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Proceedings Paper

Retrieval performance of GOSAT thermal infrared FTS sensor for measuring CO2 concentrations
Author(s): Ryoichi Imasu; Naoko Saitoh; Yosuke Niwa
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Paper Abstract

The Greenhouse gases Observing Satellite (GOSAT) is a Japanese satellite that is intended to observe CO2 concentrations from space and to contribute to advancement of research related to CO2 source/sink estimation. The GOSAT main sensor is a Fourier Transform Spectrometer (FTS) named "TANSO-FTS", which covers a wide terrestrial radiation spectrum including CO2 absorption bands at 1.6 μm (Short Wavelength InfraRed, SWIR), and 15 μm (Thermal InfraRed, TIR). The former band is used to estimate columnar concentration of CO2; the latter is used to retrieve the vertical profile of CO2 in the upper atmosphere above the ca. 700 hPa pressure level. We adopt the maximum a posteriori method (MAP) to retrieve the vertical profile of CO2 concentrations using the meteorological analysis data for temperature profiles. Key techniques for retrieving CO2 concentrations are 1) reduction of temperature estimation error through channel selection, 2) optimization of the a priori CO2 profile based on the output from a CO2 transport model, and 3) usage of SWIR data as an additional constraint in retrieval of vertical profiles of CO2. Simulation studies using the output from a CO2 transport model show that, although thermal infrared spectrum has poor sensitivity to the CO2 concentration change in the lower atmosphere, particularly in the boundary layer, we expect that CO2 concentration profiles in the lower atmosphere can be reproduced statistically by combining CO2 columnar data derived from SWIR as an additional constraint in retrieving a CO2 concentration profile from TIR data.

Paper Details

Date Published: 17 October 2007
PDF: 10 pages
Proc. SPIE 6744, Sensors, Systems, and Next-Generation Satellites XI, 67440F (17 October 2007); doi: 10.1117/12.737796
Show Author Affiliations
Ryoichi Imasu, The Univ. of Tokyo (Japan)
Naoko Saitoh, The Univ. of Tokyo (Japan)
Yosuke Niwa, The Univ. of Tokyo (Japan)

Published in SPIE Proceedings Vol. 6744:
Sensors, Systems, and Next-Generation Satellites XI
Shahid Habib; Roland Meynart; Steven P. Neeck; Haruhisa Shimoda, Editor(s)

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