The LRO Diviner Lunar Radiometer Team will host a half-day symposium on the Sunday afternoon before the LPSC meeting to acquaint the community with the Diviner experiment, its dataset and its scientific findings to date. The meeting is open to the LPSC community and anyone interested in utilizing the Diviner dataset.

Date and Time - Sunday Afternoon, February 28, 2010 1 pm - 5 pm

Location -  Woodlands Waterway Marriott Hotel and Conference Center
Montgomery Ballroom

Agenda

1:00 PM           Introduction and Experiment Overview (D. Paige)
1:30 PM           Compositional Investigation  (B. Greenhagen)
1:45 PM           Silicic Regions (T. Glotch)
2:00 PM           Apollo Landing Sites (C. Allen)
2:15 PM           Laboratory Thermal Emission Measurements (I. Thomas)
2:30 PM           Polar Observations (D. Paige)
2:45 PM           LCROSS Impact Observations (P. Hayne)
3:00 PM           Polar Volatile History (R. Elphic)
3:15 PM           Break
3:30 PM           Diviner Dataset Description (D. Paige)
4.00 PM           PDS Lunar Orbital Data Explorer (K. Bennett)
4:30 PM           Dataset Validation and Errors (D. Paige)
5:00 PM           Questions and Comments (All)
5:30 PM           Group Dinner

The Diviner lunar radiometer has been mapping the temperature of the
Moon since July, 2009. During this period, temperatures in the lunar
polar regions have changed gradually as the lunar seasons have evolved.
The tilt of the moon’s spin axis is only 1.54 degrees and as a
consequence, lunar seasons are barely noticeable in most locations on
the Moon. However, at the north and south poles, the height of the sun
above the horizon varies by more than 3 degrees over the course of the
year. This affects the percentage of sunlit regions and surface
temperatures at the poles.

During October, 2009, Diviner observed the passage of summer solstice in
the southern hemisphere and winter solstice in the northern hemisphere.
The LRO launch date was chosen so that its orbital plane passed
through the noon to midnight plane in October, allowing Diviner to
measure the extremes of polar temperatures.  Figure 1 illustrates the
configuration of the LRO orbit and the lunar seasons.

Figure 1. The configuration of the LRO orbit during October 2009 allowed Diviner to measure maximum temperatures near summer solstice in the south polar region, and minimum temperatures near winter solstice in the north polar region. (NASA/GSFC/UCLA)

Figure 2 shows a Diviner Channel 8 thermal image of the south polar
region acquired between October 3-30, 2009. The mapping period overlaps
with the LCROSS impact on October 9, 2009. Figure 3 shows an annotated
version of the image, including the location of the LCROSS impact. The
rugged south polar topography  makes it one of the most picturesque
regions on the planet. Diviner’s thermal measurements allow us to “see”
both the warm sunlit and cold shadowed regions in striking
clarity and detail. Even at their warmest, the permanently shadowed areas
in the south polar region are extremely cold. The coldest areas are
located in doubly shadowed regions inside small craters that themselves
lie within the permanently shadowed regions of larger craters. Diviner
measured minimum channel 9 brightness temperatures as low as 35K (-238C
or -397F) in these areas, even at noon on the warmest day of the year.

Figure 2. Diviner Channel 8 thermal image of the south polar region. (NASA/GSFC/UCLA)

Figure 3. Annotated version of Figure 2 including the location of the LCROSS impact. (NASA/GSFC/UCLA)

On the opposite side of the planet, Diviner mapped the north polar
region at winter solstice. Figure 4 shows a nighttime false-color
channel 9 map of the region that reveals the presence of areas with
temperatures as low as 25K (-258C or -415F).  The coldest spot on the Moon
that Diviner has detected thus far is located on the south western edge of
the floor of Hermite Crater. There are also regions on the southern
edges of the floors of Peary and Bosch Craters that are almost as cold.
To put these cold temperatures in perspective, one would have to travel
to a distance well beyond the Kuiper belt to find objects with surfaces
this cold. Diviner measures the temperature of the top millimeter of the
lunar surface. We would expect temperatures below the surface to be
warmer due to heat retention from the spring and summer seasons.

Figure 4. Diviner channel 9 nighttime brightness temperature map of the north polar region acquired close to winter solstice. (NASA/GSFC/UCLA)

Figure 5 shows an animated flyover of the north polar region that
terminates at the coldest measured areas inside of Hermite Crater.

Figure 5. Animated nighttime flyover of the north polar region during the mid-winter season. (NASA/GSFC/UCLA)

Figure 6 shows a histogram of measured daytime and nighttime Channel 9
brightness temperatures in both polar regions. The results show that
there are large regions at both poles with temperatures colder than
~106K, the temperature necessary to prevent significant loss of water
ice over billion-year timescales.  The Diviner data show that The LCROSS
impact successfully sampled one of the coldest lunar cold traps - a fact
that may help put the results of the LCROSS mission into context.

