Comparison of lunar gravity fields using GSFC range-rate data from AIMP-E
Application of VHF Doppler tracking data from Goddard Range and Range Rate system to determine lunar orbits for Explorer 35 satellite
Laczo, V. T.↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Electromagnetic measurement of lunar subsurface water
Lunar subsurface water detection from satellite in polar orbit around moon by electromagnetic measurement
Jiracek, G. R.↗
Satellite lifetime routine user's manual
A FORTRAN coded computer program which determines secular variations in mean orbital elements of earth satellites and the lifetime of the orbit is described. The dynamical model treats a point mass satellite subject to solar and lunar disturbing gravitational fields, second, third and fourth harmonics of the earth's oblate potential, earth's atmospheric drag, and solar radiation pressure. Each of these disturbing functions may be selectively simulated. Data preparation instructions, a sample problem, and definitions of output quantities are included.
Everett, H. U.↗
Beat frequency interference pattern characteristics study
The frequency spectra and corresponding beat frequencies created by the relative motions between multiple Solar Power Satellites due to solar wind, lunar gravity, etc. were analyzed. The results were derived mathematically and verified through computer simulation. Frequency spectra plots were computer generated. Detailed computations were made for the seven following locations in the continental US: Houston, Tx.; Seattle, Wa.; Miami, Fl.; Chicago, Il.; New York, NY; Los Angeles, Ca.; and Barberton, Oh.
Ott, J. H.↗
Comparison of earth rotation as inferred from radio interferometric, laser ranging and astrometric observations
Results of measurements of the earth's rotation vector for a 400-day period from late September 1980 to December 1981, for which date from VLBI, satellite laser ranging (SLR), and lunar laser ranging (LLR) were available, are compared. The acquisition of the data and their evaluation are described. VLBI, SLR, and classical astrometric determinations of the X-parameter required to describe the location of the rotation pole on the earth's surface are shown, and VLBI, LLR, and classical astrometric determinations of the angle of rotation about this pole (UT1) are presented. The results indicate that VLBI and SLR, at their present stages of development, yield standard errors under 20 cm in the determinations of X, about twofold smaller than obtained from classical measurements, and that VLBI and LLR yield determination of UT1 with standard errors less than 40 cm, somewhat smaller than that of the corresponding determinations from classical observations. Methods for improving these types of intercomparisons are suggested.
Robertson, D. S.↗
Reports of Planetary Geology and Geophysics Program, 1984
Topics include outer planets and satellites; asteroids and comets; Venus; lunar origin and solar dynamics; cratering process; planetary interiors, petrology, and geochemistry; volcanic processes; aeolian processes and landforms; fluvial processes; geomorphology; periglacial and permafrost processes; remote sensing and regolith studies; structure, tectonics, and stratigraphy; geological mapping, cartography, and geodesy; and radar applications.
Henry E. Holt↗
Earth rotation and polar motion - Measurements and implications
Several methods used to measure earth rotation and polar motion are discussed. The development of techniques for combining smoothing, and intercomparing geodetic measurements is described. Emphasis is given to measurements obtained since 1980 using VLBI, lunar laser ranging (LLR) and satellite laser ranging (SLR) techniques. The calculation of atmospheric angular momentum (AAM) excitation functions is outlined, and a comparison of AAM excitation functions with variations in the length of day (LOD) and polar motion data is presented. The geophysical implications of geodetic measurements are addressed.
Dickey, J. O.↗
Length of day and atmospheric angular momentum - A comparison of 1981-1983
In connection with the availability of observations of increasingly greater accuracy and higher time resolution, studies have been conducted regarding the relationship between the earth's rotation and the angular momentum of its atmosphere. The present paper reports an investigation conducted on the basis of earth rotation values determined during the time from 1981 to 1983 with the aid of very long baseline interferometry (VLBI), lunar laser ranging (LLR), and satellite laser ranging (SLR). The values obtained with the different techniques were compared, and a combined series of length of day (LOD) values were computed. A similar computation procedure was applied to the atmospheric angular momentum (AAM) values of U.S. and European origin to obtain corresponding series of LOD values.
