Minimize MetOp

MetOp (Meteorological Operational Satellite Program of Europe)

Launch    Mission Status    Sensor Complement    EPS Overview    Ground Segment    References

MetOp-A is Europe's first polar-orbiting (LEO) satellite dedicated to operational meteorology. The MetOp program was originally planned as a much larger satellite concept, called POEM (Polar-Orbit Earth-Observation Mission), a successor mission series to ERS-1/2 on the Columbus Polar Platform (PPF design).

However, this idea was abandoned at the ESA Ministerial Council in Granada, Spain, in 1992. Instead, Envisat and MetOp were born. Full approval of the EPS (EUMETSAT Polar System) program was granted in September 1998. The MetOp program is planned as a series of three satellites to be launched sequentially over an observational period of 14 years, starting in 2006 with MetOp-A (2010, 2014), it represents the space segment of EPS. 1) 2)

The EUMETSAT Polar System (EPS) consists of the ESA-developed MetOp (Meteorological OPerational) series of spacecraft and an associated ground segment for meteorological and climate monitoring from polar, low Earth orbit, providing "morning" service for operational meteorology. Within the framework of international agreements, the NOAA POES series will continue to provide the "afternoon" service.

The MetOp series, although an independent development, is complementary to: a) the NOAA POES system, b) the EUMETSAT/ESA MSG (Meteosat Second Generation) system, and c) the ESA ENVISAT system, where MetOp completes the mission objectives of the original POEM-1 mission.

Background: European needs for meteorological observations in polar ("morning" and "afternoon") orbits have been generously provided by NOAA S/C and payloads (including some instruments developed in Europe) over the last quarter century. The EPS (EUMETSAT Polar System) is the European contribution to the joint European/US operational polar system, through IJPS (Initial Joint Polar System). A cooperation agreement between NOAA and EUMETSAT was signed in November 1998. The EPS and POES systems form together the IJPS to provide global meteorological data from the series. With EPS, EUMETSAT is committed to take over the morning orbit service from NOAA. On the other hand, NOAA will continue to provide the POES series afternoon service. Both services are coordinated and integrated, on the basis of exchange of data, instruments and operational services

The prime objectives of the EPS MetOp mission series are as follows:

• To ensure continuity and availability for operational purposes of polar meteorological observations from the "morning" orbit to the global user community

• To provide enhanced monitoring capabilities (complimentary to ENVISAT) to fulfil the requirements to study the Earth climate system as expressed in a number of international cooperative programs such as: GCOS (Global Climate Observing System), IGBP (International Geosphere and Biosphere Program), and WCRP (World Climate Research Program). The aim is to provide continuous, long-term data sets.

EPS is an end-to-end system composed of a space segment and a full ground segment (see Figure 56). The third satellite in this series, MetOp-3, is not formally part of IJPS, because its planned launch date falls already into the era of the US NPOESS (National Polar-orbiting Operational Environmental Satellite System) era, representing in itself the merged US POES (civil) and DMSP (military) series.

Within the European framework, ESA is developing MetOp-A, the EUMETSAT procurement of MetOp-2/3 missions is under the responsibility of a joint ESA/EUMETSAT team. EUMETSAT is also directly responsible for the delivery of the following payloads: MHS, IASI, Argos/ADCS, SEM, AMSU-A, HIRS/4, and AVHRR/3. The last four payloads are contributed by NOAA under the IJPS agreement: CNES develops the IASI instrument with joint funding from EUMETSAT, and provides the Argos/ADCS, and in addition, part of the S&RSAT (Search & Rescue) auxiliary payload. EUMETSAT is responsible for the definition of the overall EPS system, the development and operations of the ground segment, and for the operation of the space segment.

Table 1: Overview of EPS (EUMETSAT Polar System)

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Figure 1: Integrated concept of NOAA/EUMETSAT meteorological polar satellites

Naming convention of MetOp satellites (the information was provided by the head of the EUMETSAT spacecraft team on Oct. 31, 2006):

The various naming of the spacecraft is due to the way the program development evolved:

• MetOp-1 is the first flight unit built, MetOp-2 the second, MetOp-3 the third.

• Due to programmatic reasons at system level, a decision was taken to fly MetOp-2 first.

• In order to avoid confusion, for the purposes of operations, the MetOp-2 flight model is referred to operationally as MetOp-A since it is the first satellite in-orbit. The international satellite designator of COSPAR is: 2006-044A, and a NORAD catalog ID is: 29499. The MetOp administration messages downlinked on HRPT/LRPT contains the COSPAR identifier (left-justified).

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Figure 2: Artist's view of the MetOp-A spacecraft in orbit (image credit: ESA, EUMETSAT)

 

MetOp-A Satellite

The overall architecture of the MetOp-A spacecraft comprises two largely independent modules, namely SVM (Service Module) and PLM (Payload Module). 3) 4) 5) 6) 7)

SVM provides the main satellite support/service functions. The SVM provides all the standard service functions of a S/C, like: attitude and orbit control, propulsion, power generation, and the on-board data handling and distribution systems. The SVM design is based on the SPOT MK3 bus (used on the SPOT series, ERS-1/2 and Helios-1A and 1B S/C). SVM is a box-shaped structure interfacing with the launch vehicle and the PLM as illustrated in Figure 5.

PLM provides accommodation and supporting subsystems (data handling, power, communications) to the payload complement. The instruments and antennas are mounted on the external panels, while most of the electronics systems are accommodated inside the PLM.

The S/C overall size is: 6.2 m x 3.4 m x 3.40 m (launch configuration) and 17.6 m x 6.7 m x 5.4 m (on-orbit configuration). The S/C is three-axis stabilized. The AOCS (Attitude and Orbit Control Subsystem) is in charge of the automatic 3-axes control of the satellite attitude, the orbit control for which the needed thrust impulses are provided by the propulsion subsystem. Attitude sensing is provided by digital Earth sensors for roll and pitch, by sun sensors for yaw, and by four independent two-axis gyros (two being in cold redundancy).

Actuation is provided by three 40 Nms reaction wheels, by two magnetotorquers (MAC) able to generate a 315 Am2 magnetic moment, and by the associated monitoring and command unit (EAIM). In addition, the propulsion subsystem works in blow-down mode; it includes four pressurized tanks of hydrazine. Two branches of eight 23.5 N thrusters are used. The pointing knowledge is: 0.07º (x-axis), 0.10º (y-axis), 0.17º (z-axis).

The overall S/C mass at launch is 4085 kg, including 316 kg of hydrazine. Single sided solar arrays provide a power of 3.890 kW (EOL), the average power over one orbit is 1.81 kW (EOL). Five 40 Ah batteries provide power during eclipse periods. The mission design life is 5 years. The prime S/C contractor is EADS Astrium SAS (France), major co-contractors are EADS Astrium GmbH, Germany (PLM), Alenia, Italy, and EADS Astrium Ltd., UK.

