David Edmund Smith

MIT · EAPS

Examining the reflectance of the Moon’s surface across a broad range of viewing geometries through photometric analysis can reveal physical and geological properties of its regolith. Since 2013 December, the Lunar Orbiter Laser Altimeter (LOLA) on board the Lunar Reconnaissance Orbiter (LRO) has been operating as a near-infrared (1064 nm) passive r...

The lunar gravity field is used to estimate and constrain the depth of mass anomalies under 19 major lunar impact basins. We use radial gravitational spectra, consisting of accelerations computed either per spherical harmonic degree or cumulatively, at surface locations to obtain the distribution of the gravity signal with spherical harmonic degree...

Upcoming missions to the lunar south pole require detailed maps over large areas to fully characterize landing sites locally and regionally and to place their data into proper geologic context. To that end, we enhanced the Lunar Orbiter Laser Altimeter altimetry data set for the south polar region, from which we produced new maps of topography, top...

Relationships between the degree of a spherical harmonic model of the gravitational field of a body and the depth of a source expressed as a density contrast can be used to study the structure of features. Here, we show that the gravitational acceleration per spherical harmonic degree of a constant density source has an extremum that depends on the...

Changes in mass distribution affect the gravitational figure and reorient a planetary body’s surface with respect to its rotational axis. The mass anomalies in the present-day lunar gravity field can reveal how the figure and pole position have evolved over the Moon’s history. By examining sequentially each individual crater and basin, working back...

Geodetic and geophysical investigations of the Galilean moon Callisto address fundamental questions regarding the formation and evolution of the Jovian system. Callisto's evolution and internal structure appear to significantly differ from the other Jovian satellites. Similarly-sized Ganymede is a highly evolved ice-rock moon with a differentiated...

Europa is a premier target for advancing both planetary science and astrobiology, as well as for opening a new window into the burgeoning field of comparative oceanography. The potentially habitable subsurface ocean of Europa may harbor life, and the globally young and comparatively thin ice shell of Europa may contain biosignatures that are readil...

Mars Polar Science is an integrated, compelling system that serves as a nearby analogue to numerous other planets, supports human exploration, and habitability. Mars possesses the closest and most easily accessible layered ice deposits outside of Earth, and accessing those layers to read the climate record would be a triumph for planetary science.

We report the development of a new type of space lidar specifically designed for missions to small planetary bodies for both topographic mapping and support of sample collection or landing. The instrument is designed to have a wide dynamic range with several operation modes for different mission phases. The laser transmitter consists of a fiber las...

Based on the previous applications of laser altimetry to planetary geodesy at GSFC, we use the recently developed PyXover software package to analyze altimetric crossovers from the Mercury Laser Altimeter (MLA). Using PyXover, we place new constraints on Mercury's geodetic parameters via least squares minimization of crossover discrepancies. We sim...

Here we present a summary of progress on NASA’s Europa Lander mission concept. The Europa Lander mission concept is mature, technologically well-developed, and ready to proceed to Phase A.

Mars Polar Science is an integrated, compelling system that serves as a nearby analogue to numerous other planets, supports human exploration, and habitability. Mars possesses the closest and most easily accessible layered ice deposits outside of Earth, and accessing those layers to read the climate record would be a triumph for planetary science.

We present new high-resolution topographic models of 4 high-priority lunar south pole landing sites based exclusively on the laser altimetry data acquired by the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter. By iteratively adjusting the LOLA tracks to the LOLA-based digital elevation model (LDEM) in a self-consisten...

We present our latest high‐resolution lunar gravity field model of degree and order 1200 in spherical harmonics using Gravity Recovery and Interior Laboratory (GRAIL) data. In addition to a model with the standard spectral Kaula regularization constraint, we determine models by applying a constraint based on topography called rank‐minus‐one (RM1)....

We present the results of a 2‐year‐long systematic campaign to monitor the lunar dust exosphere for enhancements in dust concentration at altitudes <20 km both during and outside of major meteor stream periods. We utilize the radiometric capabilities of the Lunar Orbiter Laser Altimeter Laser Ranging telescope onboard the Lunar Reconnaissance Orbit...

