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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
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NASA NTRS1992

Multi-agent planning and scheduling, execution monitoring and incremental rescheduling: Application to motorway traffic

This article describes a planning method applicable to agents with great perception and decision-making capabilities and the ability to communicate with other agents. Each agent has a task to fulfill allowing for the actions of other agents in its vicinity. Certain simultaneous actions may cause conflicts because they require the same resource. The agent plans each of its actions and simultaneously transmits these to its neighbors. In a similar way, it receives plans from the other agents and must take account of these plans. The planning method allows us to build a distributed scheduling system. Here, these agents are robot vehicles on a highway communicating by radio. In this environment, conflicts between agents concern the allocation of space in time and are connected with the inertia of the vehicles. Each vehicle made a temporal, spatial, and situated reasoning in order to drive without collision. The flexibility and reactivity of the method presented here allows the agent to generate its plan based on assumptions concerning the other agents and then check these assumptions progressively as plans are received from the other agents. A multi-agent execution monitoring of these plans can be done, using data generated during planning and the multi-agent decision-making algorithm described here. A selective backtrack allows us to perform incremental rescheduling.

Mourou, Pascal↗
NASA NTRSDate not supplied

Assessment of Long-term Trends in the Collection 4 Total Ozone Record from the Ozone Monitoring Instrument

Long-term changes in total ozone affect the amount of harmful UV radiation reaching Earth’s surface and reflect progress made towards recovery of stratospheric ozone. Satellite total ozone data are also used to estimate long-term trends in tropospheric ozone, a reactive and potent greenhouse gas, by subtracting the stratospheric column timeseries from that of total ozone. For these scientific applications, the long-term stability should be better than 1%. Left unchecked, instrument calibration drift can produce a trend of this magnitude or greater. NASA has produced nearly twenty years of total ozone data from the Ozone Monitoring Instrument (OMI) using the Total Ozone Mapping Spectrometer (TOMS) algorithm. The drift in the OMI instrument as monitored by ice radiance calibration has been relatively slow, but it has reached a level of ~3% over the mission lifetime. This drift was corrected in the recently released Collection 4 OMI calibrated radiances, updating the Collection 3 calibration released in 2006. We have reprocessed the OMI total ozone record using the Collection 4 calibration and updates to the TOMS algorithm. We summarize these changes and evaluate their impact by comparing to the previous Collection 3 OMI dataset, the Suomi NPP Ozone Mapping and Profiler Suite Nadir Mapper (OMPS-NM) and Solar Backscatter UV (SBUV) Merged Ozone Dataset (MOD) total ozone records and other independent satellite total ozone datasets. Climatological radiance residuals from OMI and OMPS-NM are calculated and compared to investigate differences in spectral calibration that can cause drifts in long-term total ozone trends. We also analyze the tropospheric ozone record produced using the Collection 4 OMI total ozone and stratospheric column ozone from MLS. Collection 3 OMI data processed with the TOMS algorithm show a positive drift relative to other satellite and ground-based data of 1-2 DU per decade. Initial results show that this drift is reduced in Collection 4 OMI, due to the updated OMI calibration. In this work we will quantify the improvements in Collection 4 OMI relative to independent data sources at both the ozone and radiance level

Collection 4 OMI Total Ozone↗
NASA NTRS1974

Parametric analysis of an imaging radar for use as an imaging radar for use as an independent landing monitor

The capabilities are analyzed of a real aperture, forward-looking imaging radar for use as an independent landing monitor, which will provide the pilot with an independent means of assessing the progress of an automatic landing during Category 3 operations. The analysis shows that adequate ground resolution and signal-to-noise ratio can be obtained to image a runway with grassy surroundings using a radar operating at 35 GHz in good weather and in most fog but that performance is severely degraded in moderate to heavy rain and wet snow. Weather effects on a 10 GHz imager are not serious, with the possible exception of very heavy rain, but the azimuthal resolution at 10 GHz is inadequate with antennas up to 2 m long.

