ERS

In the 1990s, the European Space Agency ESA launched two ERS (Earth Remote Sensing) satellites.

In July 1991 ESA’s first earth observation mission was launched into space with ERS-1. Its payload consisted of five instruments: AMI (Active Microwave Instrument), which provided the functions of an imaging synthetic aperture radar (SAR) and a wind scatterometer; RA (Radar Altimeter); MWR (Microwave Radiometer); ATSR (Along Track Scanning Radiometer); and PRARE (Precise Range and Range-rate Equipment). The ERS-1 mission ended on March 10, 2000 after more than 45,000 orbits.

Tabelle: ERS-1 Mission Parameters

Dimensions	12 m × 12 m × 2.5 m
Total mass	2.16 t
Payload	888 kg
Number of instruments	5
Launcher	Ariane 4
Launch	July 1991
End of mission	March 10, 2000

Table: ERS-1 Orbit Parameters

Semi-major axis	7159 km
Orbit altitude (mean)	782 km
Inclination angle	98.5°
Orbital period	100 min
Orbit	polar, sun-synchronous
Overflight time	absteigender Knoten 10:30 Uhr vormittag
Orbits per day	14.3
Revisit	35 days (optionally 3 days or 168 days with slightly different orbit parameters)

The successor to ERS-1, the earth observation mission ERS-2 (Earth Remote Sensing Satellite 2), was launched in April 1995. For several years, both ERS satellites simultaneous monitored our home planet. ERS-2 has the same instrument suite as ERS-1 on board, with the addition of GOME (Global Ozone Monitoring Experiment) a sensor developed to study earth’s atmosphere. After 15 years in orbit, ERS-2 is still supplying valuable data, and this long-term availability makes it possible to generate lengthy time series, an important resource for climate studies.

Tabelle: ERS-2 Missionsparameter

Dimensions	11.8 m × 11.7 m × 2.4 m
Total mass	2.52 t
Payload	1.0 t
number of instruments	6
Launcher	Ariane 4
Launch	April 21, 1995

Tabelle: ERS-2 Orbit Parameters

Semi-major axis	7147 km
Orbit altitude (mean)	785 km
Inclination angle	98.5°
Orbital period	100 min
Orbit	polar, sun-synchronous
Overflight time	descending node, 10:30 am
Orbits per day	14.3
Revisit	35 days

….. More on ERS at the ESA Website