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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Energy coupling in the magnetospheres of earth and Mercury

The mechanisms involved in the dissipation of solar-wind energy during magnetospheric substorms are considered theoretically, comparing models for earth and Mercury. In the model for terrestrial substorms, IMF lines interconnect with terrestrial field lines near the front of the magnetosphere and are dragged back, carrying plasma and energy, to form tail lobes; a magnetic neutral region is then formed by reconnection of the open lines as the plasma sheet thins, and reconnective heating and acceleration of tail plasma lead to plasma inflow at the poles and formation of a plasmoid flowing down the tail at high velocity. Analogous phenomena on Mercury could produce precipitation of particles carrying 10-1000 GW of power into 'auroral zones' on the dark side of the planet. The feasibility of remote or in situ observations to detect such processes is discussed.

Baker, D. N.↗
NASA NTRS1991

Calibration of EOS multispectral imaging sensors and solar irradiance variability

Earth Observation System (EOS) optical multispectral imaging sensors provide images of the earth at various spectral and spatial resolutions, in the visible (VIS) and infrared (IR) regions of the solar spectrum. Accurate knowledge of extraterrestrial solar spectral irradiance and its variations with time, are needed to trace sensor calibration in space, and for the development of terrestrial atmospheric models needed in data validation. A brief review of the extraterrestrial solar VIS/IR spectral irradiance available in the literature will be reviewed, and the need to develop an extraterrestrial solar spectral irradiance for the EOS studies will be pointed out. The solar calibration of the Earth Radiation Budget Experiments (ERBE), earth-viewing sensors will be discussed. Observed variations in the solar constant (solar irradiance, at the mean sun-earth distance of one astronomical unit, integrated over all wavelengths), and solar spectral irradiance with solar activity and its implications for EOS studies also will be discussed.

Mecherikunnel, Ann↗
NASA NTRS1992

From Mars to Greenland: Charting gravity with space and airborne instruments - Fields, tides, methods, results

This symposium on space and airborne techniques for measuring gravity fields, and related theory, contains papers on gravity modeling of Mars and Venus at NASA/GSFC, an integrated laser Doppler method for measuring planetary gravity fields, observed temporal variations in the earth's gravity field from 16-year Starlette orbit analysis, high-resolution gravity models combining terrestrial and satellite data, the effect of water vapor corrections for satellite altimeter measurements of the geoid, and laboratory demonstrations of superconducting gravity and inertial sensors for space and airborne gravity measurements. Other papers are on airborne gravity measurements over the Kelvin Seamount; the accuracy of GPS-derived acceleration from moving platform tests; airborne gravimetry, altimetry, and GPS navigation errors; controlling common mode stabilization errors in airborne gravity gradiometry, GPS/INS gravity measurements in space and on a balloon, and Walsh-Fourier series expansion of the earth's gravitational potential.

Colombo, Oscar L.↗
NASA NTRS1993

Scientific study in solar and plasma physics relative to rocket and balloon projects

The goals of this research are to provide scientific and technical capabilities in the areas of solar and plasma physics contained in research programs and instrumentation development relative to current rocket and balloon projects; to develop flight instrumentation design, flight hardware, and flight program objectives and participate in peer reviews as appropriate; and to participate in solar-terrestrial physics modeling studies and analysis of flight data and provide theoretical investigations as required by these studies.