Propulsion subsystem: The eight thrusters, shown in Table 2, allow the generation of torque in all three axis and of propulsion in the ±Y axis. A graphical view of the thruster pair configuration is given in Figure 3. The Cartesian reference frame indicated in the figure depicts the MetOp satellite body frame of reference in which –Z points toward the Earth center. All the eight thruster configurations as described in Table 2 are shown in detailed in Figure 3. The rectangular box on the left in Figure 3 is a rough representation of the MetOp spacecraft that complements the thruster configuration schematics on its right. The green patches signify the location of the thruster pairs grouping on the spacecraft. 8)

Thruster No

Thruster Function

Prime

Redundant

Torque

Thrust

1

2

+Y

 

3

4

-Y

 

5

6

-X

 

7

8

-Z

-Y

9

10

+Z

-Y

11

12

+X

 

13

14

+Z

+Y

15

16

-Z

+Y

Table 2: Thruster module configuration and function

Each thruster is designed to deliver a nominal thrust of 22.7 N at the beginning of life. Currently (2015), each thruster on MetOp-B is providing on average 17.5 N of thrust. The thrust provided is in the form of pulses and are designed to operate at 8 Hz. During the propulsion phase, the imbalance in the torque due to changes in the center of mass will cause one of the propulsion thrusters to pulsate less than the other. A similar imbalance in the torque and thrust applies to the slew and anti-slew maneuvers as well. Throughout the maneuver phase, the attitude control thrusters are actively controlled by the AOCS to correct the attitude pointing due to torque imbalance created by the propulsion and coupled thrusters.

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Figure 3: MetOp thruster configuration and location (image credit: EUMETSAT)

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Figure 4: Schematic view of the AOCS (image credit: ESA)

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Figure 5: Schematic of the SVM (Service Module) configuration (image credit: ESA)

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Figure 6: Exploded view of the main elements of SVM (image credit: ESA)

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Figure 7: Schematic overview of the PLM (Payload Module) configuration (image credit: ESA)

Parameter

Value

Parameter

Value

Mass of SVM

1380 kg

Mass of solar array

255 kg

Mass of PLM

1214 kg

Mass of fuel

316 kg

Mass of payload

920 kg

Overall mass of S/C

4085 kg

Power of instruments

885 W (average)

Power of PLM

491 W (average)

Power SVM

437 W (average)

Total power consumption

1.81 kW (average)

Table 3: Overview of some key spacecraft parameters

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Figure 8: Line drawing of the MetOp spacecraft (image credit: EADS Astrium)

RF communication: An omnidirectional S-band coverage provides TT&C support (uplink 2 kbit/s, downlink 4 kbit/s). Instrument data is downlinked in X-band at a rate of 70 Mbit/s. Onboard storage capacity of 24 Gbit (solid state recorder with a data rate of 70 Mbit/s) is provided. In addition to onboard recording and X-band downlink capabilities, MetOp supports the real-time broadcast of instrument data to local authorized users by the following means:

LRPT (Low-Rate Picture Transmission) links with 72 kbit/s in VHF-band for selected instrument data.

AHRPT (Advanced High-Rate Picture Transmission) links with 3.5 Mbit/s in L-band. The new AHRPT service (a WMO standard) enables regional users to receive all data relevant to their area in real time. Users operating existing HRPT stations will have to modify their stations to receive the "Advanced" MetOp data.

The provided VHF low-rate digital direct broadcast service replaces the old analog APT (Automatic Picture Transmission) service of NOAA, employing data compression (modified JPEG compression scheme) to ensure high-quality images. The digital LRPT service retains the VHF frequency and bandwidth of the APT service, but provides three channels of AVHRR data at the full instrument spatial and radiometric resolution.

Data Type

Frequency Domain

Modulation Scheme

Data Rate

TT&C uplink

S-band, 2053.4 MHz

NRZ/PSK/PM

2 kbit/s

TT&C downlink

S-band, 2230 MHz

SP-L/PSK/PM

4 kbit/s

Global data dump

X-band, 7.750-7.900 GHz

QPSK

70 Mbit/s

LRPT downlink

VHF-band, 137.1 MHz

QPSK

72 kbit/s

AHRPT downlink

L-band, 1701.3 MHz

QPSK

3.5 Mbit/s

Table 4: Summary of MetOp communication links with the ground segment

The EPS Ground Segment includes all the ground facilities required to support the orbiting MetOp satellites and the EPS mission, including both normal and degraded mission modes. Its objectives are:

• To ensure that the satellites perform their mission nominally

• To perform the ground operations to fulfil the global mission, acquiring and processing the global data received from the NOAA and MetOp satellites and disseminating the processed data to the Eumetsat member states. This includes product quality control, data archiving, and provision of user services.

• To perform all the ground operations to support the local data-access mission (HRPT/LRPT)

• To support NOAA for global data acquisition and telemetry, tracking and control during blind orbits of the NOAA ground segment (and on request for specific operations)

• To support the space environment monitoring and data-collection missions.

The core ground segment provides the following functions at the different sites:

• Central Site, at Eumetsat headquarters in Darmstadt, Germany, includes all the functions for monitoring and controlling the satellite and the ground segment. Included are the generation of the centrally extracted products and their dissemination.

• The Polar Site, at Svalbard (latitude 78ºN), hosts the CDA (Control & Data Acquisition) station that receives the MetOp recorder dump every orbit and command the satellite. The CDA receives also NOAA satellite data dumps when they are beyond their own stations.

• The BUCC (Back-Up Control Center) site, close to Madrid, Spain, was created in case of major problems with the central site.

The EPS ground segment includes the Eumetsat multi-mission dissemination system (EUMETCast) for near-realtime delivery to users of the global data and products derived from the MetOp data for the morning orbit and NOAA data for the afternoon orbit.

Onboard data handling: On the MetOp spacecraft command and control concept is implemented separately to measurement data handling. However, since this concept doesn't work for the NOAA-provided instruments (AVHRR/3, HIRS/4, AMSU-A, and SEM-2), a dedicated NIU (NOAA Interface Unit) has been developed to adapt the NOAA interfaces to European standards. The NIU performs command and control through a dedicated Instrument Control Unit (ICU) and collects measurement data through a DSP (Digital Signal Processor). It also compresses the AVHRR channels. To allow for selective encryption in the FMU (Formatting and Multiplexing Unit), the NIU provides measurement data to the FMU via four distinct data streams:

• NIU (NOAA Interface Unit)

• MHS (Microwave Humidity Sounder) Protocol conversion Unit (MPU)

• FMU

• SSR (Solid State Recorder)

General onboard data handling employs the CCSDS protocols. A selective encryption capability is used to ensure the commercial and data-denial needs of EUMETSAT and NOAA, respectively. Spacecraft operations are being performed by EUMETSAT with the Kiruna ground station serving as prime.