Bundick, W. T.↗
NASA NTRS1981

Investigation into the role of NaCL deposited on oxide and metal substrates in the initiation of hot corrosion

The conversion to Na2SO4 of NaCl deposited on oxide substrates was studied as a function of temperature, in air with various SO2 and H2O partial pressures. The substrate was either a pure oxide or an oxide scale growing on a metal specimen. The progress of the reaction was observed using the SEM-EDAX technique to monitor morphological effects and, as far as possible, establish the rate of the process. The physical characteristics of the interaction between salt and substrate were also examined with particular reference to physical damage to the underlying oxide, especially when this is a scale on a metal specimen. An effort was also made to establish the conditions under which liquid phases may form and the mechanisms by which they form.

Birks, N.↗
NASA NTRS1998

Microfabricated Chemical Sensors for Safety and Emission Control Applications

Chemical sensor technology is being developed for leak detection, emission monitoring, and fire safety applications. The development of these sensors is based on progress in two types of technology: 1) Micromachining and microfabrication (MicroElectroMechanical Systems (MEMS)-based) technology to fabricate miniaturized sensors. 2) The development of high temperature semiconductors, especially silicon carbide. Using these technologies, sensors to measure hydrogen, hydrocarbons, nitrogen oxides, carbon monoxide, oxygen, and carbon dioxide are being developed. A description is given of each sensor type and its present stage of development. It is concluded that microfabricated sensor technology has significant potential for use in a range of aerospace applications.

Hunter, G. W.↗
NASA NTRS2000

Landstat 7 Views the World

The technical innovations of precise numerical radiometry, spectral differentiation and seasonally repetitive monitoring, introduced by the Landsat series of satellites, created a new measurement approach for terrestrial monitoring. The Landsat 7 mission, successfully initiated on April 15, 1999, reflects significant progress in realizing the scientific potential of this measurement strategy. Substantial improvements in calibration procedures, both prior to launch and during normal operations, have been accomplished to insure long-term stability in the acquired spectral radiometry. For the first time, Landsat 7 will be operated with a long-term data acquisition plan that will insure, barring national emergencies, that substantially cloud-free, seasonal coverage will be recorded and archived in the US for all land areas of the globe. The expected outcome of these efforts is a rapid improvement in our understanding of the Earth system, as well as conceptual knowledge that will underpin commercial application of this technology. The Cape Town 2000 Symposium will take place approximately nine months after the Landsat 7 satellite and instrument completed its engineering checkout phase and was placed in its final orbit in late June, 1999. Thus, this presentation will provide a timely status report, in a significant international setting, regarding the early on-orbit performance of the Landsat 7 spacecraft, the ETM+ instrument, and the long-term data acquisition strategy that has been implemented. The latest data display and visualization techniques will be utilized to present this significant new source of Earth observation data.

Williams, Darrel L.↗
NASA NTRS2004

Application of MODIS-Derived Active Fire Radiative Energy to Fire Disaster and Smoke Pollution Monitoring

The radiative energy emitted by large fires and the corresponding smoke aerosol loading are simultaneously measured from the MODIS sensor from both the Terra and Aqua satellites. Quantitative relationships between the rates of emission of fire radiative energy and smoke are being developed for different fire-prone regions of the globe. Preliminary results are presented. When fully developed, the system will enable the use of MODIS direct broadcast fire data for near real-time monitoring of fire strength and smoke emission as well as forecasting of fire progression and smoke dispersion, several hours to a few days in advance.

Ichoku, Charles↗
NASA NTRS2005

The Spaceflight Revolution Revisited

This essay will first consider whether technological breakthroughs in space technology and the rational motives of ordinary institutions have the capacity to break out of this relatively static situation. Then we will survey the roles that social movements of various kinds might play and conclude with an examination of one particular nascent movement that might possibly build the foundation for a spacefaring civilization. A third of a century ago, practical nuclear fission rockets were under development, but this approach now seems environmentally unacceptable. It is hard to devise a more environmentally benign propellant than the hydrogen and oxygen used by the main engines of the Space Shuttle. There is some hope that nanotechnology will save the day with materials based on carbon nanotubes that are vastly stronger yet lighter than metals.6 However, the X-33 failure shows that it is not easy to work with radically new structural materials in demanding aerospace applications, and we may be many decades away from being able to manufacture propellant tanks, wings, and other large structures from carbon nanotubes. Satellites in low-Earth and synchronous orbit are of great importance in the collection and distribution of information, thus essential to the information economy. The wide range of civilian applications includes telephone, data transmission, television, navigation, weather observation, agriculture monitoring, and prospecting for natural resources.8 The technology is largely perfected, and incremental progress can be achieved by improvement in information systems and simply by investing in more relatively small satellites of the kinds we already have.

