Copernicus: Sentinel-2 — The Optical Imaging Mission for Land Services
Sentinel-2 is a multispectral operational imaging mission within the GMES (Global Monitoring for Environment and Security) program, jointly implemented by the EC (European Commission) and ESA (European Space Agency) for global land observation (data on vegetation, soil and water cover for land, inland waterways and coastal areas, and also provide atmospheric absorption and distortion data corrections) at high resolution with high revisit capability to provide enhanced continuity of data so far provided by SPOT-5 and Landsat-7. 1) 2) 3) 4) 5) 6) 7) 8)
Table 1: Copernicus is the new name of the former GMES program 9)
The overall GMES user requirements of the EU member states call for optical observation services in the areas of Global Climate Change (Kyoto Protocol and ensuing regulations), sustainable development, European environmental policies (e.g. spatial planning for Soil Thematic Strategy, Natura 2000 and Ramsar Convention, Water Framework Directive), European civil protection, common agricultural policy, development and humanitarian aid, and EU Common Foreign & Security Policy.
To meet the user needs, the Sentinel-2 satellite data will support the operational generation of the following high level products like:
• Generic land cover, land use and change detection maps (e.g. CORINE land cover maps update, soil sealing maps, forest area maps)
• Maps of geophysical variables (e.g. leaf area index, leaf chlorophyll content, leaf water content).
The mission is dedicated to the full and systematic coverage of land surface (including major islands) globally with the objective to provide cloud-free products typically every 15 to 30 days over Europe and Africa. To achieve this objective and to provide high mission availability, a constellation of two operational satellites is required, allowing to reach a 5-day geometric revisit time. The revisit time with only one operational satellite as it will be the case at the beginning of the deployment of the system is 10 days. - In comparison, Landsat-7 provides a 16-day geometric revisit time, while SPOT provides a 26-day revisit, and neither of them provides systematic coverage of the overall land surface.
The following list summarizes the top-level system design specifications derived from the user requirements:
• Sentinel-2 will provide continuity of data for services initiated within the GSE (GMES Service Element) projects. It will establish a key European source of data for the GMES Land Fast Track Monitoring Services and will also contribute to the GMES Risk Fast Track Services.
• The frequent revisit and high mission availability goals call for 2 satellites in orbit at a time, each with a 290 km wide swath using a single imaging instrument
• Continuous land + islands carpet mapping imaging within the latitude range of -56º to +83º (the selected orbit excludes imagery from Antarctica)
• 10 m, 20 m, and 60 m spatial resolution (in the VNIR to SWIR spectral range) to identify spatial details consistent with 1 ha MMU (Minimum Mapping Unit)
• An accurate geolocation (< 20 m) of the data is required (without GCPs) and shall be produced automatically to meet the timeliness requirements. The geolocation accuracy of Level 1 b imagery data w.r.t. WGS-84 (World Geodetic System - 1984) reference Earth ellipsoid of better than 20 m at 2σ confidence level without need of any ground control points is required.
• Very good radiometric image quality (combination of onboard absolute and on ground vicarious calibration).
• The mission lifetime is specified as 7.25 years and propellant is to be sized for 12 years, including provision for de-orbiting maneuvers at end-of-life.
• 2 weeks of satellite autonomy and maximum decoupling between flight operations and mission exploitation
Table 2: Sentinel-2 fast track service compliance to land user requirements
To provide operational services over a long period (at least 15 years following the launch of the first satellites), it is foreseen to develop a series of four satellites, with nominally two satellites in operation in orbit and a third one stored on ground as back-up.
In partnership: The Sentinel-2 mission has been made possible thanks to the close collaboration between ESA, the European Commission, industry, service providers and data users. Demonstrating Europe’s technological excellence, its development has involved around 60 companies, led by Airbus Defence and Space in Germany for the satellites and Airbus Defence and Space in France for the multispectral instruments. 10)
The mission has been supported in kind by the French space agency CNES to provide expertise in image processing and calibration, and by the German Aerospace Center DLR that provides the optical communication payload, developed by Tesat Spacecom GmbH.
This piece of technology allows the Sentinel-2 satellites to transmit data via laser to satellites in geostationary orbit carrying the European Data Relay System (EDRS). This new space data highway allows large volumes of data to be relayed very quickly so that information can be even more readily available for users.
Seven years in the making, this novel mission has been built to operate for more than 20 years. Ensuring that it will meet users’ exacting requirements has been a challenging task. Developing Sentinel-2 has involved a number of technical challenges, from early specification in 2007 to qualification and acceptance in 2015.
The satellite requires excellent pointing accuracy and stability and, therefore, high-end orbit and attitude control sensors and actuators. The multispectral imager is the most advanced of its kind, integrating two large visible near-infrared and shortwave infrared focal planes, each equipped with 12 detectors and integrating 450,000 pixels.
Pixels that may fail in the course of the mission can be replaced by redundant pixels. Two kinds of detectors integrate high-quality filters to isolate the spectral bands perfectly. The instrument’s optomechanical stability must be extremely high, which has meant the use of silicon carbide ceramic for its three mirrors and focal plane, and for the telescope structure itself.
The geometric performance requires strong uniformity across the focal planes to avoid image distortion. The radiometric performance excluded any compromise regarding stray light, dictating a tight geometry and arrangement of all the optical and mechanical elements. The instrument is equipped with a calibration and shutter mechanism that integrates a large spectralon sunlight diffuser.
Each satellite has a high level of autonomy, so that they can operate without any intervention from the ground for periods of up to 15 days. This requires sophisticated autonomous failure analysis, detection and correction on board.
The ‘carpet mapping’ imaging plan requires acquisition, storage and transmission of 1.6 TB per orbit. This massive data blast results from the combination of the 290 km swath with 13 spectral channels at a spatial resolution as high as 10 m.
In addition, the optical communication payload using the EDRS data link is a new technology that will improve the amount and speed of data delivery to the users. This was very recently demonstrated by Sentinel-1A, which also carries an optical communication payload.
Land in focus: Ensuring that land is used sustainably, while meeting the food and wood demands of a growing global population – a projected eight billion by 2020 – is one of today’s biggest challenges. The Copernicus land service provides information to help respond to global issues such as this as well as focusing on local matters, or ‘hotspots’, that are prone to specific challenges.
However, this service relies on very fast revisit times, timely and accurate satellite data in order to make meaningful information available to users – hence, the role of Sentinel-2. Through the service, users will have access to information about the health of our vegetation so that informed decisions can be made – whether about addressing climate change or how much water and fertilizer are needed for a maximum harvest.
