SEARCH · Search NASA
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Evolutionary partial differential equations are usually solved by decretization in time and space, and by applying a marching in time procedure to data and algorithms potentially parallelized in the spatial domain.
Radar measurements at 70 cm and 7.5 m wavelengths provide insight into the structure and chemical properties of the upper 5-100 m of the lunar regolith and crust. Past work has identified a number of anomalous regions and changes in echo strength, some attributed to differences in titanium content. There has been little opportunity, however, to compare calibrated long-wavelength backscatter among different units or to theoretical model results. We combine recent high-resolution (3-5 km) 70-cm radar data for the nearside with earlier calibrated full-disk observations to provide a reasonable estimate of the true lunar backscatter coefficient. These data are tested against models for quasi-specular scattering from the surface, echoes from a buried substrate, and Mie scattering from surface and buried rocks. We find that 70 cm echoes likely arise from Mie scattering by distributed rocks within the soil, consistent with earlier hypotheses. Returns from a buried substrate would provide a plausible fit to the observations only if the regolith depth were ~3 m or less and varied little across the maria. Depolarized echoes are due to some combination of single and multiple scattering events, but it appears that single scattering alone could account for the observed echo power, based on comparisons with terrestrial rocky surfaces. Backscatter strength from the regolith is most strongly affected by the loss tangent, whose variation with mineral content is still poorly defined. We compared the backscatter values for the mare deposits to the oxide contents inferred from spectral ratio methods, and found that in general the unit boundaries evident in radar images closely follow those seen in color difference images. The 70-cm data are not well correlated with TiO2 values found using the Charette relationship nor with Fe abundances derived from Clementine observations. The lack of a relationship between radar echo and Fe content is reasonable given the distribution of iron among various mineral phases, but ilmenite content (FeTiO3) has typically been cited as the dominant cause of changes in loss tangent (and thus the radar absorption). The lack of correlation between the radar data and TiO2 estimates may arise from uncertainties in the Charette technique, subtle differences in the upper surface and bulk properties of the regolith, mineralogic effects on the radar not linked to titanium content, or to some combination of these factors. Dark crater haloes in the mare and highlands, and low radar returns from apparent cryptomare regions, are used to illustrate the role radar data can play in identifying changes in regolith composition; low-return haloes around craters such as Petavius may indicate 5-25% contamination of the highlands soil by excavated mare material or a layer of rock-poor ejecta at least several meters deep. The 7.5-m data were shown to correlate to a reasonable degree with estimates of Fe abundance, suggesting that this component of the mare basalts is primarily responsible for attenuation losses at very long wavelengths. The different sensitivities of the two radar wavelengths and multispectral data offers the potential for future deep mapping of the mare lava flows and regolith.
Radar measurements at 70 cm and 7.5 m wavelengths provide insight into the structure and chemical properties of the upper 5-100 m of the lunar regolith and crust. Past work has identified a number of anomalous regions and changes in echo strength, some attributed to differences in titanium content. There has been little opportunity, however, to compare calibrated long-wavelength backscatter among different units or to theoretical model results. We combine recent high-resolution (3-5 km) 70-cm radar data for the nearside with earlier calibrated full-disk observations to provide a reasonable estimate of the true lunar backscatter coefficient. These data are tested against models for quasi-specular scattering from the surface, echoes from a buried substrate, and Mie scattering from surface and buried rocks. We find that 70 cm echoes likely arise from Mie scattering by distributed rocks within the soil, consistent with earlier hypotheses. Returns from a buried substrate would provide a plausible fit to the observations only if the regolith depth were approx.3 m or less and varied little across the maria. Depolarized echoes are due to some combination of single and multiple scattering events, but it appears that single scattering alone could account for the observed echo power, based on comparisons with terrestrial rocky surfaces. Backscatter strength from the regolith is most strongly affected by the loss tangent, whose variation with mineral content is still poorly defined. We compared the backscatter values for the mare deposits to the oxide contents inferred from spectral ratio methods, and found that in general the unit boundaries evident in radar images closely follow those seen in color difference images. The 70-cm data are not well correlated with TiO2 values found using the Charette relationship nor with Fe abundances derived from Clementine observations. The lack of a relationship between radar echo and Fe content is reasonable given the distribution of iron among various mineral phases, but ilmenite content (FeTiO3) has typically been cited as the dominant cause of changes in loss tangent (and thus the radar absorption). The lack of correlation between the radar data and TiO2 estimates may arise from uncertainties in the Charette technique, subtle differences in the upper surface and bulk properties of the regolith, mineralogic effects on the radar not linked to titanium content, or to some combination of these factors. Dark crater haloes in the mare and highlands, and low radar returns from apparent cryptomare regions, are used to illustrate the role radar data can play in identifying changes in regolith composition; low-return haloes around craters such as Petavius may indicate 5-25% contamination of the highlands soil by excavated mare material or a layer of rock-poor ejecta at least several meters deep. The 7.5-m data were shown to correlate to a reasonable degree with estimates of Fe abundance, suggesting that this component of the mare basalts is primarily responsible for attenuation losses at very long wavelengths. The different sensitivities of the two radar wavelengths and multispectral data offers the potential for future deep mapping of the mare lava flows and regolith.
