Calibration and validation (CAL/VAL) is a key expertise for quantitative utility of space-borne distant sensing knowledge. Nonetheless, the complicated area setting may cause many uncertainties and degrade calibration accuracy. In-flight calibration is at all times wanted. The thermal emission of the Moon is steady over a whole lot of years as a result of there is no such thing as a ambiance and no vital bodily or chemical change on its floor. The deep area view of the Microwave Humidity Sounder onboard NOAA-18 has seen the Moon many instances yearly. Below photo voltaic illumination, the lunar floor reveals steady and periodical variation in microwave brightness temperature (TB). The Moon is a possible calibration supply for thermal calibration
The associated work was revealed in Science China Earth Sciences as “Calibration of the space-borne microwave humidity sounder primarily based on real-time thermal emission from lunar floor.” Primarily based on the warmth conductive equation, the temperature profiles of lunar regolith at totally different areas and native time are simulated numerically with the real-time photo voltaic radiance and angle of incidence. The simulated temperatures are validated with the infrared TBs measured by the Diviner infrared sounder onboard the Lunar Reconnaissance Orbiter. The microwave TBs measured by China’s Chang’e 2 satellite tv for pc have been used to invert the loss tangents of the lunar floor. The inverted loss tangents have been utilized to modeling the microwave TBs of lunar close to aspect on the microwave humidity sounder’s channels. The simulated common microwave TBs are in keeping with the observations of the NOAA-18 microwave humidity sounder.
The evaluation reveals that microwave TB of the lunar floor is expounded to the frequency. The microwave can penetrate the lunar regolith. Microwave TB is the cumulative contribution of the regolith thermal emission. The superficial temperature performs a dominant function in microwave TB at excessive frequency channels due to the small penetration depth. The superficial temperature of regolith drops considerably with depth at daytime, leading to a excessive microwave TB at excessive frequency. At evening, the noticed TB is low at excessive frequency as a result of the superficial temperature of regolith will increase with depth.
The digital counts of the microwave humidity sounder have been used to suit the complete width at half maxima of the sounder when the deep area view scans throughout the Moon. The fitted full width at half maxima was utilized in deriving the typical lunar TB from the noticed digital counts. The simulation evaluation reveals that the gap between the satellite tv for pc and the lunar part angle will affect the inverted full width at half maxima. In keeping with the examine of Chang’e 2’s microwave statement of the Moon, the typical microwave TBs of the lunar close to aspect at totally different frequencies and part angles are modeled. The simulation could be taken as a supplemental reference for the calibration of the microwave humidity sounder onboard NOAA-18. It may be taken because the calibration supply of the microwave sounders onboard geosynchronous satellites and CubeSats as nicely.
Nonetheless, the microwave TB are measured by Chang’e 2 satellites at nadir statement. The best frequency is 37GHz. Particular statement of lunar floor at greater frequencies and enormous angles are wanted for enhancing the modeling.
Bettering climate forecasts with observations from the microwave devices onboard China’s FY-3D satellite tv for pc
Niutao Liu et al, Calibration of the space-borne microwave humidity sounder primarily based on real-time thermal emission from lunar floor, Science China Earth Sciences (2021). DOI: 10.1007/s11430-020-9701-1
Lunar brightness temperature for calibration of microwave humidity sounders (2021, April 8)
retrieved Eight April 2021
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