Precise Orbit Determination of Low Earth Satellites at AIUB using GPS and SLR Data
Jäggi, Adrian; Bock, Heike; Thaller, Daniela; Baumann, Christian; Sosnica, Krzysztof; Meyer, Ulrich; Dach, Rolf
Astronomical Institute, University of Bern, SWITZERLAND

The Astronomical Institute of the University of Bern (AIUB) has a well-documented record concerning the scientific analysis of Global Navigation Satellite System (GNSS) data with the Bernese GNSS Software. The Center for Orbit Determination in Europe (CODE), a global analysis center of the International GNSS Service (IGS) located at AIUB, generates the full IGS product line, in particular GNSS orbits and high-rate satellite clock corrections, which are a prerequisite for spaceborne GPS applications.

Precise kinematic and reduced-dynamic orbits relying on the CODE products are generated at AIUB for a variety of Low Earth Orbiting (LEO) satellites. So-called pseudo-stochastic orbit modeling techniques have been developed and refined in the previous decade and allow for efficient and flexible LEO precise orbit determination (POD) from spaceborne GPS data. Currently, the procedures are used by AIUB to derive the Precise Science Orbits for the GOCE High-level Processing Facility (HPF).

The Bernese GNSS Software has recently been extended from a pure GNSS processing software to a package also offering full capabilities for processing Satellite Laser Ranging (SLR) data. Identical orbit modeling techniques as used for GPS-based LEO POD are applied when processing SLR data to solve for orbital parameters together with SLR station coordinates, Earth rotation parameters, SLR-specific range biases, and geopotential coefficients. Currently the procedures are used at the Bundesamt für Kartographie und Geodäsie (BKG) to compute the SLR solutions for the International Laser Ranging Service (ILRS) in the frame of the BKG analysis center activities.

We discuss the methods of LEO POD and illustrate their use for classical orbit determination based on undifferenced GPS data, e.g., for the GOCE and Jason-2 satellites, for space baseline determination based on double differenced GPS data, e.g., for the TerraSAR-X and TanDEM-X satellites, and for SLR-based orbit determination of spherical satellites, e.g., for the LAGEOS, LARES, Starlette, Stella, and Ajisai satellites. First experience with the Bernese GNSS Software has been gained as well for combined orbit determination from GPS and SLR data. We present the state of research in this rather new branch at AIUB using data from Jason-2.