Known Issues in GOSAT Observation
Yokota, Tatsuya; GOSAT project, members
National Institute for Environmental Studies, JAPAN
The Greenhouse gases Observing SATellite (GOSAT), launched in early 2009, has been collecting data of solar reflected radiances in shortwave infrared bands, atmospheric thermal infrared emissions, and land/ocean images nearly seamlessly for more than four years. A few issues related to the satellite's sounding mechanisms were addressed over those years, and some changes were made to the standard observation procedures. One of the issues was the instability of the pointing mechanism. To circumvent this problem, the nominal observation pattern was switched from 5-point to 3-point mode (in cross-track direction) after 1 August 2010. Also, since that time the image motion compensator has been used during the sun-glint soundings in order to increase the chance of obtaining cloud-free sun-glint soundings. The other issue is on discrepancies between the targeted and actual locations of GOSAT soundings. The disagreements were found to be on the order of a few kilometers and depend on the sounding period. Since information on the shift distances is crucial in studies that focus on the levels of XCO2 and/or XCH4 at particular locations, we now provide data users with the FTS Estimated Geolocation Data through the GOSAT Data distribution website (http://data.gosat.nies.go.jp/). We herein summarize current issues associated with GOSAT observation and data products. This presentation is intended to provide ESA category-1 users of GOSAT data products with latest information and to assist their ongoing studies in carbon cycle.