Pioneer Venus Occultation Radio Science Data Generation

Previous to the Pioneer Venus Orbiter mission, occultation radio science data were generated at the Deep Space Stations of NASA's Deep Space Network via the analog recording of the baseband frequency output signal of a relatively wide bandwidth open-loop receiver. Signal digitization was a separate and subsequent operation at the Jet Propulsion Laboratory. During Pioneer Venus Orbiter radio science operations, the open-loop receiver baseband frequency output signal bandwidth was substantially reduced. This was made possible by programming the open-loop receiver first local oscillator with the predicted Doppler frequency profile. In addition, the receiver output signal was digitized and recorded directly on computer compatible magnetic tape in real time. Initial results obtained with this new process, referred to as "real-time bandwidth reduction," during the prime Pioneer Venus Orbiter mission, compare very favorably to results obtained with the previous occultation system.