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Flight into the Space - Development of the First Space-grade GPS Receiver in Taiwan

NSPO 2014/02/25

Space-grade GPS receiver is one of the essential components of satellite. It provides timing and navigation information for satellite in order to determine daylight/eclipse condition, attitude reference, antenna pointing direction, payload operation scenario, and so on. However, the space-grade GPS receiver is technology sensitive and usually under export control. Procurement of GPS receiver from foreign country is tedious, difficult, and result of export is uncertain.

In order to overcome export control, to control satellite key technologies, and to increase domestic satellite development capabilities, NSPO has completed development of self-reliant space-grade GPS receiver.

Traditional space-grade GPS receiver is hardware-based; it composed of multiple ASICs and therefore is heavier and power demanding. The hardware-based GPS receiver also has constraint on expansion functionality due to its application-specific IC. It may need 220 days to expand the hardware-based GPS receiver functionality. The most effort is on re-design of the application-specific IC. Besides, the cold start performance of the hardware-based GPS receiver is relative poor due to its nature of time-domain signal search mechanism.

NSPO developed space-grade GPS receiver is pure software-based receivers which uses only generic chips. Generic chips are usually not so technology sensitive compare to application-specific IC. The NSPO software-based GPS receiver uses fewer chips and therefore consumes less power and lighter in mass. Besides, if functionality expansion is required, only software changes is needed and could be completed in around 40 days.

Moreover, the receiver implements advanced algorithms therefore features high degree of fault tolerance and much better cold start performance. Usually satellite occur failure once every 3 months. For traditional hardware-based GPS receiver, it takes more than 8 minutes to complete the cold start. For a typical low earth orbit (LEO) satellite, the satellite ground contact time is around 12 minutes. Therefore, it may take two orbits time to recover the satellite back to nominal operation status. Which means the satellite is in a dangerous state for more than 3 hours. For NSPO software-based GPS receiver, its cold start time is only 1.5 minutes, when satellite failure occurred; ground station is able to recover the satellite back to its operation state in one ground contact, i.e. 12 minutes.

The NSPO space-grade GPS receiver has passed its qualification tests and planned to flight on board the FORMOSAT-7 Self-Built Satellite. This GPS receiver features excellent performance and not very expansive in cost. It will be flight with FORMOSAT series satellite in the near future and has potential to enter to satellite component market.

In the future, considering market grow up of small size satellite and therefore miniaturization of satellite components. NSPO will keep improving performance of the GPS receiver, include optimization of navigation performance and reduce power consumption and mass..