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Figure 9: Overview of PLM measurement data acquisition, handling, and storage (image credit: ESA)

The PLM (Payload Module) command and control function is performed through:

• PMC (Payload Module Computer). The PMC controls all PLM equipment and instruments via an ESA standard OBDH (On Board Data Handling) bus.

• CBS (Standard Bus Couplers)

• RTU (Remote Terminal Units)

• DBU (Digital Bus Units)

• RBI (Standard Remote Bus Interface ASICs)

• ICU Intelligent Control Units)

The data handling architecture is decentralized because the Payload Module (PLM) and Service Module (SVM) have their own computer. OBDH data buses are being used for data exchanges between SVM and PLM computers.

Broadcast service provision: 9) The MetOp program, as successor to the NOAA POES morning series, is required to provide a continuous broadcast of its meteorological data to the worldwide user community, so that any ground station in any part of the world can receive local data when the satellite passes over that receiving station. This implies continued long-term provision of LRPT and VHF downlink services.

Orbit: Near-circular sun-synchronous polar morning orbit (local solar time at 9:30 hours on descending node), mean altitude = 817 km, inclination = 98.704º, repeat cycle = 29 days (412 orbits).

S/C attitude

- Three-axis stabilized through reaction wheels
- Orbit maneuvers through a hydrazine propulsion subsystem
- Pointing knowledge: 0.07º (x-axis), 0.10º (y-axis), 0.17º (z-axis)

Data handling

- Instruments science data acquired as CCSDS packets
- Science data formatting and multiplexing, encryption for selected instruments
- Instruments and housekeeping data storage in a solid-state recorder (24 Gbit)

Communications

- Omnidirectional S-band coverage (uplink 2 kbit/s, downlink: 4.096 kbit/s
- Instrument global data stream downlinked via X-band (70 Mbit/s)
- Real-time broadcasting of instrument data in AHRPT: 3.5 Mbit/s via L-band for all instruments, and LRPT: 72 kbit/s via VHF for selected instruments

On-board power

- 2210 W from solar panel, average power over one orbit (EOL)
- Five 40 Ah batteries
- Unregulated power (22 37.5 V) and 50V regulated power lines for SVM/PLM units
- Unregulated power lines (22 37 V) for European instruments
- 28 V regulated power lines for NOAA instruments

Design life

5 years

S/C mass

- 4087 kg (launch)
- Payload: 2125 kg (instruments and supporting avionics)
- Platform: 1646 kg
- Propellent: 316 kg of hydrazine, stored in 4 tanks (including residual)

S/C size

- 6.3 m (height) by 2.5 m x 2.5 m (transverse section) in launch configuration
- 17.6 m x 6.6 m x 5.0 m, after solar array and antennas deployment

S/C operations

- S/C controlled by EUMETSAT (Kiruna ground station
- Instruments X-band data downlinked nominally over two ground stations
- Recorded data downlinked not later than one orbit after recording
- S/C autonomy required for 36 hours without ground contact

Table 5: Summary of MetOp main features and performances

The MetOp operational meteorological mission objectives consist of:

• Global sounding: To provide information about 3-D temperature and humidity fields in support of operational numerical forecasting systems

• Global imagery: To provide cloud imagery for forecasting applications, sea surface temperatures (SST), radiation budget temperatures. To support the global sounding mission through the identification of cloud-free areas

• Data collection and location: To support WWW objectives by the reception and dissemination of in-situ observations from ocean buoys and similar data collection platforms

• Preoperational data: To provide access to data from instruments which have not yet been declared fully operational

• Global data access: To primarily support global-scale weather forecasting by providing global data to the meteorological services within 2 1/4 hours of observation

• Local data access (AHRPT and LRPT): To support regional weather forecasting by providing broadcasted data to local receiving stations when the satellite is in visibility.

The MetOp climate monitoring mission contributions (for GCOS) consists of:

• Imagery and sounding

• Ocean measurements (including surfaces stress and winds)

• Clouds and Earth radiation budget: Radiation is the primary energy source of the climate system and principle heat input source to the oceans

• Sea ice information: The extent of sea ice is an important variable in connection with both ocean heat budget and radiation balance

• Atmospheric minor constituents: Concern over the depletion of stratospheric ozone suggests the importance of maintaining a continuous data set of global total column ozone and vertical profiles

• Precipitation estimates.

The MetOp Earth sciences research mission objectives include data provision to the European science community to advance investigations in fields such as:

• Atmospheric physics: chemistry, radiation and energy balance, clouds

• Oceanography: general ocean circulation and fluxes of heat, momentum and gases; modeling

• Hydrology: water cycle, continental snow and mountain glaciers, land cover, soil moisture, vegetation

• Cryosphere: sea ice, continental ice, modeling

The MetOp surveillance mission contributions to the regular monitoring of application-oriented parameters:

• Environment: pollution control, natural disasters, renewable resources

• Marine: offshore activities, ship routing, fishing, sea ice routing

 


 

Develoment status of the MetOp Project:

• November 5, 2018: Following months of simulation training, teams at ESA's European Space Operations Center have completed the all-important ‘dress rehearsal' before MetOp-C's liftoff on 7 November from Europe's Spaceport in Kourou, French Guiana. 10)

- "During this pre-launch dress rehearsal, operators were for the first time connected to the satellite through an umbilical cable as it waits upon its Soyuz launch vehicle," explains Lorenzo Guillermo, ESA's Ground Operations Manager. "We were then able to test communication links between our teams here at mission control in Darmstadt, Germany, and the satellite, currently awaiting liftoff on the launchpad".

- MetOp-C, the final of three satellites in the MetOp series, will provide observations of the global atmosphere, oceans and continents. Flying in low Earth orbit at an altitude of about 800 km, these polar-orbiting satellites are able to take images of our planet in unprecedented detail.

• October 4, 2018: Following the arrival of the MetOp-C satellite at Europe's spaceport in Kourou, French Guiana, the team has been busy testing and preparing the satellite for launch. With the alignment of the two main bodies of the satellite done and solar array attached, MetOp-C is complete and the team focuses on checking all the electrical connections. 11)

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Figure 10: MetOp-C is the third polar-orbiting satellite in the MetOp (Meteorological Operational) satellite program and its launch is set for 7 November 2018 (image credit: ESA)

• July 9, 2018: The MetOp-C launch campaign has kicked off with the first of three Antonovs landing at Cayenne Airport, French Guiana on 20 June. 12)

- The cargo aircraft transported 11 containers of equipment for ground support and IT-infrastructure, followed by the second, carrying the two main modules of the spacecraft a few days later. The third and final Antonov brought the solar array.

