The Greenhouse Gases Observing SATellite (GOSAT) is a satellite to monitor the carbon dioxide (CO2) and the methane (CH4) globally from orbit. Two instruments are accommodated on GOSAT. Thermal And Near infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) detects the Short wave infrared (SWIR) reflected on the earth's surface as well as the thermal infrared (TIR) radiated from the ground and the atmosphere. TANSO-FTS is capable of detecting wide spectral coverage, specifically, three narrow bands (0.76, 1.6, and 2 micron) and a wide band (5.5-14.3 micron) with 0.24 wavenumber spectral resolution. TANSO Cloud and Aerosol Imager (TANSO-CAI) is a radiometer of ultraviolet (UV), visible, and SWIR to correct cloud and aerosol interference. The contaminant deposition on the sensors significantly affects the sensing capability. So the spectroscopic contamination control over wide spectral range is required from the process of GOSAT development to on-orbit operation. The paper presents the instrument design of TANSO-FTS and TANSO-CAI, overview of GOSAT contamination control plan, results from spectral analysis of deposited outgas, test result of hydrazine (rocket and satellite thruster propellant) injection to an optical surface, as well as test result from contamination environment monitoring using a vacuum chamber and contamination witness plates.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.