(LOLA). M. K. Barker1, E. Mazarico1, D. E. Smith2, X. Sun1, M. T. Zuber2, T. P. McClanahan1, G. A. Neumann1, M. H. Torrence3, J. W. Head4. 1Solar System Exploration Division, NASA Goddard Space Flight Center 8800 Greenbelt Rd. Greenbelt, MD 20771 michael.k.barker@nasa.gov, 2Dept. of Earth, Atmospheric and Planetary Sciences, MIT, 77 Massachusetts Ave. Cambridge, MA 02139, 3Stinger Ghaffarian Technologies, Inc., 7701 Greenbelt Road, Suite 400, Greenbelt, Maryland 20770, USA, 4Dep. Earth, Env. & Planet. Sci., Brown Univ., Providence, RI, 02906, USA.

TIMETER (LOLA). M. K. Barker1, M. Karpenko2, E. Mazarico1, D. E. Smith3, X. Sun1, M. T. Zuber3, T. P. McClanahan1, G. A. Neumann1, J. W. Head4. 1Solar System Exploration Div., NASA Goddard Space Flight Center, 8800 Greenbelt Rd. Greenbelt, MD 20771 michael.k.barker@nasa.gov, 2Dept. of Mechanical and Aerospace Engineering, Naval Postgraduate School, Monterey, CA 93943, 3Dept. of Earth, Atmospheric & Planetary Sci., MIT, 77 Massachusetts Ave. Cambridge, MA 02139, 4Dep. Earth, Env. & Planet. Sci., Brown Univ., Providence, RI, 02912.

BITER LASER ALTIMETER (LOLA). M. K. Barker1, E. Mazarico1, D. E. Smith2, X. Sun1, M. T. Zuber2, T. P. McClanahan1, G. A. Neumann1, M. H. Torrence3, J. W. Head4. 1Solar System Exploration Division, NASA Goddard Space Flight Center 8800 Greenbelt Rd. Greenbelt, MD 20771 michael.k.barker@nasa.gov, 2Dept. of Earth, Atmospheric and Planetary Sciences, MIT, 77 Massachusetts Ave. Cambridge, MA 02139, 3Stinger Ghaffarian Technologies, Inc., 7701 Greenbelt Road, Suite 400, Greenbelt, Maryland 20770, USA, 4Dep. Earth, Env. & Planet. Sci., Brown Univ., Providence, RI, 02906, USA.

We processed and analyzed one-way laser ranging data from International Laser Ranging Service ground stations to NASA's Lunar Reconnaissance Orbiter (LRO), obtained from June 13, 2009 until September 30, 2014.We pair and analyze the one-way range observables from station laser fire and spacecraft laser arrival times by using nominal LRO orbit models based on the GRAIL gravity field. We apply corrections for instrument range walk, as well as for atmospheric and relativistic effects.In total we derived a tracking data volume of approximate to 3000 hours featuring 64 million Full Rate and 1.5 million Normal Point observations. From a statistical analysis of the dataset we evaluate the experiment and the ground station performance. We observe a laser ranging measurement precision of 12.3 cm in case of the Full Rate data which surpasses the LOLA timestamp precision of 15 cm. The averaging to Normal Point data further reduces the measurement precision to 5.6 cm.We characterized the LRO clock with fits throughout the mission time and estimated the rate to 6.9 x 10(-8), the aging to 1.6 x 10(-12) /day and the change of aging to 2.3 x 10(-14) /day(2) over all mission phases. The fits also provide referencing of onboard time to the TDB time scale at a precision of 166 ns over two and 256 ns over all mission phases, representing ground to space time transfer. Furthermore we measure ground station clock differences from the fits as well as from simultaneous passes which we use for ground to ground time transfer from common view observations. We observed relative offsets ranging from 33 to 560 ns and relative rates ranging from 2 x 10(-13) to 6 x 10(-12) between the ground station clocks during selected mission phases. We study the results from the different methods and discuss their applicability for time transfer. (C) 2016 Elsevier Inc. All rights reserved.

We used one-way laser ranging data from International Laser Ranging Service (ILRS) ground stations to NASA's Lunar Reconnaissance Orbiter (LRO) for a demonstration of orbit determination. In the one-way setup, the state of LRO and the parameters of the spacecraft and all involved ground station clocks must be estimated simultaneously. This setup introduces many correlated parameters that are resolved by using a priori constraints. Moreover the observation data coverage and errors accumulating from the dynamical and the clock modeling limit the maximum arc length. The objective of this paper is to investigate the effect of the arc length, the dynamical and modeling accuracy and the observation data coverage on the accuracy of the results. We analyzed multiple arcs using lengths of 2 and 7 days during a one-week period in Science Mission phase 02 (SM02, November 2010) and compared the trajectories, the post-fit measurement residuals and the estimated clock parameters. We further incorporated simultaneous passes from multiple stations within the observation data to investigate the expected improvement in positioning. The estimated trajectories were compared to the nominal LRO trajectory and the clock parameters (offset, rate and aging) to the results found in the literature. Arcs estimated with one-way ranging data had differences of 5–30 m compared to the nominal LRO trajectory. While the estimated LRO clock rates agreed closely with the a priori constraints, the aging parameters absorbed clock modeling errors with increasing clock arc length. Because of high correlations between the different ground station clocks and due to limited clock modeling accuracy, their differences only agreed at the order of magnitude with the literature. We found that the incorporation of simultaneous passes requires improved modeling in particular to enable the expected improvement in positioning. We found that gaps in the observation data coverage over 12 h (≈6 successive LRO orbits) prevented the successful estimation of arcs with lengths shorter or longer than 2 or 7 days with our given modeling.

