microGPS: On‐Orbit Demonstration of a New Approach to GPS for Space Applications

In February 1998, the Student Nitric Oxide Explorer (SNOE) was successfully launched and began scientific observations. In addition to three instruments designed by the University of Colorado's Laboratory of Atmospheric and Space Physics to study nitric oxide in the atmosphere, the spacecraft carried a 600 gram GPS receiver designed and built by the Jet Propulsion Laboratory (JPL). This receiver, known as microGPS, is a combination of simple low‐power hardware and portable, efficient software that was developed by JPL for spacecraft navigation in earth orbit. It is intended for micro‐ and nano‐satellite applications in which mass and power budget margins are especially limited or as a robust second string to a conventional GPS receiver on board any satellite. This paper describes on‐orbit operational experience with the microGPS receiver on the SNOE spacecraft. It also previews the next‐generation, dual‐frequency microGPS receiver, to be launched in 2000 on the Space Technology Research Vehicle (STRV‐1c), a geostationary transfer orbit spacecraft. Comparisons are made between the expected performance of microGPS and actual observations. The design, expected, and actual performance of the orbit determination software, which is rooted in the techniques and algorithms pioneered in JPL's high‐accuracy GIPSY/OASIS II software, is also described.