Bainbridge, William Sims↗
NASA NTRS2013

X-ray Follow-ups of XSS J12270-4859: A Low-mass X-ray Binary with Gamma-ray Fermi-LAT Association

Context. XSS J1227.0-4859 is a peculiar, hard X-ray source recently positionally associated to the Fermi-LAT source 1FGL J1227.9- 4852/2FGL J1227.7-4853. Multi-wavelength observations have added information on this source, indicating a low-luminosity lowmass X-ray binary (LMXB), but its nature is still unclear. Aims. To progress in our understanding, we present new X-ray data from a monitoring campaign performed in 2011 with the XMM-Newton, RXTE, and Swift satellites and combine them with new gamma-ray data from the Fermi and AGILE satellites. We complement the study with simultaneous near-UV photometry from XMM-Newton and with previous UV/optical and near-IR data. Methods. We analysed the temporal characteristics in the X-rays, near-UV, and gamma rays and studied the broad-band spectral energy distribution from radio to gamma rays. Results. The X-ray history of XSS J1227 over 7 yr shows a persistent and rather stable low-luminosity (6 × 1033 d2 1 kpcerg s−1) source, with flares and dips being peculiar and permanent characteristics. The associated Fermi-LAT source 2FGL J1227.7-4853 is also stable over an overlapping period of 4.7 yr. Searches for X-ray fast pulsations down to msec give upper limits to pulse fractional amplitudes of 15−25% that do not rule out a fast spinning pulsar. The combined UV/optical/near-IR spectrum reveals a hot component at approximately 13 kK and a cool one at approximately 4.6 kK. The latter would suggest a late-type K2−K5 companion star, a distance range of 1.4−3.6 kpc, and an orbital period of 7-9 h. A near-UV variability (6 h) also suggests a longer orbital period than previously estimated. Conclusions. The analysis shows that the X-ray and UV/optical/near-IR emissions are more compatible with an accretion-powered compact object than with a rotational powered pulsar. The X-ray to UV bolometric luminosity ratio could be consistent with a binary hosting a neutron star, but the uncertainties in the radio data may also allow an LMXB black hole with a compact jet. In this case, it would be the first associated with a high-energy gamma-ray source.

deMartino, D.↗
NASA NTRS2022

Correlated Spatio-temporal Evolution of Extreme-Ultraviolet Ribbons and Hard X-Rays in a Solar Flare

We analyze the structure and evolution of ribbons from the M7.3 SOL2014-04-18T13 flare using ultraviolet images from the Interface Region Imaging Spectrograph and the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA), magnetic data from the SDO/Helioseismic and Magnetic Imager, hard X-ray (HXR) images from the Reuven Ramaty High Energy Solar Spectroscopic Imager, and light curves from the Fermi/Gamma-ray Burst Monitor, in order to infer properties of coronal magnetic reconnection. As the event progresses, two flare ribbons spread away from the magnetic polarity inversion line. The width of the newly brightened front along the extension of the ribbon is highly intermittent in both space and time, presumably reflecting nonuniformities in the structure and/or dynamics of the flare current sheet. Furthermore, the ribbon width grows most rapidly in regions exhibiting concentrated nonthermal HXR emission, with sharp increases slightly preceding the HXR bursts. The light curve of the ultraviolet emission matches the HXR light curve at photon energies above 25 keV. In other regions the ribbon-width evolution and light curves do not temporally correlate with the HXR emission. This indicates that the production of nonthermal electrons is highly nonuniform within the flare current sheet. Our results suggest a strong connection between the production of nonthermal electrons and the locally enhanced perpendicular extent of flare ribbon fronts, which in turn reflects the inhomogeneous structure and/or reconnection dynamics of the current sheet. Despite this variability, the ribbon fronts remain nearly continuous, quasi-one-dimensional features. Thus, although the reconnecting coronal current sheets are highly structured, they remain quasi-two-dimensional and the magnetic energy release occurs systematically, rather than stochastically, through the volume of the reconnecting magnetic flux.