Wu, S. T.↗
NASA NTRS1994

Volatiles in the Earth: All shallow and all recycled

A case can be made that accretion of the Earth was a high-temperature process and that the primordial Earth was dry. A radial zone-refining process during accretion may have excluded low-melting point and volatile material, including large-ion lithophile elements toward the surface, leaving a refractory and zoned interior. Water, sediments and altered hydrous oceanic crust are introduced back into the interior by subduction, a process that may be more efficient today than in the past. Seismic tomography strongly suggests that a large part of the uppermantle is above the solidus, and this implies wet melting. The mantle beneath Archean cratons has very fast seismic velocities and appears to be strong to 150 km or greater. This is consistent with very dry mantle. It is argued that recycling of substantial quantities of water occurs in the shallow mantle but only minor amounts recycle to depths greater than 200 km. Recycling also oxidizes that mantle; ocean island ('hotspot') basalts are intermediate in oxidation state to island-arc and midocean ridge basalts (MORB). This suggests a deep uncontaminated reservoir for MORB. Plate tectonics on a dry Earth is discussed in order to focus attention on inconsistencies in current geochemical models of terrestrial evolution and recycling.

Anderson, Don L.↗
NASA NTRS1995

Vegetation species composition and canopy architecture information expressed in leaf water absorption measured in the 1000 nm and 2200 spectral region by an imaging spectrometer

Plant species composition and plant architectural attributes are critical parameters required for the measuring, monitoring, and modeling of terrestrial ecosystems. Remote sensing is commonly cited as an important tool for deriving vegetation properties at an appropriate scale for ecosystem studies, ranging from local to regional and even synoptic scales. Classical approaches rely on vegetation indices such as the normalized difference vegetation index (NDVI) to estimate biophysical parameters such as leaf area index or intercepted photosynthetically active radiation (IPAR). Another approach is to apply a variety of classification schemes to map vegetation and thus extrapolate fine-scale information about specific sites to larger areas of similar composition. Imaging spectrometry provides additional information that is not obtainable through broad-band sensors and that may provide improved inputs both to direct biophysical estimates as well as classification schemes. Some of this capability has been demonstrated through improved discrimination of vegetation, estimates of canopy biochemistry, and liquid water estimates from vegetation. We investigate further the potential of leaf water absorption estimated from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data as a means for discriminating vegetation types and deriving canopy architectural information. We expand our analysis to incorporate liquid water estimates from two spectral regions, the 1000-nm region and the 2200-nm region. The study was conducted in the vicinity of Jasper Ridge, California, which is located on the San Francisco peninsula to the west of the Stanford University campus. AVIRIS data were acquired over Jasper Ridge, CA, on June 2, 1992, at 19:31 UTC. Spectra from three sites in this image were analyzed. These data are from an area of healthy grass, oak woodland, and redwood forest, respectively. For these analyses, the AVIRIS-measured upwelling radiance spectra for the entire Jasper Ridge scene were transformed to apparent surface reflectance using a radiative transfer code-based inversion algorithm.

Green, Robert O.↗
NASA NTRS1995

Single-Winged Autorotating Brake for Sensor Deployment on Mars

The following pages describe the development of a nonlinear simulation, results for the Martian entry problem, and a sizing study to determine whether the approach is feasible. The nonlinear simulation is described here and results are presented for several cases using Martian and Terrestrial atmosphere models. The results show that a 2.5 kg payload could be successfully delivered to the Martian surface using this approach and the report suggests an earth-based test of the system. Prior to the specific analysis presented here, a theoretical study of the mechanics of autorotation was completed, and a summary of this work is also included as part of this final report.

Kroo, Ilan↗
NASA NTRS2000

A Balanced Model for Exploration of the Terrestrial Planets: Lessons from the Lunar Experience

The Moon is the only extraterrestrial rocky body for which we have a combination of surface-selected samples, high-resolution orbital photography (Lunar Orbiter), manned and robotic surface exploration (Surveyor, Apollo, Luna), and global compositional, mineralogical, and geophysical data (Galileo, Clementine, Lunar Prospector). Beginning in 1998, CAPTEM organized a series of workshops and conference sessions aimed at integrating these diverse data sets. The insights gained by bringing together scientists from the remote-sensing and sample-analysis communities have been singularly rewarding. Not least of these has been the recognition by both groups that having both kinds of data maximizes the scientific return and permits reconciling information from diverse scales and perspectives. The 20-20 hindsight of the Lunar experience thus provides important lessons; learning from mistakes as well as successes, we can derive a sensible scientific program for Mars exploration. In this abstract, we describe examples of key information from (a) in-situ geologic investigation, (b) laboratory analysis of returned samples whose geologic context and location are known, and (c) global remote sensing of mineralogy, composition, and geophysical parameters. We then show the value of integrating these diverse data sets.

