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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 415 records · Page 23
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NASA NTRS2022

Science Objectives for Flagship-Class Mission Concepts for the Search for Evidence of Life at Enceladus

Cassini revealed that Saturn's Moon Enceladus hosts a subsurface ocean that meets the accepted criteria for habitability with bio-essential elements and compounds, liquid water, and energy sources available in the environment. Whether these conditions are sufficiently abundant and collocated to support life remains unknown and cannot be determined from Cassini data. However, thanks to the plume of oceanic material emanating from Enceladus’ south pole, a new mission to Enceladus could search for evidence of life without having to descend through kilometers of ice. In this article, we outline the science motivations for such a successor to Cassini, choosing the primary science goal to be determining whether Enceladus is inhabited and assuming a resource level equivalent to NASA's Flagship-class missions. We selected a set of potential biosignature measurements that are complementary and orthogonal to build a robust case for any life detection result. This result would be further informed by quantifications of the habitability of the environment through geochemical and geophysical investigations into the ocean and ice shell crust. This study demonstrates that Enceladus’ plume offers an unparalleled opportunity for in situ exploration of an Ocean World and that the planetary science and astrobiology community is well equipped to take full advantage of it in the coming decades.

Enceladus↗
NASA NTRS1996

Radar Interferometric and Penetration Investigations using SIR-C Data

Progress, significant results, publications and future plans are discussed in relation to the following objectives: (1) To model, experimentally characterize, and verify penetration phenomena in hyperarid and vegetated regions using the SIR-C/X-SAR multiparameter radar system and groundbased receivers; (2) To invert measured radar backscatter as a function of frequency and polarization in terms of geophysical parameters of the surface, subsurface and vegetation canopy such as surface roughness, subsurface geomorphology, or tree height and density; and (3) To display subsurface and within-canopy features in an image format, thus easing the interpretability of the results.

Zebker, Howard A.↗
NASA NTRS1973

Thermal properties of the Galilean satellites.

Radiometry in the 20-micron band of eclipses of each of the four Galilean satellites of Jupiter provides information about the thermal properties of the uppermost surface layers of these bodies. Their thermal inertias are all smaller than those of the moon or of Mercury; there is no evidence for atmospheres, and where the data are of high quality vertically homogeneous thermal properties are excluded. The thermal properties, together with other observational evidence, suggest that the surfaces of these satellites are largely composed of ices. A thin coating of frost provides the upper, low-conductivity layer, while the subsurface material maintains a high thermal conductivity by fusion of a mixture of ice and rock.

Morrison, D.↗
NASA NTRS1989

On the source of cross-grain lineations in the central Pacific gravity field

The source of cross-grain lineations in marine gravity field observed in central Pacific was investigated by comparing multiple collinear gravity profiles from Geosat data with coincident bathymetry profiles, in the Fourier transform domain. Bathymetric data were collected by multibeam sonar systems operating from two research vessels, one in June-August 1985, the other in February and March 1987. The results of this analysis indicate that the lineations are superficial features that appear to result from a combination of subsurface and surface loads supported by a thin (2 km to 5 km) lithosphere.

Mcadoo, David C.↗
NASA NTRS1993

The effect of sub-surface volume scattering on the accuracy of ice-sheet altimeter retracking algorithms

The NASA and ESA retracking algorithms are compared with an algorithm based upon a combined surface and volume (S/V) scattering model. First, the S/V, NASA, and ESA algorithms were used to retrack over 400,000 altimeter return waveforms from the Greenland and Antarctic ice sheets. The surface elevations from the S/V algorithm were compared with the elevations produced by the NASA and ESA algorithms to determine the relative accuracy of these algorithms when subsurface volume-scattering occurs. The results show that the NASA algorithm produced surface elevations within 35 to 50 cm of the S/V algorithm, while the performance of the ESA algorithm was slightly worse. Next, by analyzing several thousand satellite crossover points from the Antarctic data set, we determined the retracking algorithm that produced the most repeatable surface elevations. The elevations derived from the S/V algorithm had the smallest RMS error for the region of the East Antarctic plateau examined here. The ESA algorithm produced erroneous estimates of elevation change when seasonal variations were present; it measured 0.7 to 1.6-m change in elevation over a 6-month period on the East Antarctic plateau where accumulation rates are only 10 cm/year.

