EPOXI Empirical Test of Optical Characterization of an Earth-like Planet
Abstract
The re-purposed Deep Impact spacecraft was used as part of the EPOXI mission-of-opportunity to observe the whole disc of the Earth at 57° phase angle (77% illumination) and 0.18 AU range and at 77° phase angle (62% illumination) and 0.34 AU range on March 19 and June 5, 2008 (respectively), over a range of wavelength from 350 nm to 4.8 µm. These observations sample the Earth's optical properties at the seasonal extremes of an equinox and near-solstice. A third observation was obtained on May 29, including a transit of the Earth by the Moon. These measurements constitute an empirical test of proposed methods for the remote characterization of terrestrial planets in extrasolar planetary systems. The visible-light signal was sampled with 7 filters of approximately 100 nm width at 100 nm spacing over 350-950 nm central wavelength, at 15-minute intervals in 4 selected filters and 1-hour intervals in the remaining 3 filters. Near-IR spectroscopy at 1-4.8 µm was obtained at 2-hour intervals. These data provide a rotationally-averaged optical/IR spectrum of the Earth in a typical presentation at low-to-moderate spectral resolution, and light curves of the Earth reflecting the surface distribution of clouds and terrain. Infrared spectroscopy demonstrates the signatures of H2O, CO2, and other telluric species. The visible light curve demonstrates significant time-variability of the optical spectrum associated with terrestrial terrain types. Of greatest significance to proposed extrasolar terrestrial planet characterization, these data provide a test for the suitability of the "Red Edge" as a signature for the presence of chlorophyllaceous life on an unresolved planetary body.
This work is supported by the NASA Discovery Program.- Publication:
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AAS/Division for Planetary Sciences Meeting Abstracts #40
- Pub Date:
- September 2008
- Bibcode:
- 2008DPS....40.0103L