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Actinometric Instrument

NSSDCA ID: 1973-015A-03

Mission Name: Meteor 1-14

Description

The Meteor 1 actinometric instrument was designed to measure (1) the outgoing longwave radiation (3 to 30 micrometers) from the earth-atmosphere system, (2) the outgoing shortwave solar radiation (0.3 to 3 micrometers) reflected and backscattered by the earth-atmosphere system, and (3) the effective radiation temperature of the earth's surface and cloud tops (8 to 12 micrometers) for operational use by the Soviet Hydrometeorological Service. The instrumentation consisted of four radiometers -- a pair of scanning, narrow-angle, two-channel radiometers and a pair of nonscanning, wide-angle, two-channel radiometers. The narrow-angle (4 by 5 deg field of view) radiometers measured radiation in all three spectral bands, while the wide-angle (136 to 140 deg field of view) radiometers operated only in the 0.3- to 3-micrometer and 3- to 30-micrometer bands. In the narrow-angle radiometer, the 0.3- to 3-micrometer band was measured in one channel and the 8- to 12-micrometer and 3- to 30-micrometer bands were combined in the second channel. In the second channel, the two bands were separated by the exchange of corresponding filters as the radiometer scanned in alternate directions. The earth radiation entered the narrow-angle radiometer through a cylindrical collimator and fell onto a conical scanning mirror. The radiation was reflected from the mirror through a three-lobed rotating mirror chopper that modulated the radiation flux at a frequency of 80 Hz. The chopper alternately reflected earth radiation and space radiation, which entered through a separate KRS-5 crystal window, onto one of three openings in a color filter wheel -- one filter for each spectral band. The particular spectral band that was passed through then fell on an off-axis parabolic mirror that focused the radiation flux onto a bolometric receiver. Periodic calibration was made when the scanning mirror moved to a 90-deg angle from nadir with simultaneous turning on and viewing of a silicon standard lamp. The shortwave channel did not use the two-beam system or filter switching. The output from the modulated flow of radiation on the bolometer was amplified, rectified, filtered, and fed into the radio telemetry system over eight channels. The wide-angle radiometers had identical optical systems for both channels. The earth radiation entered the radiometer through a hemispherical shell composed of quartz or KRS-5 crystal with a coating that determined the passband. The radiation was then modulated with a frequency of 64 Hz and fell on a bolometric receiver. As in the narrow-angle radiometers, the bolometer output was processed and fed into the radio telemetry system. The wide-angle radiometer was standardized simultaneously with the narrow-angle radiometer by inputting a standard 64-Hz calibrating frequency into the amplification circuit. The relative rms measuring error for both types of radiometers was about 0.5 percent. To provide a backup capability, one wide-angle and one narrow-angle radiometer were held in reserve and could be activated on command from the ground. The orientation of the Meteor 1 satellite insured that the primary optical axes of the radiometers were oriented vertically down toward nadir. The survey of the earth's surface by both radiometers was carried out by the motion of the satellite relative to the earth. In addition, the narrow-angle radiometer scanned 66 deg to either side of nadir in a plane normal to the orbital plane by rocking the scanning mirror about the optical axis. The radiometers covered a strip about 3500 km wide on the earth's surface and had a ground resolution of 50 km at nadir. The data were reduced at the ground stations and were transmitted to the Hydrometeorological Center in Moscow, where they were recorded in digital form on magnetic tape and were used to produce various analysis products such as earth-atmosphere albedo charts and radiation temperature maps. The data were archived at the Hydrometeorological Center.

Alternate Names

  • Meteor1-14/ActinometricInstrument

Funding Agency

  • Soviet Hydrometeorological Service (U.S.S.R)

Discipline

  • Earth Science: Atmospheric Dynamics

Additional Information

Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office

 

Personnel

NameRoleOriginal AffiliationE-mail
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