ERS (European Resource Sensing)

The ESA (European Space Agency) ERS satellites’ main mission was to observe Earth, in particular its atmosphere and ocean, through radar techniques. ERS 1 was retired in 2000 and ERS 2 in 2011. ERS 2, which was originally designed to last 3 years, continued to provide its harvest of data for 16 years. ERS 2 carried on board the same sensors as ERS 1. The best known of which is the Synthetic Aperture Radar (SAR) sensor, which was the first commercial radar sensor. ERS 2 was equipped with an additional instrument (GOME), which allows the monitoring of atmospheric ozone.

altitude: 785 km
inclination: 98.52 degrees
orbit: sun-synchronous polar
orbit period: 100 minutes
rvisit time: 3 days
swath width: 5 – 100 km (AMI) - 500 km (ATSR)

AMI (Active Microwave Instrument)
This instrument consists of two different radar systems, namely, a SAR, which can work in image mode or wave mode (in the latter case it measures wave heights), and a wind scatterometer, which is a radar system to measure wind speeds and direction on the sea’s surface. The very great control over their orbits (the satellites’ positions are known with great precision by means of two onboard instruments) and possibility of using two identical SARs have made ERS satellites ideal for interferometric studies.

AMI-SAR: SAR–image mode
Spectral band: C band (5.3 GHz)
Polarisation: VV
Resolution: variable, approx. 20m x 15.8m

RA (Radar Altimeter)
This radar altimeter works in the K band (13.8 GHz) and measures altitude vertical to the satellite with a maximum resolution of 10 m. It has two measuring modes, the ocean mode (which measures wave height, the altitude of the ocean’s surface, and surface wind speed), and ice mode (which gives information on the topography of the surfaces of the world’s ice-covered regions, the type of ice, and sea/ice boundaries).

ATSR (Along-Track Scanning Radiometer)
This optical sensor works in the infrared band and is used to measure sea-surface temperatures (SSTs) and cloud-top temperatures. The version that was on board ERS-1 had four bands, whereas ERS-2’s ATSR comprised seven bands (the three added bands work in the visible light spectrum). At the same time, another radar instrument, the microwave radiometer or MWR, working in two K bands (23.8 and 36.5 GHz), measures the water vapour content of the atmosphere. This increases the accuracy of the sea-surface temperature and altitude (RA sensor) measurements.

GOME(Global Ozone Monitoring Experiment) sensor
This sensor, which was on board the ERS-2 only, is a double spectrometer used to study the atmosphere. It can study the ozone concentration as well as detecting other gases, aerosols, and microparticles.

Spectral band: 0.24–0.79 µm
Resolution: 40km x 40km max. (horizontal) - 1 km (vertical)

20 years of ERS: celebration

Mission website

Data distributor:

ESA