Abstract
NASDA is developing a multiple channels and multi-functional GPS (Global Positioning System) receiver for space applications (Ref. 1). It has 48 or more channels and multi-antennas for attitude determination or dual frequencies processing. It also has rapid acquisition function using a matched filter technique in order to recover from momentary lock-loss. The development of the new GPS equipment provides an attractive navigation system for Launch Vehicle (LV). Depending on the number of GPS antenna, their configuration and the satellite geometry, the visibility of satellite and the navigation accuracy will vary. This paper presents the work to be done during the planning stage of setting up a GPS multi-antenna system is to properly select the antenna configuration to maximize the coverage of multi-antenna and the navigation performance. Visibility analysis has been performed oh two typical trajectories of LEO and GTO mission. Based on the results from this research, the multi-antenna system with five antennas is recommended for the LV applications. At least four satellites are in view at any times on the trajectories using the five antenna configuration. The simulation results show the average of GDOP (Geometrical Dilution Of Precision, which is geometric index of navigation accuracy) is below 5.0 during the angler velocity of 40 deg/s.
