GPS Receiver Satellite/Antenna Selection Algorithm for the Stanford Gravity Probe B Relativity Mission

This paper presents a GPS receiver satellite/antenna selection algorithm for the Stanford Gravity Probe B Relativity Mission. A Trimble Advanced Navigation Sensor Vector receiver onboard the space vehicle, a fourantenna six-channel GPS receiver, will provide real-time navigation solutions for orbit trim and raw measurements for ground post-processing, both for more accurate position and velocity and for attitude solutions. The GPS receiver satellite/antenna selection algorithm will determine the visibility of GPS satellites and assign a satellite and a master antenna to each receiver channel in order to maintain signal tracking. In this paper a new four-step GPS satellite selection algorithm is presented, which shows good performance with much less computations compared to the conventional algorithms. The smooth transfer between subsequent GPS satellite sets is also considered in the algorithm, such that continuity of the navigation data is maintained. The antenna selection algorithm is designed to maximize the signal to noise ratio of each master antenna. This paper also presents simulation results of performance comparisons of this new algorithm with conventional algorithms.