Abstract
Most of the current space-borne visible imagers on a geosynchronous orbit (GEO), which do not have onboard calibration devices, use a vicarious calibration. For a meteorological payload on a GEO satellite, lunar calibration is often used. The meteorological imager (MI) on the communication, ocean, and meteorological satellite (COMS) has been successfully operated for half of its entire mission lifetime (∼7 years). The visible channel of the MI uses the lunar calibration to monitor its degradation. The degradation rate of the instrument was monitored using the ratio between the calculated radiance of the Moon from the Robotic Lunar Observatory (ROLO) model and the observed radiance from the MI. Analyses of the 42-month Moon image data showed that the instrument’s mean degradation rate was about 1.88%. These values confirmed the outstanding performance of the COMS MI visible channel compared with that of the GOES-10 imager.
Highlights
The visible channels of most of the operating meteorological imagers (MIs) on geosynchronous (GEO) satellites do not have onboard calibration targets and use a vicarious calibration.[1]
The COMS MI visible channel degradation is represented by P, which is a ratio between two irradiances: the Moon irradiance based on the Robotic Lunar Observatory (ROLO) model and the observed irradiance from the MI
The Julian Century was used to remove the dependency on the measurement interval, and the direct histogram specification (DHS) scheme was used to compensate a relative variation among the eight detectors
Summary
The visible channels of most of the operating meteorological imagers (MIs) on geosynchronous (GEO) satellites do not have onboard calibration targets and use a vicarious calibration.[1]. Seo and Jin: Monitoring of COMS MI visible channel degradation based on Moon observations sensor, a lunar calibration method was adopted.[1] The lunar calibration overcomes an intrinsic limitation of comparing data with different temporal and spatial characteristics driven by the satellite viewing geometries.[6] The measured relative calibration accuracy regarding the GOES-10 was ∼0.1% compared with the vicarious calibration result of MODIS.[7] At least one Moon image acquisition per month is recommended.[5] Usually two to four times Moon observations per month are available for space-borne visible imagers.[7]. The MI on the COMS has been operating successfully since its launch (June 27, 2010) It monitors meteorological phenomena 24/7 using one visible and four infrared channels.[8] Lunar calibration has been implemented on the MI based on a robotic lunar observatory (ROLO) model to monitor MI visible-channel degradation. Earth-centered Earth-fixed (ECEF) coordinates need to be converted to Moon-centered Moonfixed (MCMF) coordinates.[11]
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