Citation
Abstract
This article presents the results of an investigation of ground antenna pointing errors which are caused by fluctuations of the receiver AGC signal due to thermal noise and a spinning spacecraft. Transient responses and steady-state errors and losses are estimated using models of the digital Conscan (conical scan) loop, the FFT, and antenna characteristics. Simulation results are given for the on-going Voyager mission and for the upcoming Galileo mission, which includes a spinning spacecraft. The simulation predicts a I-sigma pointing error of 0.5 to 2.0 mdeg for Voyager, assuming an AGC loop SNR of 35 to 30 dB with a scan period varying from 128 to 32 sec, respectively. This prediction is in agreement with the DSS 14 antenna Conscan performance of 1.7 mdeg for 32-sec scans as reported in earlier studies. The simulation for Galileo predicts I-mdeg error with a 128-sec scan and 4-mdeg with a 32-sec scan under similar AGC conditions.
Details
- Volume
- 42-95
- Published
- November 15, 1988
- Pages
- 246–260
- File Size
- 554.5 KB