Overview of the 2009 Lro

Introduction: The Diviner Lunar Radiometer Compositional Investigation will use multichannel (0.3 – 300 μm) spectral observations to constrain the composition of the lunar surface. Diviner will be the first lunar orbiting instrument capable of identifying the Christiansen feature (mid-infrared emissivity maximum), which is a good compositional identifier [1]. Diviner will also be the first instrument to measure lunar thermal emission between 13 and 300 μm using multiple channels. These unique data, along with Diviner broadband solar reflectance measurements, are sensitive to different aspects of composition. Ongoing laboratory investigations by members of the Diviner Science Team will measure lunar samples and lunar analog minerals. The Diviner Compositional Investigation’s multispectral approach has the potential to significantly improve our understanding of lunar surface composition. Diviner Lunar Radiometer: Diviner (Figure 1) is scheduled to launch in 2009 on the Lunar Reconnaissance Orbiter. Diviner will map surface temperatures to investigate the Moon’s three thermal environments (daytime, nighttime, and polar) through diurnal and seasonal changes. The temperature data and data from thermal models will be fit to determine thermalphysical properties (e.g. thermal inertia, rock abundance). The Compositional Investigation will use solar reflectance and temperature derived infrared emissivity to determine aspects of lunar surface composition. Diviner Spectral Channels. Diviner has nine spectral channels spread unevenly between 0.3 and 300 μm (Table 1). Two solar channels broadly measure reflected solar radiation with high (channel 1) and low sensitivity (channel 2). Diviner has three narrow-band 8-μm channels to identify the location of the midinfrared Christiansen feature. Diviner’s thermal channels measure emission in four roughly defined octaves of the far-infrared. Diviner Observations. Diviner will primarily employ continuous pushbroom nadir mapping. Diviner’s mapping resolution will be 320 m in track and 160 m cross track at 50 km altitude (6.7 x 3.4 mrad pixel size) with a swatch width of 3.4 km (71 mrad). Diviner’s spatial coverage for any given four lunar-hour period (e.g. pre-sunrise, midday) is expected to be ~40% at the equator, generally increasing to 100% at the poles for the scheduled 1 year mapping orbit. This coverage increases to 80% at the equator for the proposed one year extended mission (90% for two years). Figure 1: Diviner Lunar Radiometer. Diviner’s optics are contained in the central drum behind the apertures. The azimuth and elevation actuators can each rotate 270°. The white surface is the solar calibration target, which is used for photometric calibrations. Blackbody calibration targets, used for radiometric calibrations, are located in the yoke.