John Moyard (cnes, France); Alexandre Couhert (cnes, France); Robert Cullen (esa, Netherlands)



The Sentinel. 6 satellite has a new platform, with a very different geometry from the preceding missions like Jason 1,2,3. The main difference is that the solar array panel is now fixed on the satellite body, and the satellite has a fixed attitude in the local orbital frame (with small rotations for geodetical pointing and ground velocity alignment). As a consequence the sun direction relative to the panels has important variations along one orbit.

On Jason 3 the illumination of the solar array panels is always close to the normal direction : as a consequence the solar radiation pressure force produced by the panels has a well defined direction independent of the material coefficients. Also, the amplitude does not depend on the balance between the electrical energy production of the array and the material thermally absorbed part. This thermally absorbed part has no impact on the global force, due to a similar re-radiation on both surfaces of the panels.

On Sentinel 6, this property does not hold anymore, and the standard modeling of the panel surfaces (with absorbed, diffuse and specular parts), with correction for the re-radiated part, does not lead to satisfactory results.

Here, we analyze the solar array thermal behavior thanks to in flight information (temperatures variations along the orbit, for different sun orbital angle cases, and energy production of the array). A thermal model is constructed using thermal coefficients adjusted on these flight data (thermal capacity of the panels).

An updated solar radiation pressure model is then constructed.