Onboard Polarimetric Calibration Methods of Spaceborne Scanning Polarimeter

Hongchun, 杨洪春 Yang; Benyong, 杨本永 Yang; Maoxin, 宋茂新 Song; Peng, 邹鹏 Zou; Xiaobing, 孙晓兵 Sun; Jin, 洪津 Hong

doi:10.3788/cjl201845.1110002

Cited by 6 publications

(1 citation statement)

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“…In space conditions, the refectivity of spectral fuxes deteriorates due to impurities, especially in the frst months, diferently in diferent spectral channels, for example, [15,20,38]. However, scattering difusers made of Spectralon are used as a convenient working tool for orbital calibration for remote sensing satellite instruments, such as MODIS and VIIRS [15], MISR [39], POSP [40], OMI [41], and others. Spectralon was used in the APS instrument of the Glory satellite [13,22].…”

Section: Difuser Geometric Parameters and Materials Optionsmentioning

confidence: 99%

Solar Light Radiometry Calibration Unit for a ScanPol Polarimeter of the Aerosol-UA Space Mission

Syniavskyi

Oberemok

Danylevsky

et al. 2023

International Journal of Optics

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The Aerosol-UA space mission will study aerosol microphysical characteristics in the Earth’s atmosphere based on the multispectral scanning polarimeter (ScanPol) and imaging polarimeter (MSIP). Both polarimeters must be precisely calibrated on the ground and in orbit to provide correct measurements. This paper considers the results of developing an experimental device for the radiometric calibration of the ScanPol. We consider the calibration unit design and operation principle to form a luminous flux with unchanged or well-predicted characteristics in a specified direction. The construction of the radiometric calibration unit is based on a sun-illuminated reflective diffuser made from the white opal glass MS20. We evaluated the scattering and polarization characteristics of the diffuser in laboratory experiments at a wide range of wavelengths. The results suggest that the polarization properties of the diffuser are negligible. The diffuser scattering parameters are close to Lambertian for illuminance conditions, which is necessary for radiometric calibration. The calibration unit was manufactured and tested during field observations of solar radiation. The results will be used for its improvement, mainly to reduce the observed stray scattered radiation entering the telescopes of the ScanPol polarization state analyzer.

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Section: Difuser Geometric Parameters and Materials Optionsmentioning

confidence: 99%

Solar Light Radiometry Calibration Unit for a ScanPol Polarimeter of the Aerosol-UA Space Mission

Syniavskyi

Oberemok

Danylevsky

et al. 2023

International Journal of Optics

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Scan Mirror Assembly for the Multispectral Scanning Polarimeter of Aerosol-UA Space Mission

Syniavskyi

Oberemok

Ivanov

et al. 2021

International Journal of Optics

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In this paper, the scan mirror assembly for the space experiment Aerosol-UA scanning polarimeter (ScanPol) is described. The aim of the Ukrainian space mission Aerosol-UA is to create a database of the optical characteristics of aerosol and cloud particles in the Earth’s atmosphere over a long period of time. The optical characteristics of aerosol and cloud particles are derived from multiangular measurements. Multiangular scanning in ScanPol is provided by scan mirror assembly, which contains a reactive torque compensator electric motor and two scan mirrors, mounted on the shaft of the motor. The control system of the scan mirror assembly enables continuous scanning with a constant speed of the space under investigation. This control system tolerates movements of the orbiting satellite and preserves invariability of its spatial position. The polarimeter ScanPol is designed to acquire spatial, temporal, and spectral-polarimetric measurements simultaneously to minimize instrumental effects and “false” polarizations due to scene movement. Instrumental polarization, introduced by the mirrors of scan assembly, is minimized through the polarization compensated two-mirror scheme which contains two mirrors with orthogonal planes of incidence. In this paper, the polarimetric model of the polarization compensated two scan mirrors is considered. Theoretical calculations are given that substantiate the maximum allowable error of the relative angular position of the mirrors is 15 arcmin (0.25°), and the method of adjustment and control of the angular position of the mirrors is proposed. The polarization properties of mirrors are modelled in the spectral range of 370–1680 nm for bulk oxide-free aluminum. It is obtained that the maximum instrumental polarization of the unadjusted mirror system should be observed at 865 nm, and thus, the polarization characteristics of the scanning system at a given wavelength could be considered as representative for ScanPol in general. The key steps for assembling the unit are illustrated.

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Radiometer-to-imager in-flight cross calibration and verification

Zhu

Hong

et al. 2020

Opt. Express

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This work develops a method to complete the in-flight cross calibration and verification between a radiometer and an imager hosted on aircraft. The in-flight cross calibration is data transmission through time matching, space matching, and spectral matching of two polarization instruments on the same platform, and this method can not only complete the data transfer without considering the surface type to reduce the calibration cycle but also can obtain huge and rich calibration data. The radiometer is the particulate observing scanning polarimeter (POSP), which takes multi-angle, photo-polarimetric measurements in several spectral channels. The POSP measurements in the bands of 670nm and 865nm used in this work are simultaneously measured by the simultaneous imaging polarization camera (SIPC), which is on the same aircraft. The POSP is designed to provide high precision measurements of the atmospheric or earth surface radiation polarization with a substantial along-track spatial coverage, while the SIPC can provide large spatial coverage and high-resolution measurements. Through radiometer-to-imager in-flight cross calibration, the high-precision calibration coefficient of the POSP is transmitted to the SIPC, which can effectively improve the measurement accuracy of the SIPC, and realizes the remote sensing monitoring of atmospheric fine particles with large spatial coverage and high detection precision. First, we deduce the polarization models of the POSP and the SIPC, respectively, and express them in the form of Mueller matrixes, which describe the transformation from incoming polarized radiation to measured signals. Then, we deduce the in-flight cross calibration model of the POSP and the SIPC. Finally, the in-flight experiments have been carried out to validate the radiometer-to-imager in-flight cross calibration model. The results have shown the possibility to minimize the SIPC polarization degree errors with a roughly 0.01 bias relative to POSP on the land.

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Onboard Polarimetric Calibration Methods of Spaceborne Scanning Polarimeter

Cited by 6 publications

References 0 publications

Solar Light Radiometry Calibration Unit for a ScanPol Polarimeter of the Aerosol-UA Space Mission

Solar Light Radiometry Calibration Unit for a ScanPol Polarimeter of the Aerosol-UA Space Mission

Scan Mirror Assembly for the Multispectral Scanning Polarimeter of Aerosol-UA Space Mission

Radiometer-to-imager in-flight cross calibration and verification

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