In Situ Measurements of the Photometric Properties of an Area on the Lunar Surface*

Abstract

A preliminary determination has been made of the photometric properties of the lunar surface from high–resolution pictures received from the Surveyor I spacecraft. Several target areas were chosen at selected locations around the spacecraft, and photometric measurements were taken with the television camera throughout the lunar day. Surveyor I data agree within ±20% with the terrestrially observed photometric properties. Initial examination of the data indicates no anomalies of the photometric properties of homogeneous areas on scales greater than 6 cm in diameter. Luminance factors were estimated from the observed data and ranged from 7.0% to 7.5% for more than 91% of the area; however, values of 5% to 25% were recorded in some locations. The chromaticity coordinates of the disturbed area near one of the footpads were found to be very close to natural sunlight on a gray paint. A preliminary estimate of the spectral radiance factor of this area is given, using an eigenvector-analysis technique. The spacecraft characteristics, viewing geometry, and ground-recording techniques are included, along with a brief description of errors.