Jolliff, B. L.↗
NASA NTRS1994

Vegetation Species Composition and Canopy Architecture Information Expressed in Leaf Water Absorption Measured in the 1000nm and 2200 nm Spectral Region by an Imaging Spectometer

Plant species composition and plant architectural attributes are critical parameters required for the measuring, monitoring and modeling of terrestrial ecosystems. Remote sensing is commonly cited as an important tool for deriving vegetation properties at an appropriate scale for ecosystem studies, ranging from local, to regional and even synoptic scales (e.g. Wessman 1992).

ecosystem Normalized Difference Vegetation Index (↗
NASA NTRS2007

Effects of Optical-density and Phase Dispersion of an Imperfect Band-limited Occulting Mask on the Broadband Performance of a TPF Coronagraph

Practical image-plane occulting masks required by high-contrast imaging systems such as the TPF-Coronagraph introduce phase errors into the transmitting beam., or, equivalently, diffracts the residual starlight into the area of the final image plane used for detecting exo-planets. Our group at JPL has recently proposed spatially Profiled metal masks that can be designed to have zero parasitic phase at the center wavelength of the incoming broadband light with small amounts of' 00 and phase dispersions at other wavelengths. Work is currently underway to design. fabricate and characterize such image-plane masks. In order to gain some understanding on the behaviors of these new imperfect band-limited occulting masks and clarify how such masks utilizing different metals or alloys compare with each other, we carried out some modeling and simulations on the contrast performance of the high-contrast imaging testbed (HCIT) at .JPL. In this paper we describe the details of our simulations and present our results.

integrated modeling↗
NASA NTRS2016

EDL Pathfinder Missions

NASA is developing a long‐term strategy for achieving extended human missions to Mars in support of the policies outlined in the 2010 NASA Authorization Act and National Space Policy. The Authorization Act states that "A long term objective for human exploration of space should be the eventual international exploration of Mars." Echoing this is the National Space Policy, which directs that NASA should, "By 2025, begin crewed missions beyond the moon, including sending humans to an asteroid. By the mid‐2030s, send humans to orbit Mars and return them safely to Earth." Further defining this goal, NASA's 2014 Strategic Plan identifies that "Our long‐term goal is to send humans to Mars. Over the next two decades, we will develop and demonstrate the technologies and capabilities needed to send humans to explore the red planet and safely return them to Earth." Over the past several decades numerous assessments regarding human exploration of Mars have indicated that landing humans on the surface of Mars remains one of the key critical challenges. In 2015 NASA initiated an Agency‐wide assessment of the challenges associated with Entry, Descent, and Landing (EDL) of large payloads necessary for supporting human exploration of Mars. Due to the criticality and long‐lead nature of advancing EDL techniques, it is necessary to determine an appropriate strategy to improve the capability to land large payloads. This paper provides an overview of NASA's 2015 EDL assessment on understanding the key EDL risks with a focus on determining what "must" be tested at Mars. This process identified the various risks and potential risk mitigation strategies, that is, benefits of flight demonstration at Mars relative to terrestrial test, modeling, and analysis. The goal of the activity was to determine if a subscale demonstrator is necessary, or if NASA should take a direct path to a human‐scale lander. This assessment also provided insight into how EDL advancements align with other Agency Mars lander activities such as the technology portfolio investments and post‐2020 robotic Mars Exploration Program missions.