Sentinel-2 is able to distinguish between different crop types and will deliver timely data on numerous plant indices, such as leaf area index, leaf chlorophyll content and leaf water content – all of which are essential to accurately monitor plant growth. This kind of information is essential for precision farming: helping farmers decide how best to nurture their crops and predict their yield.
While this has obvious economic benefits, this kind of information is also important for developing countries where food security is an issue. The mission’s fast geometric revisit of just five days, when both satellites are operational, and only 10 days with Sentinel-2A alone, along with the mission’s range of spectral bands means that changes in plant health and growth status can be easily monitored.
Sentinel-2 will also provide information about changes in land cover so that areas that have been damaged or destroyed by fire, for example, or affected by deforestation, can be monitored. Urban growth also can be tracked.
The Copernicus services are managed by the European Commission. The five ‘pan-European’ themes covering 39 countries are addressed by the land service, including sealed soil (imperviousness), tree cover density, forest type, and grasslands. There is currently insufficient cloud-free satellite data in high resolution with all the necessary spectral bands that cover Europe fast enough to monitor vegetation when it is growing rapidly in the summer. Sentinel-2 will fill this gap.
This multi-talented mission will also provide information on pollution in lakes and coastal waters at high spatial resolution and with frequent coverage. Frequent coverage is also key to monitoring floods, volcanic eruptions and landslides. This means that Sentinel-2 can contribute to disaster mapping and support humanitarian aid work.
Leading edge: The span of 13 spectral bands, from the visible and the near-infrared to the shortwave infrared at different spatial resolutions ranging from 10 to 60 m on the ground, takes global land monitoring to an unprecedented level.
The four bands at 10 m resolution ensure continuity with missions such as SPOT-5 or Landsat-8 and address user requirements, in particular, for basic land-cover classification. The six bands at 20 m resolution satisfy requirements for enhanced land-cover classification and for the retrieval of geophysical parameters. Bands at 60 m are dedicated mainly to atmospheric corrections and cirrus-cloud screening.
In addition, Sentinel-2 is the first civil optical Earth observation mission of its kind to include three bands in the ‘red edge’, which provide key information on the vegetation state.
Thanks to its high temporal and spatial resolution and to its three red edge bands, Sentinel-2 will be able to see very early changes in plant health. This is particularly useful for the end users and policy makers to detect early signs of food shortages in developing countries (Ref. 10).
Table 3: Facts and figures
In April 2008, ESA awarded the prime contract to Airbus Defence and Space (former EADS-Astrium GmbH) of Friedrichshafen, Germany to provide the first Sentinel-2A Earth observation satellite. In the Sentinel-2 mission program, Astrium is responsible for the satellite’s system design and platform, as well as for satellite integration and testing. Astrium Toulouse will supply the MSI (MultiSpectral Instrument), and Astrium Spain is in charge of the satellite’s structure pre-integrated with its thermal equipment and harness. The industrial core team also comprises Jena Optronik (Germany), Boostec (France), Sener and GMV (Spain). 11) 12) 13) 14)
Sentinel-2 uses the AstroBus-L of EADS Astrium, a standard modular ECSS (European Cooperation for Space Standards) compatible satellite platform compatible with an in-orbit lifetime of up to 10 years, with consumables sizeable according to the mission needs. The platform design is one-failure tolerant and the standard equipment selection is based on minimum Class 2 EEE parts, with compatibility to Class 1 in most cases. The AstroBus-L platform is designed for direct injection into LEO (Low Earth Orbit). Depending on the selection of standard design options, AstroBus-L can operate in a variety of LEOs at different heights and with different inclinations. An essential feature of AstroBus-L is the robust standard FDIR (Failure Detection, Isolation and Recovery) concept, which is hierarchically structured and can easily be adapted to specific mission needs.
Figure 1: Artist's rendition of the Sentinel-2 spacecraft (image credit: ESA, Airbus DS)
The satellite is controlled in 3-axes via high-rate multi-head star trackers, mounted on the camera structure for better pointing accuracy and stability, and gyroscopes and a GNSS receiver assembly. The AOCS (Attitude and Orbit Control Subsystem) comprises the following elements: 18)
• A dual frequency GPS receiver (L1/L2 code) for position and time information
• A STR (Star Tracker) assembly for precise attitude information (use of 3 STRs)
• A RMU (Rate Measurement Unit) for rate damping and yaw acquisition purposes
• A redundant precision IMU (Inertial Measurement Unit) for high-accuracy attitude determination
• Magnetometers (MAG) for Earth magnetic field information
• CESS (Coarse Earth Sun Sensors) for coarse Earth and Sun direction determination
• 4 RW (Reaction Wheels) and 3 MTQ (Magnetic Torquers)
• RCS (Reaction Control System) a monopropellant propulsion system for orbit maintenance with 1 N thrusters
The different tasks of the AOCS are defined the following modes:
• Initial Acquisition and Save Mode (rate damping, Earth acquisition, yaw acquisition, steady-state)
• Normal Mode (nominal and extended observation)
• Orbit Control Mode (in- and out-of-plane ΔV maneuvers).
Figure 2: Overview of the AOCS architecture (image credit: EADS Astrium)
The geolocation accuracy requirements of < 20 m for the imagery translate into the following AOCS performance requirements as stated in Table 4.
For Sentinel-2 it was decided to mount both the IMU and the star trackers on the thermally controlled sensor plate on the MSI. So the impact of time-variant IMU/STR misalignment on the attitude performance can be decreased to an absolute minimum. Furthermore, the consideration of the time-correlated star tracker noises by covariance tuning was decided.
Figure 3: Sentinel-2 spacecraft architecture (image credit: Astrium GmbH)
Figure 4: Block diagram of the Sentinel-2 spacecraft (image credit: EADS Astrium)
The EPS (Electric Power Subsystem) consists of:
• Solar Array (one deployable and rotatable single wing with three panels). Total array area of 7.1 m2. Use of 2016 triple junction GaAs solar cells with integrated diode. Total power of 2300 W (BOL) and 1730 W (EOL). The mass is < 40 kg.
• SADM (Solar Array Drive Mechanism) for array articulation. Use of a two phase stepper motor with µ-stepping to minimize parasitic distortions during MSI operation, motor step angle 1.5º. Mass of < 3.2 kg.
• PCDU (Power Control and Distribution Unit). PCDU with one unregulated 28 V ±4 V main power bus. Mass of < 21.6 kg; the in-orbit life is 12.25 years.
• Li-ion batteries with 8 cells in series. Total capacity of 102 Ah @ EOL. Mass = 51 kg.
