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R. Jaumann,
T. Spohn,
H. Hiesinger,
E. K. Jessberger,
G. Neukum, J. Oberst,
J. Helbert,
U. Christensen,
H. U. Keller,
P. Hartogh,
K.-H. Glassmeier,
H.-U. Auster,
A. Moreira,
M. Werner,
M. Pätzold,
H. Palme,
R. Wimmer-Schweingruber,
Mandea
[show abstract]
[hide abstract]
ABSTRACT: LEO is planned to be launched in 2012 and shall orbit the Moon for about
four years at low altitude (<50 km) in order to map the Moon
geomorphologically, geochemically, and geophysically with resolutions
down to less than 1 m globally.
02/2008; 39:1253.
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[show abstract]
[hide abstract]
ABSTRACT: We propose to deploy small (2-3 kg) Lunar geodesy packages on the Moon's
surface, consisting of an optical Laser receiver, a small
retroreflector, as well as a radio beacon. The optical receiver will
maintain Earth pointing through the Lunar libration cycles and record
arrival times of Laser shots from Earth. Judging from the photon budget
for a 50 mJ pulse Laser, most of the existing more than 30 ILRS
(International Laser Ranging Service) stations could participate in the
experiment and produce large numbers of range measurements at high
accuracy and unbiased temporal coverage. The light-weight 0.5 sqm
retroreflector will be adequate for direct ranging measurements using
the classic Lunar Laser Ranging stations. The simultaneous acquisition
of data from the Laser receiver on the Moon and reflected Laser shots on
Earth will allow us to calibrate the onboard clock. A small radio
source shall be deployed within the package, for tracking by VLBI
stations. The experience from the past 38 years of Apollo Lunar Laser
Ranging suggests that there is enormous science potential in ranging
data to further our understanding of the Moon's internal structure, the
dynamics of the Earth-Moon system and fundamental physics. For example,
from the Moon's tidal response, inferences can be made on a solid or
liquid Lunar core and its size and oblateness. In addition, parameters
from gravitational physics, e.g., the time-stability of the
gravitational "constant", or the strong equivalence principle
(Nordtvedt-effect) could be modeled with vastly improved accuracy. While
the position of the Laser receiver will define an important anchor point
in the lunar-fixed coordinate system, the radio transmitter will firmly
tie the dynamical reference frame of the Lunar orbit into the
quasi-inertial kinematic reference frame of Quasar coordinates for
insights into the Moon's orbital behavior to as yet unknown frontiers.
AGU Fall Meeting Abstracts. 11/2007; -1:0487.
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[show abstract]
[hide abstract]
ABSTRACT: Monitoring tidally-induced deformations of the Moon from orbiting and
landed spacecraft would provide important clues on the constitution of
the lunar interior, thereby augmenting the Apollo seismic data record. A
major advantage is that the tidal forcing function for a synchronously
rotating satellite like the Moon is accurately known and precise tidal
potential catalogues can be produced. A higher temporal resolution and
precision than with space techniques alone can be achieved by
additionally emplacing one or several landers on the lunar surface.
However, tidal measurements may be significantly impeded by instrumental
drift, instrument coupling to the surface, and local sources of noise.
We will present relations between key tidal parameters that can be
retrieved from an instrument suite monitoring tidally-induced changes of
local gravity, tilt, latitude and strain at the surface and the
constitution of the deep interior of the Moon. A most promising approach
would involve time-varying gravitational field observations from an
orbiting spacecraft combined with long-term monitoring of
tidally-induced gravity changes at the lunar surface.
AGU Fall Meeting Abstracts. 11/2007; -1:07.
