A5001886502- Planetary Science and Exploration
- Space Exploration and Technology
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Galaxies: Formation, Evolution, Phenomena
- Space Science and Extraterrestrial Life
- Space Satellite Systems and Control
- Spaceflight effects on biology
- Calibration and Measurement Techniques
- Space exploration and regulation
- Astronomical Observations and Instrumentation
- Geophysics and Gravity Measurements
- Spacecraft and Cryogenic Technologies
- GNSS positioning and interference
- Adaptive optics and wavefront sensing
- Inertial Sensor and Navigation
- History and Developments in Astronomy
- Spacecraft Dynamics and Control
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- High-pressure geophysics and materials
- Robotics and Sensor-Based Localization
- Image Processing and 3D Reconstruction
Goddard Space Flight Center
2014-2024
Sigma Space (United States)
2014-2017
Royal Observatory
2009-2014
University of Edinburgh
2009-2014
UK Astronomy Technology Centre
2009-2010
Institute of Astronomy
2009
University of Florida
2002-2008
Universidad Nacional Autónoma de México
2007
Lockheed Martin (Canada)
2005
University of Maryland, College Park
2003
We present an improved lunar digital elevation model (DEM) covering latitudes within ±60°, at a horizontal resolution of 512 pixels per degree (∼60 m the equator) and typical vertical accuracy ∼3 to 4 m. This DEM is constructed from ∼4.5×109 geodetically-accurate topographic heights Lunar Orbiter Laser Altimeter (LOLA) onboard Reconnaissance Orbiter, which we co-registered 43,200 stereo-derived DEMs (each 1°×1°) SELENE Terrain Camera (TC) (∼1010 total). After co-registration, approximately...
The Lunar Orbiter Laser Altimeter instrument onboard the Reconnaissance spacecraft collected more than 5 billion measurements in nominal 50 km orbit over ~10,000 orbits. data precision, geodetic accuracy, and spatial distribution enable two-dimensional crossovers to be used infer relative radial position corrections between tracks better ~1 m. We use nearly 500,000 altimetric separate remaining high-frequency trajectory errors from periodic surface tidal deformation. unusual sampling of...
While wide-field surveys of M31 have revealed much substructure at large radii, understanding the nature and origin this material is not straightforward from morphology alone. Using deep HST/ACS data, we derived further constraints in form quantitative star formation histories (SFHs) for 14 inner halo fields which sample diverse substructures. In agreement with our previous analysis colour-magnitude diagram morphologies, find resultant behaviours can be broadly separated into two categories....
The Moon is generally depleted in volatile elements and this depletion extends to the surface where most abundant mineral, anorthite, features <6 ppm H2O. Presumably other nominally anhydrous minerals that dominate mineral composition of global surface—olivine pyroxene—are similarly water volatiles. Thus tabula rasa for study volatiles introduced wake its origin. Since formation last major basin (Orientale), from solar wind, impactors all sizes, expelled interior during volcanic eruptions...
We present observations of RR Lyrae variables in the Local Group late-type spiral galaxy M33. Using Advanced Camera for Surveys on Hubble Space Telescope, we have identified 64 ab-type stars estimated reddenings these based their minimum light V - I colors and metallicities periods. From distributions properties, conclude that belong to two populations: one associated with halo M33 other its disk. Given are produced by populations older than ∼10 Gyr, this suggests not only does field contain...
We present a detailed analysis of two fields located 26 kpc (∼5 radial scalelengths) from the centre M31 along south-west semimajor axis disc. One field samples major populations – Outer Disc while other is offset by ∼18 arcmin and warp in stellar disc field. The colour–magnitude diagrams (CMDs) based on Hubble Space Telescope Advanced Camera for Surveys imaging reach old main-sequence turn-offs (∼12.5 Gyr). apply CMD-fitting technique to reconstruct star formation history (SFH). find that...
This paper summarizes the evidence for optical effects of space weathering, as well properties surface that control changes, on asteroid (101955) Bennu. First, we set stage by briefly reviewing what was known about weathering low-albedo materials from telescopic surveys, laboratory simulations, and sample return analysis. We then look at nature Bennu recent spacecraft imaging spectroscopy observations, including visible to near-infrared thermal infrared wavelengths, followed other...
