A study of a two-dimensional scanned lunar image for Advanced Technology Microwave Sounder (ATMS) geometric calibration

Abstract

Abstract. The NOAA-20 satellite was successfully launched on 18 November 2017. It carries five key instruments, including the Advanced Technology Microwave Sounder (ATMS). On 31 January 2018, the spacecraft performed a pitch-over maneuver operation, during which two-dimensional lunar scan observations were collected. In this study, a technique has been developed by which the ATMS on-orbit geometric calibration accuracy can be validated based on this lunar scan dataset. The fully calibrated data are fitted to the antenna pattern coordinates via a Gaussian function. The deviation in the center of the fit function from the origin of the frame is taken to be the boresight pointing error of the instrument. This deviation is further transformed to the Euler angle roll and pitch defined in the spacecraft coordinate system. The estimated ATMS boresight pointing Euler angle roll (pitch) is 0.05∘ (0.22∘) at K band, −0.07∘ (0.25∘) at Ka band, 0.02∘ (0.24∘) at V band, -0.07∘ (-0.08∘) at W band, and -0.04∘ (0.02∘) at G band. The results are validated by comparing them with those derived from the coastline inflection point method, showing a good correlation. For the sounding channels where the coastline method is inapplicable, the lunar scan method is still capable of delivering reasonable estimations of their geometric calibration errors.

Calibration and Characterization of Satellite‐Borne Microwave Sounders With the Moon

“…As these values differ considerably from the results obtained with ground tests, in particular for MHS on Metop‐C, it seems desirable to carry out a pitch‐over maneuver operation with this satellite, during which two‐dimensional lunar scan observations are collected. Such a maneuver was successfully executed with the NOAA‐20 satellite (Yang et al., 2020; Zhou & Yang, 2019), and made it possible to observe the Moon at scan positions that correspond to Earth scenes during routine operations. Our method of observing the Moon, on the other hand, only provides information obtained with the deep space view and does not allow a conclusion to be drawn about the pointing error ,for example, of pixel 45 (nadir).…”