ERS-1 Orbits
To carry out its mission ERS-1's orbit had to enable its instruments to scan along predetermined paths designed to give optimum coverage for a set number of orbits. To achieve this, ERS-1 was a three-axis-stabilised, Earth-pointing satellite in yaw steering mode (YSM). The elliptical orbit was sun-synchronous, near-polar, with a mean altitude of 785 km, an inclination of 98.5° and a local solar time at the descending node of 10:30 a.m.
Orbit parameters
for the 35-day orbit
| Main characteristics | |
|---|---|
| Semi-major axis | 7159.5 km |
| Eccentricity | 0.0001042 |
| Argument of perigee | 92.4836° |
| Inclination (sun-synchronous) | 98.543° |
| Auxiliary data | |
| Mean altitude | 782 km |
| Nodal period | 50 min 25.5 s |
| Repeat cycle | 35 days |
| Number of passes per cycle | 1002 |
| Ground track separation at Equator | 80 km |
| Orbital velocity | 7.45 km/s |
For the other repeat periods:
| 3-day | 35-day | 168-day | |
| semi major axis | 7153.138 | 7159.496 | 7147.191 |
| inclination(°) | 98.516 | 98.543 | 98.491 |
| mean altitude (km) | 785 | 782 | 770 |
| orbits per cycle | 43 | 501 | 2411 |
Further information on ERS (Esa website).
Past missions 