- This is all in preparation for the launch of the third polar-orbiting satellite in the Meteorological Operational satellite program. This program was procured by ESA for Eumetsat, the European Organization for the Exploitation of Meteorological Satellites.

- The first two satellites were launched in 2006 and 2012. The launch of MetOp-C later this year will continue the success story of the most important set of sensors for weather prediction in space today.

- Launching a new satellite every 5–6 years guarantees a continuous delivery of high-quality data for medium- and long-term weather forecasting and climate monitoring until at least 2023.

- MetOp-A and -B are delivering considerable benefits to society by improving weather forecasts, thanks to their ability, among other features, to measure temperature and humidity profiles from a relatively close 800 km-altitude orbit. MetOp-C will ensure that these observations will also be available on a daily basis in the future.

- The economic and social benefits of accurate weather forecasts are huge, with the potential to impact on crop harvesting, air traffic, and simply planning day-to-day activities. In the extreme, knowing that hazardous weather conditions are on the way can save human life and property.

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Figure 11: The MetOp-C satellite is unloaded in French Guiana, where it will be prepared for liftoff later this year (image credit: ESA)

- ESA's MetOp-C project manager, Stéfane Carlier, said, "MetOp has brought about a new era in the way Earth's weather, climate and environment are observed and has significantly improved operational meteorology, particularly numerical weather predictions. The MetOp-A and -B satellites contribute approximately one third to numerical weather prediction from all data sources, including in situ, airborne and space-based. MetOp-C will ensure the continuity of the provision of this service until the next generation of MetOp spacecraft enters into service and provides even more refined data."

- Eumetsat Polar System Program Scientist, Dr. Dieter Klaes, said, "The Infrared Atmospheric Sounding Interferometer (IASI) is MetOp's key instrument for numerical weather prediction. It has been central to the significant improvement in weather forecasts up to 10 days ahead, over the past decade. MetOp satellites remain advanced technology and their instruments are still state-of-the art. We expect that adding an additional source of information, when MetOp-C is operational, will have further positive impact on forecast quality."

• April 17, 2018: The MetOp-C meteorological satellite is getting ready for upcoming launch in order to join its siblings and further improve the quality of observations and data provided for weather forecast. 13) 14)

- Built by Airbus DS, MetOp-C is the last of the first generation of EUMETSAT Polar System (EPS) series of three polar-orbiting satellites and is planned to be launched on September 18, 2018, from European Space Center in Kourou, French Guyana, aboard a Soyuz rocket.

- The MetOp program has enhanced the accuracy of weather forecasting and allowed extending the short term forecasts by one day.

- "MetOp satellites are technologically advanced and their instruments are still state-of-the-art," said EUMETSAT Director-General Alain Ratier. "We are in the fortunate and unexpected position soon having three MetOp's in orbit at the same time, because MetOp-A, which was launched in 2006, has exceeded its five-year design life time by far and will remain in orbit until 2022."

- Initially, the plan was for each satellite to replace its predecessor, however, the excellent performance of the first two MetOp satellites allows them to be operated simultaneously, providing the meteorological community with increased data. The forthcoming launch of MetOp-C will further improve the quality of observations and data provided for weather forecasts.

• August 10, 2017: MetOp-C is the third and final satellite of the first generation of MetOp polar-orbiting meteorological satellites. The payload module of MetOp-C, developed and built by Airbus in Germany, was delivered to Toulouse after it completed a series of tests at ESA/ESTEC in Noordwijk, the Netherlands. The satellite, weighing in at four tons, is now almost complete after successful coupling of its payload and service module. In preparation for the launch scheduled for October 2018 from Kourou, French Guiana, MetOp-C will undergo a further series of radio-electric tests in the coming weeks. The solar panel, which is the last outstanding major component, will be integrated in November 2017 just before vibration testing. 15)

• February 22, 2017: The payload module of MetOp-C, Europe's latest weather satellite, being lowered into Europe's largest vacuum chamber, the 10 m diameter LSS (Large Space Simulator). The LSS is part of ESA's Test Center in the Netherlands, the largest facility of its kind in Europe, providing a complete suite of equipment for all aspects of satellite testing under a single roof. 16)

- MetOp-C's instruments must be tested in space-like vacuum conditions. High-performance pumps will remove all air within the chamber to create an orbital-quality vacuum. Meanwhile, liquid nitrogen will circulate through the black walls to mimic the cold of sunless space.

- The 2.1 ton module carries a suite of meteorology and climatology instruments, variously procured by ESA or sourced from EUMETSAT, France's CNES space agency and the US NOAA (National Oceanic and Atmospheric Administration).

- Once testing is complete, MetOp-C's payload module will travel to the Airbus Defence and Space facility in Toulouse, France, to be integrated with its service module – the segment of the satellite providing attitude and orbit control, electrical power and communications, and hosting the main computer.

- The launch of MetOp-C by Soyuz from Europe's Spaceport in French Guiana is scheduled for October 2018.

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Figure 12: Photo of the MetOp-C spacecraft as it is lowered into LSS at ESA/ESTEC (image credit: ESA, G. Porter)

• January 11, 2017: MetOp-C's sensor module was transported in the first week of January from Airbus Defence and Space in Friedrichshafen, Germany to ESA's Test Center in Noordwijk in the Netherlands, which is equipped to simulate every aspect of the space environment. The 2.1 ton module carries a suite of meteorology and climatology instruments, variously procured by ESA or sourced from EUMETSAT, France's CNES space agency and the US NOAA (National Oceanic and Atmospheric Administration). 17)

- "The operation of the payload module and its instruments needs to be verified in space-like vacuum conditions," explains Jacques Mauduit of ETS (European Test Services), the company operating the center for ESA. "This ‘thermal vacuum' testing will take place in the Large Space Simulator this spring, with cryogenically cooled ‘blackbodies' fitted in front of individual instrument openings or radiators to control their temperatures to within 100–30ºC of absolute zero."

- Once testing is complete, MetOp-C's payload module will travel to the Airbus Defence and Space facility in Toulouse, France, to be integrated with its service module – the segment of the satellite providing attitude and orbit control, electrical power and communications, and hosting the main computer.

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Figure 13: Photo of the MetOp-C payload module at ESA/ESTEC (image credit: ESA/ETS, A. Kuebler)

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Figure 14: Stacking of the MetOp-B satellite on top of the Fregat stage, at launch site (image credit: Astrium, ESA, EUMETSAT ) 18)

 

Launch: MetOp-A was launched on a Soyuz-2-1A (Soyuz-2/Fregat) launch vehicle on October 19, 2006 from the Baikonur Cosmodrome, Kazakhstan. Launch provider: Starsem, a French-Russian company. 19)

Orbit: Near-circular sun-synchronous polar morning orbit (local solar time at 9:30 hours on descending node), mean altitude = 817 km, inclination = 98.704º, repeat cycle = 29 days (412 orbits).

