Abstract
The Earth Polychromatic Imaging Camera (EPIC) on the Deep Space Climate Observatory (DSCOVR) satellite observes the entire Sun-illuminated Earth from sunrise to sunset from the L1 Sun-Earth Lagrange point. The L1 location, however, confines the observed phase angles to ∼2°–12°, a nearly backscattering direction, precluding any information on the bidirectional surface reflectance factor (BRF) or cloud/aerosol phase function. Deploying an analog of EPIC on the Moon’s surface would offer a unique opportunity to image the full range of Earth phases, including observing ocean/cloud glint reflection for different phase angles; monitoring of transient volcanic clouds; detection of circum-polar mesospheric and stratospheric clouds; estimating the surface BRF and full phase-angle integrated albedo; and monitoring of vegetation characteristics for different phase angles.
Highlights
Numerous Low Earth Orbit (LEO) and Geosynchronous Equatorial Orbit (GEO) Earth-observing satellites provide a broad spectral range of viable data; it is obtained at the expense of limited geographical (GEO) or temporal (LEO) coverage
Current Earth-observing satellites can produce high-resolution views, LEO sensors can only scan a small portion of the surface at a given time, while GEO sensors can provide temporally continuous, though lower-resolution observations of a significant, though incomplete and fixed portion of the Earth’s disk
An Earth Polychromatic Imaging Camera (EPIC)-Moon camera would work in synergy with the Deep Space Climate Observatory (DSCOVR)/EPIC instrument, increasing the efficiency of both sensors
Summary
Numerous Low Earth Orbit (LEO) and Geosynchronous Equatorial Orbit (GEO) Earth-observing satellites provide a broad spectral range of viable data; it is obtained at the expense of limited geographical (GEO) or temporal (LEO) coverage. A spectroradiometer on the Moon’s surface offers a unique opportunity to provide observations of every region of the FIGURE 7 | Probability density function (pdf) of the phase angle during 25 June to 10 July and 13–28 September periods over Amazonian rainforests (0°–10°S and 60°W to 70°W) for Terra MODIS and MISR sun-sensor geometries derived from MODIS and MISR data acquired from June 2000 to May 2008. Studies of Amazon forest seasonality based on analyses of data from singleviewing sensors disagree on whether there is more greenness in the dry season than in the wet season: the observed variations in the forest BRF were explained by an increase in the leaf area, an artifact of sun-sensor geometry and changes in leaf age through the leaf flush (Huete et al, 2006; Myneni et al, 2007; Brando et al, 2010; Samanta et al, 2012; Morton et al, 2016; Saleska et al, 2016) Conflicting conclusions among these studies arise from different interpretations of surface reflectance data acquired under saturation conditions (Bi et al, 2015). Using the Earth’s atmosphere as a detector, EPIC-Moon imaging of the night-side and limb of the Earth will detect atmospheric impacts (either by a flash or from dispersion of meteoritic dust clouds; see Gorkavyi et al, 2013) from potentially threatening small (
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