Drake, Bret G.↗
NASA NTRS2018

Spatially-Explicit Monitoring of Crop Photosynthetic Capacity Through the Use of Space-Based Chlorophyll Fluorescence Data

Plant functional traits such as photosynthetic capacity are critical parameters for terrestrial biosphere models. However, their spatial and temporal characteristics are still poorly represented. In this study, we used satellite observations of sun-induced fluorescence (SIF) to estimate top-of-canopy photosynthetic capacity (maximum carboxylation rate, V(sub cmax) at a reference temperature of 25 deg C) for crops, which was in turn utilized to simulate regional gross primary production (GPP). We first estimate the key parameter, V(sub cmax), in the widely-used FvCB photosynthesis model using field measurements of CO2 and water fluxes during 2007-2012 at seven crop eddy covariance flux sites over the US Corn Belt. The results showed that satellite far-red SIF retrievals have a stronger link to V(sub cmax) at the seasonal scale (R(squared)=0.70 for C4 and R(squared)=0.63 for C3 crop) as compared with widely-used vegetation indices. We calibrate an empirical model linking V(sub cmax) with SIF that was used to estimate spatially and temporally varying crop V(sub cmax) for the US Corn Belt region. The resulting V(sub cmax) maps are used together with meteorological data from MERRA reanalysis data and vegetation structural parameters derived from the satellite- based spectral reflectance data to constrain the Soil-Canopy Observation of Photosynthesis and Energy (SCOPE) balance model in order to estimate regional crop GPP. Our results show a substantial improvement in the seasonal and spatial patterns of cropland GPP when compared with crop yield inventory data. The evaluation with tall tower atmospheric CO2 measurements further supports our estimation of spatiotemporal V(sub cmax) from space-borne SIF. Considering that SIF has a direct link to photosynthetic activity, our findings highlight the potential to infer regional V(sub cmax) using remotely sensed SIF data and to use this information for a better quantification of regional cropland carbon cycles.

Drought↗
NASA NTRS2017

New Data-Driven Estimation of Terrestrial CO2 Fluxes in Asia Using a Standardized Database of Eddy Covariance Measurements, Remote Sensing Data, and Support Vector Regression

The lack of a standardized database of eddy covariance observations has been an obstacle for data-driven estimation of terrestrial carbon dioxide fluxes in Asia. In this study, we developed such a standardized database using 54 sites from various databases by applying consistent postprocessing for data-driven estimation of gross primary productivity (GPP) and net ecosystem carbon dioxide exchange (NEE). Data-driven estimation was conducted by using a machine learning algorithm: support vector regression (SVR), with remote sensing data for 2000 to 2015 period. Site-level evaluation of the estimated carbon dioxide fluxes shows that although performance varies in different vegetation and climate classifications, GPP and NEE at 8 days are reproduced (e.g., r (exp 2) =0.73 and 0.42 for 8 day GPP and NEE). Evaluation of spatially estimated GPP with Global Ozone Monitoring Experiment 2 sensor-based Sun-induced chlorophyll fluorescence shows that monthly GPP variations at subcontinental scale were reproduced by SVR (r (exp 2)=1.00, 0.94, 0.91, and 0.89 for Siberia, East Asia, South Asia, and Southeast Asia, respectively). Evaluation of spatially estimated NEE with net atmosphere-land carbon dioxide fluxes of Greenhouse Gases Observing Satellite (GOSAT) Level 4A product shows that monthly variations of these data were consistent in Siberia and East Asia; meanwhile, inconsistency was found in South Asia and Southeast Asia. Furthermore, differences in the land carbon dioxide fluxes from SVR-NEE and GOSAT Level 4A were partially explained by accounting for the differences in the definition of land carbon dioxide fluxes. These data-driven estimates can provide a new opportunity to assess carbon dioxide fluxes in Asia and evaluate and constrain terrestrial ecosystem models.

chlorophyll fluorescence↗
NASA NTRS2019

Five Decades of Northern Land Carbon Uptake Revealed by the Interhemispheric CO2 Gradient