A simulation study was conducted to investigate aerodynamic modeling methods for prediction of post-stall flight dynamics of large transport airplanes. The research approach involved integrating dynamic wind tunnel data from rotary balance and forced oscillation testing with static wind tunnel data to predict aerodynamic forces and moments during highly dynamic departure and spin motions. Several state-of-the-art aerodynamic modeling methods were evaluated and predicted flight dynamics using these various approaches were compared. Results showed the different modeling methods had varying effects on the predicted flight dynamics and the differences were most significant during uncoordinated maneuvers. Preliminary wind tunnel validation data indicated the potential of the various methods for predicting steady spin motions.
The impact of microgravity on the human body is a significant concern for space travelers. We report here initial results from a pilot study designed to explore the utility of artificial gravity (AG) as a countermeasure to the effects of microgravity, specifically to bone loss. After an initial phase of adaptation and testing, 15 male subjects underwent 21 days of 6 head-down bed rest to simulate the deconditioning associated with space flight. Eight of the subjects underwent 1 h of centrifugation (AG, 1 gz at the heart, 2.5 gz at the feet) each day for 21 days, while 7 of the subjects served as untreated controls (CN). Blood and urine were collected before, during, and after bed rest for bone marker determinations. At this point, preliminary data are available on the first 8 subjects (6 AG, and 2 CN). Comparing the last week of bed rest to before bed rest, urinary excretion of the bone resorption marker n-telopeptide increased 95 plus or minus 59% (mean plus or minus SD) in CN but only 32 plus or minus 26% in the AG group. Similar results were found for another resorption marker, helical peptide (increased 57 plus or minus 0% and 35 plus or minus 13% in CN and AG respectively). Bone-specific alkaline phosphatase, a bone formation marker, did not change during bed rest. At this point, sample analyses are continuing, including calcium tracer kinetic studies. These initial data demonstrate the potential effectiveness of short-radius, intermittent AG as a countermeasure to the bone deconditioning that occurs during bed rest.
The impact of microgravity on the human body is a significant concern for space travelers. Since mechanical loading is a main reason for bone loss, artificial gravity might be an effective countermeasure to the effects of microgravity. In a 21-day 6 head-down tilt bed rest (HDBR) pilot study carried out by NASA, USA, the utility of artificial gravity (AG) as a countermeasure to immobilization-induced bone loss was tested. Blood and urine were collected before, during, and after bed rest for bone marker determinations. Bone mineral density was determined by DXA and pQCT before and after bed rest. Urinary excretion of bone resorption markers (n-telopeptide and helical peptide) were increased from pre-bed rest, but there was no difference between the control and the AG group. The same was true for serum c-telopeptide measurements. Bone formation markers were affected by bed rest and artificial gravity. While bone-specific alkaline phosphatase tended to be lower in the AG group during bed rest (p = 0.08), PINP, another bone formation marker, was significantly lower in AG subjects than CN before and during bed rest. PINP was lower during bed rest in both groups. For comparison, artificial gravity combined with ergometric exercise was tested in a 14-day HDBR study carried out in Japan (Iwase et al. J Grav Physiol 2004). In that study, an exercise regime combined with AG was able to significantly mitigate the bed rest-induced increase in the bone resorption marker deoxypyridinoline. While further study is required to more clearly differentiate bone and muscle effects, these initial data demonstrate the potential effectiveness of short-radius, intermittent AG as a countermeasure to the bone deconditioning that occurs during bed rest and spaceflight. Future studies will need to optimize not only the AG prescription (intensity and duration), but will likely need to include the use of exercise or other combined treatments.
