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Open AccessArticle

Spectral Calibration Algorithm for the Geostationary Environment Monitoring Spectrometer (GEMS)

1
Department of Atmospheric Science and Engineering, Ewha Womans University, 52 Ewhayeodae-Gil, Seodaemoon-gu, Seoul 03760, Korea
2
Department of Climate and Energy Systems Engineering, Ewha Womans University, 52 Ewhayeodae-Gil, Seodaemoon-gu, Seoul 03760, Korea
3
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
4
Earth System Science Interdisciplinary Center, University of Maryland, 5825 University Research Center, College Park, MD 20740, USA
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Goddard Space Flight Center, NASA, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
6
Department of Atmospheric Sciences, Yonsei University, 50 Yonsei-Ro, Seodaemoon-gu, Seoul 03722, Korea
*
Author to whom correspondence should be addressed.
Remote Sens. 2020, 12(17), 2846; https://doi.org/10.3390/rs12172846
Received: 17 July 2020 / Revised: 31 August 2020 / Accepted: 31 August 2020 / Published: 2 September 2020
(This article belongs to the Section Atmosphere Remote Sensing)
The Geostationary Environment Monitoring Spectrometer (GEMS) onboard the Geostationary Korean Multi-Purpose Satellite 2B was successfully launched in February 2020. GEMS is a hyperspectral spectrometer measuring solar irradiance and Earth radiance in the wavelength range of 300 to 500 nm. This paper introduces the spectral calibration algorithm for GEMS, which uses a nonlinear least-squares approach. Sensitivity tests for a series of unknown algorithm parameters such as spectral range for fitting, spectral response function (SRF), and reference spectrum were conducted using the synthetic GEMS spectrum prepared with the ground-measured GEMS SRF. The test results show that the required accuracy of 0.002 nm is achievable provided the SRF and the high-resolution reference spectrum are properly prepared. Such a satisfactory performance is possible mainly due to the inclusion of additional fitting parameters of spectral scales (shift, squeeze, and high order shifts) and SRF (width, shape and asymmetry). For the application to the actual GEMS data, in-orbit SRF is to be monitored using an analytic SRF function and the measured GEMS solar irradiance, while a reference spectrum is going to be selected during the instrument in-orbit test. The calibrated GEMS data is expected to be released by the end of 2020. View Full-Text
Keywords: GEMS; spectral calibration; hyperspectral instrument GEMS; spectral calibration; hyperspectral instrument
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MDPI and ACS Style

Kang, M.; Ahn, M.-H.; Liu, X.; Jeong, U.; Kim, J. Spectral Calibration Algorithm for the Geostationary Environment Monitoring Spectrometer (GEMS). Remote Sens. 2020, 12, 2846.

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