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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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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Antarctic marine gravity field from high-density satellite altimetry

High-density (about 2-km profile spacing) Geosat/GM altimetry profiles were obtained for Antarctic waters (6-deg S to 72 deg S) and converted to vertical gravity gradient, using Laplace's equation to directly calculate gravity gradient from vertical deflection grids and Fourier analysis to construct gravity anomalies from two vertical deflection grids. The resultant gravity grids have resolution and accuracy comparable to shipboard gravity profiles. The obtained gravity maps display many interesting and previously uncharted features, such as a propagating rift wake and a large 'leaky transform' along the Pacific-Antarctic Rise.

Sandwell, David T.↗
NASA NTRS1992

Mars Observer - Ready for launch

The main objectives of the Mars Observer Mission are reviewed. The activity of the mission focuses on geoscience and climatology, with observations to be made of the Mars atmosphere, surface, and interior. The mission will include seven scientific experiments involving gamma-ray spectroscopy, magnetometry, surface and atmospheric imaging, atmospheric sounding, laser altimetry, gravity mapping, and thermal emission spectroscopy. The mission plan and mapping operations are briefly discussed.

Albee, A. L.↗
NASA NTRS1995

Magellan aerobrake navigation

The Magellan spacecraft has been aerobraked into a 197 x 541 km near-circular orbit around Venus from which it is conducting a high-resolution gravity mapping mission. This was the first interplanetary aerobrake maneuver and involved flying the spacecraft through the upper reaches of the Venusian atmosphere 730 times over a 70 day period. Round-trip light-time varied from 9.57 to 18.83 minutes during this period. Navigation for this dynamic phase of the Magellan mission was planned and executed in the face of budget-driven down-sizing with all spacecraft safe modes disabled and a flight-team one-third the size of comparable interplanetary missions. Successful execution of this manuever using spacecraft hardware not designed to operate in a planetary atmosphere, demonstrated a practical cost-saving technique for both large and small future interplanetary missions.

Giorgini, Jon↗
NASA NTRS1998

Galileo Outreach Compilation

This NASA JPL (Jet Propulsion Laboratory) video production is a compilation of the best short movies and computer simulation/animations of the Galileo spacecraft's journey to Jupiter. A limited number of actual shots are presented of Jupiter and its natural satellites. Most of the video is comprised of computer animations of the spacecraft's trajectory, encounters with the Galilean satellites Io, Europa and Ganymede, as well as their atmospheric and surface structures. Computer animations of plasma wave observations of Ganymede's magnetosphere, a surface gravity map of Io, the Galileo/Io flyby, the Galileo space probe orbit insertion around Jupiter, and actual shots of Jupiter's Great Red Spot are presented. Panoramic views of our Earth (from orbit) and moon (from orbit) as seen from Galileo as well as actual footage of the Space Shuttle/Galileo liftoff and Galileo's space probe separation are also included.

Source record↗
NASA NTRS1993

Navigating the Magellan Aerobrake

The Magellan spacecraft has been aerobraked into a 197 x 541 km near-circular orbit around Venus from which it is conducting a high-resolution gravity mapping mission. This was the first interplanetary aerobrake maneuver and involved flying the spacecraft through the upper reaches of the Venusian atmosphere 730 times over a 70 day period.

Magellan aerobrake Venusian↗
DOE OSTI2013

Gravity Survey of the Carson Sink - Data and Maps

A detailed gravity survey was carried out for the entire Carson Sink in western Nevada (Figure 1) through a subcontract to Zonge Engineering, Inc. The Carson Sink is a large composite basin containing three known, blind high-temperature geothermal systems (Fallon Airbase, Stillwater, and Soda Lake). This area was chosen for a detailed gravity survey in order to characterize the gravity signature of the known geothermal systems and to identify other potential blind systems based on the structural setting indicated by the gravity data. Data were acquired at approximately 400, 800, and 1600 meter intervals for a total of 1,243 stations. The project location and station location points are presented in Figure 14. The station distribution for this survey was designed to complete regional gravity coverage in the Carson Sink area without duplication of available public and private gravity coverage. Gravity data were acquired using a Scintrex CG-5 gravimeter and a LaCoste and Romberg (L&R) Model-G gravimeter. The CG-5 gravity meter has a reading resolution of 0.001 milligals and a typical repeatability of less than 0.005 milligals. The L&R gravity meter has a reading resolution of 0.01 milligals and a typical repeatability of 0.02 milligals. The basic processing of gravimeter readings to calculate through to the Complete Bouguer Anomaly was made using the Gravity and Terrain Correction software version 7.1 for Oasis Montaj by Geosoft LTD. The gravity survey of the Carson Sink yielded a project location and station location map, a Complete Bouguer Anomaly @ 2.67 gm/cc reduction density, a Gravity Complete Bouguer Anomaly at 2.50 g/cc Contour Map, a Gravity Horizontal Gradient Magnitude Shaded Color Contour Map, a Gravity 1st Vertical Derivative Color Contour Map, and an Interpreted Depth to Mesozoic Basement incorporating drill-hole intercept values. A preliminary interpretation of these results suggests that the Carson Sink is a complex composite basin with several major depocenters. Major depocenters are present in the south-central, east-central, and northeastern parts of the basin. The distribution of gravity anomalies suggests a complex pattern of faulting in the subsurface of the basin, with many fault terminations, step-overs, and accommodation zones. The pattern of faulting implies that other, previously undiscovered blind geothermal systems are likely in the Carson Sink. The gravity survey was completed near the end of this project. Thus, more thorough analysis of the data and potential locations of blind geothermal systems is planned for future work.