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N Thomas,
T. Spohn,
J.-P. Barriot,
W. Benz,
G. Beutler,
U. Christensen,
V. Dehant,
C. Fallnich,
D. Giardini,
O. Groussin,
J. J. Lopez-Moreno,
H. Michaelis, J. Oberst,
D. Resendes,
J. L. Reynaud,
R. Rodrigo,
S. Sasakio,
K. Selferlin,
M. Wieczorek,
J. Whitby
Planetary and Space Science 01/2007; 55:1398-1413. · 2.22 Impact Factor
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N. Thomas,
T. Spohn,
J.-P. Barriot,
W. Benz,
G. Beutler,
U. Christensen,
V. Dehant,
C. Fallnich,
D. Giardini,
O. Groussin, [......],
J.J. Lopez-Moreno,
H. Michaelis, J. Oberst,
D. Resendes,
J.-L. Reynaud,
R. Rodrigo,
S. Sasaki,
K. Seiferlin,
M. Wieczorek,
J. Whitby
[show abstract]
[hide abstract]
ABSTRACT: The BepiColombo Laser Altimeter (BELA) has been selected for flight on board the European Space Agency's BepiColombo Mercury Planetary Orbiter (MPO). The experiment is intended to be Europe's first planetary laser altimeter system. Although the proposed system has similarities to the Mercury Laser Altimeter (MLA) currently flying on board NASA's MESSENGER mission to Mercury, the specific orbit and construction of the MPO force the use of novel concepts for BELA. Furthermore, the base-lined range-finding approach is novel. In this paper, we describe the BELA system and show preliminary results from some prototype testing.
Planetary and Space Science 01/2007; 55:1398-1413. · 2.22 Impact Factor
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L A Soderblom,
D C Boice,
D T Britt,
R H Brown,
B J Buratti,
R L Kirk,
M Lee,
R M Nelson, J Oberst,
B R Sandel,
S A Stern,
N Thomas,
R V Yelle
[show abstract]
[hide abstract]
ABSTRACT: The nucleus, coma, and dust jets of short-period Comet 19P/Borrelly were imaged from the Deep Space 1 spacecraft during its close flyby in September 2001. A prominent jet dominated the near-nucleus coma and emanated roughly normal to the long axis of nucleus from a broad central cavity. We show it to have remained fixed in position for more than 34 hr, much longer than the 26-hr rotation period. This confirms earlier suggestions that it is co-aligned with the rotation axis. From a combination of fitting the nucleus light curve from approach images and the nucleus' orientation from stereo images at encounter, we conclude that the sense of rotation is right-handed around the main jet vector. The inferred rotation pole is approximately perpendicular to the long axis of the nucleus, consistent with a simple rotational state. Lacking an existing IAU comet-specific convention but applying a convention provisionally adopted for asteroids, we label this the north pole. This places the sub-solar latitude at ∼ 60 • N at the time of the perihelion with the north pole in constant sunlight and thus receiving maximum average insolation.
Icarus 01/2004; 167:4-15. · 3.38 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The Deep Space One spacecraft flew by Comet 19P/Borrelly on September 22, 2001 and returned a rich array of imagery with resolutions of up to 48 m/pixel. These images provide a window into the surface structure, processes, and geological history of a comet. Additional information is contained in the original extended abstract.
05/2002;
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L A Soderblom,
T L Becker,
G Bennett,
D C Boice,
D T Britt,
R H Brown,
B J Buratti,
C Isbell,
B Giese,
T Hare, [......],
R L Kirk,
M Lee,
R M Nelson, J Oberst,
T C Owen,
M D Rayman,
B R Sandel,
S A Stern,
N Thomas,
R V Yelle
[show abstract]
[hide abstract]
ABSTRACT: The nucleus of the Jupiter-family comet 19P/Borrelly was closely observed by the Miniature Integrated Camera and Spectrometer aboard the Deep Space 1 spacecraft on 22 September 2001. The 8-kilometer-long body is highly variegated on a scale of 200 meters, exhibiting large albedo variations (0.01 to 0.03) and complex geologic relationships. Short-wavelength infrared spectra (1.3 to 2.6 micrometers) show a slope toward the red and a hot, dry surface (</=345 kelvin, with no trace of water ice or hydrated minerals), consistent with approximately 10% or less of the surface actively sublimating. Borrelly's coma exhibits two types of dust features: fans and highly collimated jets. At encounter, the near-nucleus coma was dominated by a prominent dust jet that resolved into at least three smaller jets emanating from a broad basin in the middle of the nucleus. Because the major dust jet remained fixed in orientation, it is evidently aligned near the rotation axis of the nucleus.
