true for Lago di Vico with the volcano and crater clearly visible in the top left of the image.
- The central region of Italy is an important one for the space industry. For example, ESA's center for Earth observation, which celebrates its 50-year anniversary this week, is located in this area.
- This region is also prone to earthquakes. In August 2016, a magnitude 6.2 earthquake struck the small towns of Amatrice, Accumoli and Pescara del Tronto. It was followed by two aftershocks. A magnitude 6.6 earthquake in Norcia followed in October the same year. The tremor of this last earthquake was felt across the country. It was the most powerful one to hit Italy since 1980.
Figure 39: Sentinel-1B captured this image of central Italy on 6 July 2018, is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• September 14, 2018: The Copernicus Sentinel-1B satellite takes us over Semera in northeast Ethiopia. Semera is a new town with a population of just over 2600 and serves as the capital of the Afar region. The region spans an estimated 270,000 km2, from close to the border with Eritrea towards the capital of Addis Ababa (also written as Addis Abeba). 72)
- We can see the regional capital in the top right of this false-color image (Figure 40), with the larger urban center of Dubti just south of the town. Both are found in the Great Rift Valley, which lies between the Ethiopian Plateau and the Somalia Plateau.
- The landscape of the Afar region is characterized by desert shrubland and volcanoes, particularly in the north. In this image we can see differences in altitude represented in the variations in color. The left part of the image is dominated by yellow, signifying changes in vegetation found at higher altitudes. Two lakes, Hayk Lake and Hardibo Lake, are shown in the bottom left.
- South of Dubti we can see the Awash River, which flows into the northern salt lakes rather than into the sea. Salt trade is typical of the area, whilst cotton is grown in the Awash River valley. Maize, beans, papaya and bananas are also cultivated in the Afar region. It is thought that 90% of the region's population lead a pastoral life, rearing animals such as camels, sheep and donkeys.
- Dallol, to the north of Semera in Ethiopia's Danakil Depression, is frequently cited as one of the hottest inhabited places on Earth. Lying 125 m below sea level, with temperatures in the spectacular hydrothermal fields averaging 34.4 °C year-round, and the area receiving just 100–200 mm rainfall a year, conditions are thought to be amongst the most inhospitable in the world.
Figure 40: This image of Sentinel-1B, which was captured on 5 April 2018, is of northeast Ethiopia (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO) 73)
• September 13, 2018: In July 2017, one of the largest icebergs on record calved from the Larsen C ice shelf in Antarctica. However, sea ice to the east and shallow waters to the north kept this giant berg, named A68, hemmed in. So for more than a year it wafted to and fro, but never left its parent ice shelf's side. Strong winds blowing from Larsen C have finally given it the push it was waiting for. In early September 2018, these winds pushed the southern end of the berg out into the Weddell Gyre. This clockwise drift of ocean waters and sea ice flowing north past the Larsen shelf, which can be seen in the animation as a flow from right to left, has rotated A68 out into the Weddell Sea. Here it is freer to float away and be carried further north into warmer waters. 74)
Figure 41: The animation, generated by Adrian Luckman at Swansea University (UK), uses data from the Copernicus Sentinel-1mission – a two-satellite constellation. Each satellite carries an advanced radar instrument that can image Earth's surface through cloud and rain and regardless of whether it is day or night. This is essential for monitoring the polar regions, which are shrouded in darkness during the long winter months (image credit: ESA, the image contains modified Copernicus Sentinel data (2017–18), processed by Swansea University–A. Luckman)
• August 8, 2018: Scientists with the ARIA (Advanced Rapid Imaging and Analysis) project , a collaboration between NASA's Jet Propulsion Laboratory in Pasadena, California, and Caltech, also in Pasadena, used synthetic aperture radar (SAR) data from the European Union's Copernicus Sentinel-1A and -1B satellites, operated by the European Space Agency. They generated a map of the deformation of Earth's surface caused by the Aug. 5, 2018 magnitude 6.9 earthquake under Lombok island, Indonesia (Figure 42). The deformation map is produced from automated interferometric processing of the SAR data using the JPL-Caltech ARIA data system in response to a signal received from the U.S. Geological Survey. The false-color map shows the amount of permanent surface movement that occurred almost entirely due to the quake, as viewed by the satellite, during a 6-day interval between two Sentinel-1 images acquired on July 30 and Aug. 5, 2018. 75)
- From the pattern of deformation in the map, scientists have determined that the earthquake fault slip was on a fault beneath the northwestern part of Lombok Island and caused as much as 25 cm of uplift of the ground surface. The map depicts motion towards the satellite (up and west) in the direction of the radar's line-of-sight, with contours every 5 cm. White areas are places where the radar measurement was not possible, largely due to dense forests in the middle of the islands.
Figure 42: New satellite map shows ground deformation after Indonesian quake. The map shows that the earthquake fault was under the northwest corner of Lombok island, probably extending offshore to the west. Through these maps, NASA and its partners are contributing observations and expertise that can assist with response to earthquakes and other natural or human-produced hazards (image credit: NASA/JPL-Caltech/Copernicus/ESA, the image contains modified Copernicus Sentinel-1 data (2018) processed by ESA and NASA/JPL)
• July 30, 2018: Copernicus Sentinel-1 data are highlighting the collapse of the Xe-Pian Xe-Namnoy dam in the southeastern province of Attapeu in Laos. The collapse has led to flash floods that have claimed several lives and left many more people missing, according to local news reports. 76)
- Sentinel-1's radar ability to ‘see' through clouds and rain, and in darkness, makes it particularly useful for monitoring floods. Images acquired before and after flooding offer immediate information on the extent of inundation and support assessments of property and environmental damage.
- The C-band synthetic aperture radar on Sentinel-1 can provide large swath images with a resolution of 20 m and within hours of acquisition to aid emergency response. — With construction starting back in 2013, the dam had been expected to commence commercial operations this year.
- The flood seems to have been caused by a breach in another saddle dam (not the main dam) following heavy rainfall. The effects of this can be seen clearly at larger scale, with the flood following the Vang Ngao river down to the villages. This is shown in the animation here.
Figure 43: Sentinel-1 images show the impact of the dam failure on the Xe-Pian Xe-Namnoy lake area in the southeastern province of Attapeu in Laos (image credit: ESA, the imagery contains modified Copernicus Sentinel data (2018) / processed by CESBIO) 77)
- The catastrophe triggered the International Charter Space and Major Disasters. With 16 members, the Charter takes advantage of observations from several satellites, providing a unified system of space data acquisition and delivery to support disaster management.
- With the ability to mobilize agencies around the world through a single access point that operates 24 hours a day, 7 days a week, the Charter helps civil protection authorities and the international humanitarian community in the face of major emergencies.
- By supplying reliable and accurate information, these entities are better equipped to save lives and limit damage to property, infrastructure and the environment.
- Since its first activation in 2000, the Charter has called on space assets on hundreds of occasions, helping respond to disasters such as floods, hurricanes, tsunamis and earthquakes.
