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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Satellite Data Reveals a Recent Increase in Shifting Cultivation and Associated Carbon Emissions in Laos

Although shifting cultivation is the major land use type in Laos, the spatial-temporal patterns and the associated carbon emissions of shifting cultivation in Laos are largely unknown. This study provides a nationwide analysis of the spatial-temporal patterns of shifting cultivation and estimations of the associated carbon emissions in Laos over the last three decades. This study found that shifting cultivation has been expanding and intensifying in Laos, especially in the last five years. The newly cultivated land from 2016-2020 accounted for 4.5% (±1.2%) of the total land area of Laos. Furthermore, the length of fallow periods has been continuously declining, indicating that shifting cultivation is becoming increasingly intensive. Combining biomass derived from GEDI (Global Ecosystem Dynamics Investigation) and shifting cultivation maps and area estimates, we found that the net carbon emissions from shifting cultivation declined in 2001-2015 but increased in 2016-2020. The largest carbon source is conversion from intact forests to shifting cultivation, which contributed to 89% of the total emissions from 2001 to 2020. In addition, there were increased emissions from intensified use of fallow land. This research provides useful information for policymakers in Laos to understand the changes in shifting cultivation and improve land use management. This study not only supports REDD+ (Reducing Emissions from Deforestation and forest Degradation) reporting for Laos but also provides a methodology for tracking carbon emissions and removals of shifting cultivation.

Shifting cultivation↗
NASA NTRS1994

Infrared Speckle Interferometry with 2-D Arrays

We describe results from a program of speckle interferometry with two-dimensional infrared array detectors. Analysis of observations of eta Carinae made with 58 x 62 InSb detector are discussed. The data have been analyzed with both the Labeyrie autocorrelation, a deconvolution of shift-and-add data, and a phase restoration process. Development of a new camera based on a much lower noise HgCdTe detector will lead to a significant improvement i limiting magnitude for IR speckle interferometry.

Harvey, P. M.↗
NASA NTRS1972

A high speed sequential decoder

The performance and theory of operation for the High Speed Hard Decision Sequential Decoder are delineated. The decoder is a forward error correction system which is capable of accepting data from binary-phase-shift-keyed and quadriphase-shift-keyed modems at input data rates up to 30 megabits per second. Test results show that the decoder is capable of maintaining a composite error rate of 0.00001 at an input E sub b/N sub o of 5.6 db. This performance has been obtained with minimum circuit complexity.

Lum, H., Jr.↗
NASA NTRS2015

Computational and Experimental Study of Supersonic Nozzle Flow and Shock Interactions

This study focused on the capability of NASA Tetrahedral Unstructured Software System's CFD code USM3D capability to predict the interaction between a shock and supersonic plume flow. Previous studies, published in 2004, 2009 and 2013, investigated USM3D's supersonic plume flow results versus historical experimental data. This current study builds on that research by utilizing the best practices from the early papers for properly capturing the plume flow and then adding a wedge acting as a shock generator. This computational study is in conjunction with experimental tests conducted at the Glenn Research Center 1'x1' Supersonic Wind Tunnel. The comparison of the computational and experimental data shows good agreement for location and strength of the shocks although there are vertical shifts between the data sets that may be do to the measurement technique.

Carter, Melissa B.↗
NASA NTRS1986

Interplanetary medium data book: Supplement 3A, 1977-1985

Supplement 3 of the Interplanetary Medium Data Book contains a detailed discussion of a data set compilation of hourly averaged interplanetary plasma and magnetic field parameters. The discussion addresses data sources, systematic and random differences, time shifting of ISEE 3 data, and plasma normalizations. Supplement 3 also contains solar rotation plots of field and plasma parameters. Supplement 3A contains computer-generated listings of selected parameters from the composite data set. These parameters are bulk speed (km/sec), density (per cu cm), temperature (in units of 1000 K) and the IMF parameters: average magnitude, latitude and longitude angles of the vector made up of the average GSE components, GSM Cartesian components, and the vector standard deviation. The units of field magnitude, components, and standard deviation are gammas, while the units of field direction angles and degrees.

