DETECTION OF OCEAN GLINT AND OZONE ABSORPTION USING LCROSS EARTH OBSERVATIONS

The Lunar CRater Observation and Sensing Satellite (LCROSS) observed the distant Earth on three occasions in 2009. These data span a range of phase angles, including a rare crescent phase view. For each epoch, the satellite acquired near-infrared and mid-infrared full-disk images, and partial-disk s...

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Bibliographic Details
Published in:The Astrophysical journal 2014-06, Vol.787 (2), p.1-12
Main Authors: Robinson, Tyler D, ENNICO, KIMBERLY, Meadows, Victoria S, Sparks, William, Bussey, D Ben J, Schwieterman, Edward W, Breiner, Jonathan
Format: Article
Language:English
Subjects:
ABSORPTION
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BRIGHTNESS
CALIBRATION
COMPARATIVE EVALUATIONS
Crescent
DETECTION
Earth
Glint
Mathematical models
MOON
OZONE
PLANETS
RADIANT HEAT TRANSFER
RESOLUTION
SATELLITE ATMOSPHERES
Satellite imagery
Spectra
THREE-DIMENSIONAL CALCULATIONS
VISIBLE SPECTRA
WATER VAPOR
Wavelengths
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Summary:The Lunar CRater Observation and Sensing Satellite (LCROSS) observed the distant Earth on three occasions in 2009. These data span a range of phase angles, including a rare crescent phase view. For each epoch, the satellite acquired near-infrared and mid-infrared full-disk images, and partial-disk spectra at 0.26-0.65 [mu]m ([lambda]/[Delta][lambda] ~ 500) and 1.17-2.48 [mu]m ([lambda]/[Delta][lambda] ~ 50). Spectra show strong absorption features due to water vapor and ozone, which is a biosignature gas. We perform a significant recalibration of the UV-visible spectra and provide the first comparison of high-resolution visible Earth spectra to the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional spectral Earth model. We find good agreement with the observations, reproducing the absolute brightness and dynamic range at all wavelengths for all observation epochs, thus validating the model to within the ~10% data calibration uncertainty. Data-model comparisons reveal a strong ocean glint signature in the crescent phase data set, which is well matched by our model predictions throughout the observed wavelength range. This provides the first observational test of a technique that could be used to determine exoplanet habitability from disk-integrated observations at visible and near-infrared wavelengths, where the glint signal is strongest. We examine the detection of the ozone 255 nm Hartley and 400-700 nm Chappuis bands. While the Hartley band is the strongest ozone feature in Earth's spectrum, false positives for its detection could exist. Finally, we discuss the implications of these findings for future exoplanet characterization missions.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/787/2/171