Impacts of orbital drift on the MODIS lunar calibration

Truman Wilson; Amit Angal; Xiaoxiong Xiong

doi:10.1117/12.2680308

19 October 2023 Impacts of orbital drift on the MODIS lunar calibration

Truman Wilson, Amit Angal, Xiaoxiong Xiong

Proceedings Volume 12729, Sensors, Systems, and Next-Generation Satellites XXVII; 1272917 (2023) https://doi.org/10.1117/12.2680308
Event: SPIE Remote Sensing, 2023, Amsterdam, Netherlands

Abstract

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua spacecrafts were launched in 1999 and 2002, respectively. To maintain climate quality data, each instrument performs calibration operations on-orbit using both on-board calibrators and observations of external targets, such as the Moon. For calibration consistency, the Moon is viewed during regularly scheduled spacecraft roll maneuvers in order to keep the lunar phase angle within a specified range. Changes in the view geometry are accounted for by the USGS ROLO model. However, starting in 2022, orbital maintenance maneuvers for both instruments are no longer being performed. Each instrument orbit has begun to drift to a higher beta angle, which changes the achievable phase angle range of the lunar observations. In this work, we investigate the impact of the orbital drift on the MODIS lunar calibration. We predict that the optimal phase angle range will change by approximately 20° (towards a full Moon) by the end of 2026. While differences in the view geometry can be accounted for using ROLO, phase angle residuals are seen in the model corrected results which can cause bias in the trending as the orbit drifts. Using the unscheduled Moon data, we develop a correction to these phase residuals in both instruments which shows that we expect drifts in the trends up to 1% for most bands by 2026 if left uncorrected.

Conference Presentation

(2023) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Truman Wilson, Amit Angal, and Xiaoxiong Xiong "Impacts of orbital drift on the MODIS lunar calibration", Proc. SPIE 12729, Sensors, Systems, and Next-Generation Satellites XXVII, 1272917 (19 October 2023); https://doi.org/10.1117/12.2680308

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