Figure 5: Block diagram of the electrical power subsystem (image credit: EADS Astrium)
The OBC is based on the ERC32 PM (Processor Module) architecture. The PLDHS (Payload Data Handling System) provides source data compression from 1.3 Gbit/s to 450 Mbit/s [state-of-the-art lossy compression (wavelet transform)].
The spacecraft mass is ~ 1200 kg, including 275 kg for the MSI instrument, 35 kg for the IR payload (optional) and 80 kg propellant (hydrazine). The S/C power is 1250 W max, including 170 W for the MSI and < 100 W for the IR payload. The spacecraft is designed for a design life of 7.25 years with propellant for 12 years of operations, including deorbiting at EOL (End of Life).
Table 5: Overview of some spacecraft parameters
Figure 6: Schematic view of the deployed Sentinel-2 spacecraft (image credit: EADS Astrium)
Figure 7: The Sentinel-2 spacecraft in launch configuration (image credit: ESA)
Payload data are being stored in NAND flash memory technology SSR (Solid State Recorder) based on integrated CoReCi (Compression Recording and Ciphering) units of Airbus DS, available at various capacities. The CoReCi is an integrated image compressor, mass memory and data ciphering unit designed to process, store and format multi-spectral video instrument data for the satellite downlink. The mass memory utilizes high performance commercial Flash components, ESA qualified and up-screened for their use in space equipment. This new Flash technology allows mass and surface area used in the memory to be reduced by a factor of nearly 20 when compared with the former SD-RAM (Synchronous Dynamic Random Access Memory) based equipment. The first CoReCi unit has been successfully operating on SPOT-6 since September 2012. Sentinel-2A is carrying a CoReCi unit. 19) 20)
The MRCPB (Multi-Résolution par Codage de Plans Binaires) compression algorithm used is a wavelet transform with bit plane coding (similiar to JPEG 2000). This complex algorithm is implemented in a dedicated ASIC, with speeds of up to 25 Mpixel/s. Alternatively this unit can be supplied with a CCSDS compression algorithm using a new ASIC developed with ESA support. The ciphering is based on the AES algorithm with 128 bit keys. The modularity of the design allows the memory capacity and data rate to be adapted by adjusting the number of compressor and memory boards used.
• August 9, 2021: Engineers at Airbus Defence and Space in Friedrichshafen, Germany, have spent the last 4 months completing the build-up of the Sentinel-2C satellite by integrating its all-important multispectral imager instrument, and have now transported it to IABG’s facilities in Ottobrunn for a series of exhaustive tests that will run until the end of 2021. The program includes a range of mechanical tests that simulate the noise and vibrations of liftoff, tests that check that the satellite deploys its solar wing correctly, other tests that place the satellite under the extreme temperature swings it will experience in space, and electromagnetic compatibility tests to measure radio frequency radiation levels generated by the satellite and to verify the correct operation of the satellite equipment under this environment. 21)
- Copernicus Sentinel-2 is designed to provide images that can be used to distinguish between different crop types as well as data on numerous plant indices, such as leaf area index, leaf chlorophyll content and leaf water content – all of which are essential to accurately monitor plant growth.
Figure 8: The Sentinel-2C satellite is pictured here in its transport container just after arrival at IABG (image credit: IABG)
• July 29, 2021: Airbus has finished the integration of the Copernicus Sentinel-2C satellite. It is the third of its kind and will now be shipped to Munich to undergo extensive environmental tests to prove its readiness for space. The test campaign will last until March 2022. 22)
- The data gathered by Sentinel-2 satellites are used for monitoring land use and changes, soil sealing, land management, agriculture, forestry, natural disasters (floods, forest fires, landslides and erosion) and to assist humanitarian aid missions. Environmental observation in coastal areas likewise forms part of these activities, as does glacier, ice and snow monitoring.
- Offering "color vision" for the Copernicus program, Sentinel-2C – like its precursor satellites Sentinel-2A and -2B – will deliver optical images from the visible to short-wave infrared range of the electromagnetic spectrum. From an altitude of 786 km, the 1.1 ton “C” satellite will enable continuation of imaging in 13 spectral bands with a resolution of 10, 20 or 60 m and a uniquely large swath width of 290 km.
- The telescope structure and the mirrors are made of silicon carbide, first pioneered by Airbus to provide very high optical stability and minimize thermo-elastic deformation, resulting in an excellent geometric image quality. This is unprecedented in this category of optical imagers. Each Sentinel-2 satellite collects 1.5 TB/day, after on-board compression. The data is formatted at high speed and temporarily stored on board in the highest capacity Mass Memory and Formatting unit currently flying in space. Data recording and laser-enabled downlink can take place simultaneously at high speed via the EDRS SpaceDataHighway, in addition to the direct X-band link to the ground stations.
- The current Sentinel-2-mission is based on a constellation of two identical satellites, Sentinel-2A (launched 2015) and Sentinel-2B (launched 2017), flying in the same orbit but 180° apart for optimal coverage and revisit time. The satellites orbit the Earth every 100 minutes covering all Earth’s land surfaces, large islands, inland and coastal waters every five days.
- The Sentinel-2 satellites are currently sensing systematically all land and water areas, producing excellent results. Last year, the Sentinel-2 mission remained the top European mission in terms of peer-reviewed scientific publications (1200 during 2020) and data volume distributed to users.
- The Sentinel-2 mission has been made possible thanks to the close collaboration between ESA, the European Commission, industry, service providers and data users. Its development has involved around 60 companies, led by Airbus Defence and Space in Germany for the satellites and Airbus Defence and Space in France for the multispectral instruments, while Airbus Defence and Space in Spain is responsible for the mechanical satellite structure.
- Copernicus, Europe’s environmental monitoring program, is led by the European Commission (EC) in partnership with the European Space Agency (ESA). The Copernicus Sentinels supply remote sensing data of the Earth, delivering key operational services related to environment and security.
Figure 9: Photo of the Copernicus Sentinel-2C satellite. The climate satellite will now undergo extensive testing (image credit: Airbus)
• February 27, 2017: The ninth Vega light-lift launcher is now complete at the Spaceport, with its Sentinel-2B Earth observation satellite installed atop the four-stage vehicle in preparation for a March 6 mission from French Guiana. 23)
• January 12, 2017: Sentinel-2B arrived at Europe’s spaceport in Kourou, French Guiana on 6 January 2017 to be prepared for launch. After being moved to the cleanroom and left for a couple of days to acclimatise, cranes were used to open the container and unveil the satellite. Over the next seven weeks the satellite will be tested and prepared for liftoff on a Vega rocket. 24)
• November 15, 2016: Sentinel-2B has successfully finished its test program at ESA/ESTEC in Noordwijk, The Netherlands. The second Sentinel-2 Airbus built satellite will now be readied for shipment to the Kourou spaceport in French Guiana begin January 2017. It is scheduled for an early March 2017 lift-off on Vega. 25)
- Offering "color vision" for the Copernicus program, Sentinel-2B like its twin satellite Sentinel-2A will deliver optical images from the visible to short-wave infrared range of the electromagnetic spectrum. From an altitude of 786 km, the 1.1 ton satellite will deliver images in 13 spectral bands with a resolution of 10, 20 or 60 m and a uniquely large swath width of 290 km.