Figure 44: Dam failure in the Xe-Pian Xe-Namnoy lake area (image credit: ESA, the image contains modified Copernicus Sentinel data (2018) processed by CESBIO)
• July 13, 2018: The Copernicus Sentinel-1 mission has revealed that, on average, Greenland's glaciers are now flowing more slowly into the Arctic Ocean. While glacial flow may have slowed overall, in summer glaciers flow 25% faster than they do in the winter. 78)
- While the general flow has reduced in recent years, during the summer it speeds up, with glaciers flowing up to 25% faster than in the winter.
- A paper published recently in The Cryosphere details the research led by the UK's CPOM (Centre for Polar Observation and Modelling) where the Copernicus Sentinel-1 mission was used to track Greenland's four main glaciers: Jakobshavn Isbrae, Petermann, Nioghalvfjerdsfjorden and Zachariae Isstrom between 2014 and 2017. 79)
- We all know that ice melts pretty quickly under the summer sun, but monitoring exactly how glacial flow changes according to the season is important for understanding glacial dynamics. In turn, this is vital to assess the risk of sea-level rise, which is a major concern around the world.
- Together, these four glaciers contain enough water to raise global sea levels by 1.8 m.
- Adriano Lemos from CPOM noted, "Sentinel-1 has real advantages for studying glaciers. We now get more data and more often so we can see the finer detail in even the most inaccessible and fast-moving areas."
Figure 45: The Copernicus Sentinel-1 mission has revealed that, on average, Greenland's glaciers are flowing more slowly into the Arctic Ocean. While the general flow has reduced in recent years, in the summer glaciers flow up to 25% faster than in the winter. Jakobshavn Isbrae, which is Greenland's fastest flowing glacier, reached a peak of 17 km per year in 2013, the result of an unusually warm summer. But satellite data, in particular from Sentinel-1, show that, on average, it has actually slowed down by 10% since 2012. This is overlaid by a seasonal pattern, with the glacier accelerating by up to 14% over a three-month summer period before slowing down again in winter (image credit: ESA, the image contains modified Copernicus Sentinel data (2014–17), processed by CPOM) 80)
- Part of European Union's fleet of Copernicus missions, Sentinel-1 is a two-satellite constellation that images the entire Earth every six days – important for monitoring rapid change. Each satellite carries an advanced radar instrument that can image Earth's surface through cloud and rain and regardless of whether it is day or night.
- This is essential for monitoring the polar regions, which are shrouded in darkness during the long winter months.
- "We saw this summer speed-up at all four glaciers and it is important that we continue to monitor this speed throughout the year to fully understand how the glaciers are moving" explained Adriano Lemos.
- Anna Hogg also from CPOM added, "Acquiring all this valuable radar data needed international coordination between multiple space agencies such as ESA and the German Aerospace Center DLR. This paper shows how our efforts are being rewarded through improving our understanding of environmental change in Greenland."
• June 2018: The Sentinel-1 mission has set a benchmark for achieving a high-quality end-to-end SAR performance, showing almost identical radiometric and geolocation accuracy for Sentinel-1A &-1B. 81)
- In addition, the 6-day repeat orbit interval along with small orbital baselines enables the implementation of cross-InSAR by combining data acquired by Sentinel-1A&-1B from repeat-pass orbits, reducing significantly the temporal surface decorrelation effect. This supports geophysical applications, such as the monitoring of cryosphere dynamics and the mapping of surface deformation.
- The continuous and systematic Sentinel-1 SAR and InSAR data acquisition, while providing an instantaneous wide area coverage, enables the build-up of long data time series. This has triggered a shift from individual image analysis to time-series processing.
• May 29, 2018: In what the UN describes as the world's fastest growing refugee crisis, almost 700,000 Rohingya Muslims have fled Myanmar for neighboring Bangladesh since August 2017. With the Bangladesh government proposing a vulnerable low-lying island as a relocation site for thousands, Sentinel-1 data have shown how unsuitable this site would be. 82)
- While the Rohingya have faced decades of repression, this recent mass exodus is blamed on large-scale atrocities committed by the Myanmar military. - Not only has the pace of arrivals in Bangladesh made this the fastest growing refugee crisis in the world, but the concentration of displaced people now in Bangladesh's Cox's Bazar is amongst the densest in the world. Even before the crisis, Bangladesh was hosting more than 200,000 Rohingya from Myanmar. For a country already struggling to cope with challenges of its own, this has turned into a huge humanitarian tragedy.
- Desperate to find solutions, the Bangladesh government was prompted, unsurprisingly, to revive a much criticized plan to move thousands to Thengar Char, one of several uninhabited and unstable islands in the Bay of Bengal.
- The area is particularly prone to cyclones, with coastal zones and islands at highest risk. Some nearby islands have a tidal range as high as 6 m, meaning that they are at risk of being completely submerged. - Regardless of cyclones, the region is often inundated by heavy rainfall during the South Asian monsoon, which lasts from June to October.
- Information from satellites is often used during humanitarian crises to map, for example, the extent of camps and other temporary settlements. In this case, however, the Earth Observation-based Services for Dynamic Information Needs in Humanitarian Action project used data from the Copernicus Sentinel-1 radar mission to show exactly how precarious Thengar Char is.
Figure 46: The Bangladeshi island of Thengar Char in the Bay of Bengal has been identified as a possible relocation site for Rohingya refugees. Information from the Copernicus Sentinel-1 mission has been used to show that the island is particularly susceptible to inundation. At times, flooding has reduced the island from 76 km2 to less than 40 km2 (image credit: EO4HumEn+)
- Andreas Braun from Germany's University of Tübingen said, "As well as using data from Sentinel-1, we also used data from ESA's old ERS and Envisat satellites to work out how the size of the island has changed since 1991 (Figure 47).
Figure 47: Barely an island: Based on 178 archived satellite radar images from 1991 to 2018, this image shows how often a pixel was identified as land. During this time, the island of Thengar Char mostly varied between 30% and 80% of its mean extent. This shows how vulnerable the island is to flooding (image credit: EO4HumEn+) 83)
- "It turns out that this set of islands has only been there since 2009, and were formed from silt washing down from the Himalayas into the Bay of Bengal. We calculated how big the island has ever been, how small it has ever been and how big it is on average. Importantly, we could report that since Sentinel-1 became operational in 2014, the island, which is currently about 60 km2, has been inundated several times and at the worst, the land area was reduced to 39 km2."
- The notion of placing vulnerable people on an inhospitable island that has no existing infrastructure and is two hours away by boat from the mainland is obviously questionable, but thanks to Sentinel-1, the authorities have hard evidence as to its risk of flooding.
- It remains to be seen whether the government of Bangladesh will move forward with their plan, although construction work has apparently begun.