The modeling of the solar system evolution relies on the knowledge of parameters related to helio- and fundamental physics, such as the Nordtvedt parameter (η), the temporal variation of the solar gravitational constant (GM), coefficients (e.g., β and γ) of the Parameterized Post-Newtonian (PPN) formalism for Einstein’s theory of General Relativity...

The science mission of SpaceIL consists of detailed characterization of the landing site, measuring the crustal magnetic anomalies, and ranging to the lander.

The Lunar Orbiter Laser Altimeter (LOLA) aboard the Lunar Reconnaissance Orbiter (LRO) has collected nearly seven billion measurements of surface height on the Moon with an absolute accuracy of ∼ 1 m and a precision of ∼ 10 cm . Converting time-of-flight laser altimeter measurements to topographic elevations requires accurate knowledge of the laser...

We study LOLA derived normal albedo as a function of Diviner maximum temperature, to see if lunar permanently shadowed regions cold enough (<110K) to preserve surface water frost over geologic timescales show increased reflectance.

Ceres is the largest body in the asteroid belt with a radius of approximately 470 km. In part due to its large mass, Ceres more closely approaches hydrostatic equilibrium than major asteroids. Pre-Dawn mission shape observations of Ceres revealed a shape consistent with a hydrostatic ellipsoid of revolution. The Dawn spacecraft Framing Camera has b...

Ceres’ gravity field and rotational parameters have been precisely measured using 1.5 years of radiometric Doppler and range data and optical landmark tracking from the Dawn spacecraft in orbit about the dwarf planet. As was the case with Dawn at Vesta, the gravity field, orientation parameters, landmark locations, and Ceres’ orbit are jointly esti...

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 mode...

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 i...

The identification of surface ice at Mercury's poles relied largely on correlating anomalously bright surface material identified with surface reflectance measurements from the Mercury Laser Altimeter with model temperatures that allow surface ice to be stable for billions of years. A similar data set exists for the lunar poles. The Lunar Orbiter L...

The Lunar Orbiter Laser Altimeter (LOLA) experiment on Lunar Reconnaissance Orbiter (LRO) is a laser altimeter that also measures the strength of the return pulse from the lunar surface. These data have been used to estimate the reflectance of the lunar surface, including regions lacking direct solar illumination. A new calibration of these data is...

We present initial calibration and results of passive radiometry collected by the Lunar Orbiter Laser Altimeter onboard the Lunar Reconnaissance Orbiter over the course of 12 months. After correcting for time- and temperature-dependent dark noise and detector responsivity variations, the LOLA passive radiometry measurements are brought onto the abs...

Observations from the Gravity Recovery and Interior Laboratory (GRAIL) mission indicate a marked change in the gravitational signature of lunar impact structures at the morphological transition, with increasing diameter, from complex craters to peak-ring basins. At crater diameters larger than ~200 km, a central positive Bouguer anomaly is seen wit...

We present an improved lunar digital elevation model (DEM) covering latitudes within ±60°, at a horizontal resolution of 512pixels per degree (∼60m at the equator) and a typical vertical accuracy ∼3 to 4m. This DEM is constructed from ∼4.5×109 geodetically-accurate topographic heights from the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar...

The possibility of lunar polar ice was suggested by Harold Urey in the 1950's [1], and has likely been directly detected at the North Pole of Mercury by MESSENGER. That detection was based on the presence of reflectance anomalies seen by the Mercury Laser Altimeter (MLA) that occurred only where models of the surface temperature allow long-duration...

The interiors of the lunar south circumpolar craters Haworth, Shoemaker, Faustini, and Shackleton contain permanently shadowed regions (PSRs) and have been interpreted to contain sequestered volatiles including water ice. Altimetry data from the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter provide a new means of exa...

We report preliminary results on the near-infrared lunar phase function observed with the Lunar Orbiter Laser Altimeter onboard the Lunar Reconnaissance Orbiter.

A solution for a very-high-resolution GRAIL gravity field determines lunar Love number and tidal dissipation Q, but does not detect the inner core.

