Low noise signal processing technique for monopulse pointing of DSN 34-meter diameter antennas

This paper describes a 31.8-32.3 GHz (Ka-band) monopulse antenna pointing system designed to meet a pointing precision requirement of a mean-radial-error (MRE) less than 1.5 milli-degrees for a 34-meter diameter antenna with a 17 milli-degrees 3-dB beam-width, under windy conditions up to 15 mph. The high precision is required for the Ka-band radio science experiments requiring high stability in the detected signal power. While the concept of monopulse pointing is not new, its application here is novel in that it is a physically large system tracking very weak signals with extremely fine pointing requirement. This system is modeled and analyzed as an equivalent phase-locked loop in each axis, azimuth and elevation, and also simulated as a two-dimensional system, including the cross-correlation between the two axes. Analysis and simulations agree. It is concluded that when implemented, the technique will meet the stated pointing requirement down to a signal-to-noise power spectral density ratio of 17 dB-Hz