Method and system for recognizing and characterizing bioelectric potential or electromyographic (EMG) signals associated with at least one of a coarse gesture and a fine gesture that is performed by a person, and use of the bioelectric potentials to enter data and/or commands into an electrical and/or mechanical instrument. As a gesture is performed, bioelectric signals that accompany the gesture are subjected to statistical averaging, within selected time intervals. Hidden Markov model analysis is applied to identify hidden, gesture-related states that are present. A metric is used to compare signals produced by a volitional gesture (not yet identified) with corresponding signals associated with each of a set of reference gestures, and the reference gesture that is closest to the volitional gesture is identified. Signals representing the volitional gesture are analyzed and compared with a database of reference gestures to determine if the volitional gesture is likely to be one of the reference gestures. Electronic and/or mechanical commands needed to carry out the gesture may be implemented at an interface to control an instrument. Applications include control of an aircraft, entry of data from a keyboard or other data entry device, and entry of data and commands in extreme environments that interfere with accurate entry.
In the performance of EVA by that National Aeronautics and Space Administration (NASA) astronauts, there exists a risk of DCS as the suit pressure is reduced to 4.3 pounds per square inch, absolute (psia) from the International Space Station (ISS) pressure of 14.7 psia. Several DCS-preventive procedures have been developed and implemented. Each of these procedures involve the use of oxygen (O2) prebreathe to effectively washout tissue nitrogen (N2).The management of the ISS Programs convened an expert independent peer review Team to conduct a review of the Decompression Sickness (DCS) risks associated with the Extra Vehicular Activity (EVA) Campout Prebreathe (PB) protocol for its consideration for use on future missions. The major findings and recommendations of the expert panel are: There is no direct experimental data to confirm the potential DCS risks of the Campout PB protocol. However, based on model data, statistical probability, physiology, and information derived from similar PB protocols, there is no compelling evidence to suggest that the Campout PB protocol is less safe than the other NASA approved PB protocols.
Helicopter Health Usage Monitoring Systems (HUMS) have potential for providing data to support increasing the service life of a dynamic mechanical component in the transmission of a helicopter. Data collected can demonstrate the HUMS condition indicator responds to a specific component fault with appropriate alert limits and minimal false alarms. Defining thresholds for specific faults requires a tradeoff between the sensitivity of the condition indicator (CI) limit to indicate damage and the number of false alarms. A method using Receiver Operating Characteristic (ROC) curves to assess CI performance was demonstrated using CI data collected from accelerometers installed on several UH60 Black Hawk and AH64 Apache helicopters and an AH64 helicopter component test stand. Results of the analysis indicate ROC curves can be used to reliably assess the performance of commercial HUMS condition indicators to detect damaged gears and bearings in a helicopter transmission.
Helicopter Health Usage Monitoring Systems (HUMS) have potential for providing data to support increasing the service life of a dynamic mechanical component in the transmission of a helicopter. Data collected can demonstrate the HUMS condition indicator responds to a specific component fault with appropriate alert limits and minimal false alarms. Defining thresholds for specific faults requires a tradeoff between the sensitivity of the condition indicator (CI) limit to indicate damage and the number of false alarms. A method using Receiver Operating Characteristic (ROC) curves to assess CI performance was demonstrated using CI data collected from accelerometers installed on several UH60 Black Hawk and AH64 Apache helicopters and an AH64 helicopter component test stand. Results of the analysis indicate ROC curves can be used to reliably assess the performance of commercial HUMS condition indicators to detect damaged gears and bearings in a helicopter transmission.
A digital receiver in a 1.26-GHz spaceborne radar scatterometer now undergoing development includes a module for detecting radio-frequency interference (RFI) that could contaminate scientific data intended to be acquired by the scatterometer. The role of the RFI-detection module is to identify time intervals during which the received signal is likely to be contaminated by RFI and thereby to enable exclusion, from further scientific data processing, of signal data acquired during those intervals. The underlying concepts of detection of RFI and rejection of RFI-contaminated signal data are also potentially applicable in advanced terrestrial radio receivers, including software-defined radio receivers in general, receivers in cellular telephones and other wireless consumer electronic devices, and receivers in automotive collision-avoidance radar systems.