• June 15, 2016: Airbus DS completed the manufacture of the Sentinel-2B optical satellite; the spacecraft is ready for environmental testing at ESA/ESTEC. The Sentinel-2 mission, designed and built by a consortium of around 60 companies led by Airbus Defence and Space, is based on a constellation of two identical satellites flying in the same orbit, 180° apart for optimal coverage and data delivery. Together they image all Earth’s land surfaces, large islands, inland and coastal waters every five days at the equator. Sentinel-2A was launched on 23 June 2015, its twin, Sentinel-2B, will follow early next year. 26)
- The Sentinel-1 and -2 satellites are equipped with the Tesat-Spacecom’s LCT (Laser Communication Terminal). The SpaceDataHighway is being implemented within a Public-Private Partnership between ESA and Airbus Defence and Space.
Figure 10: Sentinel-2B being loaded at Airbus Defence and Space’s satellite integration center in Friedrichshafen, Germany (image credit: Airbus DS, A. Ruttloff)
• April 27, 2015: The Sentinel-2A satellite on Arianespace’s next Vega mission is being readied for pre-launch checkout at the Spaceport, which will enable this European Earth observation platform to be orbited in June from French Guiana. — During activity in the Spaceport’s S5 payload processing facility, Sentinel-2A was removed from the shipping container that protected this 1,140 kg class spacecraft during its airlift from Europe to the South American launch site. With Sentinel-2A now connected to its ground support equipment and successfully switched on, the satellite will undergo verifications and final preparations for a scheduled June 11 liftoff. 27)
Figure 11: Sentinel-2A is positioned in the Spaceport’s S5 payload processing facility for preparation ahead of its scheduled June launch on Vega (image credit: Arianespace)
• April 23, 2015: The Sentinel-2A satellite has arrived safe and sound in French Guiana for launch in June. The huge Antonov cargo aircraft that carried the Sentinel-2A from Germany, touched down at Cayenne airport in the early morning of 21 April. 28)
• April 8, 2015: The Sentinel-2A satellite is now being carefully packed away in a special container that will keep it safe during its journey to the launch site in French Guiana. The satellite will have one final test, a ‘leak test’, in the container to ensure the propulsion system is tight. Bound for Europe’s Spaceport in French Guiana, Sentinel-2A will leave Munich aboard an Antonov cargo plane on 20 April. Once unloaded and unpacked, it will spend the following weeks being prepared for liftoff on a Vega rocket. 29)
• February 24, 2015: Sentinel-2A is fully integrated at IABG’s facilities in Ottobrunn, Germany before being packed up and shipped to French Guiana for a scheduled launch in June 2015. 30)
Figure 12: Photo of the Sentinel-2A spacecraft in the thermal vacuum chamber testing at IAGB's facilities (image credit: ESA, IABG, 2015)
• In August 2014, Airbus Defence and Space delivered the Sentinel-2A environmental monitoring satellite for testing . In the coming months, the Sentinel-2A satellite will undergo a series of environmental tests at IABG, Ottobrunn, Germany, to determine its suitability for use in space. 31) 32)
Figure 13: Sentinel-2A solar array deployment test at IABG (Airbus Defence & Space), image credit: ESA 33)
- Sentinel-2A is scheduled to launch in June 2015; Sentinel-2B, which is identical in design, is set to follow in March 2017. Together, these two satellites will be able to capture images of our planet’s entire land surface in just five days in a systematic manner.
Figure 14: Photo of the Sentinel-2A spacecraft at the satellite integration center in Friedrichshafen, Germany (image credit: Airbus DS, A. Ruttloff)
RF communications: The payload data handling is based on a 2.4 Tbit solid state mass memory and the payload data downlink is performed at a data rate of 560 Mbit/s in X-band with 8 PSK modulation and an isoflux antenna, compliant with the spectrum bandwidth allocated by the ITU (international Telecommunication Union).
Command and control of the spacecraft (TT&C) is performed with omnidirectional S-band antenna coverage using a helix and a patch antenna. The TT&C S-band link provides 64 kbit/s in uplink (with authenticated/encrypted commands) and 2 Mbit/s in downlink..
The requirements call for 4 core X-band ground stations for full mission data recovery by the GMES PDS (Payload Data System).
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-2 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. 36)
To meet the user requirements of fast data delivery, DLR (German Aerospace Center) is funding the OCP (Optical Communication Payload), i.e. the LCT of Tesat, – a new capability to download large volumes of data from the Sentinel-2 and Sentinel-1 Earth observation satellites - via a data relay satellite directly to the ground. A contract to this effect was signed in October 2010 between ESA and DLR. 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.
Orbit: Sun-synchronous orbit, altitude = 786 km, inclination = 98.5º, (14+3/10 revolutions/day) with 10:30 hours LTDN (Local Time at Descending Node). This local time has been selected as the best compromise between cloud cover minimization and sun illumination.
The orbit is fully consistent with SPOT and very close to the Landsat local time, allowing seamless combination of Sentinel-2 data with historical data from legacy missions to build long-term temporal series. The two Sentinel-2 satellites will be equally spaced (180º phasing) in the same orbital plane for a 5 day revisit cycle at the equator.
The Sentinel-2 satellites will systematically acquire observations over land and coastal areas from -56° to 84° latitude including islands larger 100 km2, EU islands, all other islands less than 20 km from the coastline, the whole Mediterranean Sea, all inland water bodies and closed seas. Over specific calibration sites, for example DOME-C in Antarctica, additional observations will be made. The two satellites will work on opposite sides of the orbit (Figure 15).
• The first stage separated 1 min 55 seconds after liftoff, followed by the second stage and fairing at 3 min 39 seconds and 3 min 56 seconds, respectively, and the third stage at 6 min 32 seconds.
• After two more ignitions, Vega’s upper stage delivered Sentinel-2B into the targeted Sun-synchronous orbit. The satellite separated from the stage 57 min 57 seconds into the flight.
