Abstract
On-orbit radiometric characterization of the multispectral (MS) imagery of the Korea Aerospace Research Institute (KARI)’s Korea Multi-Purpose Satellite-3A (KOMPSAT-3A), which was launched on 25 March 2015, was conducted to provide quantitative radiometric information about KOMPSAT-3A. During the in-orbit test (IOT), vicarious radiometric calibration of KOMPSAT-3A was performed using the Second Simulation of a Satellite Signal in the Solar Spectrum (6S) radiative transfer model. The characteristics of radiometric tarps, the atmospheric optical depth from multi-filter rotating shadowband radiometer (MFRSR) measurements, and sun–sensor–geometry were carefully considered, in order to calculate the exact top of atmosphere (TOA) radiance received by KOMPSAT-3A MS bands. In addition, the bidirectional reflectance distribution function (BRDF) behaviors of the radiometric tarps were measured in the laboratory with a two-dimensional hyperspectral gonioradiometer, to compensate for the geometry discrepancy between the satellite and the ASD FieldSpec® 3 spectroradiometer. The match-up datasets between the TOA radiance and the digital number (DN) from KOMPSAT-3A were used to determine DN-to-radiance conversion factors, based on linear least squares fitting for two field campaigns. The final results showed that the R2 values between the observed and simulated radiances for the blue, green, red, and near-infrared (NIR) bands, are greater than 0.998. An approximate error budget analysis for the vicarious calibration of KOMPSAT-3A showed an error of less than 6.8%. When applying the laboratory-based BRDF correction to the case of higher viewing zenith angle geometry, the gain ratio was improved, particularly for the blue (1.3%) and green (1.2%) bands, which exhibit high sensitivity to the BRDF of radiometric tarps during the backward-scattering phase. The calculated gain ratio between the first and second campaigns showed a less than 5% discrepancy, indicating that the determined radiometric characteristics of KOMPSAT-3A are reliable and useful to the user group for quantitative applications.
Highlights
The recently developed Korea Multi-Purpose Satellite-3A (KOMPSAT-3A), which is a continuation of the KOMPSAT-1–3 earth observation satellite (EOS) programs from the Korea Aerospace ResearchInstitute (KARI), was launched on 25 March 2015, on a Dnepr-1 launch vehicle from the JasnyDombarovsky site in Russia
KOMPSAT-3A is equipped with two distinctive sensors, a high-resolution multispectral (MS) optical sensor, namely the Advanced Earth Image Sensor System-A (AEISS-A), and the Scanner Infrared Imaging System (SIIS)
Most Earth observation (EO) satellite sensors are carefully calibrated by a laboratory experiment with a characterized radiance source, defining absolute radiometric calibration is a challenge after the launch, due to inevitable in-orbit modifications by effects such as the outgassing phenomenon and radiation emissions, that affect both the optical transmission and the charge-coupled device (CCD)
Summary
The recently developed Korea Multi-Purpose Satellite-3A (KOMPSAT-3A), which is a continuation of the KOMPSAT-1–3 earth observation satellite (EOS) programs from the Korea Aerospace ResearchInstitute (KARI), was launched on 25 March 2015, on a Dnepr-1 launch vehicle from the JasnyDombarovsky site in Russia. The recently developed Korea Multi-Purpose Satellite-3A (KOMPSAT-3A), which is a continuation of the KOMPSAT-1–3 earth observation satellite (EOS) programs from the Korea Aerospace Research. KARI performed an in-orbit test (IOT) that included radiometric calibration for a six month period between 14 April and 4 September 2015. The radiometric calibration of the optical satellite is a prerequisite for quantitative applications of remote sensing [1], in order to make full use of the physical data for Earth observation (EO) and for radiometric data continuity with different EO satellites [2]. Most EO satellite sensors are carefully calibrated by a laboratory experiment with a characterized radiance source, defining absolute radiometric calibration is a challenge after the launch, due to inevitable in-orbit modifications by effects such as the outgassing phenomenon (in early stages) and radiation emissions (on a longer-term scale), that affect both the optical transmission and the charge-coupled device (CCD)
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