As part of the National Environmental Public Health Tracking Network (EPHTN) the National Center for Environmental Health (NCEH) at the Centers for Disease Control and Prevention (CDC) is leading a project called Health and Environment Linked for Information Exchange (HELIX-Atlanta). The goal of developing the National Environmental Public Health Tracking Network is to improve the health of communities. Currently, few systems exist at the state or national level to concurrently track many of the exposures and health effects that might be associated with environmental hazards. An additional challenge is estimating exposure to environmental hazards such as particulate matter whose aerodynamic diameter is less than or equal to 2.5 micrometers (PM(2.5)) HELIX-Atlanta's goal is to examine the feasibility of building an integrated electronic health and environmental data network in five counties of Metropolitan Atlanta, GA (Clayton, Cobb, DeKalb, Fulton, and Gwinnett counties). Under HELIX-Atlanta, pilot projects are being conducted to develop methods to characterize exposure; link health and environmental data; analyze the relationship between health and environmental factors; and communicate findings. NASA Marshall Space Flight Center (NASA/MSFC) is collaborating with CDC to combine NASA earth science satellite observations related to air quality and environmental monitoring data to model surface estimates of PM(2.5) concentrations that can be linked with clinic visits for asthma. From 1999-2000 there were over 9,400 hospitalizations per year in Georgia with asthma as the primary diagnosis. The majority of these hospitalizations occurred in medical facilities in the five most populous Metro-Atlanta counties. Hospital charges resulting from asthma in Georgia are approximately $59 million dollars annually. There is evidence in the research literature that asthmatic persons are at increased risk of developing asthma exacerbations with exposure to environmental factors, including PM(2.5). Thus, HELIX-Atlanta is focusing on methods for characterizing population exposure to PM(2.5) for the Atlanta metropolitan area that could be used in on-going surveillance. While use of the Air Quality System, (AQS) PM(2.5) data alone could meet HELIX Atlanta, specifications, there are only five AQS sites in the Atlanta area, thus the spatial coverage is not ideal. Also, the AQS ground observations are made at time intervals ranging from one hour to six days leaving some temporal gaps. NASA Moderate Resolution Imaging Spectroradiometer (MODIS) satellite Aerosol Optical Depth (AOD) data have the potential for estimating daily ground level PM(2.5) at 10 km resolution over the metropolitan Atlanta area supplementing the AQS ground observations and filling their spatial and temporal gaps.
Mineralogical abundance of primary minerals versus secondary minerals, chemical mixing relationships, and elemental ratios have been used to assess the degree of aqueous alteration at Gusev Crater and Meridiani Planum. However, limited work has used Ti-normalized mass-balance analysis chemical data to quantify gains and losses of elements from altered materials as well as estimate the duration of aqueous alteration on Mars. The Ti-normalized mass-balance approach accounts for volumetric changes associated with geochemical alteration. If volumetric changes are not considered, observed geochemical trends based on un-normalized data have the potential to be misleading. Assessing gains and losses from altered materials can indicate the geochemistry of fluids involved in the alteration. Furthermore, elemental losses can be combined with dissolution rates to estimate the duration of chemical weathering. Knowledge of the duration of aqueous alteration will provide insight into the climate history of Mars as well as indicate the potential for microbial habitability. The Wishstone-Watchtower materials in Gusev Crater are suitable candidates for Ti-normalized mass-balance analysis because mixing relationships of these two materials indicate that Watchtower materials may be derived from Wishstone-like materials. The objectives of this work are to (1) employ Ti-normalized mass-balance to assess gains and losses from the Wishstone-Watchtower sequence and (2) to combine losses with laboratory dissolution rates to estimate alteration times of the Watchtower material.
During the 2008 Tawani International Expedition Schirmacher Oasis/Lake Untersee Antarctica Expedition, living and instantly motile bacteria were found in freshly thawed meltwater from ice of the Schirmacher Oasis Lakes, the Anuchin Glacier ice and samples of the that perennial ice sheet above Lake Untersee. This phenomenon of living bacteria encased in ice had previously been observed in the 32,000 year old ice of the Fox Tunnel. The bacteria found in this ice included the strain FTR1T which was isolated and published as valid new species (Carnobacterium pleistocenium) the first validly published living Pleistocene organism still alive today. Living bacteria were also extracted from ancient ice cores from Vostok, Antarctica. The discovery that many strains of bacteria are able to survive and remain alive while frozen in ice sheets for long periods of time may have direct relevance to Astrobiology. The abundance of viable bacteria in the ice sheets of Antarctica suggests that the presence of live bacteria in ice is common, rather than an isolated phenomenon. This paper will discuss the results of recent studies at NSSTC of bacteria cryopreserved in ice. This paper advances the hypothesis that cryopreserved cells, and perhaps even viable bacterial cells, may exist today--frozen in the water-ice of lunar craters, the Polar Caps or craters of Mars; or in the permafrost of Mars; ice and rocks of comets or water bearing asteroids; or in the frozen crusts of the icy moons of Jupiter and Saturn. The existence of bacterial life in ice suggests that it may not be necessary to drill through a thick ice crust to reach liquid water seas deep beneath the icy crusts of Europa, Ganymede and Enceladus. The presence of viable bacteria in the ice of the Earth s Polar Caps suggests that the possibility that cryo-panspermia (i.e., the trans-planetary transfer of microbial life by impact ejection/spallation of bacteria-rich polar ice masses) deserves serious consideration and study as a possible natural phenomenon of the solar system that may have played a profoundly important role in the Origin of Life on Earth and the Distribution of Life in the Cosmos. The paper concludes with a consideration of the protective properties of ice by absorption of UV-B, UV-C, h-rays, gamma-rays and the high energy proton environment of the Jupiter Radiation Belt. A proposed instrument that may provide additional data on the potential survivability of microbial extremophiles encased in ice and subjected to the simulated space environment will be briefly described.
