HR: 08:00h
AN: A11F-01 INVITED    [Abstracts]
TI: Overview of the Present stage of GOSAT Project
AU: * Inoue, G
EM: inouegen@nagoya-u.jp
AB: The Greenhouse gases Observing SATellite (GOSAT) project was started by Ministry of Environment, Japan Aerospace Exploration Agency and National Institute for Environmental Studies in 2004, and it will be launched in 2008. The critical design review is over and the proto-flight model is under integration. The main sensor is to observe the scattered sun light on Earth surface by an FTIR spectrometer at 1.6 mm and 2.0 mm with 0.2cm^{- 1} resolution. Additional oxygen band sensor at 760nm and thermal infrared covering 700-1800 cm^-1 range are equipped on the same interferometer. The advantage of FTS observation is that it covers wide wavelength range including no absorption or water absorption saturation, as well as the wavelength of methane band at 1.7 mm. The signal without molecular absorption give us the information on the baseline power density, and the signal at strong H₂O absorption range is a good index to evaluate a high altitude thin cloud; cirrus. The disadvantages are the viewing size is large, 10.8 km, and the cloud contamination change is large. The time required to obtain one spectrum is long, 4 second, in order to get a high quality spectrum better than 300 in SN ratio, which is a request of retrieval analysis. A pointing mechanism to fix the viewing point during the observation is required. This is used to switch between the nadir observation over land and the sun-glint observation over ocean without changing the satellite attitude. We use a Gauss-Newton method for retrieving column integrated CO₂ and CH₄ concentrations. The surface reflection spectrum is solved simultaneously assuming a relatively smooth spectrum with some parameters. The disturbances coming from path radiance caused by cirrus and aerosol are corrected. Some sensitivity analyses showed that assumptions of cirrus cloud-top height and cloud geometrical thickness had large influence on retrieved CO₂ concentration, but we are challenging to solve this problem using the water saturated band and the oxygen band information. In order to examine the validity of the retrieval algorithm, we did two flight campaigns in Australia and Russia in 2007 using a similar spectrometer as the GOSAT flight model. Some results to evaluate the performance of GOSAT retrieval algorithm will be presented.
DE: 0322 Constituent sources and sinks
DE: 0340 Middle atmosphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting