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Designation 23560 / 95021A
Launch date 21 Apr 1995
Country of origin Europe
Mission Remote sensing
Perigee/Apogee 783/786 km
Inclination 98.6°
Period 100.5 min
Launch vehicle Ariane V72

Cost: FRF 3.1 billion including FRF 2 billion for the satellite. The launch was not insured

It had gyroscope problems and was reprogrammed to operate without gyroscopes in early 2001 with the help of the Digital Earth Sensor. With some improvements, such as noise filtering, the instrument is now used to estimate pitch and roll errors. That still left the final yaw (or downward) pointing error, which could no longer be measured by the gyro-less spacecraft. The yaw drift can be checked on the ground by analysing Doppler frequency shifts in the ERS-2 radar instrument signals. However, processing the raw signal takes up to three hours, too long to keep the spacecraft correctly orientated in real time. Instead, ERS 2 was monitored over a 105-day period of time, during which recurring patterns that cause spacecraft mispointing were recorded. These patterns, mainly caused by terrestrial magnetic field variations as well as pressure from the solar wind, were rendered into a detailed model and uplinked to the satellite. This enables mispointing to be anticipated and compensated for.

In Jun 2003 the low bit rate recorder failed and a network of ground stations wat setup to collect most of the data in near-real time.

Still operating well in Apr 2010 (15 years anniversary)

End of life

Out of service Jul 2011
Cause Retired. Orbit to be decreased to 550 km to provide quicker de-orbit
Decay planned in 2030-2040

External resources

sat-index articles

Technical data


Prime contractor Dornier
Platform MMS Spot Mk 1
Mass at launch 2500 kg
Payload mass 1100 kg
Dry mass 2080 kg
Length 11.8 m
Solar array 11.7 x 2.4 m
SAR antenna 10 x 1 m
Radar altimeter 1.2 m (diameter)
Stabilization 3-axis
DC power 2500 W
Design lifetime 3 years

Downlink: 2225 MHz

AMI (Active Microwave Instrument)

Frequency 5.3 GHz (C-band)
SAR resolution 26 m
SAR swath width 99 km
Scatterometer resolution 47 km
Scatterometer swath width 613 km (fore and aft)
809 km (mid)

Mission: payload all-weather high-resolution images of land and ocean, windspeed and direction, ice mapping, pollution monitoring.

RA (Radar Altimeter)

Frequency 13.8 GHz (Ku-band)
Accuracy (wave height) +/- 0.5 m
Altitude accuracy 0.1 m

Mission: windspeed and sea surface elevation, ice sheet topography.

ATSR (Along-Track Scanning Radiometer)

Wavelengths 1.6, 3.7, 10.8 and 12.0 µm
Accuracy (sea surface temperature) +/- 0.5 K

Mission: images of sea surface temperature, total water vapour content of atmosphere, cloud, aerosols, haze, land and ice surface emissivity.

Microwave Sounder

Frequency 23.8 and 36.5 GHz
Altitude accuracy 0.02 m

GOME (Global Ozone Monitoring Experiment)

Waveband 0.24-0.79 µm
Resolution 40 x 40 km max. (horizontal)
1 km (vertical)
Swath width 120-960 km

Mission: stratospheric and tropospheric ozone profiles, cloud distribution and surface spectral reflection.

Also equipped with Laser Reflectometer (LR), Precise Range and Range-rate Equipment (PRARE) and Instrument Data Handling and Transmission (IDHT). The on board tape recorder (6.5 gigabit) can store data from a full orbit.

The telemetry is sent in S-band. The scientific data and a replication of the telemetry is sent on 2 X-band transponders.

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