• Mission status 22-28 May, 2018: The Sentinel-1 Yearly Mission Review took place on 24 May 2018, at ESA-ESRIN. The overall mission is in a very good shape, and both satellites demonstrate a good health. The occurrence of satellite anomalies and mission unavailability periods has further decreased over the past months. A major increase of the Sentinel-1 operations capacity has been achieved during the past year with the smooth integration of the EDRS service in operations, and a series of improvements were performed (e.g. systematic production of L2 OCN (Level 2 Ocean) products from IW/EW/SM modes). Substantial improvements on the data quality have been achieved (e.g. provision of de-noising information), and will be pursued. Remaining system issues are being addressed, in particular the Level 2 OCN RVL product qualification. The Copernicus operational services have expressed satisfaction on the routine use of Sentinel-1 data. Data and user access statistics, as well as the numerous exploitation activities based on Sentinel-1 data, confirm the great user uptake in various thematic application and scientific fields. 84) 85)
- The Sentinel-1A and Sentinel-1B routine operations are on-going
- The Sentinel-1 observation scenario supports the systematic coverage of Copernicus Services areas of interest, of European land and coastal waters, of global tectonic/volcanic areas, as well as of other areas worldwide for various applications. The observation plan also includes a regular mapping of all land areas worldwide.
- World maps providing a high level description of the Sentinel-1 constellation observation scenario, in terms of SAR modes, polarization, observation geometry, revisit and coverage frequency are available at: https://sentinels.copernicus.eu/web/sentinel/missions/sentinel-1/observation-scenario
- The detailed observation plan in the form of instrument acquisition segments, for both Sentinel-1A and Sentinel-1B is published at: https://sentinels.copernicus.eu/web/sentinel/missions/sentinel-1/observation-scenario/acquisition-segments
- The operational use of Sentinel-1 data by the Copernicus Marine Environment Monitoring Service (CMEMS) for sea-ice and iceberg monitoring activities is on-going.
- The European Maritime Safety Agency (EMSA) operationally uses Sentinel-1 imagery in quasi-real time in the CleanSeaNet services; operations with EMSA service providers local stations are on-going.
- Specific planning was made to support the activation EMSR286 from the Copernicus Emergency Management Service related to monitoring the risk of failure of the Ituango dam in Colombia.
- Specific actions (fast delivery of already planned acquisitions) were implemented to support the activation EMSR287 from CEMS related to floods in Saxony, Germany.
- Both Sentinel-1A and -1B spacecraft are in a stable state, operating in Nominal Mission Mode (NMM). The Flight Operations Segment (FOS) ensuring the monitoring, control and commanding of the satellites is operating nominally. Orbit control maneuvers are performed once a week.
- The use of the EDRS-A service by Sentinel-1A and -1B is on-going as part of the routine operations.
- X-Band data acquisitions are routinely performed over Matera, Svalbard and Maspalomas X-band core stations. The acquired data are circulated within the Payload Data Ground Segment (PDGS), systematically processed to Level-0 and Level-1 products and archived.
- Wave Mode data are regularly acquired over open oceans, systematically processed to Level-2 OCN products and made available. Sentinel-1 IW and EW Level-2 OCN products over regional ocean areas are available on the Data Hubs. The operational qualification of the Level-2 the OCN Radial Surface Velocity (RVL) component is on-going.
- Operations are performed regularly at the Processing and Archiving Centres (DLR-PAC and UK-PAC). All other PDGS operational services (i.e. Mission Performance, Precise Orbit Determination, Wide Area Network) are operating nominally.
- By 24th May 2018, a total of 153,443 users have self-registered on the Sentinels Scientific Data Hub; 14.6 million Sentinel-1 product downloads have been made by users, corresponding to 19 PB of data. 2.6 million Sentinel-1 products are available on-line for download, representing about 4 PB of data. Statistics of last 24 hours are available in real time at the Open Data Hub home page: https://scihub.copernicus.eu
• March 22, 2018: Two giant sinkholes near Wink, Texas, may just be the tip of the iceberg, according to a new study that found alarming rates of new ground movement extending far beyond the infamous sinkholes. That's the finding of a geophysical team from SMU (Southern Methodist University), Dallas that previously reported the rapid rate at which the sinkholes are expanding and new ones forming. - Now the team has discovered that various locations in large portions of four Texas counties are also sinking and uplifting. 86)
- Radar satellite images show significant movement of the ground across a 4000-square-mile area (10 ,360 km2) - in one place as much as 1 m over the past two-and-a-half years, say the geophysicists.
- The West Texas' Permian Basin, consisting of ancient marine rocks, is underlain by water-soluble rocks and multiple oil-rich formations. In the region that is densely populated with oil producing facilities, many localized geohazards, such as ground subsidence and micro-earthquakes, have gone unnoticed. Here we identify the localized geohazards in West Texas, using the satellite radar interferometry from newly launched radar satellites (Sentinel-1A/1B) that provide radar images freely to public for the first time, and probe the causal mechanisms of ground deformation, encompassing oil/gas production activities and subsurface geological characteristics. Based on our observations and analyses, human activities of fluid (saltwater, CO2) injection for stimulation of hydrocarbon production, salt dissolution in abandoned oil facilities, and hydrocarbon extraction each have negative impacts on the ground surface and infrastructures, including possible induced seismicity. Proactive continuous and detailed monitoring of ground deformation from space over the currently operating and the previously operated oil/gas production facilities, as demonstrated by this research, is essential to securing the safety of humanity, preserving property, and sustaining the growth of the hydrocarbon production industry. 87)
- Geohazards pose a severe threat to humanity, civilian properties, infrastructures, and industries, possibly leading to the loss of life and high economic values. Monitoring areas prone to geohazards is invaluable for locating their precursory signals on the surface, alerting civilians to potential disasters, mitigating the catastrophic outcomes, and facilitating the decision-making processes on the construction and operation of infrastructures and industrial facilities. The United States mid-continent has long been considered geologically stable with no large scale tectonic movements, volcanism, or seismic activities. Therefore, unlike California with its dense GPS networks and frequent survey (aerial, spaceborne, field) campaigns, the mid-continent has garnered less attention from scientific communities and federal/state governments. However, recent studies have revealed that some of the mid-continent, especially the Gulf Coast of the United States including Texas, Louisiana, and Mississippi, is not immune to large-scale and/or localized geohazards.
- The geohazards along the southern United States have been both naturally induced and stimulated by human activities. Besides the occasional, strong tropical storms and flooding in lowlands, natural geohazards include settlement due to sediment loading and glacial isostatic adjustment, which can make the coastline in the Gulf Coast vulnerable to sea-level changes. However, the naturally occurring surface subsidence on the coast displays characteristics of a continuous, slow progression (mm/year) and a large spatial extent (~100 km wide). In contrast, human-induced geohazards are faster growing (up to tens of cm/year) and encompass a varying but generally small area (up to a couple of km wide). The most prominent difference between natural and human-induced geohazards is the correlation between surface instability and anthropogenic activities (e.g., mining, groundwater extraction, hydrocarbon production). Although there can be a time delay of ground deformation after human activities, depending on the geological characteristics (porosity, elasticity, compressibility, pore pressure, permeability) of soils and rocks and types of the operations, human-induced surface subsidence or uplift usually has high proximal and temporal correlation with those activities.
