MODIS solar diffuser calibration strategies for the post orbital drift era

Sarid, Gal; Twedt, Kevin A.; Xiong, Xiaoxiong

doi:10.1117/12.2633379

Cited by 2 publications

(2 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To characterize over an expanded angle range, late mission yaw maneuvers will be required, however, methods for extrapolation of our current characterization as the new data is acquired are currently being explored. 3,8 For the desert data, IAMs and DMUs kept the satellites in a stable 16-day repeating ground-track cycle, where observations of selected sites at particular scan angles repeated every 16 days throughout the mission. As a result of the drifting orbits, the pattern is now lost for each instrument and the desert sites will now be observed at varying scan angles versus time.…”

Section: Introductionmentioning

confidence: 99%

Impacts of orbital drift on the MODIS lunar calibration

Wilson,

Angal,

Xiong

2023

Sensors, Systems, and Next-Generation Satellites XXVII

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

Impacts of orbital drift on the MODIS lunar calibration

Wilson,

Angal,

Xiong

2023

Sensors, Systems, and Next-Generation Satellites XXVII

View full text Add to dashboard Cite

show abstract

“…This paper focuses on the impact of the satellite orbit drift on the Earth scene data that is used in the calibration of MODIS RSB by the MODIS Characterization Support Team (MCST), particularly for the North African desert sites and the deep convective clouds (DCC). The impacts of the orbit drift on the solar diffuser calibration and lunar calibration are not discussed here but the strategies have been introduced previously 7,8 and will continue to be developed and improved. In Section 2, we review the calibration algorithms used to generate the Collection 6.1 (C6.1) and Collection 7 (C7) Level 1B (L1B) data products, focusing on how the Earth scene data are used.…”

Section: Introductionmentioning

confidence: 99%

Impact of satellite orbit drift on MODIS Earth scene observations used in calibration of the reflective solar bands

Twedt,

Xiong,

Geng

et al. 2023

Earth Observing Systems XXVIII

View full text Add to dashboard Cite

After more than 20 years in orbit, NASA's Terra and Aqua satellites have both started drifting away from their historically maintained orbits. The MODIS instruments on Terra and Aqua continue to collect valuable Earth observation data, but the changing orbits present a challenge for maintaining accurate calibration. The MODIS reflective solar bands (RSB), spanning the wavelength range from 412 nm to 2130 nm, are calibrated on orbit using a combination of regular data collections from an on-board solar diffuser, the Moon, and pseudo-invariant Earth scenes. Starting in the Collection 6 Level 1B (L1B) data products, the RSB calibration began using data from desert targets for a few of the visible bands to better track changes in the response versus scan angle that could not be captured by the on-board calibration. The use of Earth scene data has been extended recently for Terra MODIS calibration in Collection 6.1 (C6.1) and the upcoming Collection 7 (C7) L1B to also include data from ocean scenes and deep convective clouds (DCC). Drifts in both the orbit inclination and ground track of Terra and Aqua lead to changes in the solar illumination angles and satellite view angles of the Earth scenes. We discuss how these orbital changes impact the desert and DCC targets used for MODIS RSB calibration and present the accompanying changes made to our C6.1 and C7 calibration algorithms. We also discuss remaining future challenges, such as better characterization of bi-directional reflectance distribution functions, and possible alternative calibration strategies.

show abstract

MODIS solar diffuser calibration strategies for the post orbital drift era

Cited by 2 publications

References 9 publications

Impacts of orbital drift on the MODIS lunar calibration

Impacts of orbital drift on the MODIS lunar calibration

Impact of satellite orbit drift on MODIS Earth scene observations used in calibration of the reflective solar bands

Contact Info

Product

Resources

About