LEO-SLR - Improved kHz-SLR Tracking Techniques and Orbit Quality Analysis for LEO-Missions

Earth observation missions in general and gravity field sensors in particular are naturally designed as low Earth orbiting spacecraft (LEO) with orbit heights of about 200-500 km. In order to fulfil the challenging mission objectives, the precise knowledge of the satellite orbit in space becomes a crucial concern. For these missions precise orbit information is normally provided by GPS / SST observations supported by satellite laser ranging (SLR).

Short Description

Numerous present and future satellite missions, such as CHAMP and GOCE, are dedicated to provide valuable data for many Earth science related disciplines.

The role of SLR is primarily devoted to serve as an independent external tracking instrument used to calibrate and validate the on-board microwave tracking system. However, the very limited visibility of LEOs from SLR ground stations combined with the accordingly high angular rates of the satellite passes make it very difficult to track LEO missions.

At the Lustbühel Observatory the Space Research Institute of the Austrian Academy of Sciences operates a very novel SLR facility which was continuously upgraded during recent years and is today the only station worldwide capable of operating at kHz-firing rates.

The latest improvements focus on a number of further hardware upgrades and methodical improvements of the SLR facility aiming for a faster and utmost reliable target acquisition. These include upgrades of laser tracking algorithms as well as a redesign of the laser detection package tailored to LEO spacecraft. This increases the number of observations per pass and further improves the normal point accuracy as well as the overall system performance for LEO tracking, such as the pointing accuracy or the range gate control.

Another task addresses both, a geometric and dynamic arc comparison of SLR derived orbits with GPS/SST orbit solutions. The resulting one-way SLR range residuals obtained from CHAMP allow to draw conclusions on the precision of orbit solutions.

Investigations are carried out in an analogous manner by means of simulated GOCE SLR observations. An approach for a quality check of gravity field solutions by means of the detection of inaccurate potential coefficients is outlined, based on simulated GOCE orbits, succeeding gravity field solutions and SLR observations, respectively.

Project Partners

Coordinator

Institute of Space Research, Austrian Academy of Sciences - Walter Hausleitner

Partners

Institute of Navigation and Satellite Geodesy (INAS), Graz University of Technology - Roland Pail

Contact Address

Institute of Space Research
Austrian Academy of Sciences
Walter Hausleitner
Schmiedlstraße 6
A-8042 Graz
E-mail: walter.hausleitner@oeaw.ac.at
Web: www.iwf.oeaw.ac.at