GPS Orion Receiver Development

Status: Completed project
Type: GPS Receiver Algorithms Development

For use on low Earth orbit satellites and other space applications, numerous software modifications and enhancements have been made to the original firmware of the Orion receiver. These modifications include the fixes related to the implicit assumption of a low speed vehicle in the Doppler prediction and the time tagging error of the raw measurements. Aside from these fixes, an open-loop Doppler and visibility prediction algorithm has been added to the receiver code to ensure a robust tracking and rapid signal acquisition under the conditions of a high-dynamic space vehicle. Also, an active alignment of measurement epochs and navigation solutions to the integer second of GPS system time has been implemented, which ensures synchronized measurements among multiple independent receivers. To improve the overall navigation performance of the Orion receiver, integrated carrier phase measurements have been made available using a 3rd order phase lock loop (PLL) assisted by a 2nd order frequency lock loop (FLL). The loop provides accurate tracking and stable acquisition over a wide range of dynamic conditions. Raw measurement accuracies obtained in signal simulator tests are better than 1m for C/A code pseudorange, 1mm for L1 carrier phase, and 10cm/s for L1 Doppler measurements in the absence of environmental error sources such as multipath.

For more information, go to the project website.

Personnel Bill Bamford Takuji Ebinuma Greg Holt Glenn Lightsey Shaun Stewart

Facility GPS Lab UT Center for Space Research Austin, TX, 78712 Satellite Design Lab W.R. Woolrich Laboratories 210 E. 24th Street. Room 407 Austin, TX, 78712

Related Publications

Conference Papers
G. Holt, E.G. Lightsey, and O. Montenbruck, "Benchmark Testing for Spaceborne Global Positioning System Receivers," AIAA Guidance, Navigation & Control Conference, August 2003. Austin, TX.
See full text.

S. Stewart, G. Holt, "Real-Time Attitude Determination of a Nanosatellite Using GPS Signal-to-Noise Ratio Observations," 19th Annual AIAA/USU Conference on Small Satellites, Logan, UT, August, 2005.See full text.

Conference Presentations
G. Holt, E.G. Lightsey, O. Montenbruck, "Benchmark Testing For Spaceborne Global Positioning Receivers," AIAA GNC Conference, Austin, TX, 2003.See full text.

S. Stewart, G. Holt, "Real-Time Attitude Determination of a Nanosatellite Using GPS Signal-to-Noise Ratio Observations," 19th Annual AIAA/USU Conference on Small Satellites, Logan, UT, August, 2005. See full text.

Master's Thesis
Rogstad, E., "Testing and Development of the UT Orion GPS REceiver," Masters Thesis, The University of Texas at Austin, August 2008. See full text.

Research Reports
Rogstad, E., "UT Orion Users Guide," The University of Texas at Austin, August 2008. See full text.