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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

Canadian and Alaskan Wildfire Smoke Particle Properties, Their Evolution and Controlling Factors, From Satellite Observations

The optical and chemical properties of biomass burning (BB) smoke particles greatly affect the impact that wildfires have on climate and air quality. Previous work has demonstrated some links between smoke properties and factors such as fuel type and meteorology. However, the factors controlling BB particle speciation at emission are not adequately understood nor are the factors driving particle aging during atmospheric transport. As such, modeling wildfire smoke impacts on climate and air quality remains challenging. The potential to provide robust, statistical characterizations of BB particles based on ecosystem type and ambient environmental conditions with remote sensing data is investigated here. Space-based Multi-angle Imaging SpectroRadiometer (MISR) observations, combined with the MISR Research Aerosol (RA) algorithm and the MISR Interactive Explorer (MINX) tool, are used to retrieve smoke plume aerosol optical depth (AOD) and to provide constraints on plume vertical extent; smoke age; and particle size, shape, light-absorption properties, and absorption spectral dependence. These tools are applied to numerous wildfire plumes in Canada and Alaska, across a range of conditions, to create a regional inventory of BB particle-type temporal and spatial distribution. We then statistically compare these results with satellite measurements of fire radiative power (FRP) and land cover characteristics, as well as short-term climate, meteorological, and drought information from the Modern-Era Retrospective analysis for Research and Applications (MERRA-2) reanalysis and the North American Drought Monitor. We find statistically significant differences in the retrieved smoke properties based on land cover type, with fires in forests producing the thickest plumes containing the largest, brightest particles and fires in savannas and grasslands exhibiting the opposite. Additionally, the inferred dominant aging mechanisms and the timescales over which they occur vary systematically between land types. This work demonstrates the potential of remote sensing to constrain BB particle properties and the mechanisms governing their evolution over entire ecosystems. It also begins to realize this potential, as a means of improving regional and global climate and air quality modeling in a rapidly changing world.

Katherine T. Junghenn Noyes↗
NASA NTRS1986

A cascaded error control coding scheme for space and satellite communication

An error control coding scheme for space and satellite communications is presented. The scheme is attained by cascading two codes, the inner and outer codes. Error performance of the scheme is analyzed. It is shown that, if the inner and outer codes are chosen properly, extremely high reliability can be achieved even for a high channel bit-error-rate. Several exmple schemes are studied. One of the example schemes is proposed to NASA for satellite or spacecraft downlink error control.

Lin, Shu↗
NASA NTRS2001

Techniques for monitoring and controlling yaw attitude of a GPS satellite

Techniques for monitoring and controlling yawing of a GPS satellite in an orbit that has an eclipsing portion out of the sunlight based on the orbital conditions of the GPS satellite. In one embodiment, a constant yaw bias is generated in the attitude control system of the GPS satellite to control the yawing of the GPS satellite when it is in the shadow of the earth.

Lichten, Stephen M.↗
NASA NTRS1987

The control networks of the satellites of Uranus

The present photogrammetric derivation of control networks for the five Uranus satellites Miranda, Ariel, Umbriel, Titania, and Oberon, on the basis of Voyager 2 images, covers the illuminated southern hemisphere of each satellite and respectively yields 103, 52, 43, 46, and 34 coordinate points. It is found that Titania is ellipsoidal, with 241-, 235-, and 232-km radii.In addition, mean radii are determined to be 579 km for Ariel, 586 km for Umbriel, 790 km for Titania, and 762 km for Oberon. Some of the control points used have been identified on the U.S. Geological Survey maps of these satellites.

Davies, Merton E.↗
NASA NTRS1996

ATTDES: An Expert System for Satellite Attitude Determination and Control

The design, analysis, and flight operations of satellite attitude determintion and attitude control systems require extensive mathematical formulations, optimization studies, and computer simulation. This is best done by an analyst with extensive education and experience. The development of programs such as ATTDES permit the use of advanced techniques by those with less experience. Typical tasks include the mission analysis to select stabilization and damping schemes, attitude determination sensors and algorithms, and control system designs to meet program requirements. ATTDES is a system that includes all of these activities, including high fidelity orbit environment models that can be used for preliminary analysis, parameter selection, stabilization schemes, the development of estimators covariance analyses, and optimization, and can support ongoing orbit activities. The modification of existing simulations to model new configurations for these purposes can be an expensive, time consuming activity that becomes a pacing item in the development and operation of such new systems. The use of an integrated tool such as ATTDES significantly reduces the effort and time required for these tasks.