Davis, Curt H.↗
NASA NTRS2021

The Science Case for Spacecraft Exploration of the Uranian Satellites: Candidate Ocean Worlds in an Ice Giant System

The 27 satellites of Uranus are enigmatic, with dark surfaces coated by material that could be rich in organics. Voyager 2 imaged the southern hemispheres of Uranus’s five largest “classical” moons—Miranda, Ariel, Umbriel, Titania, and Oberon, as well as the largest ring moon, Puck—but their northern hemispheres were largely unobservable at the time of the flyby and were not imaged. Additionally, no spatially resolved data sets exist for the other 21 known moons, and their surface properties are essentially unknown. Because Voyager 2 was not equipped with a near-infrared mapping spectrometer, our knowledge of the Uranian moons’ surface compositions, and the processes that modify them, is limited to disk-integrated data sets collected by ground- and space-based telescopes. Nevertheless, images collected by the Imaging Science System on Voyager 2 and reflectance spectra collected by telescope facilities indicate that the five classical moons are candidate ocean worlds that might currently have, or had, liquid subsurface layers beneath their icy surfaces. To determine whether these moons are ocean worlds, and to investigate Uranus’s ring moons and irregular satellites, close-up observations and measurements made by instruments on board a Uranus orbiter are needed.

Richard J. Cartwright↗
NASA NTRSDate not supplied

Assessing Potential Geophysical and Environmental Impacts from Frequent Rocket Launch Missions at Kennedy Space Center

Kennedy Space Center (KSC) in Florida has been utilized for space missions over many years with a gradually increasing number of rocket launches. There have been multiple studies where air-coupled acoustic waves and infrasound originating from launched rockets were used for operational purposes, such as locating booster trajectories as a function of changing atmospheric conditions. However, no study has utilized the acoustoelastic waves as a signal source for subsurface seismic investigations. We conducted a dispersion analysis using the seismic energy recorded from the Artemis I rocket launch at KSC in November 2022, and from these results we generated depth-sensitivity kernels at different wave frequencies. The kernels were compared with sedimentary core data to verify boundaries of carbonate layers above the Floridan Aquifer System. Accumulative information of bedrock-sediment boundary across the sedimentary platform could especially provide geo-structural evidence that manifests the configuration of coastal features. Continuous dispersion analysis of seismic recordings from consecutive rocket launches also has potential to identify non-stationary environmental effects, such as reorientation of sedimentary structures and fluctuation of the saltwater/groundwater lens from gravitational tides, which may affect erosional susceptibility of coastal features.

Han Byul Woo↗
NASA NTRSDate not supplied

Assessing Potential Geophysical and Environmental Impacts from Frequent Rocket Launch Missions at Kennedy Space Center

Kennedy Space Center (KSC) in Florida has been utilized for space missions over many years with a gradually increasing number of rocket launches. There have been multiple studies where air-coupled acoustic waves and infrasound originating from launched rockets were used for operational purposes, such as locating booster trajectories as a function of changing atmospheric conditions. However, no study has utilized the acoustoelastic waves as a signal source for subsurface seismic investigations. We conducted a dispersion analysis using the seismic energy recorded from the Artemis I rocket launch at KSC in November 2022, and from these results we generated depth-sensitivity kernels at different wave frequencies. The kernels were compared with sedimentary core data to verify boundaries of carbonate layers above the Floridan Aquifer System. Accumulative information of bedrock-sediment boundary across the sedimentary platform could especially provide geo-structural evidence that manifests the configuration of coastal features. Continuous dispersion analysis of seismic recordings from consecutive rocket launches also has potential to identify non-stationary environmental effects, such as reorientation of sedimentary structures and fluctuation of the saltwater/groundwater lens from gravitational tides, which may affect erosional susceptibility of coastal features.

Rocket Launch Seismicity↗
NASA NTRS1991

Faulting and folding in the formation of planetary wrinkle ridges

Topographic profiles for planetary wrinkle ridges compiled from high-resolution Lunar Topographic Orthophoto maps for the moon and from monoscopic photoclinometry data for Mars reveal that many of these ridges are characterized by an elevation offset between one side of a ridge and the other. To investigate the relative importance of faulting and folding in the formation of planetary wrinkle ridges, this paper develops a model of subsurface structure, based on observations and measurements of surface physiography and topography by Golombek and Franklin (1987) and Plescia (1990), and assumptions of subsurface structure, which makes it possible to estimate shortening across wrinkle ridges on Moon and Mars. According to this model, total ridge shortening is on the order of 100 m; shortening due to faulting exceeds shortening due to folding for fault dips up to 60-80 deg, implying that faults beneath many wrinkle ridges break the surface to accomodate the greater displacement along the fault than is accomodated in the fold.

