Abstract
The CrIS FM1 is a spaceborne IR Fourier Transform Spectrometer launched on October 28th 2011 on-board the Suomi NPP satellite. For calibration purpose, CrIS acquires two types of calibration views, namely the internal calibration target (a hot black body) and the deep space or sky view.
The CrIS SDR algorithm transforms the Earth scene views into radiometrically and spectrally calibrated spectra. The radiometric calibration uses both the ICT and DS views. Unfrequently, the DS view is contaminated by the moon which must be disregarded in further processing. The current lunar intrusion detection method detects the increase of the deep space view spectra of the so-called calibration radiometric ratio (CRR). This CRR utilizes an average of 30 deep space views forming the sliding window. The issue is that lunar intrusion detection is not performed within the initial sliding window. This is an issue when the entire mission data set will be subject to reprocessing.
The new proposed lunar intrusion algorithm utilizes both calibration views. The processing steps are: 1) Accumulate 17 DS spectra, 2) Select 7 groups of 6 spectra, 3) Select the group that has the least deviation of the ICT-DS over the selected microwindow, 4) Compute the mean of the selected group, 5) Compare retroactively the 17 spectra with respect to the lunar intrusion ratio +/- threshold. 6) Flag the DS spectra as having a lunar intrusion when outside the threshold values. 7) Continue the lunar intrusion loop with new DS spectra.
The new algorithm can detect lunar intrusion during the initialization of the sliding window. Compared with the current operation code, the new algorithm has detected a larger number of lunar intrusion events.
Lunar Intrusion Detection Algorithm for the Cross-track Infrared Sounder (CrIS) Instrument on S-NPP Satellite
The CrIS FM1 is a spaceborne IR Fourier Transform Spectrometer launched on October 28th 2011 on-board the Suomi NPP satellite. For calibration purpose, CrIS acquires two types of calibration views, namely the internal calibration target (a hot black body) and the deep space or sky view.
The CrIS SDR algorithm transforms the Earth scene views into radiometrically and spectrally calibrated spectra. The radiometric calibration uses both the ICT and DS views. Unfrequently, the DS view is contaminated by the moon which must be disregarded in further processing. The current lunar intrusion detection method detects the increase of the deep space view spectra of the so-called calibration radiometric ratio (CRR). This CRR utilizes an average of 30 deep space views forming the sliding window. The issue is that lunar intrusion detection is not performed within the initial sliding window. This is an issue when the entire mission data set will be subject to reprocessing.
The new proposed lunar intrusion algorithm utilizes both calibration views. The processing steps are: 1) Accumulate 17 DS spectra, 2) Select 7 groups of 6 spectra, 3) Select the group that has the least deviation of the ICT-DS over the selected microwindow, 4) Compute the mean of the selected group, 5) Compare retroactively the 17 spectra with respect to the lunar intrusion ratio +/- threshold. 6) Flag the DS spectra as having a lunar intrusion when outside the threshold values. 7) Continue the lunar intrusion loop with new DS spectra.
The new algorithm can detect lunar intrusion during the initialization of the sliding window. Compared with the current operation code, the new algorithm has detected a larger number of lunar intrusion events.