Introduction: Since the first successful laser ranges to Earth-orbiting satellites 50 years ago, tracking spacecraft using laser beams throughout the solar system has been pursued as a practical tool for fundamental physics, planetary dynamics, and highbandwidth communication. The establishment of a 2way link between a pair of active terminals can provide time transfer and ranges with a precision of a few parts in 1012 [1]. We review the science and practical lessons of a successful 2-way link achieved between the Mercury Laser Altimeter (MLA) and the 1.2-m telescope at the NASA Goddard Geophysical and Astronomical Observatory (GGAO) in Greenbelt, a 1-way link to the Mars Orbiter Laser Altimeter (MOLA) instrument at Mars, some successful lunar experiments (LOLA, LLCD), and several unsuccessful attempts.

The Lunar Orbiter Laser Altimeter (LOLA) measures the backscattered energy of the returning altimetric laser pulse at its wavelength of 1064 nm, and these data are used to map the reflectivity of the Moon at zero-phase angle with a photometrically uniform data set. Global maps have been produced at 4 pixels per degree (about 8 km at the equator) and 2 km resolution within 20 latitude of each pole. The zero-phase geometry is insensitive to lunar topography, so these data enable characterization of subtle variations in lunar albedo, even at high latitudes where such measurements are not possible with the Sun as the illumination source. The geometric albedo of the Moon at 1064 nm was estimated from these data with absolute calibration derived from the Kaguya Multiband Imager and extrapolated to visual wavelengths. The LOLA estimates are within 2 sigma of historical measurements of geometric albedo. No consistent latitude-dependent variations in reflectance are observed, suggesting that solar wind does not dominate space weathering processes that modify lunar reflectance. The average normal albedo of the Moon is found to be much higher than that of Mercury consistent with prior measurements, but the normal albedo of the lunar maria is similar to that of Mercury suggesting a similar abundance of space weathering products. Regions within permanent shadow in the polar regions are found to be more reflective than polar surfaces that are sometimes illuminated. Limiting analysis to data with slopes less than 10 eliminates variations in reflectance due to mass wasting and shows a similar increased reflectivity within permanent polar shadow. Steep slopes within permanent shadow are also more reflective than similar slopes that experience at least some illumination. Water frost and a reduction in effectiveness of space weathering are offered as possible explanations for the increased reflectivity of permanent shadow; porosity is largely ruled out as the sole explanation. The south polar crater Shackleton is found to be among the most reflective craters in its size range globally but is not the most reflective, so mass wasting cannot be ruled out as a cause for the crater's anomalous reflectance. Models of the abundance of ice needed to account for the reflectance anomaly range from 3 to 14% by weight or area depending on assumptions regarding the effects of porosity on reflectance and whether ice is present as patches or is well mixed in the regolith. If differences in nanophase iron abundances are responsible for the anomaly, the permanently shadowed regions have between 50 and 80% the abundance of nanophase iron in mature lunar soil.

LUNAR POLES FROM LOLA AND DIVINER. P. G. Lucey, G.A. Neumann, D. A Paige, M. A. Riner, E. M. Mazarico, D.E. Smith, M.T. Zuber, M. Siegler, P. O. Hayne , D.B. J. Bussey, J. T. S. Cahill, A McGovern, P. Isaacson, L. M. Corley, M.H. Torrence, H.J. Melosh, J. W. Head, E. Song. Hawaii Inst Geophys & Planetology, 1680 East-West Road, University of Hawaii, Honolulu, HI, USA, lucey@higp.hawaii.edu;, NASA Goddard Space Flight Center, Code 698, Greenbelt, MD 20771, USA; UCLA Dept. of Earth and Planetary Sciences, Los Angeles, CA, 90095, Planetary Science Institute, Tucson, AZ 85719, Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139; NASA Jet Propulsion Laboratory, Pasadena, CA, 91109, Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA; Purdue University, Lafayette IN; Brown University, Providence RI 02912.

DERIVED LUNAR GRAVITY MODELS. S. Goossens, E. Mazarico, F.G. Lemoine, D.D. Rowlands, G.A. Neumann, M.H. Torrence, D.E. Smith, M.T. Zuber. CRESST, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore MD 21250 (sander.j.goossens@nasa.gov), NASA GSFC, Code 698, 8800 Greenbelt Road, Greenbelt MD 20771, Massachusetts Institute of Technology, MIT 54-314, 77 Massachusetts Avenue, Cambridge MA 02139, Stinger Ghaffarian Technologies, 7701 Greenbelt Road, Greenbelt, MD 20770

Shackleton crater, whose interior lies largely in permanent shadow, is of interest due to its potential to sequester volatiles. Observations from the Lunar Orbiter Laser Altimeter onboard the Lunar Reconnaissance Orbiter have enabled an unprecedented topographic characterization, revealing Shackleton to be an ancient, unusually well-preserved simple crater whose interior walls are fresher than its floor and rim. Shackleton floor deposits are nearly the same age as the rim, suggesting little floor deposition since crater formation over 3 billion years ago. At 1064 nm the floor of Shackleton is brighter than the surrounding terrain and the interiors of nearby craters, but not as bright as the interior walls. The combined observations are explainable primarily by downslope movement of regolith on the walls exposing fresher underlying material. The relatively brighter crater floor is most simply explained by decreased space weathering due to shadowing, but a 1-mm-thick layer containing approx 20% surficial ice is an alternative possibility.