The global land and ocean carbon sinks have increased proportionally with increasing carbon dioxide emissions during the past decades. It is thought that Northern Hemisphere lands make a dominant contribution to the global land carbon sink; however, the long-term trend of the northern land sink remains uncertain. Here, using measurements of the interhemispheric gradient of atmospheric carbon dioxide from 1958 to 2016, we show that the northern land sink remained stable between the 1960s and the late 1980s, then increased by 0.5 ± 0.4 petagrams of carbon per year during the 1990s and by 0.6 ± 0.5 petagrams of carbon per year during the 2000s. The increase of the northern land sink in the 1990s accounts for 65% of the increase in the global land carbon flux during that period. The subsequent increase in the 2000s is larger than the increase in the global land carbon flux, suggesting a coincident decrease of carbon uptake in the Southern Hemisphere. Comparison of our findings with the simulations of an ensemble of terrestrial carbon models over the same period suggests that the decadal change in the northern land sink between the 1960s and the 1990s can be explained by a combination of increasing concentrations of atmospheric carbon dioxide, climate variability and changes in land cover. However, the increase during the 2000s is underestimated by all models, which suggests the need for improved consideration of changes in drivers such as nitrogen deposition, diffuse light and land-use change. Overall, our findings underscore the importance of Northern Hemispheric land as a carbon sink.

Carbon cycle↗
NASA NTRS2019

Solid Fuel Ignition and Extinction (SoFIE) Project on ISS

The Solid Fuel Ignition and Extinction (SoFIE) project studies ignition and flammability of solid spacecraft materials (fuels) in practical geometries and realistic atmospheric conditions. It is an experiment insert designed for use within the existing Combustion Integrated Rack (CIR). The CIR chamber provides a level of containment and permits testing at variable oxygen concentrations and pressures representative of current and planned NASA Space Exploration Atmospheres. The applications of SoFIE include: (1) Determining safer selection of cabin materials and validating NASA materials flammability selection using 1-g test protocols for low-gravity fires, (2) Improving understanding of early fire growth behavior, (3) Validating material flammability numerical models, (4) Determining optimal suppression techniques for burning materials by diluents, flow reduction, and venting, (5) Obtaining burning behavior of actual engineering materials planned for spacecraft, (6) Developing corresponding models of microgravity flame spread, flammability, and extinction, and use the results to improve normal gravity combustion models for terrestrial applications. The hardware permits a wide range of solid-material combustion and fire suppression studies. It supports multiple investigations using common infrastructure including sample holders, flow control, test sections, external radiant heaters, igniters, and diagnostics. SoFIE has been developed to meet the requirements of five unique investigations. It is currently being built and slated to begin operations on the ISS in July 2021. Given the general capabilities of the hardware insert, it is intended to be used as a facility for future researchers who can propose to NASA for related solid combustion studies.

Ferkul, Paul↗
NASA NTRS2022

Skillful Seasonal Forecasts of Land Carbon Uptake in Northern Mid- and High Latitudes

Here we present a first look at the Gross Primary Production (GPP) forecast skill levels achievable with a state-of-the-art subseasonal-to-seasonal (S2S) forecast system. Using NASA’s retrospective S2S ensemble forecast in conjunction with a terrestrial biosphere model, and using an independent, remote sensing-based dataset for validation, we demonstrate an ability to accurately forecast spring-summer carbon uptake at multi-month leads. Averaged across mid-and high latitudes of the Northern Hemisphere land, the GPP forecast initialized on January 1 produces statistically significant skill through summer. The skill achieved, however, is spatially variable, with some regions appearing to extract skill from accurate forecasts of snowpack removal and others extracting skill from the initialization of carbon and nitrogen states. Our results reveal some heretofore unexplored facets of climate predictability and provide a look at what might be possible with future S2S forecast systems that are fully integrated with biogeochemical cycles.

Eunjee Lee↗