ERS-1 Orbits

: ERS-1 Orbit. Credits Heavens Above.

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).