Data assimilation is a potentially powerful method of extracting the maximum amount of information from observed data by combining their information with models. in this application, we will use stratospheric ozone profiles retrieved from EOS MLS and total column amounts retrieved from OMI' along with the GEOS-5 GCM, that includes a representation of ozone chemistry and transport. The presentation will discuss how well we can derive tropospheric ozone column information in this system, including its sensitivity to model errors and some assumptions made in the assimilation system. We discuss also ozone structures in the tropopause region and their sensitivity to model resolution and other fact=ors. An important issue we examine is how much more information we obtain from ozone assimilation than from model studies using state of the art chemistry models - answering such questions helps determine how useful ozone assimilation really is, given our present capabilities in chemical modeling.
The Nutrition Risk Standing Review Panel (SRP) reviewed and discussed the specific gaps and tasks for the Human Health Countermeasures (HHC) Element related to nutrition identified in the Human Research Program (HRP) Integrated Research Plan. There was general consensus that the described gaps and proposed tasks were critical to future NASA mission success. The SRP acknowledged the high scientific quality of the work currently being undertaken by the Nutritional Biochemistry group under the direction of Dr. Scott Smith. In review of the entire HRP, four new gaps were identified that complement the Element's existing research activities. Given the limitations of ground-based analogs for many of the unique physiological and metabolic alterations in space, future studies are needed to quantify nutritional factors that change during actual space flight. In addition, future tasks should seek to better evaluate the time course of physiological and metabolic alterations during flight to better predict alterations during longer duration missions. Finally, given the recent data suggesting a potential role for increased inflammatory responses during space flight, the role of inflammation needs to be explored in detail, including the development of potential countermeasures and new ground based analogs, if this possibility is confirmed.
The accuracy of streamflow predictions in the EPA's BASINS (Better Assessment Science Integrating Point and Nonpoint Sources) decision support tool is affected by the sparse meteorological data contained in BASINS. The North American Land Data Assimilation System (NLDAS) data with high spatial and temporal resolutions provide an alternative to the NOAA National Climatic Data Center (NCDC)'s station data. This study assessed the improvement of streamflow prediction of the Hydrological Simulation Program-FORTRAN (HSPF) model contained within BASINS using the NLDAS 118 degree hourly precipitation and evapotranspiration estimates in seven watersheds of the Chesapeake Bay region. Our results demonstrated consistent improvements of daily streamflow predictions in five of the seven watersheds when NLDAS precipitation and evapotranspiration data was incorporated into BASINS. The improvement of using the NLDAS data is significant when watershed's meteorological station is either far away or not in a similar climatic region. When the station is nearby, using the NLDAS data produces similar results. The correlation coefficients of the analyses using the NLDAS data were greater than 0.8, the Nash-Sutcliffe (NS) model fit efficiency greater than 0.6, and the error in the water balance was less than 5%. Our analyses also showed that the streamflow improvements were mainly contributed by the NLDAS's precipitation data and that the improvement from using NLDAS's evapotranspiration data was not significant; partially due to the constraints of current BASINS-HSPF settings. However, NLDAS's evapotranspiration data did improve the baseflow prediction. This study demonstrates the NLDAS data has the potential to improve stream flow predictions, thus aid the water quality assessment in the EPA nonpoint water quality assessment decision tool.
Reanalyses are a potentially powerful climate data collection driven by observations but also subjected to model bias. Additionally, reanalyses can produce and use essential climate variables in a consistent method. For example, snow cover and soil moisture (among other variables) will eventually be assimilated into the reanalyses, but also provide crucial validation data. Sea surface temperature can be prescribed or assimilated in a coupled reanalysis. The strength of reanalysis lies in the ancillary data that is produced from the modeling components but not routinely observed thereby providing more complete Earth system information. The weakness in this concept is that the model derived data can be affected by model bias and may also change relative to the available observing system. Here, we will review the status of existing reanalyses and the ECVs being considered for the workshop. Purpose of Michael Bosilovich's contribution to the workshop: Michael Bosilovich will represent US reanalysis community in this international discussion of Essential Climate Variables (ECVs) and the relative nature of reanalyses to ECVs.