Orbit

Sentinel-1 will be in a near-polar, sun-synchronous orbit with a 12 day repeat cycle and 175 orbits per cycle for a single satellite. Both Sentinel-1A and Sentinel-1B share the same orbit plane with a 180° orbital phasing difference. With both satellites operating, the repeat cycle is six days.

Sentinel-1 constellation

Figure 1: Sentinel-1 Constellation

 

In particular for interferometry, Sentinel-1 requires stringent orbit control. Satellite positioning along the orbit must be accurate, with pointing and timing/synchronisation between interferometric pairs. Orbit positioning control for Sentinel-1 is defined using an orbital Earth fixed "tube", 50 m (RMS) wide in radius, around a nominal operational path. The satellite is kept inside this "tube" for most of its operational lifetime.

Figure 2: Sentinel-1 Orbit Tube

 

The following table contains a summary of useful orbital information for Sentinel-1A and –1B:

Altitude

Inclination

Period

Cycle

Ref. tube deviation

Local Time at Descending Node

693 km

98.18 deg

98.6 min

12 days

+- 100 m

18:00 hours

 

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