The temperatures of Giordano Bruno crater observed by the Diviner Lunar Radiometer Experiment: Application of an effective field of view model for a point-based data set

Abstract

Point based planetary datasets are typically stored as discrete records that represent an infinitesimal location on the target body. Instrumental effects and spacecraft motion during integration time can cause single points to inadequately represent the total area on the target that contributes to an observation. Production of mapped data products from these data for scientific analysis proceeds by binning points onto rectangular grids. Empty bins occur where data coverage is insufficient relative to grid resolution, a common problem at high latitudes in cylindrical projections, and remedial interpolation can lead to high uncertainty areas and artifacts in maps.To address such issues and make better use of available data, we present a method to calculate the ground-projected effective field of view (EFOV) for point-based datasets, using knowledge of instrumental characteristics and observation geometry. We apply this approach to data from the Lunar Reconnaissance Orbiter (LRO) Diviner Lunar Radiometer Experiment, a visible to far-infrared multispectral radiometer which acquires radiometric measurements of reflected visible and emitted infrared radiation of the Moon in 9 spectral channels between 0.35 and 400µm. Analysis of gridded radiance from crater Giordano Bruno, a 22km diameter rayed crater, is used to demonstrate our gridding procedure. Diviner data, with such processing, reveals details of the surface that are seen in the high-resolution LRO Camera NAC images. Brightness temperatures and anisothermality observed in Diviner’s IR channels show the thermophysical properties of the crater ejecta to be very heterogeneous indicative of minimal mechanical disruption by micrometeoroid impacts consistent with a very young (<10Ma) formation age as the lunar surface becomes rapidly homogenized over time. This heterogeneity has implications for crater-count studies as regions of high anisothermality are characterized by large blocks of material and lower crater densities.