SUMMARYGPS receivers used in car navigation and other applications have been downsized to dozens of grams, with significant gains in power conservation. With the assistance of a vehicle GPS manufacturer, a vehicle GPS receiver has been modified and a space application GPS receiver with ultralow power consumption that generates pseudo-range data has been developed. We expanded the frequency search range for the GPS receiver, and we conducted on-orbit simulations using a GPS simulator and confirmed that the positioning accuracy performance of the receiver is less than 1 m. It has also been confirmed that the receiver has a 20-krad radiation tolerance and that it is latch-up-free with respect to 200-MeV protons. The GPS receiver will be deployed on the small scientific satellite INDEX which is under development by the Aerospace Science Research Department of the Japan Aerospace Exploration Agency.
Miniature space GPS receivers have been developed by means of automobile-navigation technology. We expanded the frequency sweep range in order to cover large Doppler shift on orbit. The GPS receiver was modified to output pseudorange data with accurate time tag. We tested the performance in low earth orbits by means of a GPS simulator. The range error caused by the receiver is measured to be 0.9 meter in RMS. Receiver was on-boarded on INDEX ("REIMEI") satellite, which was launched in 2005. Cold start positioning was confirmed repeatedly to finish within 30 minutes on orbit. The orbit determination was performed to evaluate the random position error of GPS receiver by means of the residual error. The random error of GPS position is as large as 2 meter for PDDP=2.5 on orbit. The RMS value of range error is evaluated to be 0.6m from the flight data. These results on orbit are consistent with the simulation results in use of a GPS simulator. This miniature space GPS receiver is at present in commercial market.
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