- West Texas is somewhat distant from the Gulf coast, but was inundated by relatively shallow seas during the early part of the Paleozoic Era (approximately 600 to 350 million years ago). The sediments formed during this period contributed to the accumulation of sandstone, shale, and limestone. The seas constituting broad marine environments in West Texas gradually withdrew, and by the Permian Period (approximately 299 to 251 million years ago), thick evaporites (salt, gypsum) accumulated in a hot arid land encompassing shallow basins and wide tidal flats. As a consequence of geological formation in West Texas, the deposited carbonate (reef limestone) and marine evaporite sequences played an important role in the formation of oil reservoirs by helping seal the traps and preserving the hydrocarbons. This resulted in the Permian Basin of West Texas' massive hydrocarbon reservoirs that became so lucrative to the oil and gas industry.
Figure 48: Locations of ground deformation in West Texas. Six major sites (red stars) in West Texas display the locations influenced by human activities identified based on Sentinel-1A/B multi-temporal interferometry (background image is from Sentinel-2). To estimate 2D (east-west and vertical) deformation, the ascending (path 78; black box) and descending (path 85; white box) track Sentinel-1A/B images were integrated over the overlapped regions. The West Texas' Permian Basin contains two major aquifer systems under the influence of the Pecos River, the Pecos Valley aquifer and the Edwards-Trinity aquifer (SMU, ESA)
- In West Texas, human activities such as groundwater exploitation, fluid injection, and hydrocarbon extraction have resulted in surface instability, leading to geohazards such as surface heave/subsidence, fault reactivation, induced seismicity, and sinkhole formation. The vastness of West Texas challenges our ability to identify and locate the relatively small spatial scale of the deformation corresponding to human activities, particularly for fluctuations over the course of a month or a year. Without concerted focus, the small-sized signal in a short time window can go easily undetected. There have been a few studies documenting the surge of surface uplift/subsidence, sinkhole formations, and induced seismicity in oil fields. However, the role of human activities on the surface and subsurface deformation has yet to be fully established, particularly regarding the identification of small-scale deformation signals over a vast region from big datasets spanning multiple years and analyzing them with supplementary information.
- Challenges to the effective study of the geohazards in West Texas include: identification of their locations in remote and vast regions, measurement of their long-term evolution, and characterization of the causal mechanism with accessible information. Satellite radar interferometry (InSAR) has proven capable of imaging ground surface deformation with a measurement accuracy of centimeters or better at a spatial resolution of meters or better over a large region covering tens of thousands km2. However, satellite radar acquisitions over West Texas have previously been scarce. Here we present the analysis of the ongoing ground deformations induced by various geohazards around Pecos, Monahans, Wink, and Kermit in West Texas (Figure 48), using multi-temporal InSAR observations based on radar imagery from the first free, open-source radar satellites Sentinel-1A/B.
- The objective of our study is to probe the association between the ongoing localized geohazards in West Texas and anthropogenic activities. To achieve the goal, we focus on the localized, small-sized (200 m~2 km wide), and rapidly developing (cm/yr) geohazards in the region, which are categorized based on six possible causes: i) wastewater injection, ii) CO2 injection for enhanced oil recovery (EOR), iii) salt/limestone dissolution, iv) freshwater impoundment in abandoned wells, v) sinkhole formation in salt beds, and vi) hydrocarbon production. In addition, time-series measurements from two different imaging geometries are integrated to decipher the deformation phenomena. Furthermore, through comparative analysis of records of fluid injection, hydrocarbon production, and geological characteristics, we establish the relationship between the possible causes of human activities or natural perturbation and the localized observed geohazards in West Texas.
• February 23, 2018: The Copernicus Sentinel-1 mission takes us over the Bering Strait (Figure 49), which connects the Pacific and Arctic Oceans between Russia (Siberia) and the US state of Alaska. 88)
- Since the Bering Strait lies slightly south of the polar circle, days are short during the winter. Thanks to its radar, Sentinel-1 can ‘see' through clouds and in the dark, making it especially valuable for monitoring parts of the planet that endure relatively dark winter months. Offering this ‘radar vision', images from Sentinel-1 can be used for charting icebergs and for generating maps of sea ice for year-round navigation.
- Additionally, monitoring changes in the extent of sea ice is critical for understanding the effect of climate change on our environment.
- It has been reported that sea ice in the Bering Strait has been particularly low this winter. This is because unusually warm water streamed up from the south, causing some of the sea ice to melt earlier than usual. As a result, areas that would have remained covered with reflective sea ice were open for much longer. The relatively dark surface of the sea was able to absorb a lot of energy from the Sun, which prevented sea ice forming in the autumn. Also, recent storms have helped to break up much of the sea ice that did manage to form.
Figure 49: The image was created by combining three radar scans of 11 December 2017, 23 December 2017 and 4 January 2018. Each image has been assigned a different color: blue, red and green, respectively. This creates a colorful composite that highlights how the sea ice changed over the four weeks of observation (image credit: ESA, the image contains modified Copernicus Sentinel data (2017–18), processed by ESA, CC BY-SA 3.0 IGO)
• December 15, 2017: The Sentinel-1 radar satellite mission takes us over Orange County and surrounding areas in the US state of California. 89)
- Two prominent geological features are visible in Figure 50: the coastal plains of the Los Angeles Basin in the upper-central left, and the Santa Ana Mountains running from the upper left to the lower right.
- A typical feature of Pacific Coast mountain ranges like Santa Ana is a moister western slope and drier eastern slope – reflected in this radar image by the more prominent colors on the left side of the mountain range. This is due to air masses from the Pacific bringing precipitation to the land, while the mountains force the clouds to rise and produce rain and block them from moving further east, causing a ‘rain shadow' and thus drier areas on the other side.
- To respond to dry conditions in California and all over the world, populations rely on dams and reservoirs to control the water supply. In satellite imagery, these water bodies are easy to identify by the straight-cut line of the dam blocking water flow – two of which are visible in the center-right part of the image.
Figure 50: Three passes by Sentinel-1's radar from 21 December 2014, 2 January 2015 and 14 January 2015 were combined to create this image. Each image was assigned a color – red, green and blue – and changes on the ground that occurred between passes appear as different colors (image credit: ESA, the image contains modified Copernicus Sentinel data (2014-15), processed by ESA , CC BY-SA 3.0 IGO)
Legend to Figure 50: One obvious example of changes can be seen in the boats in the water on the left side of the image, appearing in the three different colors depending on when they were present. - In other parts of the image we can see colors in agricultural fields showing changes in vegetation between the acquisitions.
• November 24, 2017: The Copernicus Sentinel-1 mission gives us ‘radar vision' over part of Antarctica's third-largest island, Thurston Island. The satellite's radar can ‘see' through clouds and in the dark, making it a valuable tool for monitoring polar regions which are prone to bad weather and long periods of darkness – such as Antarctica. 90)
- The image of Figure 51 combined three passes by Sentinel-1's radar in March, April and May 2017. Each was assigned a color – red, green and blue – and when merged, changes between the acquisitions appear in various colors.
- The ice-covered island appears grey, showing no change over the three-month period. But changes in sea ice in the upper part of the image appear as speckles of green, red and blue. In the lower part of the image we can see part of the Abbot Ice Shelf appearing in light blue.
