Evaluation of ISCCP Multisatellite Radiance Calibration for Geostationary Imager Visible Channels Using the Moon

Abstract

Since 1983, the International Satellite Cloud Climatology Project (ISCCP) has collected Earth radiance data from the succession of geostationary and polar-orbiting meteorological satellites operated by weather agencies worldwide. Meeting the ISCCP goals of global coverage and decade-length time scales requires consistent and stable calibration of the participating satellites. For the geostationary imager visible channels, ISCCP calibration provides regular periodic updates from regressions of radiances measured from coincident and collocated observations taken by Advanced Very High Resolution Radiometer instruments. As an independent check of the temporal stability and intersatellite consistency of ISCCP calibrations, we have applied lunar calibration techniques to geostationary imager visible channels using images of the Moon found in the ISCCP data archive. Lunar calibration enables using the reflected light from the Moon as a stable and consistent radiometric reference. Although the technique has general applicability, limitations of the archived image data have restricted the current study to Geostationary Operational Environmental Satellite and Geostationary Meteorological Satellite series. The results of this lunar analysis confirm that ISCCP calibration exhibits negligible temporal trends in sensor response but have revealed apparent relative biases between the satellites at various levels. However, these biases amount to differences of only a few percent in measured absolute reflectances. Since the lunar analysis examines only the lower end of the radiance range, the results suggest that the ISCCP calibration regression approach does not precisely determine the intercept or the zero-radiance response level. We discuss the impact of these findings on the development of consistent calibration for multisatellite global data sets.

In-Orbit Radiometric Calibration and Stability Monitoring of the PROBA-V Instrument

“…Different techniques are published in the literature. In [13], a threshold technique, combined with a proximity test, is used to select the on-moon pixels. In the automated processing of the PROBA-V lunar calibration images, a similar technique is used.…”

COMS Visible Channel Calibration Using Moon Observation Data

“…The phase angle refers to the reference system used to derive observation geometry for Sun-Moon-COMS; it describes the position of the Sun and the satellite within a Moon-fixed reference frame. The phase angle is represented between these two vectors [25]. Accordingly, a phase angle value between −90 • and 90 • is used in this study, indicative that at least half of the lunar disk response can be used to provide an exploitable signal.…”

“…At least one Moon image acquisition per month is recommended [25]. Of these observations, a total of 146 lunar observations were converted from Level 0-to Level 1A-equivalent data for COMS visible channel calibration.…”

Monitoring of COMS MI visible channel degradation based on Moon observations

“…Moon observations from a total of 10 satellites (from a minimum of 5 to maximum of 27 Moon image data per satellite) are usually used for the vicarious calibrations. 5 For the trend of monitoring the visible instrument of sea-viewing wide field-of-view sensor, a lunar calibration method was also adopted. 1 The lunar calibration overcomes an intrinsic limitation of comparing data with different temporal and spatial characteristics driven by the satellite viewing geometries.…”

“…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).…”