 

Launch: MetOp-B was launched on a Soyuz-2-1A (Soyuz-2/Fregat) launch vehicle on Sept. 17, 2012 from the Baikonur Cosmodrome, Kazakhstan. Launch provider: Starsem. 20)

 

Launch: MetOp-C with a mass of 4033 kg was launched on 7 November 2018 (00:47 GMT) on a Soyuz ST-A / Fregat-M launch vehicle from Kourou, French Guiana. MetOp-C is the last in the current series of MetOp satellites. 21) 22)

Some 60 minutes later Soyuz's upper stage delivered MetOp-C into orbit and contact was established through the Yatharagga ground station in Australia. MetOp-C is now in the hands of ESA's flight operations team in Darmstadt, Germany, for the three-day LEOP (Early-orbit Operations Phase), until the handover of flight operations to EUMETSAT.

The MetOp satellites are developed by ESA under a cooperation agreement to form the space segment of the EUMETSAT Polar System. This system is Europe's contribution to a multi-orbit polar system shared with the US NOAA agency.

Stéfane Carlier, ESA's MetOp Project Manager, noted, "The MetOp satellites carry an array of sensors that measure temperature, humidity, trace gases, ozone and wind speed over the ocean."

Alain Ratier, EUMETSAT Director General, said, "EUMETSAT is grateful to Arianespace for another successful launch, after those of MetOp-A and MetOp-B. We are now ready to take over flight operations from ESA's European Spacecraft Operations Center to perform in-orbit commissioning of the satellite and instruments until end of January, in partnership with ESA, CNES and NOAA. After this, EUMETSAT scientists will validate output products with expert users, such that we can release realtime products to users in spring 2019."

 

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Figure 15: Alternate view of the MetOp-A satellite configuration (image credit: ESA, EADS Astrium SAS)

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Figure 16: Schematic view of MetOp and its payload accommodation (image credit: EUMETSAT)

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Figure 17: MetOp-A and MetOp-B are in the same orbital plane (image credit: EUMETSAT, Ref. 30)

 


 

Mission status of MetOp series spacecraft

• November 12, 2018: Mission teams at ESA's ESOC operations center in Germany handed control of the recently launched MetOp-C satellite to EUMETSAT (European Organization for the Exploitation of Meteorological Satellites) on Saturday morning, just three days after launch. In doing so, they also say a final farewell to the extremely successful MetOp-series of weather-probing satellites. 23)

- MetOp-C was launched into orbit on 7 November on top of a Soyuz rocket. Since then, teams at ESA's mission control center in Darmstadt, Germany, have been carefully introducing the satellite to its new home in space.

- In space, MetOp-C joins its siblings MetOp-A and MetOp-B, two satellites that have already reduced errors in one-day weather forecasts by up to 27 percent.

- Now that MetOp-C is safely in orbit, and following in the footsteps of the previous two, ESA has handed over the mission to EUMETSAT for in-orbit commissioning, the start of routine operations and, later, distribution of its vital meteorological data.

• September 6, 2018: Zenith GNSS (Global Navigation Satellite System) data collected through the Precise Orbit Determination (POD) antennas of the GRAS receivers flying on the Metop-A and Metop-B satellites can also be exploited to determine the Total Electron Content (TEC) of the topside ionosphere from the Low Earth Orbit (LEO) GRAS receiver to any GNSS satellite in view. These 'slant' TEC data are used to determine the vertical TEC of the topside ionosphere (namely the tTEC). 24)

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Figure 18: Geolocated topside Total Electron Content data observed in the day side of the Metop-A orbit during a period of strong geomagnetic storm (16-20 March 2015). Superimposed is the evolution of the Kp index (the Planetary K-index) which provides an indication of the magnitude of geomagnetic storms (image credit: EUMETSAT)

• April 2018: The MetOp-A and -B satellites continue to provide their service to the meteorological community. The MetOp satellites in orbit have demonstrated their significant contribution to the accuracy of weather prediction and still represent the most advanced polar-orbiting meteorological satellites in the world.

• December 8, 2016: The EUMETSAT Council agreed that the ageing, but still healthy, MetOp-A satellite will be exploited on a "drifting" orbit from June 2017 onwards, in order to extend its useful lifetime from 2019 to 2022. 25)

- The nominal ground track will be maintained, but the local time at ascending node will decrease from the nominal mission value of 21:30 hr in June 2017 to 19:30 hr in 2021. This measure will enable two to three years of tri-MetOp operations with MetOp-B and MetOp-C as from 2019, after the end of MetOp-C commissioning. The launch of MetOp-C is currently planned for October 2018. Operating MetOp-A in a drifting orbit will maximize the return on investments of EUMETSAT Member States and benefit the worldwide NWP (Numerical Weather Prediction) user community.

- At the end of its operational life, MetOp-A will then be de-orbited to a lower perigee orbit for reentry within 25 years, in line with the policy adopted by Council to comply as far as possible with space debris mitigation guidelines, although MetOp satellites were designed long before these guidelines were established.

- The development of the EPS-EP (EUMETSAT Polar System of Second Generation) system progressed further at this Council session, with the approval of the contract for the PDAP ( Payload Data Acquisition and Processing) function of the ground segment. The PDAP includes ground stations to acquire payload data from the MetOp-SG satellites and a complex processing system to extract physical and environmental products in real time. With the approval of this contract, all ground segment development contract will be in force by the end of the year.

- At the end of the Council session, the Director-General signed cooperation agreements with the Chief Executive Officers of the Danish, Finnish, French, German, Italian, Portuguese, Spanish, UK National Meteorological Services each leading one EUMETSAT SAF (Satellite Application Facility), for the Third Continuous Development and Operations Phase (CDOP 3) of the eight SAFs. Each SAF is a consortium developing and providing EUMETSAT operational products and software for use in a specific application area. The CDOP-3 covers the period 2017-2022 and will further extend EUMETSAT's portfolio of operational products and develop new products extracted from Meteosat Third Generation and EPS-SG observations.

• October 19, 2016: MetOp-A, Europe's first polar orbiting weather satellite, still going strong after 10 years - double its specified lifetime. High precision weather data helps businesses, farmers and security organizations. 26)

- Global economic activity has become increasingly dependent on – and affected by – weather. Accurate weather forecasts are essential for sectors including energy, transportation, construction, agriculture and tourism, enabling them to plan and use resources more effectively and efficiently.

