Six Channel Spaceborne GPS Receiver

Rockwell International Corporation is developing a lightweight, compact GPS receiver for low earth-orbiting space vehicles. The effort is sponsored by the Defense Advanced Research Projects Agency (DARPA) and monitored by the Air Force Phillips Laboratory. Three flight receivers are scheduled for delivery prior to the end of CY 1991. The first receiver will fly on a technology for autonomous operational survivability satellite planned for launch in 1992. The receiver has six channels that continuously track four primary GPS satellites and sequentially acquire and track all other visible and healthy satellites on the fifth and sixth channels. It performs pseudorange and continuous-carrier, delta range measurements and estimates time-tagged, three dimensional user position and velocity using an eight-state extended Kalman filter. The Rockwell receiver weighs 8.0 pounds and consumes 12.5 Watts of 28 VDC. This paper will review the receiver design, and present performance results obtained by using a multichannel GPS spaceborne Simulation and Evaluation System (SEVS). The SEVS generates six GPS satellite Ll and L2 RF transmissions representing the signal environment for a low earth-orbiting user.