Golombek, M. P.↗
NASA NTRS2011

Fiber Optic Thermal Detection of Composite Delaminations

A recently developed technique is presented for thermographic detection of delaminations in composites by performing temperature measurements with fiber optic Bragg gratings. A single optical fiber with multiple Bragg gratings employed as surface temperature sensors was bonded to the surface of a composite with subsurface defects. The investigated structure was a 10-ply composite specimen with prefabricated delaminations of various sizes and depths. Both during and following the application of a thermal heat flux to the surface, the individual Bragg grating sensors measured the temporal and spatial temperature variations. The data obtained from grating sensors were analyzed with thermal modeling techniques of conventional thermography to reveal particular characteristics of the interested areas. Results were compared and found to be consistent with the calculations using numerical simulation techniques. Also discussed are methods including various heating sources and patterns, and their limitations for performing in-situ structural health monitoring.

Wu, Meng-Chou↗
NASA NTRS2017

Radar Ambiguities and Signal Processing Design Tradeoffs in the REASON Radar Sounder

NASA’s planned Europa Clipper mission would carry a radar sounder which operates at HF and VHF frequencies that can penetrate the icy shell of Europa. The sounder would be used to characterize subsurface bodies of liquid water and to measure the thickness of the icy shell. The spacecraft would make observations during flyby to reduce radiation exposure. The varying geometry during the flyby is expected to cause varying radar ambiguity and surface clutter contamination. At the same time, data down-link restrictions would require on-board pulse summation to reduce data volume which would require on-board Doppler filtering to control clutter and ambiguity contamination levels. This paper will study some of the design trade-offs involved in specifying the on-board Doppler filtering.

Hawkins, D.↗
NASA NTRS2001

Bringing data back from Mars: in-situ communications role--the rover to orbiter to Earth link

Over the coming decade, an international fleet of spacecraft will carry out the most intensive exploration to date of another world in our solar system. A wide range of orbiters, landers and rovers will conduct a linking together--detailed in-situ inbestigations, culminating in an eventual return of Martian surface, subsurface, and atmospheric samples to Earth for detailed laboratory evaluation.

Mars communication navigation in-situ↗
NASA NTRS1988

Spatially resolved ballistic electron spectroscopy of subsurface interfaces

Buried interfaces have traditionally been inaccessible to direct investigation by surface-sensitive techniques. A unique and novel electronic probe, which is sensitive to subsurface electronic structure, has been utilized to probe Schottky barrier interfaces. The method, ballistic electron emission microscopy (BEEM), is based on scanning tunnelling microscopy (STM) techniques. A theoretical treatment has been developed to describe the ballistic electron spectra obtained by BEEM and this treatment is applied to data obtained on the Au-Si Schottky barrier interface system. Excellent agreement between experiment and theory is obtained. In addition, the treatment predicts nanometer spatial resolution for interface imaging by BEEM.

Bell, L. D.↗
NASA NTRS1993

Fuzzy logic path planning system for collision avoidance by an autonomous rover vehicle

The Space Exploration Initiative of the United States will make great demands upon NASA and its limited resources. One aspect of great importance will be providing for autonomous (unmanned) operation of vehicles and/or subsystems in space flight and surface exploration. An additional, complicating factor is that much of the need for autonomy of operation will take place under conditions of great uncertainty or ambiguity. Issues in developing an autonomous collision avoidance subsystem within a path planning system for application in a remote, hostile environment that does not lend itself well to remote manipulation by Earth-based telecommunications is addressed. A good focus is unmanned surface exploration of Mars. The uncertainties involved indicate that robust approaches such as fuzzy logic control are particularly appropriate. Four major issues addressed are (1) avoidance of a fuzzy moving obstacle; (2) backoff from a deadend in a static obstacle environment; (3) fusion of sensor data to detect obstacles; and (4) options for adaptive learning in a path planning system. Examples of the need for collision avoidance by an autonomous rover vehicle on the surface of Mars with a moving obstacle would be wind-blown debris, surface flow or anomalies due to subsurface disturbances, another vehicle, etc. The other issues of backoff, sensor fusion, and adaptive learning are important in the overall path planning system.

Murphy, Michael G.↗
NASA NTRS2011

Time-Distance Helioseismology Data-Analysis Pipeline for Helioseismic and Magnetic Imager Onboard Solar Dynamics Observatory (SDO-HMI) and Its Initial Results

The Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI) provides continuous full-disk observations of solar oscillations. We develop a data-analysis pipeline based on the time-distance helioseismology method to measure acoustic travel times using HMI Doppler-shift observations, and infer solar interior properties by inverting these measurements. The pipeline is used for routine production of near-real-time full-disk maps of subsurface wave-speed perturbations and horizontal flow velocities for depths ranging from 0 to 20 Mm, every eight hours. In addition, Carrington synoptic maps for the subsurface properties are made from these full-disk maps. The pipeline can also be used for selected target areas and time periods. We explain details of the pipeline organization and procedures, including processing of the HMI Doppler observations, measurements of the travel times, inversions, and constructions of the full-disk and synoptic maps. Some initial results from the pipeline, including full-disk flow maps, sunspot subsurface flow fields, and the interior rotation and meridional flow speeds, are presented.