Couzens, David A.↗
NASA NTRS2012

Conformal Weyl Gravity and Perihelion Precession

We investigate the perihelion shift of planetary motion in conformal Weyl gravity using the metric of the static, spherically symmetric solution discovered by Mannheim and Kazanas. To this end we employ a procedure similar to that used by Weinberg for the Schwarzschild solution, which has also been used recently to study the solar system effects of the cosmological constant Lambda. We show that besides the general relativistic terms obtained earlier from the Schwarzschild-de Sitter solution, the expression for the perihelion shift includes a negative contribution which arises from the linear term gamma ray in the metric. Using data for perihelion shift observations, we obtain constraints on the value of the constant gammma similar to that obtained earlier using galactic rotational curves.

Sultana, Joseph↗
NASA NTRS1978

A wide bandwidth CCD buffer memory system

A prototype system was implemented to demonstrate that CCD's can be applied advantageously to the problem of low power digital storage and particularly to the problem of interfacing widely varying data rates. CCD shift register memories (8K bit) were used to construct a feasibility model 128 K-bit buffer memory system. Serial data that can have rates between 150 kHz and 4.0 MHz can be stored in 4K-bit, randomly-accessible memory blocks. Peak power dissipation during a data transfer is less than 7 W, while idle power is approximately 5.4 W. The system features automatic data input synchronization with the recirculating CCD memory block start address. System expansion to accommodate parallel inputs or a greater number of memory blocks can be performed in a modular fashion. Since the control logic does not increase proportionally to increase in memory capacity, the power requirements per bit of storage can be reduced significantly in a larger system.

Siemens, K.↗
NASA NTRS2005

NASA Remote Sensing Data in Earth Sciences: Processing, Archiving, Distribution, Applications at the GES DISC

The NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) is one of the major Distributed Active Archive Centers (DAACs) archiving and distributing remote sensing data from the NASA's Earth Observing System. In addition to providing just data, the GES DISC/DAAC has developed various value-adding processing services. A particularly useful service is data processing a t the DISC (i.e., close to the input data) with the users' algorithms. This can take a number of different forms: as a configuration-managed algorithm within the main processing stream; as a stand-alone program next to the on-line data storage; as build-it-yourself code within the Near-Archive Data Mining (NADM) system; or as an on-the-fly analysis with simple algorithms embedded into the web-based tools (to avoid downloading unnecessary all the data). The existing data management infrastructure at the GES DISC supports a wide spectrum of options: from data subsetting data spatially and/or by parameter to sophisticated on-line analysis tools, producing economies of scale and rapid time-to-deploy. Shifting processing and data management burden from users to the GES DISC, allows scientists to concentrate on science, while the GES DISC handles the data management and data processing at a lower cost. Several examples of successful partnerships with scientists in the area of data processing and mining are presented.

Leptoukh, Gregory G.↗
NASA NTRS1999

Space-to-Space Communications System

The Space-to-Space Communications System (SSCS) is an Ultra High Frequency (UHF) Time-Division-Multiple Access (TDMA) system that is designed, developed, and deployed by the NASA Johnson Space Center (JSC) to provide voice, commands, telemetry and data services in close proximity among three space elements: International Space Station (ISS), Space Shuttle Orbiter, and Extravehicular Mobility Units (EMU). The SSCS consists of a family of three radios which are, Space-to-Space Station Radio (SSSR), Space-to-Space Orbiter Radio (SSOR), and Space-to-Space Extravehicular Mobility Radio (SSER). The SSCS can support up to five such radios at a time. Each user has its own time slot within which to transmit voice and data. Continuous Phase Frequency Shift Keying (CPFSK) carrier modulation with a burst data rate of 695 kbps and a frequency deviation of 486.5 kHz is employed by the system. Reed-Solomon (R-S) coding is also adopted to ensure data quality. In this paper, the SSCS system requirements, operational scenario, detailed system architecture and parameters, link acquisition strategy, and link performance analysis will be presented and discussed

Kwei tU↗
NASA NTRS1993

Radio Doppler navigation of interplanetary spacecraft using different data processing modes

