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Thermal Emission Spectrometer
Observations of Earth and Mars

Figure 1a. Calibrated spectral radiance of Mars. Data were acquired from 18-21 August 1997, when MGS was an average of 5,732,960 km away from Mars. The planet filled only 1.5% of the TES field of view. This spectrum is slightly noisier than the spectrum of Earth, but the signal-to-noise ratio of martian data will improve by 50x once MGS enters orbit. Even with Mars taking up such a small portion of the TES field of view, the planet is clearly detectable, and strong absorptions due to the carbon dioxide atmosphere are present, although there is no evidence of an atmospheric temperature inversion like that observed in the Earth spectrum. Note the absence of water absorptions. The temperature curves shown match expected values at Mars, which are much cooler than at Earth.

Figure 1b. Calibrated spectral radiance of Earth, acquired 23 November 1996 from a distance of 4,776,000 km. The subearth point is approximately 152 deg. W longitude, 18 deg. N latitude (in the Pacific Ocean). The Earth filled approximately 9.3% of the TES field of view. The data clearly show absorptions due to atmospheric carbon dioxide (CO2) and ozone (O3). Absorptions due to water (H2O) vapor are also present in both the long and short wavelength regions of the spectrum. The blue blackbody curve represents the temperature of the upper atmosphere of the Earth. The small peak in radiation at the bottom/center of the carbon dioxide band arises mainly from the Earth's lower stratosphere, which lies over a slightly cooler tropopause (the deepest regions of the band); further out from the band center, radiance increases as the atmosphere warms downward to the surface.
--Christensen, P.R., and J.C. Pearl, J. Geophys. Res., 102, 10,875-10,880, 1997.

Figure 1

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