• Telemetry links and attitude control were then established by controllers at ESOC in Darmstadt, Germany, allowing activation of Sentinel’s systems to begin. The satellite’s solar panel has already been deployed.
• After this first ‘launch and early orbit’ phase, which typically lasts three days, controllers will begin checking and calibrating the instruments to commission the satellite. The mission is expected to begin operations in three to four months.
Sentinel-2B will join its sister satellite Sentinel-2A and the other Sentinels part of the Copernicus program, the most ambitious Earth observation program to date. Sentinel-2A and -2B will be supplying ‘color vision’ for Copernicus and together they can cover all land surfaces once every five days thus optimizing global coverage and the data delivery for numerous applications. The data provided by these Sentinel-2 satellites is particularly suited for agricultural purposes, such as managing administration and precision farming.
With two satellites in orbit it will take only five days to produce an image of the entire Earth between the latitudes of 56º south and 84º north, thereby optimizing the global coverage zone and data transmission for numerous applications.
To ensure data continuity two further optical satellites, Sentinel-2C and -2D, are being constructed in the cleanrooms of Airbus and will be ready for launch as of 2020/2021.
Figure 16: Illustration of the Sentinel-2B spacecraft in orbit (image credit: Airbus DS, Ref. 40)
Figure 17: This technical view of the Sentinel-2 satellite shows all the inner components that make up this state-of-the-art high-resolution multispectral mission (video credit: ESA/ATG medialab)
Figure 18: As well as imaging in high resolution and in different wavelengths, the key to assessing change in vegetation is to image the same place frequently. The Sentinel-2 mission is based on a constellation of two satellites orbiting 180° apart, which along with their 290 km-wide swaths, allows Earth’s main land surfaces, large islands, inland and coastal waters to be covered every five days. This is a significant improvement on earlier missions in the probability of gaining a cloud-free look at a particular location, making it easier to monitor changes in plant health and growth (video credit: ESA/ATG medialab)
Note: As of 30 April 2021, the Sentinel-2 file has been split into a total of five files. — As of May 2019, the previously single large Sentinel-2 file has been split into two additional files, to make the file handling manageable for all parties concerned, in particular for the user community.
• This article covers the Sentinel-2 mission and its imagery in the period 2021
Mission status and some imagery of 2021
• January 21, 2022: Part of Mecklenburg–West Pomerania, also known as Mecklenburg-Vorpommern, a state in northeast Germany is featured in this image captured by the Copernicus Sentinel-2 mission. A portion of the northwest coast of Poland can be seen in the right of the image. 42)
- Mecklenburg–West Pomerania extends along the Baltic Sea coastal plain with the region’s landscape largely shaped by glacial forces – which deposited materials that produced the coastal lowlands that are today filled with wetlands, streams and lakes.
- Mecklenburg–West Pomerania is one of Germany’s least populated states. Nearly two-thirds is covered by farmland with the main crops being rye, wheat, barley and hay. The green areas present in this image are most likely winter wheat and winter rapeseed. The region’s pastures typically support sheep, horses and cattle.
- On the state’s coastline on the Baltic Sea lie many holiday resorts, unspoilt nature and the islands of Rügen (partly visible in the top left) and Usedom (in the centre of the image), as well as many others. The most populous island in the Baltic Sea, the 445 sq km island of Usedom is mostly flat and is partly covered by marshes.
- The Baltic Sea is no stranger to algae blooms, with two annual blooms taking place each year (the spring bloom and the cyanobacterial bloom in late spring.) Given this image was captured in February, it is most likely an onset of a spring bloom.
- Although algal blooms are a natural and essential part of life in the sea, human activity is also said to increase the number of annual blooms. Agricultural and industrial run-off pours fertilisers into the sea, providing additional nutrients algae need to form large blooms.
Figure 19: The icy Szczecin Lagoon, or Szczeciński Lagoon, dominates this week’s image, which was captured on 22 February 2021. An extension of the Oder estuary, the lagoon is shared between Germany and Poland, and is drained (via the Świna, Peene, and Dziwna rivers) into Pomeranian Bay of the Baltic Sea, between Usedom and Wolin. - From the south, it is fed by several arms of the Oder River, Poland’s second-longest river, and several smaller rivers. The distinct line across the lagoon depicts the shipping waterway that connects the port cities of Świnoujście and Szczecin. Several emerald-green algae blooms can be seen in the image, with the most visible near Peenestrom, an arm of the Baltic Sea, in the left of the image. Peenestrom separates the island of Usedom from the mainland and is an important habitat for waterfowl, especially because of its fish population, such as white-tailed eagles and herons. This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2021), processed by ESA, CC BY-SA 3.0 IGO)
• December 17, 2021: Ahead of the upcoming Ariane 5 launch of the James Webb Space Telescope, the Copernicus Sentinel-2 mission takes us over Kourou – home to Europe’s Spaceport in French Guiana, an overseas department of France. 43)
- Long, white sandy beaches line the town’s ocean coast, while the riverbank and inland area consists mostly of mangrove and dense tropical rainforest. The surrounding area’s economy is largely agricultural, with coffee, cacao and tropical fruits being grown.
- Just northwest of Kourou lies Europe’s Spaceport – chosen as a base from which to launch satellites in 1964 by the French Government, and currently home to ESA-developed rocket families Ariane and Vega.
- As Kourou lies just 500 km north of the equator, it makes it ideally placed for launches into orbit as the rockets gain extra performance thanks to a ‘slingshot effect’ from the speed of Earth’s rotation. In addition, there is no risk of cyclones or earthquakes. This launch base and the jungle that surrounds it covers 690 km2 and protects an abundance of wildlife and plants.
- From here, the largest and most powerful telescope ever launched into space – the James Webb Space Telescope – is scheduled for launch. After liftoff, it will embark on a month-long journey to its destination, around one and a half million kilometers from Earth.
- Following the footsteps of the Hubble Space Telescope, Webb is designed to answer questions about the Universe and to make breakthrough discoveries in all fields of astronomy. The telescope will be able to detect infrared light generated by galaxies as they formed more than 13.5 billion years ago, in the aftermath of the Big Bang. Webb will see farther into our origins – from the Universe's first galaxies, to the birth of stars and planets, to exoplanets.
Figure 20: Located around 60 km northwest of the French Guyanese capital Cayenne, Kourou is a coastal town in the north-central part of the country and is visible in the lower right of the image. The town lies at the estuary of the Kourou River which, after its journey of 144 km, empties into the Atlantic Ocean. Its muddy waters appear brown most likely due to sediments picked up from the surrounding forest. This image is also featured on the Earth from Space video program (image credit: ESA)
- In the first month after launch, Webb will unfold its sunshield, which is around the size of a tennis court, and deploy its 6.5-meter primary mirror. This will be used to detect the faint light of distant stars and galaxies with a sensitivity of a hundred times greater than that of Hubble.