Science 05/2002; 296(5570):1087-91. · 31.20 Impact Factor
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L. A. Soderblom,
D. C. Boice,
D. T. Britt,
R. H. Brown,
B. J. Buratti,
M. D. Hicks,
R. M. Nelson, J. Oberst,
B. R. Sandel,
S. A. Stern,
N. Thomas,
R. V. Yelle
[show abstract]
[hide abstract]
ABSTRACT: Images from the DS1 MICAS CCD camera reveal in three dimensions, the
complex characteristics of Borrelly's nucleus, coma, and jets. The
images acquired during the last 2 hours of the approach, as the nucleus
became resolved and grew to roughly 150 pixels in length, provide stereo
coverage of both the nucleus and inner coma over a wide range of phase
angle and exposure time. The principal structure in the coma is a
sunward-pointed collimated jet that is also visible in ground-based
images. This jet is canted about 30 degrees off the sun line and appears
to be roughly aligned with the local vertical at the surface from where
it originates. Long-exposure images reveal details of the structure of
the inner coma. They show the jet, visible at long range, to be composed
of at least three discrete components whose locations evidently
correspond to specific surface features. The elongated nucleus exhibits
topographically distinct terrains and strong albedo variegations (of at
least a factor of 2). The jets emanate from within the brighter smoother
rolling plains. A consistent model is that the main jets are co-aligned
with the rotation axis of the nucleus and issue from regions on the
plains that are currently in constant sunlight. The other major terrain
is a rough unit that is darker than the average, includes even darker
isolated spots, and appears as a jumbled topography. Other surface
features include parallel ridges, crater-like depressions, numerous
narrow dark fracture-like features, and areas of mottled albedo. However
no small fresh impact craters are evident attesting to a geologically
young, actively evolving surface.
10/2001; 33:1087.
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[show abstract]
[hide abstract]
ABSTRACT: The successful Deep Space 1 flyby of Comet P/19 Borrelly offers an
unprecedented opportunity to perform disk-resolved photometry and
photometric modeling of a comet's nucleus. The flyby occurred at a
favorable ground-based apparition, enabling concomitant telescopic
observations that provided both the "big picture" in time and space and
observations at photometric viewing geometries not attained by the
spacecraft. The solar phase angle of the encounter period changed from
87 to 52 degrees over a period of 1.5 hours; this range is ideal for
determining the macroscopic roughness of the comet's surface. The
microphysical texture of the surface is best determined by ground based
observations at aphelion and near opposition. The combination of both
disk resolved measurements from DS1 and disk integrated measurements
from both DS1 and the ground permits a constrained set of photometric
parameters to be derived. Preliminary analysis of the global geometric
albedo yields a value at V wavelengths (550 nm) between 0.031 +/- 0.005
(for a Mathilde-type solar phase curve at phase angles less than 10
degrees) and 0.042 +/- 0.005 (for an average C-type phase curve). Albedo
variegations of at least a factor of two exist on Borrelly's surface:
Its light curve amplitude of nearly a magnitude may thus not be due to
shape alone. The image resolution of 60 m allows mapping of albedo
variegations in terms of active jet morphology. Funded by NASA.
10/2001; 33:1091.
