Sun, Junqiang; Xiong, Xiaoxiong; Li, Yonghong; Madhavan, Sriharsha; Wu, Aisheng; Wenny, Brian N. (2014). Evaluation of Radiometric Improvements With Electronic Crosstalk Correction for Terra MODIS Band 27. IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, 52(10), 6497-6507.

Abstract
The MODerate-resolution Imaging Spectroradiometer (MODIS) has 36 bands, covering a wavelength range from 0.4 to 14.4 mu m. Terra MODIS band 27 (6.72 mu m), a water vapor band, was found to have electronic crosstalk from other bands located on the same focal plane assembly, which causes surface feature contamination and pronounced detector level striping in the images. In a previous study, an algorithm using a linear approximation derived from on-orbit lunar observations was developed to correct the crosstalk effect. Results demonstrated that the correction substantially reduces the striping and removes the contaminated surface features. However, it was also demonstrated that the crosstalk effect might bring about a long-term increase in the brightness temperatures (BTs) in Terra band 27. In this paper, it is shown that there is a long-term drift (or decrease), which is strongly detector dependent, in the BT for the band induced by the crosstalk effect. It is also shown that the crosstalk correction with the linear algorithm substantially removes the detector-dependent long-term drift and greatly improves the radiometric accuracy of the band. The comparison between the BT of Terra band 27 in the most recent MODIS Level 1B (L1B) collection [Collection 6 (C6)] and those from the Infrared Atmospheric Sounding Interferometer using simultaneous-nadir-overpass observations shows that the detector-averaged long-term drift in the BT in Terra band 27 varies from approximately 1 K to 3 K. The detector difference can be as large as 9 K for a few detectors during the last five years in the northern and southern polar areas. With crosstalk correction applied, the long-term drift is reduced to be less than 0.5 K, and the detector difference is within 1 K. The crosstalk effect-induced detector-dependent long-term drift in Terra band 27 and the capability of the crosstalk correction algorithm to remove the drift are also assessed at three well-characterized sites with different radiance levels, namely, Dome Concordia (Dome C), Libya 1, and the Pacific Ocean at various radiometric levels. The long-term drift and the strong detector dependence of the drift are clearly observed at the three sites with the BT in the Terra band 27 C6 L1B products. The band-averaged BT drifts are about 0.8 K, 5 K, and 5.5 K, and the detector differences can be as large as 4 K, 12 K, and 15 K, respectively, for the three sites. With the crosstalk correction applied, the long-term drifts in the BT over the three sites are substantially removed, and the observed detector differences of Terra band 27 at the three sites are also significantly reduced. The crosstalk correction greatly improves the radiometric accuracy of the band as well as the image quality.

DOI:
10.1109/TGRS.2013.2296747

ISSN:
0196-2892; 1558-0644