S. J. Naus↗
NASA NTRS2016

Real-Time Safety Monitoring and Prediction for the National Airspace System

As new operational paradigms and additional aircraft are being introduced into the National Airspace System (NAS), maintaining safety in such a rapidly growing environment becomes more challenging. It is therefore desirable to have both an overview of the current safety of the airspace at different levels of granularity, as well an understanding of how the state of the safety will evolve into the future given the anticipated flight plans, weather forecasts, predicted health of assets in the airspace, and so on. To this end, we have developed a Real-Time Safety Monitoring (RTSM) that first, estimates the state of the NAS using the dynamic models. Then, given the state estimate and a probability distribution of future inputs to the NAS, the framework predicts the evolution of the NAS, i.e., the future state, and analyzes these future states to predict the occurrence of unsafe events. The entire probability distribution of airspace safety metrics is computed, not just point estimates, without significant assumptions regarding the distribution type and or parameters. We demonstrate our overall approach by predicting the occurrence of some unsafe events and show how these predictions evolve in time as flight operations progress.

National Airspace System↗
NASA NTRS2011

Evaluating the Application of Multi-Satellite Observations in Hydrologic Modeling

When monitoring local or regional hydrosphere dynamics for applications such as agricultural productivity or drought and flooding events, it is necessary to have accurate, high-resolution estimates of terrestrial water and energy storages. Though in-situ observations provide reliable estimates of hydrologic states and fluxes, they are only capable of accurately capturing the dynamics at relatively discrete points in space and time, which makes them inadequate for characterizing the variability of the water budget across scales. In contrast, satellite-based remote sensing is ideal for providing observations of hydrological states and fluxes because it provides spatially-distributed observations at spatial and temporal scales required for regional land surface process modeling. Due to the continued progress in algorithm development and emerging satellite technology, we now have near-real time monitoring of several components of the water cycle including precipitation, soil moisture, lake and river height, terrestrial water storage, snow cover, and evapotranspiration. As these data become more readily available, their application to hydrologic modeling is becoming more common, however there remains little consensus on the most appropriate method for optimal integration and evaluation in regard to hydrological applications. Here we present two case studies operationally applying several remotely sensed products from AMSR-E, GRACE, and MODIS and discuss assimilation strategies, ease of integration and interpretation, and methods for quantifying the success of the application methodology.

Bolten, John↗
NASA NTRS1996

IMACCS: A Progress Report on NASA/GSFC's COTS-Based Ground Data Systems, and their Extension into New Domains

The integrated monitoring, analysis and control commercial off-the-shelf system (IMACCS) for the provision of real-time satellite command and telemetry support, orbit and attitude determination, events prediction and data trend analysis, is considered. The upgrades made to the original commercial, off-the-shelf (COTS) prototype are described. These upgrades include automation capability, and spacecraft integration and testing capability. A further extension to the prototype is the establishment of a direct radio frequency interface to a spacecraft. The systems development approach employed is described.

Scheidker, E. J.↗
NASA NTRS2014

Retrospective Analysis of Inflight Exercise Loading and Physiological Outcomes

Astronauts perform exercise throughout their missions to counter the health declines that occur as a result of long-term exposure to weightlessness. Although all astronauts perform exercise during their missions, the specific prescriptions, and thus the mechanical loading, differs among individuals. For example, inflight ground reaction force data indicate that subject-specific differences exist in foot forces created when exercising on the second-generation treadmill (T2) [1]. The current exercise devices allow astronauts to complete prescriptions at higher intensities, resulting in greater benefits with increased efficiency. Although physiological outcomes have improved, the specific factors related to the increased benefits are unknown. In-flight exercise hardware collect data that allows for exploratory analyses to determine if specific performance factors relate to physiological outcomes. These analyses are vital for understanding which components of exercise are most critical for optimal human health and performance. The relationship between exercise performance variables and physiological changes during flight has yet to be fully investigated. Identifying the critical performance variables that relate to improved physiological outcomes is vital for creating current and future exercise prescriptions to optimize astronaut health. The specific aims of this project are: 1) To quantify the exercise-related mechanical loading experienced by crewmembers on T2 and ARED during their mission on ISS; 2) To explore relationships between exercise loading variables, bone, and muscle health changes during the mission; 3) To determine if specific mechanical loading variables are more critical than others in protecting physiology; 4) To develop methodology for operational use in monitoring accumulated training loads during crew exercise programs. This retrospective analysis, which is currently in progress, is being conducted using data from astronauts that have flown long-duration missions onboard the ISS and have had access to exercise on the T2 and the Advanced Resistive Exercise Device (ARED). The specific exercise prescriptions vary for each astronaut. General exercise summary metrics will be developed to quantify exercise intensities, volumes, and durations for each subject. Where available, ground reaction force data will be used to quantify mechanical loading experienced by each astronaut. These inflight exercise metrics will be investigated relative to changes in pre- to post-flight bone and muscle health to identify which specific variables are related with improved or degraded physiological outcomes. The information generated from this analysis will fill gaps related to typical bone loading characterization, exercise performance capability, exercise volume and efficiency, and importance of exercise hardware. In addition, methods for quantification of exercise loading for use in monitoring the exercise programs during future space missions will be explored with the intent to inform exercise scientists and trainers as to the critical aspects of inflight exercise prescriptions.