15 GEOTHERMAL ENERGY↗
NASA NTRS2010

GRAIL - A Microwave Ranging Instrument to Map Out the Lunar Gravity Field

Gravity Recovery and Interior Laboratory, or GRAIL, is a NASA mission to map out the gravity field of the moon to an unprecedented level of detail. The instrument for this mission is based on GRACE (Gravity Recovery and Climate Experiment), an earth-orbiting mission currently mapping out the gravity field of the earth. This paper will describe the similarities and differences between these two instruments with a focus on the microwave ranging measurements used to determine the gravity parameters and the testbed built at Jet Propulsion Laboratory to demonstrate micron level ranging capability. The onboard ultrastable oscillator and RF instruments will be described and noise contributions discussed.

Enzer, Daphna G.↗
DOE OSTI2016

Lensing-induced morphology changes in CMB temperature maps in modified gravity theories

Lensing of the Cosmic Microwave Background (CMB) changes the morphology of pattern of temperature fluctuations, so topological descriptors such as Minkowski Functionals can probe the gravity model responsible for the lensing. We show how the recently introduced two-to-two and three-to-one kurt-spectra (and their associated correlation functions), which depend on the power spectrum of the lensing potential, can be used to probe modified gravity theories such as f ( R ) theories of gravity and quintessence models. We also investigate models based on effective field theory, which include the constant-Ω model, and low-energy Hořava theories. Estimates of the cumulative signal-to-noise for detection of lensing-induced morphology changes, reaches O(10{sup 3}) for the future planned CMB polarization mission COrE{sup +}. Assuming foreground removal is possible to ℓ{sub max}=3000, we show that many modified gravity theories can be rejected with a high level of significance, making this technique comparable in power to galaxy weak lensing or redshift surveys. These topological estimators are also useful in distinguishing lensing from other scattering secondaries at the level of the four-point function or trispectrum. Examples include the kinetic Sunyaev-Zel'dovich (kSZ) effect which shares, with lensing, a lack of spectral distortion. We also discuss the complication of foreground contamination from unsubtracted point sources.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1990

The vibro-acoustic mapping of low gravity trajectories on a Learjet aircraft

Terrestrial low gravity research techniques have been employed to gain a more thorough understanding of basic science and technology concepts. One technique frequently used involves flying parabolic trajectories aboard the NASA Lewis Research Center Learjet aircraft. A measurement program was developed to support an isolation system conceptual design. This program primarily was intended to measure time correlated high frequency accelerations (up to 100 Hz) present at various locations throughout the Learjet during a series of trajectories and flights. As suspected, the measurements obtained revealed that the environment aboard such an aircraft can not simply be described in terms of the static level low gravity g vector obtained, but that it also must account for both rigid body and high frequency vibro-acoustic dynamics.

Grodsinsky, C. M.↗
NASA NTRS1990

The vibro-acoustic mapping of low gravity trajectories on a Learjet aircraft

The NASA LeRC Learjet aircraft is used to fly parabolic trajectories for carrying out in-flight microgravity experiments. To derive full benefit from data obtained in such experiments, it is not only required to understand the low- to moderate-frequency accelerations present but also necessary to characterize the broadband aircraft vibro-acoustic environment. A vibro-acoustic measurement program was conducted during a series of low-gravity trajectories flown on the Learjet. The fuselage and an experiment rack were instrumented with 13 channels of accelerometers and three channels of pressure transducers. The locations of these sensors were determined in order to build a time history of the dynamics involved in the flight of such a parabolic trajectory and thus determine the typical rigid-body and vibro-acoustic loading a payload would experience. The instrumentation, data acquisition sequence, and experimental results showing residual accelerations and high-frequency dynamics are presented. As suspected, the measurements revealed that the aircraft environment cannot simply be described in terms of the static level low-gravity g-vector obtained, but that it also must account for both rigid-body and high-frequency vibro-acoustic dynamics.

Grodsinsky, C. M.↗
NASA NTRS1988

Gravity domains and assembly of the North American continent by collisional tectonics

A gravity trend map of North America, based on a horizontal Bouguer gravity gradient map produced from gravity data for Canada and the conterminous United States, is presented and used to define a continental mosaic of gravity trend domains akin to structural domains. Contrasting trend characteristics at gravity domain boundaries support the concept of outward growth of the continent primarily by accretionary tectonics. Gravity patterns, however, indicate a different style of tectonics dominated in the development of now-buried Proterozoic orogenic belts in the south-central United States, supporting a view that these belts formed along the leading edge of a southward-migrating Proterozoic continental margin.