- Dieter Klaes, program scientist at EUMETSAT said: "The MetOp satellites have significantly improved numerical weather prediction. By itself MetOp-A contributes roughly 25% of all data gathered for meteorological purposes, and 38% of all satellite platforms. The MetOp fleet's performance in measuring trace gases and in the field of atmospheric chemistry, e.g. methane, sulphur dioxide, volcanic ash, has exceeded all expectations. Furthermore, climate and environmental monitoring benefits from the long-lasting program with three satellites designed to operate for more than two decades."

- Since its launch in October 2006, MetOp-A has operated like clockwork and has achieved double its designed five-year lifetime. In September 2012 MetOp-B, the second in the series, was launched and operates in tandem with MetOp-A. The two satellites fly the same orbit, half an orbit apart, to better observe rapid atmosphere evolutions. The duo has increased the wealth of data even further, collecting data from low Earth orbit essential for accurate forecasts up to 12 days ahead. MetOp-C is scheduled for launch in 2018.

- In the MSG (MetOp Second Generation), currently being developed by Airbus Defence and Space, there will be a fleet of six satellites, with pairs of satellites carrying different packages to deliver complementary meteorological information. The A series of satellites (as of 2021) will be equipped with atmospheric sounders as well as optical and infrared imagers, while the B series (as of 2022) will focus on microwave sensors.

- German insurance provider Munich Re's natural disasters report 2015 listed 1060 natural disasters in 2015 with overall losses of US$100 billion and 23,000 fatalities. Floods and mass movements accounted for 28% of the losses, while 47% were caused by storms, 18% resulted from extreme temperatures, droughts and forest fires, and 7% were due to earthquakes, tsunamis and volcanic activity.

• On June 10, 2016 at 02:30 GMT, the MetOp-A meteorological satellite crossed the equator to begin its 50,000th orbit since its launch from Baikonur, Kazakhstan, on October 19, 2006. So far, MetOp-A has downlinked more than 100 TB of raw meteorological data. 27)

• May 2016: EUMETSAT has currently seven operational weather satellites. Meteosat-7,-8, 9 and 10, MetOp-A, MetOp-B and Jason-2. The Copernicus satellites, Sentinel-3A and Jason-3, are due to become operational in 2016. 28)

• EUMETSAT released a major update of the PMAp (Polar Multi-Sensor Aerosol properties) product on 17 March 2016. The new release extends the coverage of the previous AOD (Aerosol Optical Depth) product, which was restricted to water surfaces. Now, this AOD product has global coverage, even for solar zenith angles lower than 70 º, and includes AOD over almost all land surface types, including desert areas, but excluding surfaces with snow/ice cover. This updated product also contains a realistic AOD error estimate. 29)

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Figure 19: PMAp-derived AOD values from both MetOp-A and MetOp-B satellites, using level-1b data from GOME-2 PMD and AVHRR measurements (image credit: EUMETSAT)

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Figure 20: Overview of EUMETSAT programs (image credit: EUMETSAT) 30)

• October 2015: Two of the three MetOp satellite series are currently in orbit with MetOp-A close to its end-of-life operation. The three satellites are foreseen to provide polar data for climate monitoring over a minimum period of 14 years.

- An observed discrepancy in the along-track acceleration contribution from the slew and anti-slew maneuvers of MetOp-B has prompted the development of an accurate attitude model to be used in the POD (Precise Orbit Determination) to improve the calibration of each maneuver segment. It is of importance to flight dynamics operations planning in understanding the actual contribution in acceleration by the slew and anti-slew maneuvers if an anomaly does exist between two MetOp spacecraft that have the same design and assembly (Ref. 8).

- The performance of the maneuver calibration for each segment using the reconstructed and more accurate attitude model has shown noticeable improvement. The results from this analysis have provided a better indication of MIS-performance of the slew and anti-slew maneuvers of MetOp-B. Its along-track acceleration contribution is almost double the past calibrated slew/anti-slew maneuvers of MetOp-A. For proper comparison and assessment, it is foreseen that all past OOP (Out-Of-Plane) maneuvers for MetOp-A and MetOp-B will be calibrated using a reconstructed attitude model. If the mis-performance persists in all MetOp-B OOP maneuvers, this may indicate a possible misalignment in the coupled thruster on MetOp-B thus changing the direction of the parasitic accelerations. These accelerations contribution is observed in all three components of the orbit but it is the along-track component contribution that is of interest to flight operations planning. If a thruster misalignment is present, this will have to be taken into account in all future maneuver planning of MetOp-B. With the experience gained from this analysis and the basic resources developed, future OOP maneuver calibration in the POD can be readily performed for the future MetOp-C as well as the EPS-SG satellites to aid operations planning.

- Future work: The analysis undertaken thus far has shown very promising outcome by accounting for accurate modeling of the spacecraft attitude during the maneuver phase in the POD. It is foreseen that further improvement in the maneuver calibration performance can be achieved by including the following:

1) Fine tuning of the start and stop times of the maneuver segments

2) Modeling of the parasitic thrust effect caused by the attitude control thrusters in between the maneuver segments. This involves defining more smaller thrust segments

3) Divide the slew and anti-slew maneuvers into sub-segments to better represent the actual force exerted

4) Model the thrust, especially in the slew and anti-slew, as linearly increasing/decreasing variable acceleration over time.

• May 20, 2015: Four MHS instruments are currently on orbit (on MetOp-A and -B and NOAA-18 and -19) and are in good health — the only exception being one channel on NOAA-19. A fifth instrument will be launched on board MetOp-C in 2018.
The MHS instrument is a radiometer providing operational data from polar orbit in five microwave channels, used to retrieve vertical profiles of atmospheric water vapor. These are key inputs for numerical weather prediction models, which are used operationally for weather forecasting worldwide. The MHS instrument was developed by Matra Marconi Space UK (now Airbus Defence & Space). 31)

• July 7, 2014: MetOp-B acquired an image of the super Typhoon Neoguri, so far the strongest typhoon in the 2014 Western Pacific season. The system became a typhoon, the Western Pacific equivalent of a Atlantic hurricane, on 4 July and intensified to Super Typhoon strength, maximum sustained winds of 240 km/h, on 6 July. 32)

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Figure 21: The image of the MetOp-B AVHRR with ASCAT wind overlay, was captured on July 7, 2014 (00:40 UTC), when Neoguri as a category-4 storm was located east of the northern tip of the Philippines (image credit: EUMETSAT)

Legend to Figure 21: The enhanced infrared MetOp-B image shows the structure of the storm with a very well defined eye. The colors indicate temperature, with red showing areas where the cloud tops are colder than -70ºC. The well-defined eye can also be clearly seen on the MetOp-B Natural color RGB. The cyan color denotes ice clouds.
Note: On July 8, 2014, the MetOp-A acquired Neoguri as it crossed the Japanese island of Okinawa.