We present updated global and local gravity field models of the Moon using GRAIL data only.

During its low-altitude gravity campaign, MESSENGER was tracked to altitudes down to 25 km. We present an updated, higher-resolution gravity field of Mercury.

We have analyzed three years of radio tracking data from the MESSENGER spacecraft in orbit around Mercury and determined the gravity field, planetary orientation, and ephemeris of the innermost planet. With improvements in spatial coverage, force modeling, and data weighting, we refined an earlier global gravity field both in quality and resolution...

ABSTRACT: DOI: 10.1002/2014JE004678 The small crater Airy-0 was selected from Mariner 9 images to be the reference for the Mars prime meridian. Initial analyses in the year 2000 tied Viking Orbiter and Mars Orbiter Camera images of Airy-0 to the evolving Mars Orbiter Laser Altimeter global digital terrain model to update the location of Airy-0. Bas...

The small crater Airy-0 was selected from Mariner 9 images to be the reference for the Mars prime meridian. Initial analyses in the year 2000 tied Viking Orbiter and Mars Orbiter Camera images of Airy-0 to the evolving Mars Orbiter Laser Altimeter global digital terrain model to update the location of Airy-0. Based upon this tie and radiometric tra...

International Laser Ranging Service Ground Stations perform one‐way laser ranging to NASA’s Lunar Reconnaissance Orbiter which has operated in a lunar orbit since June 2009. We carried out precision orbit determination for LRO with one‐way laser ranging observations only. We estimated LRO’s initial state and clock as well as the clocks of the parti...

A 20th degree ellipsoidal harmonic gravity field of Vesta is determined by processing radiometric Doppler and range data from the Dawn mission. The gravity field shows sensitivity up to degree 18 and the coefficients are globally determined on average to degree 15. Gravity anomalies are mapped to the Brillouin ellipsoid (304 × 289 × 247-km), which...

The Vesta gravity field and related physical parameters have been precisely measured using 10-months of radiometric Doppler and range data and optical landmark tracking from the Dawn spacecraft. The gravity field, orientation parameters, landmark locations, and Vesta’s orbit are jointly estimated. The resulting spherical harmonic gravity field has...

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) an...

We have derived a gravity field solution in spherical harmonics to degree and order 900, GRGM900C, from the tracking data of the GRAIL Primary (March 1 – May 29, 2012) and Extended Missions (August 30 – December 14, 2012). A power law constraint of of 3.6 × 10−4/ℓ2, was applied only for degree ℓ greater than 600. The model produces global correlati...

We estimated a high-resolution local gravity field model over the south pole of the Moon using data from the Gravity Recovery and Interior Laboratory's extended mission. Our solution consists of adjustments with respect to a global model expressed in spherical harmonics. The adjustments are expressed as gridded gravity anomalies with a resolution o...

The Lunar Orbiter Laser Altimeter instrument onboard the Lunar Reconnaissance Orbiter spacecraft collected more than 5 billion measurements in the nominal 50 km orbit over ∼10,000 orbits. The data precision, geodetic accuracy, and spatial distribution enable two-dimensional crossovers to be used to infer relative radial position corrections between...

GRAIL gravity data reveals a quasi-rectangular pattern of linear anomalies encompassing the Procellarum region, which are interpreted as magma-flooded rifts.

A GRAIL S21 value implies a misalignment of principal axes derived by Lunar Laser Ranging. A fluid outer core shaped by internal gravity can affect axes.

Dawn's geophysical data reveal density variations within the crust and mantle of Vesta that are consistent with serial magmatism during Vesta's formation.

A high-resolution view of the Orientale Basin and surroundings from the Gravity Recovery and Interior Laboratory (GRAIL).

We analyze the process of magmatic intrusion emplacement beneath lunar floor-fractured craters including surface morphologies and Bouguer gravity anomalies.

Impact melt sheets at lunar basins make a moderate positive contribution to the free-air gravity. At Orientale, the melt sheet is 5-10% of the observed anomaly.