Thomas, M. D.↗
NASA NTRS1984

Accuracy of mapping the Earth's gravity field fine structure with a spaceborne gravity gradiometer mission

The spaceborne gravity gradiometer is a potential sensor for mapping the fine structure of the Earth's gravity field. Error analyses were performed to investigate the accuracy of the determination of the Earth's gravity field from a gravity field satellite mission. The orbital height of the spacecraft is the dominating parameter as far as gravity field resolution and accuracies are concerned.

Kahn, W. D.↗
NASA NTRS1989

Advances in understanding the gravity wave spectrum during MAP

Prior to MAP, virtually nothing was known about gravity wave spectra in the atmosphere. The development of observational techniques has played a major role in these studies. Radar and lidar have been particularly important since they can measure atmospheric parameters continuously over large height ranges. Some advances made are: (1) The observed fluctuations and power spectra in the free atmosphere are mostly if not entirely due to a superposition of gravity waves, which can be modeled by the Garrett Munk (GM) model; (2) There is no evidence that 2-D turbulence makes a significant contribution to the observed fluctuations. In any case, the agreement between observations and the GM model shows that the 2DT contribution must be relatively small; (3) Spectra versus vertical wave number are saturated at large wave number, with theory and observations indicating that t approximately equals 3; and (4) Vertical velocity fluctuations and spectra measured near rough terrain are strongly contaminated by mountain waves. But over very flat terrain the spectra are dominated by gravity waves at periods shorter than about 6 hours and apparently by synoptic scale velocities at periods longer than 6 hours. Thus it may be possible to study synoptic scale vertical velocities using radars located in very flat terrain.

Vanzandt, T. E.↗
NASA NTRS1981

Venus gravity - A high-resolution map

The Doppler data from the radio tracking of the Pioneer Venus Orbiter (PVO) have been used in a two-stage analysis to develop a high-resolution map of the gravitational potential of Venus, represented by a central mass and a surface mass density. The two-stage procedure invokes a Kalman filter-smoother to determine the orbit of the spacecraft, and a stabilized linear inverter to estimate the surface mass density. The resultant gravity map is highly correlated with the topographic map derived from the PVO radar altimeter data. However, the magnitudes of the gravity variations are smaller than would be expected if the topography were uncompensated, indicating that at least partial compensation has taken place.

Reasenberg, R. D.↗
NASA NTRS1983

The Geopotential Research Mission - Mapping the near earth gravity and magnetic fields

The Geopotential Research Mission (GRM), NASA's low-level satellite system designed to measure the gravity and magnetic fields of the earth, and its objectives are described. The GRM will consist of two, Shuttle launched, satellite systems (300 km apart) that will operate simultaneously at a 160 km circular-polar orbit for six months. Current mission goals include mapping the global geoid to 10 cm, measuring gravity-field anomalies to 2 mgal with a spatial resolution of 100 km, detecting crustal magnetic anomalies of 100 km wavelength with 1 nT accuracy, measuring the vectors components to + or - 5 arc sec and 5 nT, and computing the main dipole or core field to 5 nT with a 2 nT/year secular variation detection. Resource analysis and exploration geology are additional applications considered.

Taylor, P. T.↗
NASA NTRS1990

Magellan mission to Venus

The Magellan spacecraft arrived at Venus on August 10, 1990 to begin global high-resolution radar image and altimeter mapping and gravity field determination of the planet. Mapping of this cloud covered planet is done from an elliptical orbit with a 3.15 hour period and a 275 km periapsis. After the initial checkout of the spacecraft, the primary missions lasts for 243 days (one Venus day); the time it takes for Venus to make one revolution beneath the spacecraft. The data collected by Magellan is expected to provide an understanding of the geological and geophysical nature of the planet Venus, and the general processes that control planetary evolution.

Boyce, Joseph M.↗
NASA NTRS2022

Gravity Poppers: Hopping Probes for the Internal Mapping of Small Solar System Bodies

This paper presents the results of NIAC Phase I study into the feasibility of a novel mission architecture for highresolution gravity science on small Solar System bodies. The “Gravity Poppers” mission concept (see Fig. 1) consists of a swarm of small, minimalistic probes that are deployed from a mother spacecraft to the surface of a small body and which periodically and randomly hop around the surface. By tracking the ballistic sub-orbital trajectories of this hopping swarm, a very high resolution gravity field can be measured, which can then be used to answer a number of scientific questions of interest regarding the interior mass distribution of the body. This paper describes the three core focus areas of our study to demonstrate concept feasibility: (1) the design of hopping probes to be small, simple, robust, and “visible” to a distant spacecraft, (2) the tracking strategy for detecting and estimating the trajectories of a large number of ballistic probes, and (3) the algorithmic framework by which such measurements can be used to estimate the body’s gravity field. Our results suggest the ability to estimate the gravity field of a 500m asteroid beyond degree-and-order 40 through days to weeks of optical tracking of several LED-strobing probes, with a mass of only 200 g each. Collectively, this study demonstrates that the high-resolution gravity mapping of small body interiors is technically possible, economically feasible, and would enable a compelling set of science objectives aligned with NASA’s goals in planetary science, planetary defense, and future interests in resource prospecting.

McMahon, Jay↗