Multicolor Spin-Scan Cloudcover Camera (MSSCC)

Description

The ATS 3 Multicolor Spin-Scan Cloudcover Camera (MSSCC) represented a significant advance over a similar but monochromatic spin-scan camera on ATS 1. The MSSCC was mounted with its optical axis perpendicular to the spacecraft's spin axis and viewed the earth through a special aperture in the spacecraft's side. The camera consisted of a high-resolution telescope, three photomultiplier light detectors (red, blue, and green), and a precision latitude step mechanism. Light entering the system was focused alternately on a set of three 0.038-mm aperture plates and then passed through various filters to impinge on the appropriate photodetector. The telescope multiplier assembly could be tilted in discrete steps to provide pole-to-pole coverage in 2400 scan lines. East-to-west scan was provided by the spin of the satellite itself. A total time of 24 min was required to scan one frame and 2.4 min to retrace with a nominal satellite rotation of 100 rpm. From its geosynchronous orbit, the camera had a ground resolution of better than 4 km at nadir. The experiment was successful, with ATS 3 being the first spacecraft to transmit operational multicolor earth-cloud photographs. Approximately 3 months after launch, however, the red and blue channels failed, and the system subsequently was limited to producing black-and-white pictures. Good quality black-and-white pictures were received daily until December 11, 1974, when operations were curtailed to three pictures a week. Experiment operation was completely discontinued on October 30, 1975. For a listing and description of the different forms of photographic data, see the "Meteorological Data Catalog for The Applications Technology Satellites" (TRF B09264), available from NSSDC. Data can be obtained through SDSD.