Analysis of the on-orbit response-versus-scan-angle for the MODIS SWIR bands derived from lunar observations

Truman Wilson; Emily Aldoretta; Amit Angal; Xu Geng; Kevin Twedt; Xiaoxiong Xiong

doi:10.1117/12.2572877

20 September 2020 Analysis of the on-orbit response-versus-scan-angle for the MODIS SWIR bands derived from lunar observations

Truman Wilson, Emily Aldoretta, Amit Angal, Xu Geng, Kevin Twedt, Xiaoxiong Xiong

Author Affiliations +

Proceedings Volume 11530, Sensors, Systems, and Next-Generation Satellites XXIV; 115301E (2020) https://doi.org/10.1117/12.2572877
Event: SPIE Remote Sensing, 2020, Online Only

Abstract

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua platforms is a multi-spectral, whiskbroom scanning radiometer with 36 spectral bands covering wavelengths from 0:4 - 14:2 μm. Among these bands, the 20 reflective solar bands (RSB, 0:4 - 2:1 μm) use an on-board solar difuser (SD) and SD stability monitor (SDSM) to track the detector gain changes on orbit. In addition to this, lunar and Earth-view (EV) observations are used in order to characterize the scan-mirror response versus scan angle (RVS), which improves the Earth-view retrieval over the full width of each scan. For the short-wave infrared bands (SWIR, 1:2 - 2:1 μm), the prelaunch RVS has been used for both Aqua and Terra MODIS throughout each mission. While these bands are not expected to have a significant change in the RVS on-orbit, issues such as electronic crosstalk and an out-of-band optical leak have prevented the use of the Moon for deriving the on-orbit RVS for validation. However, recent improvements to the MODIS lunar calibration for the SWIR bands allow us to mitigate the electronic crosstalk impact and derive the RVS for the SWIR bands. In this work, we will assess the impact of this newly derived RVS on the EV data compared to MODIS Collection 6.1. By comparing to EV data obtained from pseudo-invariant calibration sites at different angles-of-incidence on the scan mirror, we can assess the effectiveness of the newly derived RVS from the Moon. We find that while the change in the RVS on-orbit for the SWIR bands is relatively small, applying a correction to the RVS based on the Moon and SD data can provide an improvement for some bands.

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Citation Download Citation

Truman Wilson, Emily Aldoretta, Amit Angal, Xu Geng, Kevin Twedt, and Xiaoxiong Xiong "Analysis of the on-orbit response-versus-scan-angle for the MODIS SWIR bands derived from lunar observations", Proc. SPIE 11530, Sensors, Systems, and Next-Generation Satellites XXIV, 115301E (20 September 2020); https://doi.org/10.1117/12.2572877

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