GPS tracking of microsatellites - PCSAT flight experience

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GPS tracking of microsatellites - PCSAT flight experience

Leung, Sunny / Montenbruck, O. / Bruninga, B.

An experimental GPS receiver modified and built by the German Space Operation Center at DLR was integrated into the PCsat Prototype Communication satellite as an experimental payload, which provides an excellent opportunity to study the operation and performance of the receiver onboard a microsatellite flying in a low Earth orbit. A series of GPS tracking experiments had been carried out in the past 12 months. Results obtained from these experiments demonstrated both the 'hot' and 'warm' start capability of the GPS receiver, with an achieved time-to-first-fix in no more than 60 sec and 3 min correspondingly. GPS tracking data suggested accurate tracking performance of the receiver, despite infavorable tracking condition. On average the receiver tracked 10-11 GPS satellites out of the possible 12 available tracking channels. The large number of tracked GPS satellites from an elevation angle of -15 degree, led to a favorable geometry for the single point navigation solution, where an average PDOP value of unity was observed. Despite such tracking condition, the onboard navigation solution yields a 3D r.m.s. of about 10-15 m due to the presence of measurement outliers.