- Antarctica is surrounded by ice shelves, which are thick bands of ice that extend from the ice sheet and float on the coastal waters. They play an important role in buttressing the ice sheet on land, effectively slowing the sheet's flow as it creeps seaward.
- The ice sheet that covers Antarctica is, by its very nature, dynamic and constantly on the move. Recently, however, there has been a worrying number of reports about its floating shelves thinning and even collapsing, allowing the grounded ice inland to flow faster to the ocean and add to sea-level rise.
Figure 51: Sentinel-1 ‘radar vision' over part of Antarctica's third-largest island, Thurston Island. The image combines three passes by Sentinel-1's radar in March, April and May 2017 - each was assigned a color – red, green and blue which were merged (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
• November 7, 2017: In late August, the 60 m-long US Coast Guard Cutter Maple completed its navigation through the Arctic's ice-ridden Northwest Passage (Figure 52). While this was not the first time ships had taken this route, it was the first time that the IIP (International Ice Patrol) had provided iceberg information based exclusively on satellite imagery. — Established in 1914 in response to the sinking of the Titanic, the US Coast Guard IIP monitors iceberg danger in the North Atlantic Ocean for shipping safety. 91)
Figure 52: The US Coast Guard Cutter Maple being escorted by the Canadian Coast Guard Ship Terry Fox (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by Polar TEP)
- When the Maple departed from Alaska in mid-July en route through the Arctic to Maryland, USA, the IIP was on guard to assist the crew to navigate through the notoriously icy waters.
- The IIP used data from the Copernicus Sentinel-1 satellite mission, among others, to create charts showing the risk of encountering icebergs after exiting from the Northwest Passage and during transit through the Baffin Bay, Davis Strait and Labrador Sea.
Figure 53: Maple's course. The region through which the ship Maple transited 14–18 August 2017, with approximate ship locations identified in yellow on each day. The map has been overlaid with images from the Sentinel-1 radar satellite mission (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by Polar TEP)
- Sentinel-1 is equipped with radar that can detect icebergs through cloud cover, a capability particularly beneficial in the IIP's operating area. Sentinel-1 can also distinguish between the thinner, more navigable first-year ice and the hazardous, much thicker multiyear ice to help assure safe year-round navigation in ice-covered Arctic and sub-Arctic zones. These radar images are particularly suited to generating high-resolution ice charts, monitoring icebergs and forecasting ice conditions.
- Scientists at the IIP used iceberg detection software available on ESA's online Polar TEP (Thematic Exploitation Platform) to access satellite data to detect icebergs and analyze their densities and trajectories.
- "This experience using the Polar TEP cloud-based technology opens the door for future evaluations of a more robust version of the iceberg detection and iceberg trajectory processors," said Michael Hicks, Chief Scientist of the International Ice Patrol. "Cloud-based technology such as that used by Polar TEP is expected to be an important tool for handling the ever-growing amount of data coming from space."
- Polar TEP is one of six Thematic Exploitation Platforms developed by ESA to serve data user communities. These cloud-based platforms provide an online environment to access information, processing tools and computing resources for collaboration. TEPs allow knowledge to be extracted from large environmental datasets produced through Europe's Copernicus program and other Earth observation satellites.
Figure 54: Navigating with Polar TEP. Using ESA's online Polar TEP, the International Ice Patrol accessed satellite data to detect icebergs and analyze their densities and trajectories (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by Polar TEP)
• October 31, 2017: In this image from the Copernicus Sentinel-1 satellite mission, we can see the location of the ‘Halloween crack' on Antarctica's Brunt Ice Shelf, highlighted in red. The former and current locations of the British Antarctic Survey's Halley research stations are also marked. 92)
- Discovered on 31 October 2016, the swiftly lengthening Halloween crack prompted the temporary withdrawal of staff from the Halley VI research station for the duration of the 2017 Antarctic winter. Information from the Copernicus Sentinel-1 and Sentinel-2 satellites helped in making this decision.
- The base had already been moved 23 km inland during last Antarctica's summer months because another ice chasm (highlighted in red) had begun to show signs of growth.
- In this image of Figure 55, Sentinel-1's radar was also able to pick up lines in the snow and ice marking the researchers' routes from the former location of the Halley VI station to the coast and to the Halloween crack. To help us identify them, these lines have been colored in black.
Figure 55: This image was created by combining three Sentinel-1 radar scans in September and October. The colors in the Weddell Sea indicate changes in sea ice between the acquisitions. A ‘polynya' – an area of open water surrounded by ice – is visible in the lower-central part of the image (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
• October 25, 2017: This year's Atlantic hurricane season has been a harsh reminder of the grief and devastation brought by these vast storms. Imaging the top of hurricanes from space is nothing new, but the Sentinel-1 satellites can see right through these towering spinning weather systems, measuring the sea surface below to help predict the storm's path. 93)
- The 2017 hurricane season isn't even over yet, but 10 Atlantic storms in a row have already reached hurricane strength – the first time this has happened in more than a century.
- Since understanding and predicting these powerful weather systems is essential to saving lives and property, scientists have been looking into how the Copernicus Sentinel-1 radar mission can help.
- Information from this state-of-the art mission is used for numerous applications, from monitoring sea ice and marine oil spills to mapping floods and land-surface deformation caused by earthquakes.
- Observing hurricanes wasn't part of its original remit. Unlike satellites that carry optical instruments, from which we get the familiar images of the top of hurricanes, radar can penetrate clouds to image the sea underneath these powerful and destructive weather systems.
- Taking Sentinel-1 beyond its original scope, scientists at DLR (German Aerospace Center) have developed a technique that allows the radar to probe sea-surface wind and wave heights. - Importantly, this information about the state of the sea can help to assess how destructive a hurricane is and predict its path – and, therefore, where and when it is likely to make landfall. The same information can also be used to warn ships and to issue warnings of coastal flooding.
- This new technique was used for the first time when hurricane Irma struck Cuba and the Florida Keys in early September. Here, waves up to 10 m high were measured.
- Sentinel-1 works in several different operational modes, but it is its ‘wide swath mode', which is 250 km wide with a resolution of 5 x 20 m, is particularly valuable for understanding ocean waves. This is especially important because in situ measurements of wind and sea state cannot be gained from buoys or dropped probes in such extreme weather or over such a wide area.
- ESA's Sentinel-1 project manager, Ramón Torres, said, "We see the Sentinel-1 mission being used for many different applications that benefit society, but this is a particularly good example of how the mission could make a real difference to people's lives. Sentinel-1 is delivering beyond our expectations."
Figure 56: Wave height during Hurricane Irma. Copernicus Sentinel-1 radar mission images were used to measure waves of up to 10 m high under Hurricane Irma as it struck Cuba and the Florida keys on 9 and 10 September 2017, respectively (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by DLR)
Figure 57: Sentinel-1 radar image under Hurricane Irma (released on 25 Oct. 2017). Scientists at DLR (German Aerospace Center) are using radar images from the Copernicus Sentinel-1 mission to gain information about the wind and waves at the sea surface under hurricanes. This information is not obvious in this image, but novel processing techniques can reveal important information that can be used to assess how destructive a hurricane is and predict its path. This image was acquired on 9 September 2017 under Hurricane Irma as it passed over Cuba (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by DLR)
• October 20, 2017: The Copernicus Sentinel-1A satellite brings us over part of the Sagaing Division in northwest Myanmar (formerly Burma), and along the border with India. 94)
- Snaking through the image of Figure 58 is the Chindwin River, which breached its banks during a period of severe flooding in 2015. Monsoon rains beginning that July caused multiple rivers in the region to overflow, causing widespread damage and affecting up to a million people.