Figure 6. Histograms of Diviner Channel 9 brightness daytime and nighttime temperatures acquired in in the north and south polar regions (square regions to +/- 80 degrees latitude) during their respective winter and summer solstice seasons. The measured pre-impact daytime and nighttime summer solstice brightness temperatures for LCROSS impact site are also indicated. (NASA/GSFC/UCLA)

The Diviner team will host a symposium on the Sunday afternoon before the LPSC meeting to acquaint the community with the Diviner experiment, its dataset and its scientific findings to date. The meeting will be held in the Montgomery Ballroom of the the Woodlands Waterway Marriott Hotel and Conference Center in Houston, TX - the same hotel that is hosting the LPSC meeting, and the Brown-Vernadsky Microsymposium entitled “Compositional Structure of the Lunar Crust: The New View from the Moon” (http://www.planetary.brown.edu/html_pages/micro51.htm).  The Diviner symposium will directly follow  the Brown-Vernadsky Microsymposium which is scheduled for all  day Saturday and Sunday morning. A detailed agenda for the Diviner Symposium will be posted in advance of the meeting.

The LRO Diviner instrument obtained infrared observations of the LCROSS impact this morning. LRO flew by the LCROSS Centaur impact site 90 seconds after impact at a distance of ~80 km. Diviner was commanded to observe the impact site on eight successive orbits, and obtained a series of thermal maps before and after the impact at approximately two hour intervals at an angle of approximately 48 degrees off nadir. In this viewing geometry, the spatial footprint of each Diviner detector was roughly 300 by 700 meters.

Figure 1. Diviner thermal map of the LCROSS impact sites (NASA/GSFC/UCLA).

Figure 1 shows the locations of the Diviner LCROSS impact swaths overlain on a grayscale daytime thermal map of the Moon’s south polar region. Diviner data were used to help select the final LCROSS impact site inside Cabeus Crater, which sampled an extremely cold region in permanent shadow that can serve as an effective cold trap for water ice and other frozen volatiles. Figure 2 shows preliminary, uncalibrated Diviner thermal maps of the impact site acquired two hours before the impact, and 90 seconds after the impact. The thermal signature of the impact was clearly detected in all four Diviner thermal mapping channels. Since the LCROSS impact feature is predicted to be significantly smaller than a Diviner footprint, its detection is consistent with the notion that the LCROSS  impact resulted in significant local heating of the lunar surface.

Figure 2. Uncalibrated Diviner thermal maps of the LCROSS impact region acquired before and after the LCROSS Centaur impact (NASA/GSFC/UCLA).

Overview

The Diviner Lunar Radiometer Experiment is mapping the temperature of the surface of the Moon in unprecedented detail. Diviner is one of seven instruments aboard NASA’s Lunar Reconnaissance Orbiter (LRO) http://lunar.gsfc.nasa.gov/ which launched June 18, 2009.

The Moon’s surface temperatures are among the most extreme of any planetary body in the solar system. Noontime surface temperatures near the lunar equator are hotter than boiling water, whereas nighttime surface temperatures on the Moon are almost as cold as liquid oxygen. It has been estimated that near the lunar poles, in areas that never receive direct sunlight, temperatures can dip to within a few tens of degrees of absolute zero. During the course of LRO’s mapping mission, Diviner will map the entire surface of the Moon at a resolution of better than 500 meters to create the first global picture of the current thermal state of the moon and its daily and seasonal variability.

The Moon’s extreme temperature environment is of interest to future human and robotic explorers, especially if they plan on visiting the Moon for extended periods. Detailed thermal maps of the Moon can also yield information regarding the locations of rocky areas that may be hazardous to landing vehicles, and for mapping compositional variations in lunar rocks and soils. In the Moon’s polar regions, temperature maps also point to the locations of cold traps where water ice and other volatile materials may have accumulated. Mapping the locations of these lunar cold traps and searching for the presence of frozen water is one of the main goals of the LRO mission.

Diviner is designed, built, and operated by the California Institute of Technology Jet Propulsion Laboratory (JPL) in Pasadena, CA. Prof. David A. Paige of the University of California, Los Angeles (UCLA) is the Principal Investigator.

How Diviner Works

Diviner determines the temperature of the Moon by measuring the intensity of infrared radiation emitted by the lunar surface. The hotter the surface, the greater the intensity of emitted infrared radiation. Diviner measures infrared radiation in seven infrared channels (Channels 3-9) that cover a wavelength range from 7.6 to 400 microns. Diviner is the first instrument designed to measure the full range of lunar surface temperatures, from the hottest to the coldest. Diviner also includes two solar channels (Channels 1-2) that measure the intensity of reflected solar radiation.