The static gravity field and the thermosphere of Mars from radio science data of the Mars Reconnaissance Orbiter (MRO) mission.

Modeling of the illumination conditions at the poles of the Moon and Mercury enable data calibration and analysis of other measurements (Ly-alpha, neutron).

MESSENGER MLA reflectance observations suggest the presence of widespread small-scale cold traps in Mercury's north polar region.

The darker it gets the brighter it is.

We use GRAIL data to constrain the extent of brecciation and subsurface fracturing associated with the formation of lunar impact craters.

High-degree GRAIL data were analyzed using admittance. Mare regions are readily identified; South Pole-Aitken basin exhibits a shallower low-density layer.

We present high-resolution gravity field models of the Moon using GRAIL primary and extended mission data.

Subsurface thermal density anomalies related to the 3:2 resonance-driven surface temperature distribution may explain Mercury's second-degree shape and geoid.

Dawn gravity, topography and spectral data provide constraints on Vesta's origin and evolution. Surface heterogeneity supports evidence from the gravity field for intracrustal compositional variations consistent with discrete magmatic systems.

We use Vesta gravity and topography in connection with the geochemically derived constraints to study Vesta’s internal structure, rotational history and compensation state.

The Dawn mission determined the gravity field of Vesta to degree and order 20 and mapped its shape relative to the center of mass to high accuracy. The Bouguer gravity field can be calculated as the difference between the observed gravity field and one calculated under varying assumptions of the internal density structure that minimizes the misfit...

The Lyman Alpha Mapping Project (LAMP) UV spectrograph on the Lunar Reconnaissance Orbiter (LRO) was positioned to directly view the expanding gas plumes from the two GRAIL spacecraft impacts on 17 December 2012. LAMP detected resonantly scattered emissions from Hg and H atoms in the sunlit regions of these plumes. The spectral, spatial, and light-...

The Gravity Recovery and Interior Laboratory (GRAIL) is a spacecraft-to-spacecraft tracking mission that was developed to map the structure of the lunar interior by producing a detailed map of the gravity field. The resulting model of the interior will be used to address outstanding questions regarding the Moon’s thermal evolution, and will be appl...

Dawn, a solar-powered, ion-propelled mission, was launched on September 27, 2007, reaching its first target, Vesta, on July 16, 2011. Dawn orbited Vesta until September 5, 2012, and is now on its way to Ceres, where it will enter orbit in early 2015 [Fig.1].

Abstract The prospect of a future soft landing on the surface of Europa is enticing, as it would create science opportunities that could not be achieved through flyby or orbital remote sensing, with direct relevance to Europa's potential habitability. Here, we summarize the science of a Europa lander concept, as developed by our NASA-commissioned S...

The lunar gravity field and topography provide a way to probe the interior structure of the Moon. Prior to the Gravity Recovery and Interior Laboratory (GRAIL) mission, knowledge of the lunar gravity was limited mostly to the nearside of the Moon, since the farside was not directly observable from missions such as Lunar Prospector. The farside grav...

The recent determination of the gravity field of Mercury and new Earth-based radar observations of the planet's spin state afford the opportunity to explore Mercury's internal structure. These observations provide estimates of two measures of the radial mass distribution of Mercury: the normalized polar moment of inertia and the fractional polar mo...

During the past 20 years the NASA Goddard Space Flight Center has developed five different lidar for space, and has successfully used them in orbital missions to map Mars, the Earth, the Moon and Mercury. Although similar in some ways, each of these lidar has had a different combination of measurement requirements, payload constraints, and operatio...

The Gravity Recovery and Interior Laboratory (GRAIL) mission has completed its primary three-month tour that resulted in a gravitational field of 660 degree-and-order or equivalent surface resolution of 8 km. The primary measurement for the gravity field is the inter-spacecraft K-Band Range Rate (KBRR) measurement derived from dual spacecraft one-w...

The tracking of artificial earth satellites by other earth satellites offers the potential for increased accuracy in estimating orbit and geopotential coefficients. The improvement in accuracy is due primarily to the near-continuous coverage possible, the addition of new geometry between tracker and tracked satellite, and the decrease in sensitivit...