• December 10, 2021: The city of Fairbanks, the largest city in the Interior region of Alaska, and its surroundings, are featured in this Copernicus Sentinel-2 image. 44)
Figure 21: Visible in the top-left corner of the image, Fairbanks is located in the central Tanana Valley, straddling the Chena River near its confluence with the Tanana River – a 940 km tributary of the Yukon River. Dominating this week’s image, the Tanana River’s name is an Athabascan word meaning ‘river trail’. Many low streams and rivers flow into the Tanana River. This image, captured on 11 September 2021, is also featured on the Earth from Space video program (image credit:
- The river flows in a northwest direction along the base of the Alaska Range (visible in the bottom of the image) before joining the Yukon River near the village of Tanana. The river drains the north slopes of the high Alaska Range and is fed by several glaciers. The sediment-laden Tanana is rich in minerals, which gives it its milky color.
- South of the Tanana River lies the Tanana Flats, an area of marsh and bog that stretches for more than 160 km until it rises into the Alaska Range. One of the components of the Alaskan mountains, the Alaska Range extends for around 650 km in a generally east-west arc from the Aleutian Range to the boundary of Yukon. The mountain range can sometimes be seen from Fairbanks on clear days. The highest mountain in North America, the Denali, lies in the Alaska Range and reaches an elevation of over 6000 m (not visible).
- Around 20 km from Fairbanks lies the city of North Pole. Despite its name, the city is around 2700 km south of Earth’s geographic North Pole and around 200 km south of the Arctic Circle.
- Light green colors in the image indicate deciduous forest, while dark green represents evergreen forests.
• December 03, 2021: White Nile is one of the 18 states of Sudan. Covering an area of around 40,000 km2, the state is divided into four districts: Ad Douiem, Al Gutaina, Kosti and Al Jabalian. The area pictured here is located just north of Kosti, also spelled Kūstī, which lies on the west bank of the White Nile River (not visible). 45)
Figure 22: This false-color image, captured on 25 August 2021, was processed in a way that also includes information from the near-infrared channel and shows vegetation in tones of red. This band combination is routinely used to monitor vegetation health. Although the area lies within an arid climatic region, low vegetation covering the valley floors between the sand dunes can be seen in bright shades of red. This image is also featured on the Earth from Space video program (image credit: ESA)
- Many agricultural plots can also be seen in red, particularly in the far-right and far-bottom of the image. Agriculture plays an important role in Sudan’s economy. The country’s main crops include cotton, peanuts, sesame and sugarcane, while the main subsistence crops include wheat, corn, sorghum and millet. Several small villages can also be spotted in the image, with many of them visible near artificial water reservoirs (easily spotted with their rectangular shape) and are most likely utilized during the dry season.
- Owing to seasonal rainfall, many ephemeral bodies of water can be spotted in shades of turquoise and blue in the image.
- Flooding is common in Sudan in August and September. During these months each year, monsoon rains pour into the Ethiopian Highlands and flow down to the Blue and White Nile and can often lead to floodwaters swamping nearby communities. Starting in August 2021, a series of torrential downpours overwhelmed streams and rivers and unleashed floods in the area, with the White Nile being one of the hardest hit areas.
- Copernicus Sentinel-2 has two satellites, each carrying a high-resolution camera that images Earth’s surface in 13 spectral bands. The type of band combination from Copernicus Sentinel-2 used to process this image is commonly utilized to assess plant density and health, as plants reflect near-infrared and green light, while absorbing red. Since they reflect more near-infrared than green, dense, plant-covered land appears in bright red.
• November 26, 2021: Kainji Lake, a reservoir on the Niger River in western Nigeria, is featured in this true-color image captured by the Copernicus Sentinel-2 mission. 46)
- The creation of the lake submerged Foge Island, the town of Bussa and permanently flooded other riverine settlements – leaving around 50 000 people displaced. Foge Island can be seen dividing the river into two channels at the northern end, and the channels merge again north of Old Bussa. During low water tides, large parts of Foge Island rise above and are temporarily inhabited by migrating fishermen.
- Kainji Dam, located in the center of the image, produces electricity for most of Nigeria’s cities. The dam is the largest of the dams on the Niger, over 66 m high and 550 m across. The dam provides electrical power, improved river navigation, water control of the Niger, as well as waters for irrigation and fishing.
- Kainji Lake National Park, visible as a dark green patch of land in the left of the image, is Nigeria’s oldest national park. Covering an area of around 5300 km2, the park contains three distinct areas: a part of the Kainji Lake, the Borgu Game Reserve to the west of the lake, and the Zugurma Game Reserve to the southeast. Around 65 mammal species, 350 species of birds and 30 species of reptiles and amphibians have been recorded in the park.
Figure 23: Kainji Lake was created in 1968 by the construction of the Kainji Dam and covers an area of around 1300 km2 with a mean depth of 12 m. Water from the Niger River, the third-longest river in Africa, enters the lake in the north. The grey-colored waters here mix with the striking, yellow-colored waters of Kainji Lake, creating a distinct sediment plume moving southwards. The emerald-green streaks are vegetation and algae floating on the surface of the lake. This image, captured on 11 November 2020, is also featured on the Earth from Space video program (image credit: ESA)
• November 19, 2021: Located in west-central Malaysia, Kuala Lumpur is the country’s largest urban area and its cultural, commercial and transportation center. The city lies in the hilly countryside of the Klang Valley and lies astride the confluence of the Kelang and Gombak rivers. Its name in Malay means ‘muddy estuary.’ 47)
- The city’s commercial quarter, known as the Golden Triangle, is the site of the Petronas Twin Towers, the tallest twin towers (452 m) in the world. Kuala Lumpur International Airport, one of the busiest airports in Asia, can be seen in the bottom of the image.
- The Klang Valley is bordered by the Titiwangsa Mountains to the east, some minor ranges in the north and the Strait of Malacca in the west. Visible in the far left of the image, the Strait of Malacca is a narrow stretch of water between the Malay Peninsula and the Indonesian island of Sumatra. A main shipping channel between the Indian and Pacific oceans, it is one of the most important shipping lanes in the world. Port Klang, is the main gateway by sea into Malaysia and lies around 40 km southwest of Kuala Lumpur.
