On-orbit characterization of RVS for MODIS thermal emissive bands

Xiaoxiong Xiong; Vincent V. Salomonson; Kwo-Fu Chiang; Aisheng Wu; Bruce W. Guenther; William Barnes

doi:10.1117/12.578344

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30 December 2004 On-orbit characterization of RVS for MODIS thermal emissive bands

Xiaoxiong Xiong, Vincent V. Salomonson, Kwo-Fu Chiang, Aisheng Wu, Bruce W. Guenther, William Barnes

Proceedings Volume 5652, Passive Optical Remote Sensing of the Atmosphere and Clouds IV; (2004) https://doi.org/10.1117/12.578344
Event: Fourth International Asia-Pacific Environmental Remote Sensing Symposium 2004: Remote Sensing of the Atmosphere, Ocean, Environment, and Space, 2004, Honolulu, Hawai'i, United States

Abstract

Response versus scan angle (RVS) is a key calibration parameter for remote sensing radiometers that make observations using a scanning optical system, such as a doubled sided scan mirror (MODIS and GLI) or a rotating telescope (SeaWiFS and VIIRS). This is because the calibration is typically performed at a fixed viewing angle whereas the Earth scene observations are made over a range of viewing angles and the system’s response is a function of the scan angle. The NASA EOS Terra MODIS has been in operation for more than four years since its launch in December 1999. It has 36 spectral bands covering wavelengths from visible (VIS) to long-wave infrared (LWIR). It is a cross-track scanning radiometer with a two-sided paddle wheel scan mirror, making observations over a wide field of view (FOV) of ±55° from nadir thereby enabling frequent global coverage. Due to pre-launch measurement limitations, the Terra MODIS thermal emissive bands (TEB) RVS characterization did not produce valid data sets that could be used to derive a reliable system level RVS. Because of this, a RVS was developed for use at launch and subsequent efforts have been made to characterize the RVS using on-orbit observations. This paper describes the Terra MODIS on-orbit characterization of TEB RVS, including the data from scanning the instrument’s closed nadir aperture door (CNAD) and the use of Earth view data collected during spacecraft deep space maneuvers (DSM). Comparisons of pre-launch analysis and early on-orbit measurements are also provided. Noticeable improvements have been made for several thermal emissive bands for observations at large angles of incidence (AOI). Using the correct RVS improves the image quality and the radiometric calibration accuracy. For bands 34-36, an adjustment of as much as 0.5-1.5K can be made at the end of scan (worst case) for mirror side 2. The impacts at smaller AOI and from mirror side 1 are much smaller. Based on RVS comparison studies and science test results, the on-orbit derived DSM RVS has been chosen for the ongoing L1B data processing and future reprocessing.

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Xiaoxiong Xiong, Vincent V. Salomonson, Kwo-Fu Chiang, Aisheng Wu, Bruce W. Guenther, and William Barnes "On-orbit characterization of RVS for MODIS thermal emissive bands", Proc. SPIE 5652, Passive Optical Remote Sensing of the Atmosphere and Clouds IV, (30 December 2004); https://doi.org/10.1117/12.578344

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