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D. C. Boice,
L. A. Soderblom,
D. T. Britt,
R. H. Brown,
B. R. Sandel,
R. V. Yelle,
B. J. Buratti,
Hicks,
Nelson,
Rayman, J. Oberst,
N. Thomas
[show abstract]
[hide abstract]
ABSTRACT: NASA's Deep Space 1 (DS1) spacecraft successfully encountered comet 19P/Borrelly near perihelion and the Miniature Integrated
Camera and Spectrometer (MICAS) imaging system onboard DS1 returned the first high-resolution images of a Jupiter-family comet
nucleus and surrounding environment. The images span solar phase angles from 88° to 52°, providing stereoscopic coverage of
the dust coma and nucleus. Numerous surface features are revealed on the 8-km long nucleus in the highest resolution images(47–58
m pixel). A smooth, broad basin containing brighter regions and mesa-likestructures is present in the central part of the
nucleus that seems to be the source ofjet-like dust features seen in the coma. High ridges seen along the jagged terminator
lead to rugged terrain on both ends of the nucleus containing dark patches and smaller series of parallel grooves. No evidence
of impact craters with diameters larger thanabout 200-m are present, indicating a young and active surface. The nucleus is
very dark with albedo variations from 0.007 to 0.035. Short-wavelength, infrared spectra from 1.3 to 2.6 μm revealed a hot,
dry surface consistent with less than about10% actively sublimating. Two types of dust features are seen: broad fans and highlycollimated
“jets” in the sunward hemisphere that can be traced to the surface. The source region of the main jet feature, which resolved
into at least three smaller “jets” near the surface, is consistent with an area around the rotation pole that is constantly
illuminated by the sun during the encounter. Within a few nuclear radii, entrained dustis rapidly accelerated and fragmented
and geometrical effects caused from extended source regions are present, as evidenced in radial intensity profiles centered
on the jet features that show an increase in source strength with increasing cometocentric distance. Asymmetries in the dust
from dayside to nightside are pronounced and may show evidence of lateral flow transporting dust to structures observed in
the nightside coma. A summary of the initial results of the Deep Space 1 Mission is provided, highlighting the new knowledge
that has been gained thus far.
Earth Moon and Planets 09/2000; 89(1):301-324. · 0.67 Impact Factor
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P H Smith,
J F Bell,
N T Bridges,
D T Britt,
L Gaddis,
R Greeley,
H U Keller,
K E Herkenhoff,
R Jaumann,
J R Johnson, [......], J Oberst,
T J Parker,
R J Reid,
R Sablotny,
L A Soderblom,
C Stoker,
R Sullivan,
N Thomas,
M G Tomasko,
E Wegryn
[show abstract]
[hide abstract]
ABSTRACT: Images of the martian surface returned by the Imager for Mars Pathfinder (IMP) show a complex surface of ridges and troughs covered by rocks that have been transported and modified by fluvial, aeolian, and impact processes. Analysis of the spectral signatures in the scene (at 440- to 1000-nanometer wavelength) reveal three types of rock and four classes of soil. Upward-looking IMP images of the predawn sky show thin, bluish clouds that probably represent water ice forming on local atmospheric haze (opacity approximately 0.5). Haze particles are about 1 micrometer in radius and the water vapor column abundance is about 10 precipitable micrometers.
Science 01/1998; 278(5344):1758-65. · 31.20 Impact Factor
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L. Prockter,
J. W. Head,
R. Greeley,
K. C. Bender,
R. T. Pappalardo,
G. Neukum,
R. Wagner,
B. Giese, J. Oberst,
A. Cook,
B. Schreiner,
Galileo IMAGING Team
[show abstract]
[hide abstract]
ABSTRACT: As some of the oldest tectonic features on Ganymede and Callisto, furrow
systems can provide valuable information about the state of the
lithosphere at the time of their formation and its subsequent thermal
evolution. We present new results from Galileo of the furrow systems in
Galileo Regio, Ganymede, and the multiring systems of the Valhalla and
Asgard impact basins on Callisto. Furrows on Ganymede are found only in
the older, heavily cratered dark terrain. Three main systems of furrows
have been identified from Voyager data with different primary
orientations and ages. Using the classification system of Murchie et al.
(1990), Systems I and II are found in the anti-Jovian hemisphere, in
both Marius Regio and Galileo Regio. System I furrows predate those of
System II and are generally interpreted to be of impact origin. Murchie
et al. suggest that these furrows are reactivated impact basin rings.
Callisto possesses at least eight systems of concentric and radial
fracture zones arranged around degraded palimpsests. These are
interpreted to be impact structures. Cratering models indicate that
furrows on Ganymede may only be 100-200 My younger than Valhalla,
therefore direct morphological comparisons are reasonable.
02/1997; 28:1141.
