Search

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2010.05.024 Byline: Edward J. Kennelly (a), Stephan D. Price (b), Kathleen E. Kraemer (b), Ryan Aschbrenner (a) Keywords: Moon, Surface Abstract: We present a model of the absolute radiance of the disk-resolved Moon at visible to near infrared wavelengths. It has been developed in order to use the Moon as a calibration reference, particularly by space-based sensors observing the Earth. We begin with the development of Hillier et al. (Hillier, J., Buratti, B., Hill, K. [1999]. Icarus 141, 205-225) for the reflectance as a function of phase angle and base the lunar reflectance on the Clementine 0.750[mu]m basemap. We adopt Hapke's (Hapke, B. [2002]. Icarus 157, 523-534) expression for the multiple scattering term, including the more accurate approximation to the Chandrasekhar H function. The geometry is based on the Jet Propulsion Laboratory Lunar Ephemeris DE 421, and the topographic slope is from the Kaguya-LALT laser altimetry (). We define three types of terrain by combining the reflectance from the Clementine basemap and the topographic model to specify maria, highlands, and crater regions, and allow mixed types between each class. Parameters of the model are solved for as a function of surface type and wavelength by comparison against data 'chips' from the Robotic Lunar Observatory (ROLO; Kieffer, H.H., Stone, T.C. [2005]. Astron. J. 129, 2887-2901). The reflectance in any waveband may be computed by spectral interpolation of the model predictions relative to the scaled Apollo 16 soil spectrum. The accuracy of the model, evaluated against ROLO imagery, was found to be 2-4%. Author Affiliation: (a) Atmospheric and Environmental Research, Inc., 131 Hartwell Avenue, Lexington, MA 02421, United States (b) Air Force Research Laboratory, Space Vehicles Division, 29 Randolph Road, Hanscom AFB, MA 01731, United States Article History: Received 18 December 2009; Revised 7 May 2010; Accepted 27 May 2010

The Cloud Depiction and Forecast System version 2 (CDFS II) is the operational global cloud analysis and forecasting model of the 557th Weather Wing, formerly the U.S. Air Force Weather Agency. The CDFS II cloud-detection algorithms are threshold-based tests that compare satellite-observed multispectral reflectance and brightness temperature signatures with those expected for the clear atmosphere. User-prescribed quantitative differences between sensor observations and the expected clear-scene radiances denote cloudy pixels. These radiances historically have been modeled at 24-km resolution from a running 10-day statistical analysis of cloud-free pixels that requires the entire global cloud analysis to be executed twice in real time: once in operational cloud detection mode and a second time in a cloud-clearing mode that is designed explicitly for generating clear-scene statistics. Having to run the cloud analysis twice means the availability of fewer compute cycles for other operational models and requires costly interactive maintenance of distinct cloud-detection and cloud-clearing threshold sets. Additionally, this technique breaks down whenever a region is persistently cloudy. These problems are eliminated by means of the optimal spectral sampling (OSS) radiative transfer model of Moncet et al., optimized for execution in the CDFS run-time environment. OSS is particularly well suited for real-time remote sensing applications because of its user-tunable computational speed and numerical accuracy, with respect to a reference line-by-line model. The use of OSS has cut cloud model processing times in half, eliminated the influence of cloudy pixel artifacts in the statistical time series prescription of cloud-cleared radiances, and improved cloud-mask quality. [ABSTRACT FROM AUTHOR]