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32
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"... The Moon is a key to deciphering the evolutionary history of the terres-trial planets because it is the most accessible planetary body that pre-serves a surface record spanning most of solar system history. Reconstructing the evolution of a planet requires an understanding of the structure of its in ..."
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The Moon is a key to deciphering the evolutionary history of the terres-trial planets because it is the most accessible planetary body that pre-serves a surface record spanning most of solar system history. Reconstructing the evolution of a planet requires an understanding of the structure of its interior, which contains information on bulk composition, differentiation, and the nature of heat generation and heat loss that has influenced the style, extent, and duration of volcanism and tectonics. The Gravity Recovery and Interior Laboratory (GRAIL) mission (1) was undertaken to map the lunar gravity field to address, in the context of other remote sensing and in situ observations, fundamental questions on lunar evolution. Aside from the influence of the Moon’s gravity throughout Earth history in producing oceanic tides, lunar gravity has been an observation of interest since the earliest satellites orbited the Moon and revealed the presence of mass concentrations or “mascons ” associated with the large
Earth Planets Space, 56, 1041–1047, 2004 VLBI observation of narrow bandwidth signals from the spacecraft
, 2004
"... We carried out a series of VLBI observations of Nozomi by using a dedicated narrow bandwidth VLBI system. The three carrier waves with frequency interval of 515 kHz were recorded in 3 channels of the system and correlated by a software method. As a result of the correlation, the residual fringe phas ..."
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We carried out a series of VLBI observations of Nozomi by using a dedicated narrow bandwidth VLBI system. The three carrier waves with frequency interval of 515 kHz were recorded in 3 channels of the system and correlated by a software method. As a result of the correlation, the residual fringe phases of the main carrier wave are obtained for every 1.3 seconds. We can also continuously track them for 100 minutes. The variation of the residual fringe phase is +/ − 150 degrees. Moreover, we can derive succesively the group delay for every 100 seconds by using these three carrier waves. The RMS of the group delays is 13 nsec and its average is well accorded with the delay determined by the range and Doppler measurements within an error of 2 nsec. Consequently, we confirmed the validity of the narrow bandwidth VLBI system, and it could be expected that this system, in addition to range and Doppler measurements, can be applied to three-dimensional tracking of a spacecraft and the precise gravity measurement of the Moon and the planets.
Correspondence should be addressed to Rodolpho Vilhena de Moraes,
"... under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Low-altitude, near-polar orbits are very desirable as science orbits for missions to planetary satellites, such as the Earth’s M ..."
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under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Low-altitude, near-polar orbits are very desirable as science orbits for missions to planetary satellites, such as the Earth’s Moon. In this paper, we present an analytical theory with numerical simulations to study the orbital motion of lunar low-altitude artificial satellite. We consider the problem of an artificial satellite perturbed by the nonuniform distribution of the mass of the Moon J2–J5, J7, and C22. The conditions to get frozen orbits are presented. Using an approach that considers the single-averaged problem, we found families of periodic orbits for the problem of an orbiter travelling around the Moon, where frozen orbits valid for long periods of time are found. A comparison between the models for the zonal and tesseral harmonics coefficients is presented. 1.
Author's personal copy Geophysical constraints on the water content of the lunar mantle and its implications for the origin of the Moon
, 2013
"... Although the Moon was considered to be "dry", recent measurements of hydrogen content in some of the lunar samples showed a substantial amount of water comparable to the water content in the Earth's asthenosphere. However, the interpretation of these observations in terms of the dist ..."
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Although the Moon was considered to be "dry", recent measurements of hydrogen content in some of the lunar samples showed a substantial amount of water comparable to the water content in the Earth's asthenosphere. However, the interpretation of these observations in terms of the distribution of water in the lunar interior is difficult because the composition of these rocks reflects a complicated history involving melting and crystallization. In this study, I analyze geophysically inferred properties to obtain constraints on the distribution of water (and temperature) in the lunar interior. The electrical conductivity inferred from electromagnetic induction observations and the geodetically or geophysically inferred Q are interpreted in terms of laboratory data and the theoretical models on the influence of water (hydrogen) on these properties. Both electrical conductivity and Q are controlled by defect-related processes that are sensitive to the water (hydrogen) content and temperature but less sensitive to the major element chemistry. After a correction for the influence of the major element chemistry constrained by geophysical observations and geochemical considerations, I estimate the temperature-water content combinations that are consistent with the geophysically inferred electrical conductivity and Q . I conclude that the lunar interior is cooler than Earth (at the same depth) but the water content of the lunar mantle is similar to that of Earth's asthenosphere. A possible model is presented to explain the not-so-dry Moon where a small degree of water loss during the Moon formation is attributed to the role of liquid phases that play an important role in the Moon-forming environment.
The gravity and topography of the . . .
, 2007
"... This chapter reviews our current knowledge of the gravity and topography of the terrestrial planets and describes the methods that are used to analyze these data. First, a general review of the mathematical formalism that is used in describing the properties of gravitational fields and topography is ..."
