Flat Plate Radiometer (FPR)

Description

The ESSA 7 Flat Plate Radiometer (FPR) system was designed to provide a measurement of the global distribution of reflected solar and long-wave radiation leaving the earth. The FPR system was comprised of four infrared sensors, an analog-to-digital converter, a commutator, and a tape recorder. Two pairs of radiometers were mounted on opposite sides of the spacecraft with their axes perpendicular to the spin axis. A cone shield was employed on two of the radiometers to isolate or reduce any response due to direct solar radiation. The field of view on the other two instruments was unrestricted. Both types of radiometers used a coated (either black or white) aluminum disc as the sensing element. The disc temperature was measured by two thermistors mounted on the back surface of the disc. The black-coated disc responded to the sum of the reflected solar, direct solar, and emitted long-wave radiation. The white disc reflected in the visual range but absorbed in the infrared (7 to 30 micron) range. Identical experiments were flown on the ESSA 3, ESSA 5, and ESSA 9 spacecraft. For a full description of the ESSA FPR, see 'Studies in Atmospheric Energetics Based on Aerospace Probings, Annual Report - 1966,' University of Wisconsin, pp 111-129, March 1967. The radiometer performed normally, and good data were obtained from launch until June 23, 1969, when the radiometer failed. Data from this experiment are avaiable on magnetic tape from NOAA-NESS, Suitland, Maryland.