10:00 〜 10:15
[ACG36-05] Realization of ocean color remote sensing using the micro-satellite RISESAT
キーワード：小型衛星、海色、リモートセンシング
RISEAT (Rapid International Scientific Experiment Satellite, RISESAT) is one of the micro satellite developed by Tohoku University, Hokkaido University etc., and is equipped with the Ocean Observation Camera (OOC). It was launched at 9:50 a.m. on January 18, 2019. After the launch, satellite operations, data reception and processing were all carried out by the universities, and the first scientific data of ocean color remote sensing was also acquired. In this presentation, we show the first ocean color remote sensing data acquired by RISESAT, including the data during the red tide that occurred in the Hokkaido Sea area in September 2021, and an example of the data analysis.
The OOC was calibrated in orbit using the Moon, and the data were downlinked by the satellite receiving antenna (X-band) installed at the Hakodate International Fisheries and Oceanographic Center. The RISESAT data were geometrically corrected using Ground Control Points, and then atmospheric correction was performed in a manner similar to the Second Generation Global Imager (SGLI) onboard JAXA's Earth observation satellite GCOM-C, except that the it was performed specifically for the OOC wavelength bands. The water-leaving radiance was used to determine chlorophyll-a (Chla, mg m-3) of marine aglae as well as the optical absorption coefficient (aCDOM, [m-1]) of colored dissolved organic matter (CDOM) at a wavelength of 412 nm.
The Chla and aCDOM values obtained from RISESAT were validated against their in-situ values obtained in Atsukishi Bay, Hokkaido (42.99-43.05°N, 144.79-144.84°E). The variation of Chla from April to September 2021 based on field observations ranged from 1.17-8.15 mg/m3, whereas the variation based on satellite observations during the same period ranged from 1.53-6.18 mg/m3. On the other hand, the errors for each measurement were 423%, 206%, -34%, -72%, 9% 17% for Chla. The aCDOM from in-situ observations during the same period was 0.77 1/m, while the aCDOM from satellite observations was 0.19 1/m, with the error of 75%.
Although improving the accuracy of ocean observations remains an issue, the fact that a series of processes (such that the development of satellites and instruments, their operation, ocean observations, and data processing, but excluding satellite launches using rockets) were conducted by universities is considered to be a milestone for a new era of ocean observations.
The OOC was calibrated in orbit using the Moon, and the data were downlinked by the satellite receiving antenna (X-band) installed at the Hakodate International Fisheries and Oceanographic Center. The RISESAT data were geometrically corrected using Ground Control Points, and then atmospheric correction was performed in a manner similar to the Second Generation Global Imager (SGLI) onboard JAXA's Earth observation satellite GCOM-C, except that the it was performed specifically for the OOC wavelength bands. The water-leaving radiance was used to determine chlorophyll-a (Chla, mg m-3) of marine aglae as well as the optical absorption coefficient (aCDOM, [m-1]) of colored dissolved organic matter (CDOM) at a wavelength of 412 nm.
The Chla and aCDOM values obtained from RISESAT were validated against their in-situ values obtained in Atsukishi Bay, Hokkaido (42.99-43.05°N, 144.79-144.84°E). The variation of Chla from April to September 2021 based on field observations ranged from 1.17-8.15 mg/m3, whereas the variation based on satellite observations during the same period ranged from 1.53-6.18 mg/m3. On the other hand, the errors for each measurement were 423%, 206%, -34%, -72%, 9% 17% for Chla. The aCDOM from in-situ observations during the same period was 0.77 1/m, while the aCDOM from satellite observations was 0.19 1/m, with the error of 75%.
Although improving the accuracy of ocean observations remains an issue, the fact that a series of processes (such that the development of satellites and instruments, their operation, ocean observations, and data processing, but excluding satellite launches using rockets) were conducted by universities is considered to be a milestone for a new era of ocean observations.