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This chapter reviews our current knowledge of the gravity and topography of the terrestrial planets and describes the methods that are used to analyze these data. First, a general review of the mathematical formalism that is used in describing the properties of gravitational fields and topography is given. Next, the basic properties of the gravity and topography of the Earth, Venus, Mars, and the Moon are characterized. Following this, the relationship between gravity and topography is quantified, and techniques by which geophysical parameters can be constrained are detailed. Such analysis methods include crustal thickness modeling, the analysis of geoid/topography ratios, and modeling of the spectral admittance and correlation functions. Finally, the major results that have been obtained by modeling the gravity and topography of the Earth, Venus, Mars,
Lunar Laser Ranging Science 1
, 2004
"... Analysis of Lunar Laser Ranging (LLR) data provides science results: gravitational physics and ephemeris information from the orbit, lunar science from rotation and solidbody tides, and Earth science. Science from the orbit: Sensitive tests of gravitational physics include the Equivalence Principle, ..."
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Analysis of Lunar Laser Ranging (LLR) data provides science results: gravitational physics and ephemeris information from the orbit, lunar science from rotation and solidbody tides, and Earth science. Science from the orbit: Sensitive tests of gravitational physics include the Equivalence Principle, limits on the time variation of the gravitational constant G, and geodetic precession. The equivalence principle test is used for an accurate determination of the parametrized post-Newtonian (PPN) parameter β. Lunar ephemerides are a product of the LLR analysis used by current and future spacecraft missions. The analysis is sensitive to astronomical parameters such as orbit, masses and obliquity. The dissipation-caused semimajor axis rate is 37.9 mm/yr and the associated acceleration in orbital longitude is −25.7 ′ ′ /cent 2, dominated by tides on Earth with a 1 % lunar contribution. Lunar science: Lunar rotational variation has sensitivity to interior structure, physical properties, and energy dissipation. The second-degree lunar Love numbers are detected; k2 has an accuracy of 11%. Lunar tidal dissipation is strong and its Q has a weak dependence on tidal frequency. A fluid core of about 20 % the Moon’s radius is indicated by the dissipation data. Evidence for the oblateness of the lunar fluid-core/solid-mantle boundary is getting stronger. This would be independent evidence for a fluid lunar core. Moon-centered coordinates of four retroreflectors are determined. Earth science: Station positions and motion, Earth rotation variations, nutation, and precession are determined from analyses. Future: Extending the data span and improving range accuracy will yield improved and new scientific results. Adding either new retroreflectors or precise active transponders on the Moon would improve the accuracy of the science results.
� Post LRO Frames/Products � Recommendations & DiscussionI. Systems and Frames Some Definitions
, 2006
"... (not meant to be complete) Reference systems vs. frames � System is overall concept, physical environment, theory, conventions forming an idealized model � Frame is specific realization of a system, e.g. a solution which defines from observational data a list of point coordinates, usually with assoc ..."
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(not meant to be complete) Reference systems vs. frames � System is overall concept, physical environment, theory, conventions forming an idealized model � Frame is specific realization of a system, e.g. a solution which defines from observational data a list of point coordinates, usually with associated uncertainties
We acknowledge support from our colleagues David Beaty, members of the MEPAG,
, 2010
"... Committee On Space Research (COSPAR) COSPAR Panel on Exploration (PEX) “All truths are easy to understand once they are discovered; the point is to discover them.” Galileo Galilei (1564- 1642) ..."
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Committee On Space Research (COSPAR) COSPAR Panel on Exploration (PEX) “All truths are easy to understand once they are discovered; the point is to discover them.” Galileo Galilei (1564- 1642)
IAC-04-IAA.4.11.P.05 Mission Scenarios for a Controlled Lunar Impact of a Small Satellite
"... The Institute of Space Systems (IRS) at the University of Stuttgart is currently planning a lunar small satellite mission. The satellite will be equipped with a 6 mN and a 100 mN electric propulsion system. At the end of its primary science mission, it will perform a controlled impact-experiment on ..."
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The Institute of Space Systems (IRS) at the University of Stuttgart is currently planning a lunar small satellite mission. The satellite will be equipped with a 6 mN and a 100 mN electric propulsion system. At the end of its primary science mission, it will perform a controlled impact-experiment on the lunar surface, including the soft landing of a small surface unit. In this paper we present the results of a numerical simulation and optimization of possible impact trajectories starting from the satellite’s initial 100 km polar, circular orbit. The perturbing accelerations being in the same order of magnitude as the thrust, we used thrust vector control for efficient orbit manipulation. First results show that an impact using the electrical thrusters is principally feasible. Using the 6 mN thrusters by themselves for the deorbit maneuver is unadvisable due to the long thrust durations and the very low impact angle, making the impact inaccurate and difficult to control. The 100 mN thruster, however, together with an additional solid rocket motor for a final aposelene boost, yields much more favorable impact conditions at the price of a higher subsystem mass.
QUICK EVALUATION OF SMALL BODY GRAVITATION
, 2002
"... Numerical integration of ordinary differential equations resulting from the gravitation of nearby celestial small bodies is the subject of this thesis. We present three methods that alleviate the computational burden of evaluating gravitational force near a small body: i) adaptive polynomial interpo ..."
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Numerical integration of ordinary differential equations resulting from the gravitation of nearby celestial small bodies is the subject of this thesis. We present three methods that alleviate the computational burden of evaluating gravitational force near a small body: i) adaptive polynomial interpolation, ii) adaptive polynomial least squares approximation, and iii) acceleration via specialized, commodity hardware. Each method is evaluated on its quantitative accuracy with respect to a reference model, and its observance of qualitative features of gravity. We conclude with a summary of methods available for computing small body gravitation, and recommendations for different scenarios.
