VISUAL PHOTOMETRIC EXPERIMENT - A GETAWAY SPECIAL PAYLOAD ABOARD STS-042

Visible-light sensors were flown aboard the Space Shuttle in order to measure, without contamination by atmospheric airglow, the zodiacal li ght (sunlight reflected from interplanetary dust). A photomultiplier t ube and four selectable optical filters constituted the primary sensor . This filter-wheel photometer was supplemented by two video cameras, which imaged star fields for aspect determination and provided an asse ssment of contaminating radiation. The suite of instruments was config ured as part of a Getaway Special (GAS) experiment, in order to obtain the measurements at the lowest possible cost. As a GAS payload, the i nstruments were required to operate nearly autonomously. The payload h ad no gimbaled optics and no influence on the attitude timeline of the space shuttle. Only the enabling and disabling of data collection in accordance with prelaunch scheduling was controlled by the GAS payload specialist. Despite these limitations, the diffuse character of the z odiacal light permitted the serendipitous measurements described here. Several scans across the zodiacal dust plane were recorded, and provi ded peak brightness values for the zodiacal light at several solar elo ngation angles. A preliminary analysis of data redundantly recorded on a VHS audio track indicates ratios of zodiacal-light brightness in th ree spectral bands that are comparable to solar brightness ratios, con firming a result obtained previously with a balloon-based experiment.