- The image was created using two passes by Sentinel-1's radar. This information was then released in the form of a map under the International Charter Space and Major Disasters to assist relief efforts.
- Currently led by ESA, the Charter is an international collaboration between 16 owners or operators of Earth observation missions. It provides rapid access to satellite data to help disaster management authorities in the event of a natural or man-made disaster.
- Sentinel-1's radar ability to ‘see' through clouds, rain and in darkness makes it particularly useful for monitoring floods.
Figure 58: This image was created using two passes by Sentinel-1's radar: one before the flooding on 20 March 2015 and the other during the event on 4 September 2015. Combining them shows changes between the images, such as the inundation of some 111,000 hectares of land on either sides of the river bank appearing in red (image credit: ESA, the image contains modified Copernicus Sentinel data (2015), processed by ESA, CC BY-SA 3.0 IGO)
• September 28, 2017: A NASA-produced map showing areas of eastern Puerto Rico that were likely damaged by Hurricane Maria has been provided to responding agencies, including FEMA (Federal Emergency Management Agency). The hurricane, a Category 4 storm at landfall on Puerto Rico on Sept. 20, caused widespread damage and numerous casualties on the Caribbean island, an unincorporated U.S. territory with a population of about 3.4 million. 95)
- To assist in disaster response efforts, scientists at NASA's Jet Propulsion Laboratory and Caltech, both in Pasadena, California, obtained and used before-and-after interferometric synthetic aperture radar (InSAR) satellite imagery of areas of Eastern Puerto Rico to identify the areas that are likely damaged. The imagery — acquired before the storm on March 25, 2017 and again one day after landfall on Sept. 21, 2017 — is from the radar instruments on the Copernicus Sentinel-1 satellites operated by the European Space Agency.
- The views indicate the extent of likely damage caused by the hurricane, based on changes to the ground surface detected by radar. The color variations from yellow to red indicate increasingly more significant ground and building surface change. The map is used as guidance to identify potentially damaged areas and may be less reliable over vegetated and flooded areas.
- The radar data were processed by the ARIA (Advanced Rapid Imaging and Analysis) team at JPL and Caltech. ARIA is a NASA-funded project that is building an automated system for demonstrating the ability to rapidly and reliably provide GPS and radar satellite data to support local, national and international hazard-monitoring and response communities. InSAR can "see" through clouds and is sensitive to changes in the roughness of the ground or building surfaces.
- Using space-based radar imagery of disasters, ARIA data products can aid responders in making rapid assessments of the geographic region affected by a disaster, as well as detailed imaging of locations where damage occurred.
Figure 59: NASA/JPL-Caltech-produced map of damage in and around San Juan, Puerto Rico (orange inset box) from Hurricane Maria, based on ground and building surface changes detected by ESA satellites. Color variations from yellow to red indicate increasingly more significant ground and building surface change (image credit: NASA-JPL/Caltech/ESA/Copernicus/Google)
Legend to Figure 59: The map is derived from SAR (Synthetic Aperture Radar) images from the Copernicus Sentinel-1A and Sentinel-1B satellites, operated by the ESA. The images were taken before (March 25, 2017) and after (Sept. 21, 2017) the storm's landfall. The map was delivered to responding agencies, including FEMA (Federal Emergency Management Agency), on Sept. 22, 2017. FEMA combined the map with building infrastructure data to estimate a damage density map, which was sent to its Urban Search and Rescue teams in the field in Puerto Rico. 96)
The map covers an area of 169 x 96 km, shown by the large red polygon in the figure. The inset, denoted by the orange rectangle, shows the extent of damage in and around the capital city of San Juan. Each pixel measures about 30 m across. The color variation from yellow to red indicates increasingly more significant ground surface change. Preliminary validation was done by comparing the map with anecdotal reports of damage. This damage proxy map should be used as guidance to identify damaged areas, and may be less reliable over vegetated and flooded areas. Sentinel-1 data were accessed through the Copernicus Open Access Hub. The image contains modified Copernicus Sentinel data (2017), processed by ESA and analyzed by the NASA-JPL/Caltech ARIA team. This research was carried out at JPL under a contract with NASA.
• September 20, 2017: Witnessed by the Copernicus Sentinel-1 mission on 12 July 2017, a lump of ice more than twice the size of Luxembourg broke off the Larsen C ice shelf, spawning one of the largest icebergs on record and changing the outline of the Antarctic Peninsula forever. Over the following two months, systematic observations from Sentinel-1 showed that the A68 berg remained close, buffeting back and forth against the ice shelf. It was unclear what would happen to the berg because they can remain in one place for years. 97)
- However, the mission has revealed that A68 is now on the move and drifting out to sea. Images from 16 September show that there is a gap of about 18 km as the berg appears to be turning away from the shelf.
Figure 60: Until a few days ago, the huge chunk of ice that broke off Antarctica's ice shelf in July has remained close, buffeting back and forth against the shelf. A68 is now on the move and drifting out to sea (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
• August 17, 2017: For the first time in India, a state government is using satellites to assess lost crops so that farmers can benefit from speedy insurance payouts. — The southern Indian state of Tamil Nadu is home to around 68 million people, of which almost a million are rice farmers. However, Tamil Nadu is facing the worst drought in 140 years, leading to the land being too dry for paddy fields, lost yield, widespread misery and unrest. 98)
- The Copernicus Sentinel-1 radar mission has been used to alleviate a little of the suffering by providing evidence of damaged land and failed crops so that the Agricultural Insurance Company of India can compensate farmers as quickly as possible. So far, more than 200 000 farmers have received payouts.
- Malay Kumar Poddar, the company's general manager, said, "Assessing damages based on remote-sensing technology is introducing much objectivity into the crop insurance program. "Beyond the area loss assessment, we are also keen to apply the technology to assess actual yields at the end of the season."
- Satellites carrying optical cameras can provide images of Earth's surface only in daylight and in the absence of cloud, but the Sentinel-1 satellites carry radar which works regardless. This makes it an ideal mission to use in tropical and subtropical regions, which are often cloudy.
- Sentinel-1 radar imagery combined with rice-yield modelling is at the heart of the German–Swiss RIICE (Remote-Sensing based Information and Insurance for Crops in Emerging Economies initiative). — Francesco Holecz, from sarmap, set up the service in collaboration with the International Rice Research Institute, RIICE partners, Indian authorities and universities. He said, "The reliable repetitiveness of the Sentinels, their short revisit intervals, the free, quick and easy access to the products and the high quality of the data have contributed a lot to the practicability of satellite-based rice monitoring systems."
