[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

*今井 正尭^1,2、栗原 純一³、神山 徹^1,2、桒原 聡文⁴、藤田 伸哉⁴、坂本 祐二⁴、齊藤 誠一⁵、平田 貴文⁵、山本 浩万⁶、佐藤 悠司 ⁴、高橋 幸弘³ (1.産業技術総合研究所, 人工知能研究センター、2.産業技術総合研究所, 産総研・東大 先端オペランド計測技術オープンイノベーションラボラトリ、3.北海道大学, 大学院理学研究院、4.東北大学, 大学院工学研究科、5.北海道大学, 北極域研究センター、6.産業技術総合研究所, 地質調査総合センター)

キーワード：リモートセンシング 、地球観測、超小型衛星、月校正

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.