On April 24, 2013, MetOp-B replaced MetOp-A as EUMETSAT's prime operational polar-orbiting satellite following the end of its commissioning period. MetOp-A will continue operations as long as its available capacities bring benefits to users. 33)

- MetOp-B began delivering first data within two weeks of its launch, allowing expert users to participate in the product calibration and validation activities. The satellite was declared operational on 29 January, 2013, bringing operational quality products from most instruments to the user community within three months of launch.

- In the fall of 2013, the MetOp-A satellite continues to perform very well. MetOp-A will be operated in a dual operations scenario with MetOp-B initially until 2018 or the completion of MetOp-C calibration and validation.

• February 2014: The MetOp satellites are Europe's first operational weather satellites in polar orbit providing data for weather forecasting up to 10 days and for climate monitoring. 34)

- On 17 September 2012, MetOp-B, the second of the series of three identical weather satellites, was launched, and joined its predecessor, MetOp-A, in the same polar orbit. The following year, in April 2013, MetOp-B took over as the primary operational satellite.

- Although the ageing MetOp-A has now exceeded its design lifetime of five years, it is being kept in orbit as a secondary satellite, for as long as it continues to bring benefits to users and does not need to be deorbited to avoid generating debris in the precious low earth orbit. The two satellites are flying in the same mid-morning orbital plane, but are separated in time by half an orbit (48 minutes).

- Dieter Klaes, EUMETSAT's EPS Program Scientist said, "While MetOp-A continues to function, it means that the MetOp system is more robust to orbit anomalies and failures. It also means that with two satellites in operation there are more data being collected, in particular for Numerical Weather Prediction, the basis of modern weather forecasting."

- Global AVHRR winds from MetOp: The dual MetOp operation is also bringing other benefits. One example is in the observation of global winds, or Atmospheric Motion Vectors (AMVs), from the AVHRR (Advanced Very High Resolution Radiometer) instrument onboard the MetOp satellites. — AMVs are produced from satellite images by tracking the movement of atmospheric features, mainly cloud patterns, through successive images to estimate wind speed and direction. AMVs are useful as input for numerical weather prediction, especially over ocean areas where other wind observations are sparse. The AMVs collected by polar-orbiting satellites, such as MetOp, are particularly important as they provide coverage of winds in the polar regions, which are not well observed by geostationary satellites.

- GOME-2 – more detailed data: Having two MetOp satellites in orbit also creates an opportunity to collect more detailed data from the onboard GOME-2 (Global Ozone Monitoring Experiment) instrument. Since 15 July 2013, GOME-2 on MetOp-A has been operating in a "reduced swath" mode of 960 km resulting in a ground pixel size of 40 x 40 km, half that of the GOME-2 instrument on MetOp-B which still operates in "normal" mode, with a swath width of 1920 km and a ground pixel size of 40 x 80 km resolution. — Rose Munro, EUMETSAT's Atmospheric Composition Manager said, "This operational configuration has several benefits. The provision of data from two GOME-2 instruments ensures full daily coverage, without the gaps in equatorial regions which occur with only one instrument in operation. At the same time the smaller ground pixels from GOME-2 on MetOp-A, with more cloud-free scenes and improved resolution, are better adapted for monitoring atmospheric composition in the troposphere."

• Feb. 8, 2013: Satellites show that the recent ozone hole over Antarctica was the smallest seen in the past decade. Long-term observations also reveal that Earth's ozone has been strengthening following international agreements to protect this vital layer of the atmosphere. According to the ozone sensor on Europe's MetOp weather satellite, the hole over Antarctica in 2012 was the smallest in the last 10 years. 35)

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Figure 22: Hurricane Sandy captured by MetOp-A as the huge storm hit the east coast of the USA on October 29, 2012 (image credit: EUMETSAT)

• Nov. 2012: The commissioning phase of MetOp-B, also called SIOV (Satellite In-Orbit Verification) phase was conducted at the EUMETSAT control center, with the support of an Astrium team. It has been formally concluded by a successful SIOV review held in November 2012 (Ref. 18).

- The detailed verification of the satellite platform and PLM avionics has allowed confirming the very good performance of the various subsystems and units for which nominal, and in many cases better than originally budgeted performance has been measured. The satellite resources situation at the end of the SIOV has been found fully satisfactory, with an ample power budget margin, and a large reserve of propellant due to a nominal launch and few orbit correction maneuvers. Overall, the performance situation fully compares to the one of MetOp-A at beginning of life.

- Regarding instruments, the excellent data quality obtained from the very beginning and the experience gained with MetOp-A allowed EUMETSAT to begin trial dissemination of data to partners before end of October 2012. This covered data for AMSU, GRAS, MHS, ASCAT, AVHRR and HIRS. GOME data followed in December and IASI ones in January 2013.

• On Oct. 24, 2012, the IASI instrument on MetOp-B produced first calibrated data. 36)

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Figure 23: First calibrated IASI spectrum on MetOp-B observed on Oct. 24, 2012 (image credit: EUMETSAT)

• Sept. 28, 2012: Four of the instruments on the MetOp-B weather satellite (AMSU-A, ASCAT, MHS, GRAS) have been activated this week and are delivering data. After a commissioning phase of 6 months, MetOp-B is expected to replace the services of MetOp-A as prime operational spacecraft. 37)

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Figure 24: First MetOp-B MHS data of orbit 110 on Sept. 25, 2012 over parts of Europe (image credit: ESA)

• On Sept. 20, 2012, EUMETSAT took control of MetOp-B operations, following the three-day LEOP (Launch and Early Orbit Phase) conducted by the European Space Operations Center (ESOC) of the European Space Agency (ESA). 38)

• The MetOp-A spacecraft is operating nominally in 2012 — with the known limitations/restrictions regarding the functions of LRPT, A-HRPT, and the AMSU-A1 channel 7. 39)

• On Oct. 19, 2011, the MetOp-A spacecraft completed its 5th year on orbit. All systems continue to perform excellently. 40)

• In June 2011, EUMETSAT declared ADA (Antarctic Data Acquisition) operational for MetOp-A. The EPS Ground System received next to Svalbard (Spitsbergen) a second ground station at McMurdo, Antarctica due to long-term international partnership agreements of EUMETSAT, NOAA, NSF and NASA. Hence, MetOp -A became the first polar-orbiting environmental satellite to achieve the 65-minute data latency operationally (see ADA project description at end of this file). 41)

• In May 2011, after 4 ½ years of operation, the satellite is performing well. HRPT data transmission continues, but with restricted coverage area due to potential radiation issues; Eumetsat increased the coverage from January 2011. The assessment review and trend analysis shows that MetOp-A could operate for another six years or more, well beyond its design life. 42)

• MetOp-A is operating nominally in January 2011. The spacecraft completed its 4th year on orbit in October 2010. All instruments are performing excellently, with a few exceptions: Eumetsat discontinued the LRPT (Low Rate Picture Transmission) service in 2007 and AMSU-A1's channel 7 was declared as failed in 2009. The A-HRPT data transmission continues in restricted coverage area due to radiation potential issues. 43)

- GOME-2 is operating well, although an investigation group has been set up to evaluate the in-orbit throughput degradation which could lead to some limitations in science data. MetOp-A deorbiting studies have started, planning for the first maneuvers around the MetOp-C launch date.

