Gosat Calibration Plan

نویسندگان

  • Kei Shiomi
  • Shuji Kawakami
  • Tomoko Kina
  • Mayumi Yoshida
  • Nami Sekio
  • Yasushi Mitomi
  • Fumie Kataoka
چکیده

Greenhouse gases Observing SATellite (GOSAT) is a Japanese MOE/NIES/JAXA joint program to observe greenhouse gases, such as CO2 and CH4, from space. The GOSAT will be launched in 2008. The GOSAT carries a Fourier transform spectrometer and a push broom imager. The GOSAT development is going on in phase-C/D and characterized the sensor performance in laboratory. The post-launch calibration items are planned and the methods will be developed before the launch. In this study, post-launch calibration methods are investigated by analyzing the current MODIS data, which has similar wavelength bands to GOSAT. The calibration sites are selected on the basis of this study. 1. GOSAT SATELLITE AND SENSORS Thermal And Near infrared Sensor for carbon Observation (TANSO) is carried on the GOSAT satellite for precise measurement of GHGs [1]. The TANSO is composed of 2 sensors, Fourier Transform Spectrometer (FTS) for greenhouse gases observing sensor, and Cloud and Aerosol Imager (CAI) for cloud detection and correction of optical thin cirrus and aerosol interference within the FTS instantaneous field of view (IFOV). Fig.1 shows the TANSO sensors on the GOSAT satellite. The FTS observes at wide spectral range from shortwave infrared (SWIR) to thermal infrared (TIR) with the same optics. The incident lights are modulated by double cube corner mirrors. The modulated lights are separated into SWIR 3 bands with P/S polarization and TIR band by dichroic mirrors settled after optics. The FTS sensor characteristics are shown in Tab. 1. The SWIR bands are utilized for retrieval of CO2 and CH4 column density, on the other hand the TIR band for CO2 and CH4 concentration soundings. Both observations are efficient to improve the measurement accuracy of GHGs. Moreover, the FTS TIR band is utilized for retrieval of another trace gases, such as O3. The CAI has continuous spatial coverage swath, and higher spatial resolution than the FTS in order to detect the aerosol spatial distribution and cloud coverage. The CAI sensor characteristics are shown in Tab. 2. Using the multi-spectral bands from UV to SWIR, the spectral characteristics of the aerosol scattering can be retrieved together with optical thickness. Figure 1. GOSAT satellite and TANSO sensors Figure 2. TANSO-FTS spectral coverage Table 1. TANSO-FTS characteristics Band Band1 Band2 Band3 Band4 Polarization P, S P, S P, S Wavelength 0.75-0.78 μm 1.56-1.73 μm 1.92-2.09 μm 5.5-14.3 μm Target Gases O2 A band CO2, CH4 CO2 CO2, CH4, O3 Spectral Res. 0.5 cm 0.2 cm 0.2 cm 0.2 cm SNR > 300 > 300 > 300 > 300 Time Res. 4 sec / interferogram (5-point observation CT) Spatial Res. 10 km (nadir view at sub-satellite) Swath Width 750 km (5-point observation cross track) TANSO-FTS TANSO-CAI GOSAT _____________________________________________________ Proc. ‘Envisat Symposium 2007’, Montreux, Switzerland 23–27 April 2007 (ESA SP-636, July 2007) Table 2. TANSO-CAI characteristics Band Band1 Band2 Band3 Band4 Center Wavelength 0.38 μm 0.67 μm 0.87 μm 1.60 μm Bandwidth 20 nm 20 nm 20 nm 90 nm Spatial Res. 0.5 km 0.5 km 0.5 km 1.5 km Num. of Pixels 200

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تاریخ انتشار 2007