The emphasis of GOSAT is on atmospheric monitoring to clarify the sources and sinks of carbon dioxide (CO₂) on a sub-continental scale. Through analysing the GOSAT data, scientists accumulate new knowledge on the global distribution and temporal variation of greenhouse gases. 

The overall mission objective is to contribute to environmental administration by estimating the Green House Gases (GHGs) source and sink on a sub-continental scale and to support the Kyoto protocol that was announced at COP3/UNFCCC (Third session of the conference in the framework of climate change) in 1997. The protocol calls for a reduction of greenhouse gases, in particular CO₂; it requires all parties to reduce their emissions by 5% below the level of the year 1990, for the period of 2008-2012.

GOSAT observes infrared light reflected and emitted from Earth's surface and the atmosphere. Column abundances of CO₂ and CH₄ (methane) are calculated from the observational data.