- The Greater Kuala Lumpur area is around 2,700 km2 and is an urban agglomeration of over seven million people – making it one of the fastest growing metropolitan regions in Southeast Asia. Like many other growing cities and areas in the world, the region is facing the daunting challenge of urban sprawl. This puts pressure on urban land in the city, but also on agricultural land in the periphery, as well as on other natural resources.
- Urban areas are already home to 55% of the world’s population and that figure is expected to grow to 68% by 2050. In order to gain a better understanding of current trends in global urbanization, ESA and the German Aerospace Center (DLR), in collaboration with the Google Earth Engine team, have jointly developed the World Settlement Footprint (WSF) – the world’s most comprehensive dataset on human settlement.
- The World Settlement Footprint Evolution has been generated by processing seven million images from the US Landsat satellite collected between 1985 and 2015. The animation in Figure 25 illustrates the growth of Kuala Lumpur on a year-by-year basis, from 1985 to 2015.
Figure 24: Kuala Lumpur, the capital city of Malaysia, is featured in this image captured by the Copernicus Sentinel-2 mission. This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2020), processed by ESA, CC BY-SA 3.0 IGO)
Figure 25: Kuala Lumpur, Malaysia. The World Settlement Footprint Evolution has been generated by processing seven million images from the US Landsat satellite collected between 1985 and 2015 and illustrates the worldwide growth of human settlements on a year-by-year basis (image credit: DLR/ESA)
- This unprecedented collection of information on human settlement will not only advance our understanding of urbanization on a global scale but will also become an asset for national statistical offices, local authorities, civil society and international organizations.
• November 18, 2021: The US State of Washington is under a state of emergency following days of severe wind and rain leading to extensive flooding in parts of the state. The extreme weather was caused by an atmospheric river, a huge plume of moisture extending over the Pacific and into Washington. Different satellites in orbit carry different instruments that can provide us with a wealth of complementary information to understand and to respond to flooding disasters. 48)
- More than 158,000 people were affected by power outages and disruptions to other services. The conditions triggered mudslides in the region, prompting the closure of the Interstate 5, but it has since reopened.
- Optical satellite instruments such as the Copernicus Sentinel-2 satellites cannot see through clouds, which is why radar missions like Sentinel-1 are particularly useful. Radar images acquired before and after flooding events offer immediate information on the extent of inundation, thanks to Sentinel-1’s ability to ‘see’ through clouds and rain.
Figure 26: This image, captured by the Copernicus Sentinel-2 mission on 16 November, shows the extent of the floods in the Nooksack River, which spilled over its banks this week and washed out several roads in the process. The flooding forced the evacuation of hundreds of residents and lead to the closure of schools (image credit: ESA, the image contains modified Copernicus Sentinel data (2021), processed by ESA, CC BY-SA 3.0 IGO )
Figure 27: This SAR (Synthetic Aperture Radar) image uses information from two separate acquisitions captured by the Copernicus Sentinel-1 mission on 4 November and 16 November 2021 and shows the extent of the flooding of the Nooksack River in dark blue (image credit: ESA)
• November 12, 2021: Cancún, situated in Quintana Roo on the northeast coast of Mexico’s Yucatán Peninsula, is featured in this image captured by the Copernicus Sentinel-2 mission. 49)
- Cancún’s location on the Caribbean Sea, tropical climate and string of beaches have made the city and the Riviera Maya to the south of Cancún one of Mexico’s top tourist destinations. In this image, captured on 16 April 2021, the city can be seen in the bottom-right corner, shrouded in clouds. Cancun International Airport, Mexico’s second busiest airport, is located around 20 km south of the city.
- The Cancún Island resort area, visible just off the coast, is shaped like the number seven and is around 22 km in length. The island is separated from the city by the Nichupté Lagoon but is linked by two causeways at each end. Most of the tourist industry is centered on Cancún Island with its Caribbean-facing beaches.
- Isla Mujeres, Spanish for ‘Island of Women,’ is visible just north of Cancún Island and is most famous for its beaches and snorkelling. Isla Contoy, visible in the top-right of the image, is considered one of the most important nesting places for sea birds in the Mexican Caribbean with more than 150 species of birds.
- Quintana Roo covers an area of around 42,000 km2 and is home to several protected areas including the El Eden Ecological Reserve, located 50 km northwest of Cancún, and Yum Balam Flora and Fauna Protected Area, located in the north of the state. Encompassing more than 150,000 hectares, Yum Balam is home to several endangered species including jaguars, crocodiles and monkeys.
- With its 13 spectral channels, Copernicus Sentinel-2’s novel imager can capture water quality parameters such as the surface concentration of chlorophyll, detect harmful algal blooms, and measure turbidity (or water clarity) – giving a clear indication of the health and pollution levels.
Figure 28: This image of Cancún on the Caribbean Sea was captured on 16 April 2021 by the Sentinel-2 mission. The color of the water in the image varies from emerald green to turquoise owing to the changing water depths along the coast, turbidity and differences on the ocean floor – from sand to seaweed to rocky areas. The image is also featured on the Earth from Space video program (image credit: ESA)
• November 5, 2021: Lying roughly 100 km north of the Scottish mainland, the Shetland Islands separate the Atlantic Ocean on the west from the North Sea to the east. The archipelago comprises around 100 islands and islets, with fewer than 20 of them inhabited. The islands cover an area of around 1468 km2 and have a rugged coastline approximately 2700 km long. 50)
- The largest island, known as the Mainland, has an area of around 900 km2, making it the third-largest Scottish island. The next largest are Yell, Unst and Fetlar, which lie in the north, as well as Bressay and Whalsay, which lie to the east. Lerwick, located on Mainland, is the capital and largest settlement of the archipelago.
Figure 29: The Shetland Islands, an archipelago in the Northern Isles of Scotland, are featured in this Copernicus Sentinel-2 image. The most striking feature in this week’s image, captured on 1 July 2021, is the vivid, turquoise-colored bloom visible to the east of the islands. This type of bloom is slightly different to the harmful cyanobacteria often visible around the Baltic Sea. This image of the Shetland Islands is also featured in this week's edition of the Earth from Space video program (video credit: ESA)
- In the absence of any known samples being analyzed, it is assumed that it is a coccolithophore bloom – a type of microscopic marine algae living in the upper layer of the sea. Like all phytoplankton, coccolithophores contain chlorophyll and have the tendency to multiply rapidly near the surface.
- In large numbers, coccolithophores periodically shed their tiny scales called ‘coccoliths’ into the surrounding waters. These calcium-rich coccoliths turn the normally dark water a bright, milky-turquoise color. Although invisible to the eye, in large quantities, they are easy to spot in satellite imagery. These types of algae play a huge role in the ocean uptake of atmospheric carbon dioxide, as their shells sink to deeper ocean depths after they die, storing carbon in the process.