Doppler shift measurements derived from closed-loop radio tracking of distant spacecraft by ground stations of the Deep Space Network (DSN) are one of the principal means used for interplanetary navigation. This paper describes an investigation of the navigation accuracy that can be achieved with two-way coherent X-band (7.2 to 8.4 GHz) Doppler phase and frequency data; both theoretical and practical aspects of the two Doppler formulations are addressed. A new filtering strategy is also proposed, which differs from current approaches in that most of the ground system calibration errors affecting the Doppler data are represented as filter parameters, in addition to the spacecraft trajectory parameters. Error covariance computations for application of the proposed filter to a navigation scenario derived from the Mars Observer mission are provided, in order to assess the performance that might be obtained in practice. The results indicate that with a phase formulation of the Doppler data and the new filter, navigation accuracies of 15 km at Mars (0.05 microrad in an angular sense) are possible with the DSN's present X-band Doppler tracking system.

Thurman, S. W.↗
NASA NTRS1982

Improved Parallel-Access Alinement Network

Network channels elements of data array from memory ports to processor ports using a hardware-generated binary control work. Depending on control work selected, data may be shifted in increments or transposed in each of three levels to reach appropriate processing ports. A similar arrangement with reversed wiring is used to return data from processing ports to respective memory modules. Selection gate used in network incorporates two AND gates feeding an OR gate. In some logic families the OR gate may be fabricated as a "wired OR".

Barnes, G. H.↗
NASA NTRSDate not supplied

The Crustal Dynamics Data Information System (CDDIS) – Updates and Future Developments

As earth observing services and techniques have flourished, data and products have exponentially grown, like the proliferation of GNSS stations capable of providing real-time data, SLR stations shifting to kHz lasers, and VLBI’s implementation of VGOS telescopes. The CDDIS is continually evolving to fulfill the new storage, quality check, and latency requirements that these changes bring, as well as meet new standards such as the shift toward FAIR and open science. These have shaped how the CDDIS develops new software and resources. Beginning next year, the CDDIS will begin to transition their data and products to the AWS cloud, beginning with DORIS data. This poster will highlight the CDDIS’s recently updated processing system, new data and products available, and future work.

Justine Woo↗
NASA NTRS1994

Stable water isotope behavior during the last glacial maximum: A general circulation model analysis

Global water isotope geochemisty during the last glacial maximum (LGM) is simulated with an 8 deg x 10 deg atmospheric general circulation model (GCM). The simulation results suggest that the spatial delta O-18/temperature relationships observed for the present day and LGM climates are very similar. Furthermore, the temporal delta O-18/temperature relationship is similar to the present-day spatial relationship in regions for which the LGM/present-day temperature change is significant. This helps justify the standard practice of applying the latter to the interpretation of paleodata, despite the possible influence of other factors, such as changes in the evaportive sources of precipitation or in the seasonality of precipitation. The model suggests, for example, that temperature shifts inferred from ice core data may differ from the true shifts by only about 30%.

Jouzel, Jean↗
NASA NTRS1999

Optical Properties of Aerosols from Long Term Ground-Based Aeronet Measurements

AERONET is an optical ground-based aerosol monitoring network and data archive supported by NASA's Earth Observing System and expanded by federation with many non-NASA institutions including AEROCAN (AERONET CANada) and PHOTON (PHOtometrie pour le Traiteinent Operatonnel de Normalisation Satellitaire). The network hardware consists of identical automatic sun-sky scanning spectral radiometers owned by national agencies and universities purchased for their own monitoring and research objectives. Data are transmitted hourly through the data collection system (DCS) on board the geostationary meteorological satellites GMS, GOES and METEOSAT and received in a common archive for daily processing utilizing a peer reviewed series of algorithms thus imposing a standardization and quality control of the product data base. Data from this collaboration provides globally distributed near real time observations of aerosol spectral optical depths, aerosol size distributions, and precipitable water in diverse aerosol regimes. Access to the AERONET data base has shifted from the interactive program 'demonstrat' (reserved for PI's) to the AERONET homepage allowing faster access and greater development for GIS object oriented retrievals and analysis with companion geocoded data sets from satellites, LIDAR and solar flux measurements for example. We feel that a significant yet under utilized component of the AERONET data base are inversion products made from hourly principal plane and almucanter measurements. The current inversions have been shown to retrieve aerosol volume size distributions. A significant enhancement to the inversion code has been developed and is presented in these proceedings.