Ploutz-Snyder, L. L.↗
NASA NTRS2004

Assessing Videogrammetry for Static Aeroelastic Testing of a Wind-Tunnel Model

The Videogrammetric Model Deformation (VMD) technique, developed at NASA Langley Research Center, was recently used to measure displacements and local surface angle changes on a static aeroelastic wind-tunnel model. The results were assessed for consistency, accuracy and usefulness. Vertical displacement measurements and surface angular deflections (derived from vertical displacements) taken at no-wind/no-load conditions were analyzed. For accuracy assessment, angular measurements were compared to those from a highly accurate accelerometer. Shewhart's Variables Control Charts were used in the assessment of consistency and uncertainty. Some bad data points were discovered, and it is shown that the measurement results at certain targets were more consistent than at other targets. Physical explanations for this lack of consistency have not been determined. However, overall the measurements were sufficiently accurate to be very useful in monitoring wind-tunnel model aeroelastic deformation and determining flexible stability and control derivatives. After a structural model component failed during a highly loaded condition, analysis of VMD data clearly indicated progressive structural deterioration as the wind-tunnel condition where failure occurred was approached. As a result, subsequent testing successfully incorporated near- real-time monitoring of VMD data in order to ensure structural integrity. The potential for higher levels of consistency and accuracy through the use of statistical quality control practices are discussed and recommended for future applications.

Spain, Charles V.↗
NASA NTRS2014

The International Space Station 2B Photovoltaic Thermal Control System (PVTCS) Leak: An Operational History

As early as 2004, the Photovoltaic Thermal Control System (PVTCS) for the International Space Station's 2B electrical power channel began slowly leaking ammonia overboard. Initially, the operations strategy was "feed the leak," a strategy successfully put into action via Extra Vehicular Activity (EVA) during the STS-134 Space Shuttle mission. This recharge was to have allowed for continued power channel operation into 2014 or 2015, at which point another EVA would have been required. In mid-2012, the leak rate increased from 1.5lbm/year to approximately 5lbm/year. As a result, an EVA was planned and executed within a 5 week timeframe to drastically alter the architecture of the PVTCS via connection to an adjacent dormant thermal control system. This EVA, US EVA 20, was successfully executed on November 1, 2012 and left the 2B PVTCS in a configuration where the system was now being adequately cooled via a different radiator than what the system was designed to utilize. Data monitoring over the next several months showed that the isolated radiator had not been leaking, and the system itself continued to leak steadily until May 9th, 2013. It was on this day that the ISS crew noticed the visible presence of ammonia crystals escaping from the 2B channel's truss segment, signifying a rapid acceleration of the leak from 5lbm/year to 5lbm/day. Within 48 hours of the crew noticing the leak, US EVA 21 was in progress to replace the coolant pump - the only remaining replaceable leak source. This was successful, and telemetry monitoring has shown that indeed the coolant pump was the leak source and was thus isolated from the running 2B PVTCS. This paper will explore the management of the 2B PVTCS leak from the operations perspective.

Vareha, Anthony N.↗
NASA NTRS1975

Recent NASA contributions to biomedical telemetry

The present work reviews technological progress over the past five years in the field of long-term telemetric monitoring of physiological parameters during space flight. Emphasis is placed on those developments that have direct application to animal or human use on earth. An effort was made in these recent developments to free subjects from encumbering wires: a swallowable telemetry capsule for monitoring body temperature and a wristwatch transmitter connected to EKG leads were two of the devices developed.

Sandler, H.↗