- This year’s edition of the United Nations climate change conference – COP26 – is taking place in Scotland from 31 October to 12 November. The summit aims to inspire faster and more ambitious action from the international community to achieve the goal of limiting global temperature rise to 1.5°C. As in previous years, ESA has a strong presence at COP26, showcasing how satellite data strengthens our understanding of climate from space. Read more about ESA’s role at COP.
• October 29, 2021: Glasgow, host of the 26th UN Climate Change Conference of Parties (COP26), is featured in this image captured by the Copernicus Sentinel-2 mission. 51)
Figure 30: Situated in west-central Scotland, Glasgow is the largest city in the country. It lies along both banks of the River Clyde, the ninth-longest river in the United Kingdom and the third-longest in Scotland. The city occupies much of the lower Clyde valley, and its suburbs extend into the surrounding districts. This image is also featured in this week's edition of the Earth from Space video program (image credit: ESA - European Space Agency)
- Edinburgh, Scotland’s capital, can be seen in the center-right of the image, located in Lothian on the southern shore of the Firth of Forth. Both Edinburgh and Glasgow, along with Stirling and Dundee, all lie in the Central Lowlands, where over half of Scotland’s population lives.
- The Highlands, visible in the upper-left of the image, is the largest region in Scotland covering more than 25,600 km 2 of land and is home to stunning scenery. The area is divided in two parts: the Great Glen divides the Grampian Mountains to the southeast from the northwest Highlands. The area is very sparsely populated, with many mountain ranges dominating the region and includes the highest mountain in the British Isles, Ben Nevis, as well as the legendary Loch Ness.
- From 31 October to 12 November, the COP26 summit will take place in Glasgow – bringing together parties to accelerate action towards the goals of the Paris Agreement and the UN Framework Convention on Climate Change (UNFCC).
- As in previous years, ESA will have a strong presence at COP26. ESA’s theme at COP26 will be ‘Taking the pulse of the planet from space and supporting climate action’ which aims to demonstrate the role of ESA’s missions and satellite data to strengthen our understanding of climate from space. This will support policymakers, society, businesses and communities to mitigate and adapt to a changing climate and develop resilience in support of the UNFCC Paris agreement.
- During COP26, the much-anticipated documentary which covers the ESA-led science expedition to the Gorner Glacier in Switzerland will be released for the first time. The documentary follows ESA astronaut Luca Parmitano, along with Susanne Mecklenburg, Head of ESA’s Climate Office, and their scientific team to one of the biggest ice masses in the Alps: the Gorner Glacier. Owing to its dramatic retreat, the glacier is one of the most extensively studies glaciers in the world.
• October 22, 2021: The metropolitan area of Perth is located in the South West Division of Western Australia, between the Indian Ocean and a low coastal escarpment known as the Darling Range. The metropolitan area stretches around 125 km along the coast, from Two Rocks in the north, to Singleton in the south. The central business district and suburbs of Perth, Australia’s fourth-most populous city, are situated on the banks of the Swan River. 52)
- Before European colonization, the area had been inhabited by the Whadjuk Noongar people for over 40,000 years. The area where Perth now stands, was called Boorloo by the Aboriginals living there at the time of their first contact with Europeans in 1827.
- Perth is one of the most isolated cities on Earth, with its nearest city, Brisbane, located around 2000 km away. Perth is closer to Bali in Indonesia than Australia’s capital, Canberra. Despite its isolation, Perth is one of the fastest-growing cities of Australia. Its airport is visible just south of Swan River.
- Rottnest Island, known as Wadjemup to the Noongar people, is located 19 km off the coast of Perth. This 19 sq km, sandy island is known for its population of quokkas, one of the smallest wallaby species in Australia. Several ferries can be seen journeying to and from Rottnest Island and Fremantle Harbor, Western Australia’s largest and busiest general cargo port.
- The most striking feature in this week’s image is the difference between forested land (visible in dark brown) and agricultural plots and crops (visible in green). Some of the forested land pictured here includes John Forrest National Park and the Mundaring, Jarrahdale and Youraling State Forests.
- The intricate pattern visible in the bottom of the image is the Huntly Bauxite Mine, the world’s second largest bauxite mine. Australia is the world’s largest producer of bauxite – a raw material used primarily in the production of aluminum.
Figure 31: Perth, Western Australia’s capital and largest city, is featured in this true-color image captured by the Copernicus Sentinel-2 mission. This image is also featured on the Earth from Space video program (image credit: ESA)
- The image also includes the location of ESA's deep-space ground station at New Norcia, about 120 km northeast of Perth. The station supports missions like ExoMars/TGO, BepiColombo and Solar Orbiter, and a new 35 m-diameter dish antenna is planned for the site.
• October 15, 2021: New Delhi, the capital and second-largest city of India, is featured in this image captured by the Copernicus Sentinel-2 mission. 53)
- New Delhi is situated in the north-central part of the country and lies within the massive metropolitan area of Delhi, India’s capital territory. To the east, Delhi is bounded by the state of Uttar Pradesh, and to the north, west and south it is bounded by the state of Haryana.
- Delhi’s urban area consists of the historical city of Old Delhi in the north, New Delhi in the south and now also includes the nearby cities of Ghaziabad, Faridabad, Gurugram and Noida. From space, these cityscapes together appear light grey in tone.
- New Delhi sits, primarily, on the west bank of the Yamuna River, visible in black in the right of the image. One of the country’s most sacred rivers, the Yamuna is a tributary of the Ganges River, located around 160 km south of the Himalayas.
- New Delhi, the government, commercial and financial center of India, is considered one of the fastest growing cities in the country and in the world. The straight and diagonal pattern of the broad, tree-lined avenues in New Delhi, which features extensive green spaces, makes it appear as a darker-toned region and contrasts with the narrower, winding streets of Old Delhi.
- The city is dotted with numerous museums, monuments, botanical gardens, places of worship and cultural buildings including the Hindu Akshardham Temple.
- Other notable features in the image include Indira Gandhi International Airport visible in the left, and Hindon Airport to the right. Some perfectly squared plots of land can be seen in the image, particularly in the west side of the city.
- As well as providing detailed information about Earth’s vegetation, Copernicus Sentinel-2 is designed to play a key role in mapping differences in land cover to understand the landscape, map how it is used and monitor changes over time. As cities continue to expand, Sentinel-2 can also be used to track urban expansion and assist urban planners.
Figure 32: New Delhi, the capital and second-largest city of India, is featured in this image captured by the Copernicus Sentinel-2 mission. This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2021), processed by ESA)