GPS Tracking of a Nanosatellite – The CanX-2 Flight Experience

Kurzfassung

CanX-2, which was launched in April 2008, is a Canadian “triple-CubeSat” satellite that carries a dualfrequency GPS receiver to assess the feasibility of ionospheric profiling from a nanosatellite platform. A NovAtel OEM4-G2L receiver is employed on CanX-2, which offers geodetic grade measurements at favorably low power. While various other CubeSats have carried GPS receivers into space before, CanX-2 is apparently the first mission to successfully deliver GPS navigation fixes and raw measurements thanks to proper attitude control and onboard data handling systems. Even though the achieved signal quality falls below expectations due to limitations of the employed antenna system, the receiver provides both L1 C/A tracking and semicodeless L2 P(Y) tracking on a regular basis. The paper presents the CanX-2 GPS subsystem, the receiver qualification for space use and the necessary tasks for receiver operations. The in-flight performance is characterized in terms of tracking coverage, raw measurements and navigation accuracy. Furthermore, shortarc precise orbit determination results based on dual-frequency carrier phase measurements are presented, which are considered to be accurate to the meter level.