AVCS Nimbus-2
type: Concept
change note: 2015-05-12 13:12:34.0 [saritz] update AltLabel (Advanced Vidicon Camera System on Nimbus-2); update PrefLabel (AVCS Nimbus-2);
in scheme: instruments
definition: [Source: National Space Science Data Center, http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1966-040A-01 ] The Nimbus 2 Advanced Vidicon Camera System (AVCS) was a combination of cameras, tape recorder, and transmitter that could record and store a series of remote daytime cloudcover pictures for subsequent playback to a ground-data acquisition station. The AVCS sensors consisted of three vidicon cameras mounted on the satellite sensory ring, facing earthward and deployed in a fan-like array to produce a three-segment composite picture. Each camera covered a 35-deg field of view with the center camera pointing straight down. The optical axes of the other two cameras were directed 35 deg to either side. Each of the cameras employed an f/4 lens with a focal length of 18.2 mm. A potentiometer attached to the solar array controlled the lens opening from f/16 when the spacecraft was over the equator to f/4 when it was near the poles. The 800-scan-line, 2.54-cm vidicon pickup tubes yielded a linear resolution of better than 1 km at nadir from an approximate altitude of 1100 km. At this altitude, the camera array could produce a composite picture covering an area of 720 by 3400 km. Successive frames were taken at 91-s intervals providing about 20% overlap in coverage. A 40-ms exposure time was used, and the image was scanned by the electron beam in 6.5 s. The resulting signal was frequency modulated and recorded on three tracks of a magnetic tape, one track for each camera. Sufficient tape was provided for recording 53 pictures (about 1-2/3 orbits of data). The AVCS data were multiplexed with the High-Resolution Infrared Radiometer (HRIR) data and, using a transmission frequency of 1707.5 MHz, were telemetered to a ground station in 4 min. The experiment operated normally until August 31, 1966, when the tape recorder malfunctioned. Sporadic operation was continued until September 2, 1966, when the recorder failed completely, terminating data acquisition except for …

Cameras
type: Concept