Brightness temperatures of the lunar surface: Calibration and analysis of Clementine long-wave infrared camera images

This dissertation presents the calibration and analysis of the Clementine long-wave infrared (LWIR) camera images. The scientific payload on the Clementine spacecraft included a LWIR camera with a single passband centered at a wavelength of 8.75 μm. The Clementine orbit deviated by ±30° from Sun synchronous, and for two lunar months, dayside nadir-looking images were obtained near local noon. During the systematic mapping phase of the Clementine mission, approximately 220,000 thermal-infrared images of the lunar surface were obtained. I have completed the calibration of the LWIR camera. Here I present the various steps involved in the calibration routine and the associated uncertainty analysis. The LWIR calibration routine can be outlined as follows: convert measured data number values to radiance via a calibration equation; subtract a zero-flux background image from each lunar image; divide by a flatfield frame; identify bad pixels; smooth over only bad pixels; adjust radiances to reflect the absolute calibration; and convert radiances to brightness temperatures via the Planck function. Observed LWIR radiances can be converted to brightness temperatures, which provide information on various physical properties of the lunar surface. I also present here the LWIR global data set. The LWIR data from noontime orbits demonstrate that the Lambertian temperature model of cos1/4 (i) is a fair approximation for nadir-looking temperatures, rather than the cos1/6(i) behavior observed for ground-based measurements of the full Moon. Deviations from the Lambertian model are likely due to surface roughness effects.; In an effort to understand the influence of large-scale topography on remote lunar surface measurements, I constructed a model which calculates the correlation between reflectance and temperature for a macroscopically rough surface with varying albedo. In this dissertation, LWIR temperatures are directly compared to Clementine ultraviolet-visible (UVVIS) camera 750-nm reflectances. The lunar surface response in different highland and mare locations is explored as a function of varying phase angle. At very low phase angles, the variation in single-scattering albedo primarily governs the temperature and reflectance response regardless of the presence of topography. As the phase angle increases, the influence of surface roughness grows. Finally, at moderate to high phase angles, the affect of surface roughness dominates. In the absence of large-scale topography, the variation in single-scattering albedo governs the temperature and reflectance response of the lunar surface at all phase angles.; LWIR-measured temperature variations yield local topographic information at high incidence angles that is unavailable via the reflectance, while UVVIS-measured reflectance variations yield local topographic information at low incidence angles that is unavailable via the temperature. The largest factors affecting the lunar surface daytime temperatures are the albedo and the incidence angle of solar insolation. The quality of the LWIR data has proven to be exceptional.