As LRO orbits the Moon every two hours, Diviner maps a nearly continuous ~3.5 km-wide swath on the lunar surface. Diviner’s swath samples the full range of lunar longitudes once per month to create thermal maps. Diviner will acquire 24 thermal maps of the Moon over the course of a year - 12 daytime maps and 12 nighttime maps, each covering a different range of lunar local times.

Diviner Commissioning Orbit Operations

Diviner has been mapping the Moon continuously during the LRO commissioning phase. Since the instrument was first activated on July 5, 2009, it has acquired over 8 billion calibrated radiometric measurements, and has mapped almost 50% of the surface area of the Moon. “The performance of the instrument has been excellent, and closely matches our predictions” quotes Instrument Engineer Marc Foote at JPL. Says Principal Investigator David Paige of UCLA, “We have already accumulated an enormous amount of high-quality data”.

Diviner has obtained enough data during the LRO commissioning phase to characterize many aspects of the Moon’s current thermal environment. There are large gaps between Diviner’s individual ground tracks at the equator, but in the polar regions, the ground tracks overlap to create continuous high-resolution maps. The plane of the LRO orbit sampled from 5:40 am to 5:40 pm lunar local time at the start of commissioning and gradually drifted to sampling from 1:10 am to 1:10 pm by the end of commissioning. It will take about six months for LRO’s orbit to sample the full range of lunar local times.

In addition to mapping the Moon, Diviner executed a series of specialized calibration sequences to during the commissioning phase. These included scans of the limb of the Moon to better define the instruments fields of view, an infrared panorama of a portion of the LRO spacecraft (See Figures 1a-c), as well as infrared scans of the Earth from lunar orbit, which are presently being analyzed. “Diviner’s operations have run very smoothly” says JPL scientist and lead observational sequence designer Benjamin Greenhagen, “Diviner has been put through her paces and has executed our commands brilliantly”.

Figures 1a-c. Diviner acquired this infrared panorama of the LRO spacecraft between September 4 and 12, 2009. The panorama was constructed by combining over 7000 individual observations as Diviner used its azimuth and elevation actuators to raster across all areas of the LRO spacecraft within its field of regard. To protect Diviner from pointing at the sun, the panorama was acquired over seven orbits while LRO was on the night side of the Moon. Diviner successfully imaged two other LRO instruments: Mini-RF and CRaTER, as well as portions of LOLA and LAMP. The spacecraft panorama is useful for planning observation sequences and calibrations. (NASA/GSFC/UCLA)

First Global Temperature Maps

Figures 2a-b show the first global daytime and nighttime thermal maps of the Moon, created using Diviner data accumulated during August and the first-half of September, 2009. The maps show Channel 8 (50-100 micron wavelength range) brightness temperatures which approximate actual surface physical temperatures. Equatorial and mid-latitude daytime temperatures are close to 380K (224° F), and then decrease sharply poleward of 70° north latitude. Equatorial and mid-latitude nighttime temperatures are close to 95K (-298° F) and then decrease poleward of 80° north latitude. At low and mid-latitudes, there are isolated warmer regions with nighttime temperatures of 140K (-208° F). These correspond to the locations of larger fresh impact craters that have excavated rocky material that remains significantly warmer than the surrounding lunar soil throughout the long lunar night. The thermal behavior at high latitudes contrasts sharply with that of the equatorial and mid-latitudes. Close to the poles, both daytime and nighttime temperatures are strongly influenced by local topography and the thermal outlines of many partially illuminated impact craters are apparent. “Getting a look at the first global thermal maps of the lunar surface has been very exciting” says David Paige, “it’s a whole new way of seeing the Moon”.

Figures 2a-b. Diviner has acquired the first global daytime and nighttime thermal maps of the Moon. These maps were assembled using Diviner data obtained during August and the first half of September, 2009. (NASA/GSFC/UCLA)

High-Resolution North and South Polar Thermal Maps

Figures 3a-b, 4a-b and 5a-b show Diviner high-resolution daytime thermal maps of the north and south polar regions acquired between July 17 and August 14, which corresponds to 5 pm and 3 pm lunar local time. Because of the eccentricity of the LRO commissioning orbit, the north polar maps have a spatial resolution of 700 m and the south polar maps have a spatial resolution of 250 m. Figures 3a and 4a show Diviner Channel 3 (8 micron wavelength) brightness temperatures. Channel 3 is Diviner’s shortest wavelength infrared channel and is insensitive to extremely low temperatures in unilluminated areas. This property makes it useful for mapping the extent of shadowed regions, which appear black just as in a visible image. Figures 3b and 4b show Diviner Channel 8 (50-100 micron wavelength) brightness temperatures. Channel 8 is one of Diviner’s longest wavelength infrared channels and it has excellent capability to measure extremely low temperatures in unilluminated areas.