Volcanic plains identified on Mercury are morphologically similar to lunar mare plains but lack constructional and erosional features that are prevalent on other terrestrial planetary bodies. We analyzed images acquired by the MESSENGER spacecraft to identify features on Mercury that may have formed by lava erosion. We used analytical models to est...

We use GRAIL data with hydrocode and finite-element modeling to explain the origin of lunar mascon basins. This is Part 2/2, covering FEM results.

Gravity over the south pole is compared with other data, including Bouguer gravity, crustal thickness and density, surface temperatures, and neutron results.

The GRAIL extended mission has provided gravity models that are being used to map the upper crust of the Moon in unprecedented detail.

Analyses of GRAIL data indicate a relatively thin lunar crust, leading to the conclusion that the Moon is not enriched in refractory elements compared to Earth.

GRAIL gravity data show that the crust of the Moon has been highly fractured by billions of years of impact cratering.

A method to improve LOLA DTMs with the help of NAC DTMs is shown at Connecting Ridge, a candidate landing site for the ESA Lunar Lander at the lunar south pole.

We use GRAIL data with hydrocode and finite-element modeling to explain the origin of lunar mascon basins. This is Part 1/2, covering hydrocode results.

The inventory of lunar basins revealed by GRAIL does not indicate a more extensive history of lunar impacts as has been previously suggested.

We present high-resolution lunar gravity field models derived from GRAIL primary and extended mission data.

We present an updated gravity field of Mercury based on nearly two years of MESSENGER tracking data.

The lunar gravity field solutions obtained with the GRAIL data alone provide significant improvements to the orbit reconstruction quality of the LRO spacecraft.

RF occultations measurements of Mercury's southern hemisphere show polar flattening, which has implications for rotational history and internal structure.

We measure GRAIL gravity anomaly profiles of peak-ring basins on the Moon and compare these with their morphometries to better understand peak-ring formation.

Reflectance measurements from LOLA show that normal albedos of permanently shadowed regions at the south pole to be anomalously bright.

The Mercury Laser Altimeter has confirmed that near-polar impact craters contain both water ice and unusually dark material postulated to include organic compounds.

GRAIL analyses provide lunar gravity field, Love number, and moment of inertia with improved uncertainties.

We report a free space laser communication experiment from the satellite laser ranging (SLR) station at NASA Goddard Space Flight Center (GSFC) to the Lunar Reconnaissance Orbiter (LRO) in lunar orbit through the on board one-way Laser Ranging (LR) receiver. Pseudo random data and sample image files were transmitted to LRO using a 4096-ary pulse po...

Laser communication and ranging experiments were successfully conducted from the satellite laser ranging (SLR) station at NASA Goddard Space Flight Center (GSFC) to the Lunar Reconnaissance Orbiter (LRO) in lunar orbit. The experiments used 4096-ary pulse position modulation (PPM) for the laser pulses during one-way LRO Laser Ranging (LR) operation...

New and improved models of the lunar gravity field to 420×420 in spherical harmonics have been derived from the analysis of the Gravity Recovery And Interior Laboratory (GRAIL) intersatellite Ka-band tracking data. We discuss the measurement and force modeling applied to the analysis of the GRAIL data from the primary mission (March 1 to May 29, 20...

The high resolution of the LOLA lunar topography data and continuing advances in computational processing together provide intriguing prospects for the correlation of impact cratering model results with observed lunar features. We have developed a cratered terrain model to investigate the statistical properties of such landscapes and how they depen...

Floor-Fractured Craters (FFCs) are a class of lunar craters characterized by anomalously shallow floors cut by radial, concentric, and/or polygonal fractures; additional interior features are moats, ridges, and patches of mare material. Two formation mechanisms have been hypothesized—floor uplift in response to shallow magmatic intrusion and sill f...

Three years of continuous observations by the laser altimeter (LOLA) on the Lunar Reconnaissance Orbiter (LRO) spacecraft have provided unique data on spatial scales of 5 m and above for the reflectance, surface roughness and topographic shadowing over the south polar region of the Moon.