Computation of Satellite Orbits

Precise satellite orbits are a prerequisite for the determination of accurate and reliable geodetic parameters such as station coordinates, Earth Orientation Parameters (EOP) and coefficients of the Earth gravity field. The computation of satellite orbits is done at DGFI-TUM with its own developed software package called 'DGFI Orbit and Geodetic parameter estimation Software' (DOGS).The software is used in order to process laser ranging observations to various retro-reflector equipped satellites.

Basically, the currently by DGFI-TUM analyzed satellites can be divided into two main categories: (i) spherical passive satellites such as Etalon 1/2, Lageos 1/2, LARES, Larets, Ajisai, Stella, Starlette, Blits, Westpac1, GFZ-1 and (ii) non-spherical satellites such as JASON-1/2, Cryosat, TOPEX/Poseidon, Envisat, SARAL, HY-2A, Champ, GRACE-A/-B, GOCE and the SWARM constellation which are equipped with an active attitude control system.

In particular the precise orbit determination of non-spherical satellites is a highly challenging task. Various additional observations such as star camera measurements, solar panel rotation angles and fuel consumption measurements have to be taken into account. Furthermore, optical and infrared properties as well as atomic characteristics of the satellite panel areas (satellite body and solar panels) are used in order to accurately model non-conservative perturbations.