Mackison, Donald L.↗
NASA NTRS1985

Automatic charge control system for satellites

The SCATHA and the ATS-5 and 6 spacecraft provided insights to the problem of spacecraft charging at geosychronous altitudes. Reduction of the levels of both absolute and differential charging was indicated, by the emission of low energy neutral plasma. It is appropriate to complete the transition from experimental results to the development of a system that will sense the state-of-charge of a spacecraft, and, when a predetermined threshold is reached, will respond automatically to reduce it. A development program was initiated utilizing sensors comparable to the proton electrostatic analyzer, the surface potential monitor, and the transient pulse monitor that flew in SCATHA, and combine these outputs through a microprocessor controller to operate a rapid-start, low energy plasma source.

Shuman, B. M.↗
NASA NTRS1971

A method for attitude control of a satellite in circular orbit by actively varying its inertia.

Equations are developed for a vehicle consisting of a system of particles which move in a generally prescribed fashion. These equations are then specialized to apply to a rigid vehicle with a constant amount of fluid contained in tanks and flowing through interconnecting lines. Various simplifications and specialized forms of the equations are derived, and relationships between mass and inertia that result from the fluid transfer logic and the physical constraints of the configuration are formulated. A tank arrangement and fluid transfer logic are devised which permit each vehicle product of inertia to be varied without varying the remaining elements of the inertia matrix or shifting the center of mass. Vehicle control is achieved by sensing angular rate and the local vertical and by transferring fluid as a function of these variables.

Clarke, W. D.↗
NASA NTRS1988

The Orbital Maneuvering Vehicle - A new capability

NASA's Orbital Maneuvering Vehicle (OMV) is a reusable remotely-controlled spacecraft for support of orbiting platforms through such functions as satellite delivery, satellite retrieval, satellite reboost, controlled satellite deorbit, satellite inspection, and subsatellite missions. The OMV will be a critical component of the Space Station program's operational scenario; it will be able to operate either from the Space Shuttle Orbiter or the Space Station, and can also be space-based. The maiden flight of the first OMV is projected for 1993.

Arcilesi, Charles J.↗
NASA NTRS1979

Satellite aided orbit capture

The paper surveys the developments leading to the use of satellites for orbit control. Previous satellite gravity assist work is analyzed, emphasizing powered and unpowered aided capture schemes. In addition, a parametric study characterizes potential gains of satellite aided capture for various satellite systems. Finally, potential applications of aided capture such as for the Galilean System and for Saturn and Titan are given.

Nock, K. T.↗
NASA NTRS1981

Solar Power Satellite antenna phase control system hardware simulation, phase 4: Volume 1: Executive summary

The phase control system is described. Potential sources of phase error are identified and the performance leading to selection of the allowable phase error for each source is summarized. The pilot transmitter, the effects of ionospheric, the master slave returnable timing system (MSRTS), the SPS receiver, and the high power amplifier for dc to microwave conversion are considered separately. Design parameters of the pilot transmitter and spacetenna transponder are presented.

Lindsey, W. C.↗
NASA NTRS1981

Solar Power Satellite antenna phase control system hardware simulation, phase 4. Volume 2: Analytical simulation of SPS system performance

The pilot signal parameter optimization and power transponder analyses are presented. The SPS antenna phase control system is modeled and the hardware simulation study described. Ionospheric and system phase error effects and the effects of high power amplifier phase and amplitude jitters are considered. Parameter optimization of the spread spectrum receiver, consisting of the carrier tracking loop and the code tracking loop, is described.

Lindsey, W. C.↗
NASA NTRS1981

Solar Power Satellite antenna phase control system hardware simulation, phase 4. Volume 3: SOLARSIM users manual

Documentation of the interactive software package designed to predict the effect of certain electrical and mechanical imperfections on the performance of the SPS system is presented. The capabilities of the SOLARSIM program to quantify the spacetenna performance parameter values are described. The SOLARSIM package can compute the RMS pointing error, title effects, MPTX code tracking loop performance, MPTX carrier tracking loop performance, averaged power pattern, and the power transfer efficiency.

Lindsey, W. C.↗