Mars Express Analyses the Earth
OMEGA Spectral Analysis
July 3, 2003, OMEGA acquired spectra of the Earth and its Moon.
From the 8 millions of km distance, the Earth filled about one OMEGA pixel. Thus, the spectrum corresponds to the entire illuminated crescent, dominated by the Pacific Ocean. The spectrum covers the visible and near-infrared spectral domain, from 0.35 to 5.15 µm, with a spectral sampling varying from 4 to 20 nm.
These Earth observations by OMEGA, in the 0.35-5.15 micron range, have several unique features, of interest for a variety of scientists. The NASA/Galileo mission observed the Earth during two encounters in 1990 and 1992, and some interesting observations were reported from the NIMS IR investigation, but without the possibility of observing the global spectrum, due to saturation effects on the instrument, not designed for observing too bright objects. For OMEGA, small integration times have been purposely chosen. In addition, the global disk of the Earth was observed at high phase angle, contrary to usual low orbit observation. Such global disk spectra are useful to prepare future observations of Earth-like planets, as for the Darwin mission.