Morgan, P. J.↗
Transportation and operations aspects of space energy systems
A brief comparative analysis was made for three concepts of supplying large-scale electrical energy to Earth from space. The concepts were: (1) mining helium-3 on the Moon and returning it to Earth; (2) constructing solar power satellites in geosynchronous orbit from lunar materials (the energy is beamed by microwave to receivers on Earth); and (3) constructing power collection and beaming systems on the Moon itself and transmitting the energy to Earth by microwave. This analysis concerned mainly space transportation and operations, but each of the systems is briefly characterized to provide a basis for space transportation and operations analysis.
Woodcock, Gordon R.↗
Cryptoblemes: A New Discovery with Major Economic Implications and Profound Changes to the Geologic Paradigm
Cryptoblemes are subtle impact shock signatures imprinted by cosmic debris on the crustal surfaces of lunar planetary bodes. These signatures constitute a complex cumulative overprinting of topographic, structural geophysical, and tectonic patterns that have a conspicuous radial centric multiringed symmetry. The geometry and distribution of cryptoblemes on Earth is comparable to the size and density of impact features on lunar planetary surfaces. Analysis of satellite imagery, sea-floor sonar, side-looking radar and aerial photographs of specific sites reveals new criteria for the identification and confirmation of impact-shock signatures. These criteria include joint and foliation patterns with asbestiform minerals, ribbon-quartz, spheroidal weathering, domal exfoliation, pencil shale, and shock spheres, which may originate from hydrocavitation of water-saturated sedimentary rocks. Cryptoblemes may also be associated with breccia pipes, sinkholes, buttes, mesas, and bogs, high-Rn anomalies, nodular concentrations, and earthquake epicenters. Major implications of cryptobleme identification include exploratory targeting of hydrocarbon and mineral deposits and the explanation of their origins. Analysis of known mineral deposits, structural traps and sedimentary basins show a direct correlation with cryptobleme patterns. Significant geologic paradigm shifts related to cryptoblemes include mountain building processes, structural orogenies, induced volcanism, earthquake origins, hydrocarbon diagenesis, formation mineral deposits, continental rifting, and plate movements, magnetic overprinting and local regional, and global geologic extinction and speciation patterns. Two figures provide a comparison between a multiring impact overprint in water and multiring cryptobleme in the U.S. basin range. (Additional information is contained in the original document).
Windolph, J., Jr.↗
NASA's Lunar Robotic Architecture Study
This report documents the findings and analysis of a 60-day agency-wide Lunar Robotic Architecture Study (LRAS) conducted by the National Aeronautics and Space Administration (NASA). Work on this study began in January 2006. Its purpose was to: Define a lunar robotics architecture by addressing the following issues: 1) Do we need robotic missions at all? If so, why and under what conditions? 2) How would they be accomplished and at what cost? Are they within budget? 3) What are the minimum requirements? What is the minimum mission set? 4) Integrate these elements together to show a viable robotic architecture. 5) Establish a strategic framework for a lunar robotics program. The LRAS Final Report presents analysis and recommendations concerning potential approaches related to NASA s implementation of the President's Vision for Space Exploration. Project and contract requirements will likely be derived in part from the LRAS analysis and recommendations contained herein, but these do not represent a set of project or contract requirements and are not binding on the U.S. Government unless and until they are formally and expressly adopted as such. Details of any recommendations offered by the LRAS Final Report will be translated into implementation requirements. Moreover, the report represents the assessments and projects of the report s authors at the time it was prepared; it is anticipated that the concepts in this report will be analyzed further and refined. By the time some of the activities addressed in this report are implemented, certain assumptions on which the report s conclusions are based will likely evolve as a result of this analysis. Accordingly, NASA, and any entity under contract with NASA, should not use the information in this report for final project direction. Since the conclusion of this study, there have been various changes to the Agency's current portfolio of lunar robotic precursor activities. First, the Robotic Lunar Exploration Program (RLEP) has been renamed the Lunar Precursor and Robotic Program (LPRP). On May 17, 2006, the Lunar Reconnaissance Orbiter (LRO) was confirmed to enter its implementation phase. Last, a new low-cost secondary payload known as the Lunar Crater Observation and Sensing Satellite (LCROSS) was co-manifested to launch with LRO in 2008. These changes are consistent with the conclusions and recommendations of this study, but came too late to be specifically reflected in this report.
