[M-SD39] Micro-satellite and its constellation in remote sensing

[MSD39-P08] Lunar Observations with a Multispectral Sensor Onboard RISESAT Microsatellite and its Radiometric Calibration

*Masataka Imai^1,2, Junichi Kurihara³, Toru Kouyama^1,2, Toshinori Kuwahara⁴, Shinya Fujita ⁴, Yuji Sakamoto⁴, Sei-Ichi Saitoh⁵, Takafumi Hirata⁵, Hirokazu YAMAMOTO⁶, Yuji Sato⁴, Yukihiro Takahashi³ (1.Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology (AIST)), 2.AIST-UTokyo Advanced Operand-Measurement Technology Open Innovation Laboratory (OPERAN-DO-OIL), AIST, 3.Faculty of Science, Hokkaido University, 4.Department of Aerospace Engineering, Tohoku University, 5.Arctic Research Center, Hokkaido University, 6.Geological Survey of Japan, AIST)

Keywords:Remote sensing, Earth observation, Nano/microsatellite, Lunar calibration

Lunar calibration is one of the radiometric calibration methods by utilizing the Moon as a standard reflector. It provides sufficient calibration opportunities without requiring any special equipment and is suitable for nano/microsatellites. This study applies lunar calibration to a multispectral sensor, Ocean Observation Camera (OOC), onboard a microsatellite named Rapid International Scientific Experiment Satellite (RISESAT). We used two Moon models of the RObotic Lunar Observatory (ROLO) and SELENE/Spectrum Profiler (SP) and simulated the irradiance of the Moon at each Moon observation. Comparing the observed and simulated Moon irradiance, we proved OOC had experienced negligible sensitivity degradation in any of the four spectral bands during 16 months of our monitoring period from August 2019. However, a bluing trend in the OOC’s sensor sensitivity was revealed, which indicating a 15% alternation in the sensitivity at maximum. Also, the sensor performance was changing due to the sensor temperature variation. We derived calibration parameters from the Moon observations and validated them by comparing the top-of-atmosphere reflectance of Railroad Valley Playa with the Radiometric Calibration Network dataset. Although we successfully corrected the bluing trend in the visible range, the lunar and vicarious calibration parameters for the infrared band were unexpectedly inconsistent. Stray light contamination can be a plausible explanation of this inconsistency, and further discussion is introduced in this presentation.