Holben, B. N.↗
NASA NTRS1974

Signal simulator model A-111

A signal simulator designed to function as a signal source for Doppler tracking high data rate receivers is described. The simulator produces modulated signals whose carrier frequency can be varied between 200 and 900 MHz at rates greater than 20 MHz/sec. The modulation is phase shift keying with data rate up to 300 megabits per second.

Flattau, T.↗
NASA NTRS2014

Advancing Navigation, Timing, and Science with the Deep Space Atomic Clock

NASA's Deep Space Atomic Clock mission is developing a small, highly stable mercury ion atomic clock with an Allan deviation of at most 1e-14 at one day, and with current estimates near 3e-15. This stability enables one-way radiometric tracking data with accuracy equivalent to and, in certain conditions, better than current two-way deep space tracking data; allowing a shift to a more efficient and flexible one-way deep space navigation architecture. DSAC-enabled one-way tracking will benefit navigation and radio science by increasing the quantity and quality of tracking data. Additionally, DSAC would be a key component to fully-autonomous onboard radio navigation useful for time-sensitive situations. Potential deep space applications of DSAC are presented, including orbit determination of a Mars orbiter and gravity science on a Europa flyby mission.

radio science↗
NASA NTRS1986

Studies of extended planetary atmospheres

There was a theoretical study of physical and chemical processes in the stratosphere, later broadened to include the mesosphere. Particular emphasis was laid on testing of proposed height profiles of the eddy diffusion coefficient against observed tracer data. Eventually the effort shifted to study of ozone time series in satellite data, and interpretation in terms of aeronomical processes. Since all this work is computer-intensive, the first year of funding also contributed to the acquisition of a powerful minicomputer system, in collaboration with several other faculty members. This proved to be highly successful and cost effective.

Hunten, D. M.↗
NASA NTRS2022

Quantifying urban, industrial, and background changes in NO2 during the COVID-19 lockdown period based on TROPOMI satellite observations

The COVID-19 lockdown had a large impact on anthropogenic emissions of air pollutants and particularly on nitrogen dioxide (NO 2 ). While the overall NO 2 decline over some large cities is well-established, understanding the details remains a challenge since multiple source categories contribute. In this study, a new method of isolation of three components (background NO 2 , NO 2 from urban sources, and NO 2 from industrial point sources) is applied to estimate the impact of the COVID-19 lockdown on each of them. The approach is based on fitting satellite data by a statistical model with empirical plume dispersion functions driven by a meteorological reanalysis. Population density and surface elevation data as well as coordinates of industrial sources were used in the analysis. The tropospheric NO 2 vertical column density (VCD) values measured by the Tropospheric Monitoring Instrument (TROPOMI) on board the Sentinel-5 Precursor over 261 urban areas for the period from 16 March to 15 June 2020 were compared with the average VCD values for the same period in 2018 and 2019. While the background NO 2 component remained almost unchanged, the urban NO 2 component declined by −18 % to −28 % over most regions. India, South America, and a part of Europe (particularly, Italy, France, and Spain) demonstrated a −40 % to −50 % urban emission decline. In contrast, the decline over urban areas in China, where the lockdown was over during the analysed period, was, on average, only -4.4± 8 %. Emissions from large industrial sources in the analysed urban areas varied greatly from region to region from -4.8 ± 6 % for China to -40 ± 10 % for India. Estimated changes in urban emissions are correlated with changes in Google mobility data (the correlation coefficient is 0.62) confirming that changes in traffic were one of the key elements in the decline in urban NO2 emissions. No correlation was found between changes in background NO2 and Google mobility data. On the global scale, the background and urban components were remarkably stable in 2018, 2019, and 2021, with averages of all analysed areas all being within ±2.5 % and suggesting that there were no substantial drifts or shifts in TROPOMI data. The 2020 data are clearly an outlier: in 2020, the mean background component for all analysed areas (without China) was -6.0 % ± 1.2 % and the mean urban component was -26.7 ± 2.6 % or 20σ below the baseline level from the other years.

COVID-19↗