Diviner

Experiment Goals

• Map global day/night surface temperatures
• Characterize thermal environments for habitability
• Determine rock abundances at landing sites
• Identify polar cold traps and potential polar ice deposits
• Map variations in silicate mineralogy

Team

Status and Schedule

Images and Movies

The Lunar Thermal Environment

With the exception of Mercury, the Moon has the most extreme surface thermal environment of any planetary body in the solar system. The moon receives the same flux of solar radiation as the Earth. The distribution of incident solar radiation is controlled by the moon's shape, the length of the lunar day (~1 month) and the tilt of the lunar spin axis relative to the normal to it orbital plane (~1.54 degrees). At the lunar equator, surface temperatures reach almost 400K at noon and then drop to less than 100K during the lunar night. In the lunar polar regions, horizontal surfaces that receive continuous solar illumination during summer range between 120K and 180K during the lunar day. Inside permanently shadowed regions within polar impact craters, and on horizontal surfaces at the pole during winter, temperatures may be lower than 60K. Lunar surface temperatures are strongly affected by slopes and shadows and can exhibit significant variations over lenght-scales of meters. The moon's extreme temperature environment represents a significant challenge for extended human and robotic lunar exploration.

Instrument Overview

Diviner is a nine channel infrared filter radiometer based on the design of the Mars Reconnaissance Orbiter Mars Climate Sounder (MCS). Diviner's nine channels distributed between two identical, boresighted telescopes (A and B). An articulated elevation/azimuth mount allows the telescopes to view the lunar surface, space, and calibration targets. The instantaneous field-of-view (FOV) response of each channel is defined by a linear, 21-element, thermopile detector array at the telescope focal plane, and its spectral response is defined by a focal plane bandpass filter.

Spectral Channels

Diviner includes two broad-band solar reflectance channels, three mineralogy channels and four thermal channels. The solar channels have identical spectral response, but different sensitivies for wide dynamic range. The three mineralogy channels are intended to map the wavlength peak of the Christiansen thermal emission spectral feature, which is diagnostic of silicate mineralogy (Greenhagen and Paige, 2006). The four broad thermal channels are intended to characterize the surface thermal emission over a wide range of temperatures, as well as the presence of anisothermal emission due to the presence of slopes, shadows and rocks with Diviner's field of view. In channels B2 and B3, Diviner's minimum detectable temperature is less then 30K. Diviner's mineralogy channels should allow confident determination of the wavelength peak of the Christiensen feature at temperatures above 300K.

Mapping Configuration

During the LRO mapping mission, Diviner will operate continuously obtaining 189 separate radiometric measurements every 0.128 seconds. Diviner will normally map the lunar surface in pushbroom nadir orientation, with periodic space, blackbody and solar target calibrations. For an orbital elevation of 50 km above the lunar surface, the width of Diviner's mapping swath will be approximately 3.75 km. The nominal instantaneous field of view of each detector will be approximately 179x307 meters. Diviner's surface fields of view will be reconstructed to a one-sigma accuracy of less than 500 meters. Since the LRO orbit is fixed in inertial space, so Diviner will acheive full diurnal coverage after half a year of After one year of contious mapping, Diviner will achieve nearly complete spatial coverage of the surface of the moon, with significant spatial overlap in the polar regions. However, Diviner's coverage will not be sufficient to observe the entire moon at all times of day, which will imply widening gores in Diviner's spatial coverage as more stringent time of day constraints are applied. If full diurnal coverage is defined as measurements at six random times of day, Diviner will achieve full diurnal coverage poleward of 80 degrees latitude after one year of mapping. If nighttime coverage is defined as measurements within 5 hours local midnight, then Diviner will obtain nighttime coverage over 75% of the of the moon at the equator, and 100% of the the moon poleward of 70 degrees. Also in one year of mapping, Diviner will obtain mineralogy measurements for surfaces above 300K over 70% of the moon from the equator to 70 degrees latitude.

Data Products

The Diviner team will produce and archive a range of data products. These include low-level products derived from instrument telemetry (Level 0); calibrated data with associated geometry (Level 1); and higher-level data products that include gridded temperatures (Level 2); and derived fields such as thermal inertia, rock abundance, and mineralogy that will be created with the aid of topographic data and models (Level 3). Additionaly, the Diviner team will provide specialized data products relating to permanently shadowed regions at the lunar poles (Level 4). These products will be made available to the public online through this web site, and archived through the Geosciences Node of NASA's Planetry Data System.

Thermal Mapping Channel Spectral Response

The end-to-end spectral response of the Diviner flight instrument has been determined. Representative response curves for the four Diviner thermal mapping channels are shown at right.

Mineralogy Channel Spectral Response

The end-to-end spectral response of the Diviner flight instrument has been determined. Representative response curves for the three Diviner mineralogy mapping channels are shown at right.

Signal To Noise Ratio

The signal to noise ratio of the Diviner flight instrument has been characterized. Representative Noise Equivalent Temperature Delta (NETD) curves for Diviner's four thermal mapping channels are shown at right. Diviner's minimum detectable temperature is in the neighborhood of 30K.