Abstract The lunar polar regions are high-priority targets for scientific investigation and exploration. To aid these endeavors, we produced enhanced altimetry data from the Lunar Orbiter Laser Altimeter north region, which computed new maps of surface height slope as well topographic roughness on horizontal baselines 100–1600 m. We also a map permanently shadowed (PSRs) that contains fewer artifacts is higher resolution than previous maps. These were then compared to an analogous set...
The outer regions of disc galaxies are becoming increasingly recognized as key testing sites for models assembly and evolution. Important issues the epoch at which bulk stars in these formed how discs grow radially over time. To address issues, we use Hubble Space Telescope Advanced Camera Surveys imaging to study star formation history (SFH) two fields 9.1 11.6 kpc along M33's northern major axis. These lie ∼ 4 5 V-band scalelengths straddle break surface brightness profile....
Ground-based surveys have mapped the stellar outskirts of Local Group galaxies in unprecedented detail, but extending this work to other is necessary overcome stochastic variations evolutionary history and provide more stringent constraints on cosmological galaxy formation models. As part our continuing program ultra-deep imagery beyond Group, we present a wide-field analysis isolated late-type spiral NGC2403 using data obtained with Suprime-Cam Subaru. The survey reaches maximum projected...
Abstract Upcoming missions to the lunar south pole require detailed maps over large areas fully characterize landing sites locally and regionally place their data into proper geologic context. To that end, we enhanced Lunar Orbiter Laser Altimeter altimetry set for polar region, from which produced new of topography, topographic roughness, permanently shadowed regions (PSRs). The roughness reveal a diversity terrains characterized by hectometer-scale is controlled in this region primarily...
We present a detailed analysis of the star formation history (SFH) three fields in M33 located approximately four to six visual scale lengths from its nucleus. These were imaged with Advanced Camera for Surveys on Hubble Space Telescope and reach ∼2.5 mag below red clump core helium-burning stars. The observed color-magnitude diagrams are modeled as linear combinations individual synthetic populations different ages metallicities. To gain better understanding systematic errors, we have...
We present a wide field census of resolved stellar populations in the northern half M81, conducted with Suprime-Cam on 8-m Subaru telescope and covering an area ~ 0.3 square degrees. The resulting color-magnitude diagram reaches over one magnitude below red giant branch (RGB) tip, allowing detailed comparison between young old spatial distributions. surface density stars ages <~ 100 Myr is correlated that neutral hydrogen manner similar to disk-averaged Kennicutt-Schmidt relation. trace this...
The concentrations of the cuspy dark matter halos predicted by simulations cold are related to cosmology in which form. Observational constraints on halo concentration therefore map into cosmological parameters. In order explain observed matter-dominated low surface brightness galaxies, we require a with rather little power galaxy scales. Formally, σ8Γ0.6 < 0.23, where Γ0.6 is modified shape parameter appropriate this problem. Practically, means that either Ωm 0.2 or σ8 0.8. These limits...
We present deep CCD photometry in the VI passbands using WIYN 3.5 m telescope of a field located approximately 20' southeast center M33; this includes region studied by Mould & Kristian 1986. The color-magnitude diagram (CMD) extends to I ∼ 25 and shows prominent red giant branch (RGB), along with significant numbers asymptotic young main-sequence stars. clump core helium burning stars is also discernable near limit our CMD. I-band apparent magnitude tip implies distance modulus (m - M)I =...
Abstract Condensed volatiles within lunar permanently shadowed regions are of high scientific and resource utilization importance. Volatiles remain elusive difficult to observe directly, due low direct solar illumination. In this work, we investigate correlations between, as well possible effects of, condensed surface roughness. We analyze topographic roughness at 50 m 30–120 baselines the south pole (poleward 85° S). focus on six polar craters interest their directly surrounding...
Studying the stellar populations in outskirts of spiral galaxies can provide important constraints on their structure, formation, and evolution. To that end, we present VI photometry obtained with Advanced Camera for Surveys three fields located ∼20'-30' projected distance southeast M33's nucleus (corresponding to approximately four six visual scale lengths or ∼9-13 kpc deprojected radius). The color-magnitude diagrams reveal a mixed population whose youngest constituents have ages no...