Share Email Print

Journal of Applied Remote Sensing • new

Alternative method of on-orbit response-versus-scan-angle characterization for MODIS reflective solar bands
Author(s): Hongda Chen; Xiaoxiong Xiong; Amit Angal; Xu Geng; Aisheng Wu
Format Member Price Non-Member Price
PDF $20.00 $25.00
cover GOOD NEWS! Your organization subscribes to the SPIE Digital Library. You may be able to download this paper for free. Check Access

Paper Abstract

The moderate resolution imaging spectroradiometer (MODIS) has 20 reflective solar bands (RSB), covering a spectral range from 0.41 to 2.2  μm, which are calibrated on-orbit using its onboard calibrators, which include a solar diffuser, a solar diffuser stability monitor, and a spectroradiometric calibration assembly. A space view (SV) port is used to provide a background reference and also facilitates near-monthly lunar observations through a spacecraft roll. In every scan, the Earth’s surface, SV, and onboard calibrators are viewed via a two-sided scan mirror, the reflectance of which depends on the angle of incidence (AOI) as well as the wavelength of the incident light. Response-versus-scan-angle (RVS) is defined as a dependence function of the scan mirror’s reflectance over AOI. An initial RVS for each RSB was measured prelaunch for both Terra and Aqua MODIS. Algorithms have been developed to track the on-orbit RVS variation using the measurements from the onboard calibrators, supplemented with the earth view (EV) trends from pseudoinvariant desert targets obtained at different AOI. Since the mission beginning, the MODIS characterization support team (MCST) has dedicated efforts in evaluating approaches of characterizing the on-orbit RVS. A majority of the approaches focused on fitting the data at each AOI over time and then deriving the relative change at different AOI. The current version of the on-orbit RVS algorithm, as implemented in the collection 6 (C6) level-1B (L1B), is also based on the above rationale. It utilizes the EV response trends from the pseudoinvariant Libyan desert targets to supplement the gain derived from the onboard calibrators. The primary limitation of this approach is the assumption of the temporal stability of these desert sites. Consequently, MCST developed an approach that derives the on-orbit RVS change using measurements from a single desert site, combined with the on-orbit lunar measurements. In addition, the EV and onboard responses are fit first as a function of AOI before fitting temporally in order to eliminate the dependence on the stability of the desert site. Comprehensive comparisons are performed with current C6 RVS results for both Terra and Aqua MODIS. Results demonstrate that this alternative method provides a supplemental means to monitor the on-orbit RVS for MODIS RSB.

Paper Details

Date Published: 9 June 2016
PDF: 15 pages
J. Appl. Remote Sens. 10(2) 024004 doi: 10.1117/1.JRS.10.024004
Published in: Journal of Applied Remote Sensing Volume 10, Issue 2
Show Author Affiliations
Hongda Chen, Science Systems and Applications, Inc. (United States)
Xiaoxiong Xiong, NASA Goddard Space Flight Ctr. (United States)
Amit Angal, Science Systems and Applications, Inc. (United States)
Xu Geng, Science Systems and Applications, Inc. (United States)
Aisheng Wu, Science Systems and Applications, Inc. (United States)

© SPIE. Terms of Use
Back to Top