ul 2004 
  
CARBON DIOXIDE MONITORING FROM THE GOSAT SATELLITE 
T. Hamazaki, Y. Kaneko, A. Kuze 
GoSat Project Team , Japan Aerospace Exploration Agency, 2-1-1 Sengen, Tsukuba-city, Ibaraki, 305-8505, Japan 
hamazaki.takashi, kaneko.yutaka, kuze.akihiko@jaxa.jp 
KEY WORDS: Atmosphere, Monitoring, Global-Environmental-Databases, Infrared, Interferometer, Satellite, Spectral, Hyper 
spectral 
ABSTRACT: 
The Greenhouse gases Observing SATellite (GOSAT) is design to monitor the global distribution of carbon dioxide (CO,) from 
orbit. It is a joint project of Japan Aerospace Exploration Agency, the Ministry of Environment (MOE), and the National Institute 
for Environmental Studies (NIES). JAXA is responsible for the satellite and instrument development, MOE is involved in the 
instrument development, and NIES is responsible for the satellite data retrieval. It is scheduled to be launched in 2008. As existing 
ground monitoring stations are limited and still unevenly distributed, the satellite observation has advantages of global and frequent 
observations. The objective of the mission is response to COP3 (Kyoto Protocol): Observation of Green House Gases (GHGs) 
including CO, with 1% relative accuracy in sub-continental spatial resolution and to identify the GHGs source and sink from the 
data obtained by GOSAT in conjunction with the data from the ground instruments, with simulated models. In order to detect the 
CO, variation of boundary layers, the technique to measure the column density and the retrieval algorithm to remove cloud and 
aerosol contamination are investigated. The simultaneous observation of methane (CH,), which is the second largest contribution 
molecule, is studied. The spectrometer with high optical throughput and spectral resolution has been designed. The performance 
demonstration with flight-like instrument from air planes will be presented. The camera to retrieve cloud and aerosol properties will 
also be borne on GOSAT. 
1. INTRODUCTION required by the Kyoto Protocol and to advance earth 
observation technologies for future missions. 
The Greenhouse gases Observing Satellite (GOSAT) is a 
satellite to monitor the carbon dioxide (CO,) globally from (2) Mission Targets 
orbit as illustrated in Figure 1, and it aims to contribute to the The targets of the mission are observation of CO, density in 3- 
international efforts to prevent global warming, such as the month average with 1% (4ppmv) relative accuracy in sub- 
Kyoto Protocol. It is a joint project of Japan Aerospace continental spatial resolution during the first commitment 
Exploration Agency (JAXA), the Ministry of Environment period (2008 to 2012) of the Kyoto Protocol and reducing errors 
(MOE) and National Institute for Environmental Studies (NIES). by half in identifying the GHGs source and sink in Sub- 
JAXA is responsible for satellite development, launch and continental scale with the data obtained by GoSat in 
satellite operation. JAXA and MOE are in charge of the sensor conjunction with the data gathered by the ground instruments. 
development. MOE and NIES are responsible for satellite data 
utilization. It is scheduled to be launched in early 2008. 
3. GOSAT ONBOARD SENSORS 
The greenhouse gases sensor, which is to be accommodated on 
GOSAT, is a Fourier Transform Spectrometer with high optical 
throughput and spectral resolution. The instrument detects the 
interferogram of solar short wave infrared spectra (SWIR) 
reflected on the earth’s surface and thermal infrared spectra 
(TIR) radiated from the ground and the atmosphere. The 
interferogram then are transformed with the fast Fourier 
transformation (FFT) algorithm into spectra, which include the 
absorption spectra of GHGs. Table 1 show the specification of 
the greenhouse gases observation sensor. Figure 2 illustrate the 
instrument configuration and Figure 3 shows the optical layout 
which consist of the pointing mechanism, relay optics, 2 FTSs, 
and detectors. The 2 FTSs cover the wide spectral range from 
0.76 to 15 micron as shown in Figure 4. 
To monitor greenhouse gases, it is essential to measure the 
troposphere where the greenhouse effect occurs. In general, it 
is more difficult to measure the troposphere from space than the 
stratosphere. Nadir-looking measurement is the only feasible 
way to measure the flux that passes through the lower 
troposphere. Figure 5 and 6 show the geometry of nadir- 
looking measurements and the concept of the GOSAT altitude 
control and pointing system, respectively. 
    
Figure 1. Image of GoSat on orbit. 
2. GOSAT MISSION OBJECTIVES 
(I) Mission Objectives 
The objectives of the GOSAT mission are to contribute to 
Japanese environmental administration by estimating the Green 
House Gases (GHGs) source and sink in Sub-continental scale 
and verifying the reduction of GHG’s emission which is 
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