The Evaluation of MII/SDGSAT-1 in Red Tide Detection Along the Guangdong Middle Coast

The Sustainable Development Goal Satellite 1 (SDGSAT-1) is the world's first science satellite dedicated to serving the United Nations 2030 Agenda for Sustainable Development. The Multispectral Imager for Inshore (MII) onboard SDGSAT-1 provide an alternative data source to effectively monitor the coastal water environments. In this study, the performances of MII in red tide detection were evaluated along the Guangdong middle coast. First, the radiometric performances of MII were estimated. The in-orbit signal-to-noise ratios (SNRs) of the blue and green bands were in the range of 270-360 while those of the red and near-infrared red bands were in the range of 100-140. The spectral resolution of MII is sufficient to generate atmospheric correction (AC) and red tide indexes calculation based on its own spectral bands. Two types of red tide indexes were compared. The results showed that the hue angle red tide index (HA-RI) better distinguished red tide and turbid water pixels. Two small red tides that occurred in Daya Bay and Mirs Bay were detected by HA-RI with areas of 13.1 and 5.7 km(2), respectively. As the spatial resolution of MII has been improved to 10 m, its ability to detect small-scale red tides has been significantly enhanced, and more detailed spatial characteristics can be observed. In addition, multisource data are required to compensate for the weakness of SDGSAT-1 in temporal resolution for red tide tracing. The design of a three-satellite constellation will further enhance the monitoring capacities of SDGSAT series.