- Gagandeep Singh Bedi, agricultural production commissioner and principle secretary to the government in Tamil Nadu added, "RIICE remote-sensing technology allows us to assess crop loss and damages in a more transparent and timely manner. "It was particularly useful during the last cropping season to identify villages that had been hit by drought, and farmers benefited from the technology by getting claims in a record time."
- The research network is also working with partners in other countries to develop the method further. For example, the Tamil Nadu Agricultural University and the International Rice Research Institute in the Philippines are looking to use it to assess yields at the end of the season. Sellaperumal Pazhanivelan, from the university, said, "We believe that this technology can help the state governments to obtain objective and transparent data on actual rice yields so that farmers affected by natural hazards can be identified quickly."
Figure 61: Assessing rice crops with Sentinel-1: Using radar data from the Copernicus Sentinel-1 mission, areas where rice is grown in the southern Indian state of Tamil Nadu can be assessed. Light blue to magenta colors represent cultivated fields and light to dark green represents forests (image credit: ESA, the image contains modified Copernicus Sentinel data (2016), processed by RIICE/TNAU)
• July 12, 2017: Over the last few months, a chunk of Antarctica's Larsen C ice shelf has been hanging on precariously as a deep crack cut across the ice. Witnessed by the Copernicus Sentinel-1mission, a lump of ice more than twice the size of Luxembourg has now broken off, spawning one of the largest icebergs on record and changing the outline of the Antarctic Peninsula forever. 99)
- The fissure first appeared several years ago, but seemed relatively stable until January 2016, when it began to lengthen.
- In January 2017 alone it travelled 20 km, reaching a total length of about 175 km.
- After a few weeks of calm, the rift propagated a further 16 km at the end of May, and then extended further at the end of June.
- More importantly, as the crack grew, it branched off towards the edge of the shelf, whereas before it had been running parallel to the Weddell Sea. With just a few km between the end of the fissure and the ocean by early July, the fate of the shelf was sealed.
- Scientists from Project MIDAS, an Antarctic research consortium led by Swansea University in the UK, used radar images from the Copernicus Sentinel-1 mission to keep a close eye on the rapidly changing situation.
- Since Antarctica is heading into the dark winter months, radar images are indispensable because, apart from the region being remote, radar continues to deliver images regardless of the dark and bad weather.
- Adrian Luckman, leading MIDAS, said, "The recent development in satellite systems like Sentinel-1 has vastly improved our ability to monitor events such as this."
Figure 62: Witnessed by the Copernicus Sentinel-1 mission on 12 July 2017, a lump of ice more than twice the size of Luxembourg has broken off the Larsen-C ice shelf, spawning one of the largest icebergs on record and changing the outline of the Antarctic Peninsula forever. The iceberg weighs more than a million million tons and contains almost as much water as Lake Ontario in North America. Since the ice shelf is already floating, this giant iceberg will not affect sea level. However, because ice shelves are connected to the glaciers and ice streams on the mainland and so play an important role in ‘buttressing' the ice as it creeps seaward, effectively slowing the flow. If large portions of an ice shelf are removed by calving, the inflow of glaciers can speed up and contribute to sea-level rise. About 10% of the Larsen C shelf has now gone (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
- Noel Gourmelen from the University of Edinburgh added. "We have been using information from ESA's CryoSat-2 mission, which carries a radar altimeter to measure the surface height and thickness of the ice, to reveal that the crack was several tens of meters deep."
- As predicted, a section of Larsen C – about 6000 km2 – finally broke away as part of the natural cycle of iceberg calving. The behemoth iceberg weighs more than a million million tons and contains about the same amount of water as Lake Ontario in North America.
- "We have been expecting this for months, but the rapidity of the final rift advance was still a bit of a surprise. We will continue to monitor both the impact of this calving event on the Larsen C ice shelf, and the fate of this huge iceberg," added Prof. Luckman.
- The iceberg's progress is difficult to predict. It may remain in the area for decades, but if it breaks up, parts may drift north into warmer waters. Since the ice shelf is already floating, this giant iceberg does not influence sea level.
Figure 63: ESA's CryoSat-2 mission measured the depth of the crack in the Larsen C ice shelf, which led to the birth of one of the largest icebergs on record. Carrying a radar altimeter to measure the surface height and thickness of the ice, the mission revealed that the crack was several tens of meters deep (image credit: University of Edinburgh) 100)
- With the calving of the iceberg, about 10% of the area of the ice shelf has been removed.
- The loss of such a large piece is of interest because ice shelves along the peninsula play an important role in ‘buttressing' glaciers that feed ice seaward, effectively slowing their flow.
- Previous events further north on the Larsen A and B shelves, captured by ESA's ERS and Envisat satellites, indicate that when a large portion of an ice shelf is lost, the flow of glaciers behind can accelerate, contributing to sea-level rise.
- Thanks to Europe's Copernicus environmental monitoring program, we have the Sentinel satellites to deliver essential information about what's happening to our planet. This is especially important for monitoring remote inaccessible regions like the poles.
- ESA's Mark Drinkwater said, "Having the Copernicus Sentinels in combination with research missions like CryoSat-2 is essential for monitoring ice volume changes in response to climate warming. In particular, the combination of year-round data from these microwave-based satellite tools provides critical information with which to understand ice-shelf fracture mechanics and changes in dynamic integrity of Antarctic ice shelves."
• June 13, 2017: On 20 May, over a million tons of dirt and rock buried part of California's Highway 1 along the Pacific coastline in the state's Big Sur region. In addition to cutting off the route, the landslide added some 5 hectares of land to the shoreline. — Sentinel-1's radar shows that the ground that slid down the mountain was moving in the two years before the landslide. 101)
Figure 64: The Sentinel-1 radar data were processed using Small Baseline Subset interferometry (SBAS), a technique that can detect and monitor movements over wide areas with high sensitivity. In this image, red dots represent points where the ground was moving away from the satellite at a rate of more than 70 mm per year. Green dots show stable ground in the surrounding area (image credit: ESA, the image contains modified Copernicus Sentinel data (2015–17), processed by Norut)
• May 12, 2017: Rapid acceleration of an Arctic glacier over the past year has been detected by the Copernicus Sentinel-1 satellites. Sitting on Norway's Spitsbergen island in the Svalbard archipelago, the Negribreen glacier has recently seen a surge in ice surface speed, increasing from 1 m to 13 m a day over the winter. 102)
- When a glacier ‘surges' a large amount of ice flows to the end in an unusually short time. While the causes are not completely understood, they are believed to be linked to changes in the amount of heat or water in the lowest layers of the glaciers.
- The last time Negribreen experienced a surge like this was in the 1930s, as documented in aerial photographs. At that time, it advanced almost 12 km into the fjord in one year along a 15 km-wide section of the front. Since then the front of the glacier had been steadily retreating, with large icebergs breaking off.
- This latest jump in speed began in July 2016 and has been climbing ever since – even over the cold winter months. - Monitoring glaciers in areas prone to bad weather and long periods of darkness – like the Arctic – was difficult before the advent of satellites. Radar satellites can ‘see' through clouds and in the dark, and Sentinel-1 offers frequent and systematic coverage of the Arctic.
