Improved Lunar Intrusion Detection Algorithm for the CrIS Sensor Data Record | IEEE Journals & Magazine | IEEE Xplore

Improved Lunar Intrusion Detection Algorithm for the CrIS Sensor Data Record


Abstract:

As one of the calibration reference targets used to calibrate the cross-track infrared sounder (CrIS) earth scene (ES) measurements, the stable deep space (DS) reference ...Show More

Abstract:

As one of the calibration reference targets used to calibrate the cross-track infrared sounder (CrIS) earth scene (ES) measurements, the stable deep space (DS) reference spectrum in the 30-scan DS calibration moving window is very important for the accuracy of the calibrated ES radiances. The DS view changes when the lunar radiation intrudes into the observation field of view (FOV). In the original CrIS lunar intrusion (LI) detection algorithm implemented in the operational ground processing system, the contaminated DS spectra were not effectively removed from the DS moving window due to large threshold values and the assumption that the first DS spectrum in the moving window was not contaminated. As a result, inaccurate, degraded, or invalid ES radiances were produced in the operational CrIS sensor data record (SDR) during LI events. In this article, an improved LI detection algorithm is developed and implemented into the operational system. First, the new algorithm efficiently finds a contamination-free DS spectrum in the DS 30-scan calibration moving window to use as the reference spectrum. Second, based on the phase characteristics of the complex raw DS spectra during LI events, the LI band-dependent thresholds were derived to effectively reject the contaminated DS spectra and to make the valid DS window size consistent among the three CrIS bands. The new LI algorithm implemented in the operational system shows a successful detection and removal of all the lunar-contaminated DS spectra in the DS moving window, resulting in an improved calibration of ES radiances during LI events.
Published in: IEEE Transactions on Geoscience and Remote Sensing ( Volume: 58, Issue: 2, February 2020)
Page(s): 1134 - 1145
Date of Publication: 16 October 2019

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I. Introduction

The cross-track infrared sounder (CrIS) is a Fourier transform spectrometer (FTS), currently on board the Suomi National Polar-Orbiting Partnership (S-NPP) and NOAA-20 satellites. S-NPP was launched on October 28, 2011, while NOAA-20 was launched on November 18, 2017. The CrIS ground processing software Interface Data Processing Segment (IDPS), part of the Joint Polar Satellite System (JPSS) ground processing system, transforms the measured raw interferograms [raw data records (RDRs)] into calibrated and geolocated spectra in the form of sensor data records (SDRs). The SDRs cover three spectral bands: the long-wave IR (LWIR) band from 650 to 1095 cm−1, mid-wave IR (MWIR) band from 1210 to 1750 cm−1, and short-wave IR (SWIR) band from 2155 to 2550 cm−1 with the nominal spectral resolutions (NSRs) of 0.625, 1.25, and 2.5 cm−1, respectively. CrIS also provides a full spectral resolution (FSR) SDR with a spectral resolution of 0.625 cm−1 for all three bands since December 4, 2014. For an 8-s scan, CrIS sequentially measures 34 interferogram sweeps or fields of regard (FORs) with a 3 3 array of fields of view (FOVs), including 30 earth scene (ES), two deep space (DS), and two internal calibration target (ICT) measurements. Among them, half of the ES, DS, and ICT interferograms are measured in a forward direction and the other half in the reverse direction according to the moving direction of the interferometer porchswing mirror. Radiometric calibrations are separately performed for different sweeping directions, FOVs, and bands using ICT and DS measurements as calibration references.

References

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