Inter-calibration of Infrared Channels of Geostationary Meteorological Satellite Imagers

Abstract

This article examines a method of inter-calibration for MSU-GS imager of the Russian Geostationary Earth Orbit (GEO) satellite Elektro-L No. 2. Since the launch (December 11, 2015), the satellite's radiation cooler has been operating in an abnormal mode, so the calibration of the IR channels of the MSU-GS imager differed from that pre-flight and, in general, could have a daily variability. To ensure the satellite's further operation in orbit, it was necessary to calibrate imager channels at a frequency that would allow to identify daily calibration course to detect and compensate its sources. In order to do this, we have developed a special method of GEO-GEO inter-calibration. The calibration of MSU-GS was performed using SEVIRI imager installed on the GEO satellite Meteosat-10. SEVIRI was chosen as a reference instrument because its spectral channels are similar to those of MSU-GS. The MSU-GS was calibrated according to the regressions calculated from the simultaneous images of the field of regard selected between the sub-satellite points. The dynamic brightness temperature range was determined by deep convective clouds in high troposphere and warm ocean surface. Using the proposed method of inter-calibration, it was possible to confirm the absence of a significant daily variation of the calibration since November 2017. The amplitude of the variation smoothly increases from ∼0.2 K at high (∼300 K) BTs to ∼1.0 K when the brightness temperature decreased to 200 K. These estimates allow the use of the Fourier spectrometer IKFS-2 installed on the Russian Low-Earth-Orbit (LEO) satellite Meteor-M No. 2 to verify the developed GEO-GEO scheme of inter-calibration. Despite the specifics of the situation on board Elektro-L No. 2, the proposed method of GEO-GEO inter-calibration can be applied to radiometers of other neighboring satellites that differ in SSP and spatial resolution.

Advantages of Inter‐Calibration for Geostationary Satellite Sensors Onboard Twin Satellites

“…Ray‐matching between GEO‐GEO sensors, however, has not been fully investigated as the FORs of GEO sensors cover distinct regions, like in the case of GEMS and TEMPO. Consequently, this technique has primarily been applied to infrared sensors on the same platform (Di et al., 2023) or across a series of satellites, such as the Meteosat or the Geostationary Operational Environmental Satellites (GOES) series (Doelling et al., 2004; Rublev et al., 2018). The characteristic has alternately led to inter‐calibration of the GEO sensors through intermediary means such as numerical weather prediction models (Chander et al., 2013; S. J. Lee & Ahn, 2021).…”