- A team of scientists working under ESA's Climate Change Initiative in the Glaciers_cci project are using satellite radar and optical coverage to map glaciers at different times and determine their changes in extent, elevation and speed.
Figure 65: Radar images from the Copernicus Sentinel-1 mission show the sudden advance of the Negribreen glacier in Norway in early 2017 [image credit: ESA, the image contains modified Copernicus Sentinel data (2016–17), processed by T. Strozzi (Gamma)]
- A team of scientists working under ESA's Climate Change Initiative in the Glaciers_cci project are using satellite radar and optical coverage to map glaciers at different times and determine their changes in extent, elevation and speed.
- "Sentinel-1 provides us with a near-realtime overview of glacier flow across the Arctic, remarkably augmenting our capacity to capture the evolution of glacier surges," said Tazio Strozzi from Swiss company Gamma Remote Sensing and scientist on Glaciers_cci.
- "This new information can be used to refine numerical models of glacier surging to help predict the temporal evolution of the contribution of Arctic glaciers to sea-level rise."
Figure 66: Radar images from the Copernicus Sentinel-1 mission were used to create these two ice speed maps of the Negribreen glacier in Norway. In October 2015, only the front of the glacier was moving by more than 300 m a year. By late 2016, the entire glacier was advancing at this accelerated rate.
• May 2, 2017: Over two decades of observations by five radar satellites show the acceleration of ice loss of 30 glaciers in Antarctica's Western Palmer Land in the southwest Antarctic. 103)
- Radar is particularly suited for monitoring polar regions that are prone to bad weather and long periods of darkness because it can collect information regardless of cloud cover, day or night. Mapping 30 glaciers in the region, the research team found that between 1992 and 2016, most of the glaciers sped up by 20 and 30 cm per day. This is equivalent to an average 13% increase in flow speed across the area as a whole (Figure 67).
- The study in Geophysical Research Letters combines over 24 years of radar data from satellites including ESA's Envisat and ERS missions, as well as from the Copernicus Sentinel-1 mission. 104)
- A decrease in the mass and volume of Western Palmer Land has raised the prospect that ice speed has increased in this marine-based sector of Antarctica. To assess this possibility, we measure ice velocity over 25 years using satellite imagery and an optimized modelling approach. More than 30 unnamed outlet glaciers drain the 800 km coastline of Western Palmer Land at speeds ranging from 0.5 to 2.5 m/day, interspersed with near-stagnant ice. Between 1992 and 2015, most of the outlet glaciers sped up by 0.2 to 0.3 m/day, leading to a 13 % increase in ice flow and a 15 km3/yr increase in ice discharge across the sector as a whole. Speedup is greatest where glaciers are grounded more than 300 m below sea level, consistent with a loss of buttressing caused by ice shelf thinning in a region of shoaling warm circumpolar water.
- The two-satellite Sentinel-1 mission for Europe's Copernicus program routinely monitors polar areas at a high resolution, continuing the long-term data record from European satellites.
Figure 67: Ice speed in the Western Palmer Land measured by the Copernicus Sentinel-1 mission between 2014 and 2016 (image credit: ESA, the image contains modified Copernicus Sentinel data (2014-16), processed by J. Wuite, ENVEO)
• April 20, 2017: Two Sentinel-1 radar images from 7 and 14 April 2017 were combined to create this interferogram showing the growing crack in Antarctica's Larsen-C ice shelf (Figure 68). Polar scientist Anna Hogg said: "We can measure the iceberg crack propagation much more accurately when using the precise surface deformation information from an interferogram like this, rather than the amplitude – or black and white – image alone where the crack may not always be visible." 105)
- When the ice shelf calves this iceberg it will be one of the largest ever recorded – but exactly how long this will take is difficult to predict. The sensitivity of ice shelves to climate change has already been observed on the neighboring Larsen-A and Larsen-B ice shelves, both of which collapsed in 1995 and 2002, respectively.
- These ice shelves are important because they act as buttresses, holding back the ice that flows towards the sea.
Figure 68: Larsen-C crack interferogram of Sentinel-1 showing the growing crack of the Larsen-C ice shelf (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by A. Hogg/CPOM/Priestly Centre, CC BY-SA 3.0 IGO)
• April 21, 2017: Earthquake Emergency Management Service in Italy. — A series of strong earthquakes struck Central Italy starting in August 2016, killing over 300 people, injuring some 360 and leaving over 2000 without homes. The Copernicus Emergency Management service was activated by the Italian Civil Protection authorities during this period and produced a total of 120 maps of the damaged areas, supporting their decision-making, rescue and aid delivery activities during these disastrous events. 106)
- Susceptible tectonics: Italy's tectonic and geological characteristics make it a country which is particularly susceptible to the risk of major earthquakes. It straddles the boundary between the Eurasian and African tectonic plates in the south, and a complex series of fault lines run down the entire length of the country along the Apennine mountain chain, collectively known as the Apennine fault. This geological "spine" is clearly visible in the map below, produced by the Italian National Institute for Environmental Protection and Research, ISPRA (Istituto Superiore per la Protezione e la Ricerca Ambientale).
Figure 69: Map of capable fault lines in Italy. "Capable" faults are defined as having "significant potential for displacement at or near the ground surface"(image credit: ISPRA)
- A series of major earthquakes: During the period between the end of August 2016 and January 2017, a series of significant earthquakes ravaged Central Italy:
1) 24 August 2016: A large earthquake measuring 6.2 Mw (Moment magnitude scale) struck Central Italy in the early hours of the morning.
2) 26 October 2016: Two months later, the Marche region was hit by two major earthquakes on the same day, measuring 5.4 and 5.9 Mw, respectively. Within a week, Umbria suffered a massive 6.5 Mw earthquake.
3) 18 January 2017: A set of large earthquakes struck Lazio and Abruzzo, of which the largest measured 5.7 Mw.
Large earthquakes are usually accompanied by large numbers of smaller shocks of varying intensity, some occurring prior to the main quake. These smaller events can amplify the destruction of the main tremor by further weakening already damaged buildings and infrastructure. The Italian Institute for Geophysics and Volcanology, INGV (Istituto Nazionale di Geofisica e Vulcanologia) maintains a network of sensors across Italy to measure earthquakes. The map (Figure 70) shows the earthquakes recorded by INGV in the regions of Central Italy between August 2016 and February 2017; the total number registered exceeds 45.000, and the sheer quantity and density of the events is overwhelmingly apparent.
Figure 70: Map of the over 45.000 seismological events recorded by INGV over Central Italy between August 2016 and February 2017. In total, these earthquakes claimed the lives of over 300 people, injured around 360, and caused the temporary displacement of some 2000 citizens from their damaged homes (image credit: INGV)
Table 8: Rapidly mapping the damages: the Copernicus Emergency Management Service (Ref. 106)
Figure 71: Copernicus EMS Grading Map (Monitoring) of Accumoli, Italy. The village of Accumoli is shown in the zoomed inset, and the map legend has been enlarged for readability. The small, widely spaced settlements are visible (image credit: Copernicus Emergency Management Service)