Spin-Scan Cloudcover Camera (SSCC)

Description

The ATS 1 Spin-Scan Cloudcover Camera (SSCC) was designed to provide nearly continuous observations of cloudcover patterns over the whole sunlit earth disk. The optical system consisted of a two-element Cassegrain-type telescope. Light entering the system was reflected from a 13.7-cm-diameter (25.4-cm focal length) primary parabolic mirror onto a flat secondary quartz mirror to produce an image on the face of an aperture plate. The light then passed through the 0.025-mm-diameter aperture and a haze filter to impinge on a photocathode in front of a photomultiplier tube. The telescope photomultiplier assembly could be tilted in discrete steps from +7.5 to -7.5 deg to produce a north-south scan, corresponding to an earth coverage from 52 deg N to 52 deg S. The east-to-west scan was provided by the spin of the satellite itself. Twenty minutes were required to scan one picture, and 2 min to retrace it at a nominal satellite rotation of 100 rpm. From its geosynchronous orbit the camera system had a ground resolution of better than 4 km at the subsatellite point. The experiment was highly successful through October 16, 1972. For a listing and description of the different forms of photographic data available from this experiment and their location, see the "Meteorological data catalog for the Applications Technology Satellites" (TRF B09264), available through NSSDC.