Inter-Calibration of the OSIRIS-REx NavCams with Earth-Viewing Imagers
Lauretta, Dante S.
AffiliationUniv Arizona, Lunar & Planetary Lab
MetadataShow full item record
CitationDoelling, D.; Khlopenkov, K.; Haney, C.; Bhatt, R.; Bos, B.; Scarino, B.; Gopalan, A.; Lauretta, D.S. Inter-Calibration of the OSIRIS-REx NavCams with Earth-Viewing Imagers. Remote Sens. 2019, 11, 2717.
RightsCopyright © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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AbstractThe Earth-viewed images acquired by the space probe OSIRIS-REx during its Earth gravity assist flyby maneuver on 22 September 2017 provided an opportunity to radiometrically calibrate the onboard NavCam imagers. Spatially-, temporally-, and angularly-matched radiances from the Earth viewing GOES-15 and DSCOVR-EPIC imagers were used as references for deriving the calibration gain of the NavCam sensors. An optimized all-sky tropical ocean ray-matching (ATO-RM) calibration approach that accounts for the spectral band differences, navigation errors, and angular geometry differences between NavCam and the reference imagers is formulated in this paper. Prior to ray-matching, the GOES-15 and EPIC pixel level radiances were mapped into the NavCam field of view. The NavCam 1 ATO-RM gain is found to be 9.874 x 10(-2) Wm(-2)sr(-1)mu m(-1)DN(-1) with an uncertainty of 3.7%. The ATO-RM approach predicted an offset of 164, which is close to the true space DN of 170. The pre-launch NavCam 1 and 2 gains were compared with the ATO-RM gain and were found to be within 2.1% and 2.8%, respectively, suggesting that sensor performance is stable in space. The ATO-RM calibration was found to be consistent within 3.9% over a factor of +/- 2 NavCam 2 exposure times. This approach can easily be adapted to inter-calibrate other space probe cameras given the current constellation of geostationary imagers.
NoteOpen access journal
VersionFinal published version
SponsorsNational Aeronautics & Space Administration (NASA) [NNM10AA11C]