Development of a Spaceborne GPS Receiver for Precise Relative Navigation of Formation Flying Small Satellites

Use of the differential carrier phase measurements of the Global Positioning System (GPS) can achieve centimetre-level accuracy thus it can be applied to the relative positioning in formation flying missions. This paper describes the development of a spaceborne GPS receiver upon the UNSW’s Namuru GPS receiver, which is built on the field of field programmable gate array (FGPA). Operating a GPS receiver in low earth orbit (LEO) spacecraft represents a significant challenge compared to normal terrestrial operation. To achieve a high relative accuracy, the spacecraft’s relative navigation algorithms should be carefully designed to deal with the carrier phase measurements. The firmware of the Namuru receiver is revised to address on the concerns of in-orbit operation as well as the precise relative navigation by using the carrier phase measurements of the Namuru receiver. The Spirent GSS6560 GNSS signal simulator is used to test the Namuru receiver as well as the relative navigation algorithm. For two LEO satellites in a 400 km orbit with a separation of 6 km, the relative position of centimetre accuracy has been successfully obtained from the Namuru receivers in the simulations.