Position-Velocity Aiding of a Mitel ORION Receiver for Sounding-Rocket Tracking

Abstract

The paper describes a simple and effective concept for aiding the signal acquistion of a GPS receiver in sounding rocket applications. A segmented, low-order polynomial representation of the norminal flight path is employed to provide the receiver with approximate position and velocity values of the host vehicle. These are used for an open-loop Doppler and visibility prediction, which in turn assists the channel allocation and code search. The prosposed concept has been implemented in the 12-channel GPS Orion receiver, which employs Mitel`s GP 2000 chipset and suports firmware modifications via the Architect developer kit. Using hardware-in-the-loop simulations in a GPS signal simulator testbed, the modified receiver`s robustness against temporary signal losses has been demonstrated. While the unaided receiver is essentially unable to reacquire signals in case of intermitted signals, the position-velocity aiding allows a stable and reliable operation both during the boost and free-flight phase. Test flights on actual sounding rockets are currently planned for spring (Kiruna) and summer (Alcantara, VS30/Orion) of 2001.