Sun: helioseismology↗
NASA NTRS2014

Real-Time Science Operations to Support a Lunar Polar Volatiles Rover Mission

Future human exploration of the Moon will likely rely on in situ resource utilization (ISRU) to enable long duration lunar missions. Prior to utilizing ISRU on the Moon, the natural resources (in this case lunar volatiles) must be identified and characterized, and ISRU demonstrated on the lunar surface. To enable future uses of ISRU, NASA and the CSA are developing a lunar rover payload that can (1) locate near subsurface volatiles, (2) excavate and analyze samples of the volatile-bearing regolith, and (3) demonstrate the form, extractability and usefulness of the materials. Such investigations are important both for ISRU purposes and for understanding the scientific nature of these intriguing lunar volatile deposits. Temperature models and orbital data suggest near surface volatile concentrations may exist at briefly lit lunar polar locations outside persistently shadowed regions. A lunar rover could be remotely operated at some of these locations for the approx. 2-14 days of expected sunlight at relatively low cost. Due to the limited operational time available, both science and rover operations decisions must be made in real time, requiring immediate situational awareness, data analysis, and decision support tools. Given these constraints, such a mission requires a new concept of operations. In this paper we outline the results and lessons learned from an analog field campaign in July 2012 which tested operations for a lunar polar rover concept. A rover was operated in the analog environment of Hawaii by an off-site Flight Control Center, a rover navigation center in Canada, a Science Backroom at NASA Ames Research Center in California, and support teams at NASA Johnson Space Center in Texas and NASA Kennedy Space Center in Florida. We find that this type of mission requires highly efficient, real time, remotely operated rover operations to enable low cost, scientifically relevant exploration of the distribution and nature of lunar polar volatiles. The field demonstration illustrated the need for science operations personnel in constant communications with the flight mission operators and the Science Backroom to provide immediate and continual science support and validation throughout the mission. Specific data analysis tools are also required to enable immediate data monitoring, visualization, and decision making. The field campaign demonstrated that this novel methodology of real-time science operations is possible and applicable to providing important new insights regarding lunar polar volatiles for both science and exploration.

Moon; Volatiles; Rover; Missions↗
NASA NTRS1993

Evaluation of a distributed catchment scale water balance model

The validity of some of the simplifying assumptions in a conceptual water balance model is investigated by comparing simulation results from the conceptual model with simulation results from a three-dimensional physically based numerical model and with field observations. We examine, in particular, assumptions and simplifications related to water table dynamics, vertical soil moisture and pressure head distributions, and subsurface flow contributions to stream discharge. The conceptual model relies on a topographic index to predict saturation excess runoff and on Philip's infiltration equation to predict infiltration excess runoff. The numerical model solves the three-dimensional Richards equation describing flow in variably saturated porous media, and handles seepage face boundaries, infiltration excess and saturation excess runoff production, and soil driven and atmosphere driven surface fluxes. The study catchments (a 7.2 sq km catchment and a 0.64 sq km subcatchment) are located in the North Appalachian ridge and valley region of eastern Pennsylvania. Hydrologic data collected during the MACHYDRO 90 field experiment are used to calibrate the models and to evaluate simulation results. It is found that water table dynamics as predicted by the conceptual model are close to the observations in a shallow water well and therefore, that a linear relationship between a topographic index and the local water table depth is found to be a reasonable assumption for catchment scale modeling. However, the hydraulic equilibrium assumption is not valid for the upper 100 cm layer of the unsaturated zone and a conceptual model that incorporates a root zone is suggested. Furthermore, theoretical subsurface flow characteristics from the conceptual model are found to be different from field observations, numerical simulation results, and theoretical baseflow recession characteristics based on Boussinesq's groundwater equation.

Troch, Peter A.↗
NASA NTRS1994

Inference of subsurface thermohaline structure from fields measurable by satellite

Satellites now provide global measurements of the ocean's surface height and temperature. Ocean climatologies for the northwest Pacific and northwest Atlantic Oceans that relate sea surface height, sea surface temperature, day of the year, latitude, and longitude to temperature and salinity profiles were produced using least-squares regression. These analyses use over 33,000 profiles of historical temperature and salinity data and are considerably streamlined and compacted by expressing each profile in terms of empirical orthogonal functions. Evaluations and error analyses of the climatologies, including a comparison to the navy's Generalized Digital Environmental Model, were performed and differences between the regions are discussed. Two sample vertical sections are shown to be closely reproduced with the climatologies. Climatologies based on surface height and temperature are found to offer considerable improvement over climatologies based only on position.

Carnes, Michael R.↗