[U-04] Geospatial Applications for Societal Benefits

[U04-P02] The oceanographic observation by OOC/RISESAT

*Takafumi Hirata¹, Sei-Ichi Saitoh¹, Tomonori Isada¹, Jun-Ichi Kurihara², Kan-Ichiro Mochizuki³, Hiroshi Murakami⁴, Yukihiro Takahashi¹ (1.Arctic Research Center, Hokkaido University, 2.Hokkaido Information University, 3.PASCO, 4.JAXA)

Keywords:micro satellite, Ocean Color, Remote Sensing

The micro satellite RISEAT (Rapid International Scientific Experiment Satellite, RISESAT) was launched at on January 18, 2019. It carries the Ocean Observation Camera (OOC), challenging the first micro-satellite-based oceanographic observation in Japan at scientific level. Universities were the main body of satellite operations such as reception, calibration and processing of the data. Here we show that an example of the marine environmental/ecological observation by the OOC/RISESAT. Specific quantities to observe with the OOC/RISERSAT is the optical absorption coefficient of the chromophoric dissolved organic matter (aCDOM) at 412nm as well as chlorophyll-a (Chla, mg/m3) of marine aglae, both of which were validated against in-situ data taken in Hokkaido from April to September in 2021. While a limited number of in data available for the validation, a good agreement was found between the OCC/RISESAT and the in situ data for Chla: Median error of Chla was 13% (N=6), while 75% (N=1) of error was found for aCDOM. While only one data available for aCDOM, the OOC/RISESAT aCDOM was 0.19 m^-1 against in situ aCDOM of 0.77 m^-1. With this result, a subsequent image analysis of the coastal waters in the other region of Hokkaido was conducted to show a distinct oceanographic structure: presumably the Red Tide (or Harmful Algal Bloom) known to have occurred during the OOC/RISESAT’s observation. Thus, the Japanese first ocean observation by the microsatellite showed high-quality data and a milestone towards utilization of microsatellites for science.