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[show abstract]
[hide abstract]
ABSTRACT: Laser reflectors near the landing sites of Apollo 11, 14, and 15 and on
the Lunochod 2 spacecraft are in use for Earth-Moon ranging up to the
present day. However, owing to the tight link budget and the complexity
of the observational task, only a handful terrestrial Laser ranging
stations (e.g. McDonald, US; Grasse, F) are capable to routinely carry
out the measurements. We propose a next-generation Lunar ranging
experiment. Lunar landers, as those currently discussed within ESA's
Aurora and Cosmic Vision program, shall carry laser "beacons" pointed at
Earth, where Laser shots are to be received by multiple terrestrial
ground stations. Owing to the Moon's librations, laser shots from a
fixed mounted instrument on the Moon must be spread over a cone of
approx. 20 deg pointed at the Earth's mean position. Alternatively, the
laser must be mounted on a pivoted platform to maintain Earth-pointing.
We estimate that the received pulse strength from a 50 mJ Laser (like
the one that is currently being developed for the Laser Altimeter on
Bepi- Colombo, BELA) is 3 orders of magnitude larger than a ranging
signal from Earth reflected from the largest of the Lunar
retroreflectors (the approx. 0.5 m2 Apollo 15 reflector). Such laser
shots could be received by most existing Satellite Laser Ranging
Stations having receiver mirror diameters larger than 1m. From the use
of multiple stations, systematic measurement errors can be identified
and removed. Using picosecond laser shots, measurement accuracies at
mm-level can be accomplished. We propose to deploy Laser beacons near
the poles or the Lunar limb as these locations are more suited for the
tracking of Lunar librations in latitude and longitude, respectively,
than the current ones close to the sub-Earth point. The experience from
the past 35 years suggests that there is enormous science potential in
Lunar ranging data to further our understanding of the Moon's internal
structure and the dynamics of the Earth-Moon system. For example, from
the tidal response at the expected mm accuracy, inferences can be made
on a solid or liquid Lunar core and its size and oblateness. The
experiment will probably also detect free global oscillations of the
Moon as a response to large quakes or meteoroid impacts for a
comprehensive modeling of elastic parameters of the Lunar interior. In
addition, parameters from gravitational physics (e.g., stability of the
gravitational "constant") or the Nordtvedt-effect (strong equivalence
principle) could be modeled with vastly improved accuracy. This proposal
has 1 been put forward at the Workshop on European Lunar Polar Landers
at ESA/ESTEC in December 15/16, 2005. 2
-1:516.
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Lunar Base Symposium;
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Lunar Base Symposium;
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[show abstract]
[hide abstract]
ABSTRACT: We describe techniques which we will use to determine regional control point networks, DTMs (Digital Terrain Models) and rectified color image mosaics from large collections of spacecraft stereo images in particular Clementine data. First, overlapping images suitable for stereo analysis are identified, and tiepoints in overlapping images are selected manually. Next, latitudes, longitudes and heights of these tiepoints are determined in combination with the camera pointing data of all images and the spacecraft trajectory in a "bundle block adjustment". Thus, the resulting planetary coordinates are used as control points subsequent analysis. Next, stereo disparity data between image pairs are determined using the "Gruen-Otto-Chau stereo matching algorithm". These data are converted to planetary coordinates based on the spacecraft trajectory and altitude data determined during the bundle adjustment and are interpolated to form the DTM grid. Finally, all images are rectified on the basis of the elevation model, reprojected onto a map, and combined to mosaics. The procedure allows us to archive precise registrations of the color filter images. Furthermore, precise surface slopes and illumination angles can be computed from the DTM to perform a physically more meaningful spectrophotometric analysis of the terrain. The performance of the bundle block adjustment and of the matching software will be demonstrated. Examples will be given of DTMs near Mare Orientale and the polar regions of the Moon. Software contributions from TUM, TUB, and UCL (Technical University Munich, Technical University Berlin, and University College London) are acknowlegded.
AGU Fall Meeting, 1994;
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[show abstract]
[hide abstract]
ABSTRACT: We have carried out a search for degraded impact basins on the Moon using as a basis the near-global digital terrain model (GLD100), derived from LROC-WAC stereo images.
42nd Lunar and Planetary Science Conference;
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4th European Planetary Science Congress (EPSC);
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4th European Planetary Science Congress (EPSC);