Mulville, Daniel R.↗
NASA Ames Research Center Overview
A general overview of the NASA Ames Research Center is presented. The topics include: 1) First Century of Flight, 1903-2003; 2) NACA Research Centers; 3) 65 Years of Innovation; 4) Ames Projects; 5) NASA Ames Research Center Today-founded; 6) Astrobiology; 7) SOFIA; 8) To Explore the Universe and Search for Life: Kepler: The Search for Habitable Planets; 9) Crew Exploration Vehicle/Crew Launch Vehicle; 10) Lunar Crater Observation and Sensing Satellite (LCROSS); 11) Thermal Protection Materials and Arc-Jet Facility; 12) Information Science & Technology; 13) Project Columbia Integration and Installation; 14) Air Traffic Management/Air Traffic Control; and 15) New Models-UARC.
Boyd, Jack↗
Dilution-of-Precision-Based Lunar Surface Navigation System Analysis Utilizing Earth-Based Assets
The NASA Vision for Space Exploration is focused on the return of astronauts to the Moon. Although navigation systems have already been proven in the Apollo missions to the Moon, the current exploration campaign will involve more extensive and extended missions requiring new concepts for lunar navigation. In contrast to Apollo missions, which were limited to the near-side equatorial region of the Moon, those under the Exploration Systems Initiative will require navigation on the Moon's limb and far side. These regions are known to have poor Earth visibility, but unknown is the extent to which a navigation system comprised solely of Earth-based tracking stations will provide adequate navigation solutions in these areas. This report presents a dilution-of-precision (DoP)-based analysis of the performance of a network of Earth-based assets. This analysis extends a previous analysis of a lunar network (LN) of navigation satellites by providing an assessment of the capability associated with a variety of assumptions. These assumptions pertain to the minimum provider elevation angle, nadir and zenith beam widths, and a total single failure in one of the Earth-based assets. The assessment is accomplished by making appropriately formed estimates of DoP. Different adaptations of DoP, such as geometrical DoP and positional DoP (GDoP and PDoP), are associated with a different set of assumptions regarding augmentations to the navigation receiver or transceiver.
Welch, Bryan W.↗
BAE Systems Radiation Hardened SpaceWire ASIC and Roadmap
An Application Specific Integrated Circuit (ASIC) that implements the SpaceWire protocol has been developed in a radiation hardened 0.25 micron CMOS, technology. This effort began in March 2003 as a joint development between the NASA Goddard Space Flight Center (GSFC) and BAE Systems. The BAE Systems SpaceWire ASlC is comprised entirely of reusable core elements, many of which are already flight-proven. It incorporates a 4-port SpaceWire router with two local ports, dual PC1 bus interfaces, a microcontroller, 32KB of internal memory, -and a memory controller for additional external memory use. The SpaceWire ASlC is planned for use on both the Geostationary Operational Environmental Satellites (GOES)-R and the Lunar Reconnaissance Orbiter (LRO). Engineering parts have already been delivered to both programs. This paper discusses the SpaceWire protocol and those elements of it that have been built into the current SpaceWire reusable core. There are features within the core that go beyond the current standard that can be enabled or disabled by the user and these will be described. The adaptation of SpaceWire to BAE Systems' On Chip Bus (OCB) for compatibility with the other reusable cores will be discussed. Optional configurations within user systems will be shown. The physical imp!ementation of the design will be described and test results from the hardware will be discussed. Finally, the BAE Systems roadmap for SpaceWire developments will be discussed, including some products already in design as well as longer term plans.
Berger, Richard↗
International Laser Ranging Service (ILRS) 2003-2004 Annual Report
The International Laser Ranging Service (ILRS) organizes and coordinates Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) to support programs in geodetic, geophysical, and lunar research activities and provides the International Earth Rotation and Reference Systems Service (IERS) with products important to the maintenance of an accurate International Terrestrial Reference Frame (ITRF). This reference frame provides the stability through which systematic measurements of the Earth can be made over thousands of kilometers, decades of time, and evolution of measurement technology. This 2003-2004 ILRS annual report is comprised of individual contributions from ILRS components within the international geodetic community for the years 2003-2004. The report documents changes and progress of the ILRS and is also available on the ILRS Web site at http://ilrs.gsfc.nasa.gov/reports/ilrs_reports/ilrsar_2003.html.