Figures 3a-b. High-resolution thermal maps of the north polar region of the Moon. The maps cover the region to 80° north latitude and were assembled from Diviner observations obtained in July and August, 2009. Fig. 3a shows Diviner Channel 3 observations and Fig. 3b shows Diviner Channel 8 observations. Diviner’s Channel 3 observations map illuminated and unilluminated areas of the Moon as they appeared when the observations were acquired. Diviner’s observations provide the first measurements of temperatures inside permanently shadowed polar craters that may contain deposits of cold-trapped water ice. (NASA/GSFC/UCLA)

Figures 4a-b. High-resolution thermal maps of the south polar region of the Moon. The maps cover the region to 80° south latitude and were assembled from Diviner observations obtained during July and August, 2009. Fig. 4a shows Diviner Channel 3 observations and Fig. 4b shows Diviner Channel 8 observations. Diviner’s Channel 3 observations map illuminated and unilluminated areas of the Moon as they appeared when the observations were acquired. Diviner’s observations provide the first measurements of temperatures inside permanently shadowed polar craters that may contain deposits of cold-trapped water ice. (NASA/GSFC/UCLA)

The Channel 8 maps reveal richly detailed thermal behavior throughout the north and south polar regions that extends to the limit of Diviner’s spatial resolution (see Figures 5 and 6). Most notable are the measurements of extremely cold temperatures within the permanently shadowed regions of large polar impact craters in the south polar region. Diviner has recorded minimum daytime brightness temperatures in portions of these craters of less than 35K (-397° F) in the coldest areas. These are to our knowledge, these super-cold brightness temperatures are among the lowest that have been measured anywhere in the solar system, including the surface of Pluto. According to science team member Ashwin Vasavada of JPL, “After decades of speculation, Diviner has given us the first confirmation that these strange, permanently dark and extremely cold places actually exist on our Moon. Their presence greatly increases the likelihood that water or other compounds are frozen there. Diviner has lived up to its name.”

Figure 5. Close-up view of Diviner Channel 8 high-resolution thermal maps of a portion of the south polar region, including super cold areas in permanent shadow. (NASA/GSFC/UCLA)

Figure 6. Annotated version of Figure 5 showing the locations of named impact craters.

The Diviner commissioning phase observations provide a snapshot in time of current polar temperatures that will evolve with the lunar seasons. However, it is safe to conclude that the temperatures in these super-cold regions are definitely low enough to cold-trap water ice, as well as other more volatile compounds for extended periods. The existence of such cold traps has been predicted theoretically for almost 50 years. Diviner is now providing detailed information regarding their spatial distribution and temperatures. Diviner’s thermal observations represent one component of LRO’s strategy for determining the nature and distribution of cold-trapped water ice in the lunar polar regions. Future comparisons between Diviner data, physical models, and other polar datasets may provide important scientific conclusions regarding the nature and history of the Moon’s polar cold traps, and any cold-trapped volatile materials they contain.

Diviner was commanded to begin its nominal scanning sequence this morning and we have received engineering telemetry that indicates that everything is going well. The chart shows the positions of Diviner’s elevation and azimuth actuators over a 25 minute period that included three blackbody/space calibrations and one solar calibration. Diviner’s first radioimetric data should be available tomorrow morning.

Diviner has powered up successfully in lunar orbit. Everything looks nominal. The instrument will stay in a stowed position while we assess its health and observe its thermal behavior until tomorrow, when we may be ready give the command to start mapping.

Diviner is scheduled to be turned on in the morning of July 5, 2009. After activation, the instrument will stay in its stowed configuration to give the operations team an opportunity to assess its status. If all looks well, Diviner will begin scanning and mapping the moon early next week.

At 8:34am EDT today LRO initiated LOI-5 which was a 230.8 second burn (36 m/s). This placed LRO in a 31 x 199 km 90.2 degree inclination polar orbit. Tomorrow LRO will transition from solar-inertial pointing to lunar nadir pointing and begin spacecraft commissioning activities.

At 6:26:26am EDT today LRO completed a flawless Lunar Orbit Insertion (LOI-1) burn and placed itself in a 220 km x 3100 km polar orbit about the moon. Over the next 5 days LRO will execute 4 more LOI burns to eventually place it in the 30 km (south pole) x 216 km (north pole) commissioning orbit.