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Seen from Space 2009

  Greenhouse Gases Observing Satellite "IBUKI" (GOSAT) "
First Thermal infrared spectra" Acquired by Onboard Sensors

  The Japan Aerospace Exploration Agency (JAXA) successfully acquired the "First Thermal Infrared (TIR) spectra" using the Greenhouse Gases Observing Satellite "IBUKI" (GOSAT) during its initial functional check. The data were acquired by sensors on board IBUKI, including the Thermal And Near infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS) after the functional check of detector cooler. which had recently been completed.
IBUKI was launched by JAXA at 12:54 p.m. on January 23, 2009, (Japan Standard Time, JST) from the Tanegashima Space Center. Its initial functional check is on schedule, and the satellite is in good condition.

Figure 1 and 2 present the observation results achieved by the TANSO FTS thermal infrared band (Band 4) when IBUKI passed over the southern Pacific Ocean at around 7:30 a.m. and Egypt around 8:20 a.m. on March 12, 2009 (JST).
We confirmed the TANSO-FTS worked normally in all observation bands and verified the successful results of TANSO-FTS shortwave infrared (SWIR) Bands 1, 2 and 3 on February 7.

We will continue to carry out the initial functional check, which is scheduled to be completed three months after IBUKI’s launch. JAXA, the National Institute for Environmental Studies (NIES), and the Ministry of the Environment (MOE) will then cooperatively carry out the initial calibration and validation including comparing IBUKI data and the ground data, confirming the data accuracy, and making compensations based on the data.

Fig. 1. Spectra from "IBUKI" TANSO-FTS TIR Observation Data both Daytime and Nighttime on March 12, 2009.
Greenhouse gases, such as carbon dioxide and methane, absorb infrared light at specific wavelengths. Figure 1 depicts the light intensity of each wavelength (spectrum) obtained from data of the TANSO-FTS TIR. The data for point 1 were acquired over the Pacific Ocean in the daytime, and that of point 2 were acquired over Egypt in the nighttime. The SWIR bands mainly observe in the daytime because they measure the solar spectra reflected from the Earth’s surface. However, the TIR is able to observe both in the nighttime and daytime because it measures the spectra of Earth radiation. This figure demonstrates that each absorption line is clearly visible. We confirmed that TIR could observe the absorption spectra of carbon dioxide and methane during both day and night.

Fig. 2. Comparison of "IBUKI" TANSO-FTS TIR Observation Data and Simulation Data on March 12, 2009.
Figure 2 presents the observation data and the simulation results (*). The comparison demonstrated that the absorption line positions are in good agreement. We could thus confirm that the spectroscope performed as designed.

We will evaluate the accuracy of relative intensity of each spectrum during calibration activities by comparison with the data measured by instruments on the ground.

(*) The simulation data was calculated by the radiative transfer model (LBLRTM), using sea-surface temperature from NOAA, and temperature and water vapor profiles from Grid Point Value of the Japan Meteorological Agency.

Figure 3 presents an image of the Moon acquired by IBUKI’s monitor camera when the Moon calibration functional test was performed by pointing the satellite towards the moon.

Fig. 3. Image of the Moon acquired by the monitor camera on IBUKI.



Explanation of the Images:

Satellite: Greenhouse Gases Observing Satellite (GOSAT) (IBUKI)
Sensor: Fourier-Transform Spectrometer (TANSO-FTS)
Date: 0726 (JST), Mar 12, 2009
0823 (JST), Mar 12, 2009

The TANSO-FTS covers a wide spectral range from short wave infrared (SWIR) to thermal infrared (TIR). It has about 18,500 spectral channels.

Related Sites:
Launch of IBUKI Special Site
IBUKI(GOSAT) "First Light"
Atmosphere, Seen from Space
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