Pearlman, Michael↗
Bounding Extreme Spacecraft Charging in the Lunar Environment
Robotic and manned spacecraft from the Apollo era demonstrated that the lunar surface in daylight will charge to positive potentials of a few tens of volts because the photoelectron current dominates the charging process. In contrast, potentials of the lunar surface in darkness which were predicted to be on the order of a hundred volts negative in the Apollo era have been shown more recently to reach values of a few hundred volts negative with extremes on the order of a few kilovolts. The recent measurements of night time lunar surface potentials are based on electron beams in the Lunar Prospector Electron Reflectometer data sets interpreted as evidence for secondary electrons generated on the lunar surface accelerated through a plasma sheath from a negatively charged lunar surface. The spacecraft potential was not evaluated in these observations and therefore represents a lower limit to the magnitude of the lunar negative surface potential. This paper will describe a method for obtaining bounds on the magnitude of lunar surface potentials from spacecraft measurements in low lunar orbit based on estimates of the spacecraft potential. We first use Nascap-2k surface charging analyses to evaluate potentials of spacecraft in low lunar orbit and then include the potential drops between the ambient space environment and the spacecraft to the potential drop between the lunar surface and the ambient space environment to estimate the lunar surface potential from the satellite measurements.
Minow, Joseph I.↗
Fast Ray Tracing of Lunar Digital Elevation Models
Ray-tracing (RT) of Lunar Digital Elevation Models (DEM)'s is performed to virtually derive the degree of radiation incident to terrain as a function of time, orbital and ephemeris constraints [I- 4]. This process is an integral modeling process in lunar polar research and exploration due to the present paucity of terrain information at the poles and mission planning activities for the anticipated spring 2009 launch of the Lunar Reconnaissance Orbiter (LRO). As part of the Lunar Exploration Neutron Detector (LEND) and Lunar Crater Observation and Sensing Satellite (LCROSS) preparations RI methods are used to estimate the critical conditions presented by the combined effects of high latitude, terrain and the moons low obliquity [5-7]. These factors yield low incident solar illumination and subsequently extreme thermal, and radiation conditions. The presented research uses RT methods both for radiation transport modeling in space and regolith related research as well as to derive permanently shadowed regions (PSR)'s in high latitude topographic minima, e.g craters. These regions are of scientific and human exploration interest due to the near constant low temperatures in PSRs, inferred to be < 100 K. Hydrogen is thought to have accumulated in PSR's through the combined effects of periodic cometary bombardment and/or solar wind processes, and the extreme cold which minimizes hydrogen sublimation [8-9]. RT methods are also of use in surface position optimization for future illumination dependent on surface resources e.g. power and communications equipment.
McClanahan, Timothy P.↗
A High Power Density Power System Electronics for NASA's Lunar Reconnaissance Orbiter
A high power density, modular and state-of-the-art Power System Electronics (PSE) has been developed for the Lunar Reconnaissance Orbiter (LRO) mission. This paper addresses the hardware architecture and performance, the power handling capabilities, and the fabrication technology. The PSE was developed by NASA s Goddard Space Flight Center (GSFC) and is the central location for power handling and distribution of the LRO spacecraft. The PSE packaging design manages and distributes 2200W of solar array input power in a volume less than a cubic foot. The PSE architecture incorporates reliable standard internal and external communication buses, solid state circuit breakers and LiIon battery charge management. Although a single string design, the PSE achieves high reliability by elegantly implementing functional redundancy and internal fault detection and correction. The PSE has been environmentally tested and delivered to the LRO spacecraft for the flight Integration and Test. This modular design is scheduled to flight in early 2009 on board the LRO and Lunar Crater Observation and Sensing Satellite (LCROSS) spacecrafts and is the baseline architecture for future NASA missions such as Global Precipitation Measurement (GPM) and Magnetospheric MultiScale (MMS).
Hernandez-Pellerano, A.↗