- Since its launch in 2006, the MetOp-A polar-orbiting satellite has helped transmit data from thousands of animals, oceanographic buoys, weather stations, and other platforms around the world with its on-board Argos-3 instrument. As of January 2011, there are over 20,000 active Argos transmitters on platforms ranging from high-tech oceanographic buoys and weather stations to the heads of elephant seals. Polar-orbiting satellites such as MetOp-A play their part in the Argos system by relaying the data they receive from Argos transmitters back down to earth for processing. 44) 45)

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Figure 25: Transmitters developed by the University of St. Andrews (UK) are used to collect information from animals (image credit: EUMETSAT)

- On 18 January 2011, EUMETSAT commenced its extended AHRPT (Advanced High Resolution Picture Transmission) communication service. This enhancement effectively extends the geographical coverage of the AHRPT service to parts of Africa, Asia and the Pacific region where previously users were unable to receive the service. For the first time since the start of zone-based operations, transmissions will take place over ascending portions of the orbit, thereby further benefiting currently served geographic zones. Figure 26 indicates the new coverage zones for both descending and ascending passes. For spacecraft safety reasons, the service still maintains the same operational restrictions when passing over the polar regions and the SAA (South Atlantic Anomaly). 46)

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Figure 26: MetOp-A switch-on zone - effective as of Jan. 18, 2011 as a pre-operational service (image credit: EUMETSAT)

 

• MetOp-A is operating nominally in 2010. All instruments continue to perform excellently in orbit. However, the HRPT-B system is transmitting in restrictive mode. 47)

- On Aug. 27, 2010, MetOp-A completed its 20,000th orbit delivering its data to the EUMETSAT Polar System ground station on Svalbard around lunchtime. 48)

• After more than three years in orbit, the IASI instrument shows very good functional health and very good performances. No symptom of degradation has been observed since launch. From a functional point of view, there is no use of redundancy and no hardware anomaly. - All functional anomalies have a SEU/SET origin. These SEU/SET (Single Event Upset/ Single Event Transient) anomalies had a small but non negligible impact on the instrument availability in the beginning of life. During the first years of operations, a significant number of SEU/SET events occurred mainly over the SAA (South Atlantic Anomaly) region and the polar regions. The consequences were mission outages lasting from a few hours to a few days. 49)

A fruitful cooperation between EUMETSAT, CNES and TAS allowed to implement different ways to minimize the IASI down time w.r.t. SEU anomalies. The instrument availability was improved, and in addition the amount and complexity of operations in case of SEU anomaly was reduced.

• The ASCAT level-2 Soil Moisture products became operational on Dec. 18, 2008. The trial dissemination of Soil Moisture products started on May 26, 2008. 50)

The operational phase of MetOp-A started on May 15, 2007 when the spacecraft was officially declared operational after six months of commissioning. This official start of regular operations marks a new milestone in the ongoing development of the US-European Initial Join Polar System - and for the overall global cooperation between Europe and the US. It should be noted that some calibration and validation activities are still ongoing, and not all Level 1 products are operational yet. 51)

• The geographical coverage of the measured occultations of the GRAS instrument is shown in Figure 27 for Nov. 1, 2006. On that day 660 occultations were recorded, 338 setting ones and 322 rising ones. The coverage is globally homogenous, which demonstrate that GRAS will provide precious profiles over sparsely covered regions such as oceans and polar regions. The required number of occultation per day is 500, which is met with substantial margins. All performances for GRAS as a simple GNSS receiver and as an atmospheric sounder are well within specifications (Ref. 96).

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Figure 27: Geographical coverage of the GRAS occultations within a day period (image credit: ESA)

• The LRPT (Low Rate Picture Transmission) system experienced an on-orbit failure just 11 days after turn-on and the HRPT-A after 6 months of operation - due to harsh particle radiation effects. 52) 53)

After the LRPT and HRPT-A subsystems failed, EUMETSAT engineers tested the system components in the laboratory and found that a component common to both failed instruments as well as the still functional HRPT-B was susceptible to impacts from particles with high linear energy transfer (LET). Particles with high LET are heavy energetic particles that create enough charge separation as they pass through semiconducting material to cause damage. Activation of the HRPT-B system was delayed until a plan could be developed to operate the instrument safely given its vulnerabilities. That plan required a better understanding of the space particle radiation environment, particularly the heavy ion population.

However, the cooperative effort of engineers and space physicists from EUMETSAT, NOAA and NRL (Naval Research Laboratory) salvaged some of the capability of the HRPT by identifying limited areas in the spacecraft's orbit with low particle radiation where the remaining HRPT-B subsystem could be used safely. Upon completing the analysis of anomaly rates, NOAA physicists provided EUMETSAT operators with 3 sets of tables containing anomaly rates as a function of geographic latitude and longitude. The new operating mode accommodated customers in need of local weather forecasting data while still protecting the instrument and extending the lifetime. Due to these efforts the HRPT-B has been in use since September 2008 lasting now 3 times as long as its failed counterpart (Ref. 52).

• On Oct. 27, 2006, the ASCAT instrument was switched on for measurement.

• On 26 October 2006 the GRAS instrument was switched on. Within 23 seconds the instrument tracked a first GPS satellite, and 64 seconds after the first navigation solution was achieved. On 27 October, the instrument was switched to occultation mode and the first occulting GPS satellites were measured (Ref. 96).

• The SIOV (Satellite In-Orbit Verification) phase started Oct. 23, 2006, following the Metop-A handover from the LEOP service, performed by ESA/ESOC, to EUMETSAT. After a very intense period, some anomalies and many successes, the SIOV activities eventually came to an end and the SIOV Review formally closed this phase on 29 March 2007. 54)

• After separation from the launcher Fregat upper stage, the satellite entered an automated sequence which allowed to initialize its in-orbit operations. The solar array was deployed successfully, and the attitude acquisition and control sequence was executed nominally. The deployment of several antennas was also performed flawlessly. First orbit correction maneuvers were achieved with very good accuracy, and the Launch and Early Orbit Phase (LEOP) operations were concluded, allowing the start of the commissioning phase.