The Pioneer-Venus Solar Flux Radiometer

Abstract

The goals, design and performance characteristics of the Solar Flux Radiometer flown on the Large Probe of the Pioneer-Venus Multiprobe spacecraft launched on 8 August 1978 are described. Radiance measurements of the Venusian atmosphere in several spectral channels between 400 and 1800 nm as a function of altitude were made to further understand the role of solar radiation in the thermal balance of the atmosphere. Elevation and azimuthal measurements on the radiation field were made with five optical channels. Twelve filtered Si and Ge photovoltaic detectors were maintained near 30 C with a phase-change material. The detector output currents were processed with logarithmic transimpedance converters before being multiplexed and digitized with an 11-bit A/D converter. Atmospheric sampling in both elevation and azimuth was done according to a Gaussian integration scheme. The data output was serial digital at an average rate of 20 bits/sec and included housekeeping (sync, spin period, sample timing and mode). The received data were used to determine the deposition of solar energy in the atmosphere of Venus between 67 km and the surface along with upward and downward fluxes and radiances with an altitude resolution of several hundred meters.