The TANSO-FTS-2 Instrument for the GOSAT-2 Greenhouse Gas Monitoring Mission

Exelis has been selected to design and build the next-generation interferometric instrument for the second Greenhouse Gases Observing Satellite, or GOSAT-2. This satellite is being built by Mitsubishi Electric Corporation under prime contract with Japan Aerospace Exploration Agency (JAXA), and will be launched in 2018. The interferometric instrument is called the Thermal And Near-infrared Sensor for carbon Observation (TANSO) Fourier Transform Spectrometer (FTS), or TANSO-FTS-2. The TANSO-FTS-2 instrument measures upwelling earth radiance at very high spectral resolution, in multiple spectral bands ranging from 755nm to 14.3 microns. The hyperspectral data is used to determine atmospheric concentrations of carbon dioxide and methane, which are critical greenhouse gases, on a global basis. Its spatial resolution of <10km permits the detection of the sources and sinks of greenhouse gasses on a global basis. It is a critical asset for the monitoring and trending of gases which contribute to global warming.

The Exelis TANSO-FTS-2 instrument includes a number of new design features intended to improve mission performance. In particular, a new Intelligent Pointing camera system is used to identify cloud-free locations within the field of view, and the instrument's line of sight is autonomously adjusted to collected hyperspectral data from this location. This is expected to greatly increase the yield of useful earth observations, uncontaminated by effects from clouds. Another improvement is a comprehensive set of onboard calibration targets that are used to accurately calibrate the instrument over its entire spectral range. Other improvements include a larger aperture for improved SNR, improvements to the interferometer to ensure high data quality throughout mission life, and an improved scanning system with excellent line of sight stability.

The TANSO-FTS-2 instrument is built upon the successful heritage of the Exelis Cross-track Infrared Sounder (CrIS) instrument, which was launched in 2011 and has been successfully collecting hyperspectral data which produces atmospheric vertical profiles of temperature, water vapor, and pressure. Several key CrIS subsystems are being used as part of the TANSO-FTS-2 design. This paper will summarize the GOSAT-2 mission, the requirements for the TANSO-FTS-s instrument, and key design trade-offs. It will then describe the TANSO-FTS-2 design, and summarize its expected performance compared to its requirements. Top level development plans and schedules will also be provided.