Julie Anton (Thales Alenia Space, France); Halima Jmili (Thales Alenia Space, France); Sébastien Trilles (Thales Alenia Space, France); Thierry Authié (Thales Alenia Space, France); Flavien Mercier (CNES, France)

LEO observation missions now require orbit solutions with increasing accuracy and shorter time delays. These orbit solutions could be processed on ground, as well as on board in some cases.
The targeted accuracy is better than 30 cm 3D RMS (Root Mean Square) for single frequency GPS measurements (code-phase iono-free combination). To assess this level of performance, we have been working on the Gokturk data and Merlin (TOPSTAR receiver). Meeting these requirements has been possible by developing a new in house real time POD software. Thales Alenia Space and CNES have developed a set of algorithms and software that satisfy these needs using a SRIF (square root information filter) formulation. This software can also process dual-frequency measurements, as was validated on Jason 3 and METOP-A.
A least squares SRIF formulation has also been implemented in order to cross validate our results and tune the real time solution. Performance results for both formulations are presented and discussed in this paper.