Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Geostationary”

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.

At least 1,189 records · Page 66
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The inference of tropical cyclone dynamics using GOES VISSR/VAS data

The sequence of events observed during tropical cyclone Emily, was suggested as a possible mechanism for cyclogenesis. Geostationary Operational Environmental Satellite (GOES) East VISSR/VAS sensors were used. The VISSR visible imagery obtained every 15 minutes was used to define the low tropospheric cyclonic vortex and upper tropospheric horizontal convergence. The VAS water vapor (channels 9 and 10) and carbon dioxide (channels 3 and 4) channels were used to infer upper and middle tropospheric subsidence by monitoring the Adiabatic compressional drying and warming, respectively, occurring within this layer. Evidence of an existing lower tropospheric cyclonic vortex was seen. The satellite derived wind vectors (length of vector is proportional to wind velocity, where the strongest winds were approximately 35 knots) are superimposed on the GOES visible image of tropical storm Emily. Vectors and low level clouds depict the center of the cyclonic vortex immediately south of the large convective cell in the center of the image. Upper tropospheric cloud tracers and rawinsonde reports along the Eastern United States suggest that the southwesterly environmental upper atmospheric flow is converging with the outflow from the convective cell north of the vortex.

Rodgers, E. B.↗
NASA NTRS1983

Evaluation of the effect of VAS data on some NMC analyses and forecasts

The effect of visible/infrared atmospheric sounder (VAS) data on the limited area fine mesh model (LFM) analysis forecast system were examined. The VAS data obtained from the Pacific geostationary satellite are valuable for LFM analysis because temperatures from the polar orbiting satellite over the east Pacific are received too late for 1200 GMT LFM analysis. Because the VISSR has only infrared channels, retrievals are possible only in regions with little or no cloudiness.

Olenic, E. A.↗
NASA NTRS1981

Ground truth for oceanic rainfall

Communications systems operating at frequencies in excess of 10 GHz are degraded significantly by rainfall. To provide the information needed for design of these millimeter wave systems, rain attentuation models were developed and data bases of propagation related information were accumulated. These data bases were developed based on the signal level measurements of geostationary satellite beacons at selected frequencies. Groundbased radar reflection measurements were able to develop data bases for system design. The rain attenuation models allow accurate correlation between the rain rate and the attenuation.

Dorman, C. E.↗
NASA NTRS1981

The estimation of convective precipitation from GOES imagery with the Griffith/Woodley technique

Improved rainfall monitoring using satellite and conventional data are described. A method was developed to: (1) provide rainfall evaluations more uniform, accurate and complete than can be derived from satellite or conventional data alone; (2) serve current operational environmental program in countries with special needs for improved rainfall data; (3) invoke either polar orbiting and/or geostationary imagery as the satellite inputs; (4) utilize global telecommunication system (GTS) SYNOP messages as the basic conventional data inputs; (5) be applicable to any and all types of weather situations in the operational areas; (6) be undemanding in hardware and software so as to be an option available for use even by nations or agencies with very limited financial resources.

Griffith, C. G.↗
NASA NTRS1983

Evaluation of the use of on-board spacecraft energy storage for electric propulsion missions

On-board spacecraft energy storage represents an under utilized resource for some types of missions that also benefit from using relatively high specific impulse capability of electric propulsion. This resource can provide an appreciable fraction of the power required for operating the electric propulsion subsystem in some missions. The most probable mission requirement for utilization of this energy is that of geostationary satellites which have secondary batteries for operating at high power levels during eclipse. The study summarized in this report selected four examples of missions that could benefit from use of electric propulsion and on-board energy storage. Engineering analyses were performed to evaluate the mass saved and economic benefit expected when electric propulsion and on-board batteries perform some propulsion maneuvers that would conventionally be provided by chemical propulsion. For a given payload mass in geosynchronous orbit, use of electric propulsion in this manner typically provides a 10% reduction in spacecraft mass.

Poeschel, R. L.↗
NASA NTRS1981

A Satellite Frost Forecasting System for Florida

Since the first of two minicomputers that are the main components of the satellite frost forecast system was delivered in 1977, the system has evolved appreciably. A geostationary operational environmental satellite (GOES) system provides the satellite data. The freeze of January 12-14, 1981, was documented with increasing interest in potential of such systems. Satellite data is now acquired digitally rather than by redigitizing the GOES-Tap transmissions. Data acquisition is now automated, i.e., the computers are programmed to operate the system with little, if any, operation intervention.

Martsolf, J. D.↗
NASA NTRS1983

Pacific area data collection stations

The installation of environmental data collection systems at several remotely located sites in islands in the Pacific Ocean is summarized. The effort was designed to enhance the ability to collect hydrological information. The data collection station consists of a data acquisition system for handling data, a transmitter for uplinking information to the GOES-W geostationary satellite, and a variety of environmental sensors for data accumulation. Each system was assembled, tested, and deployed on designated islands. The concept of using microprocessors for handling data at remote sites and relaying it via a satellite link is a cost effective approach. Such systems require high reliability and proven performance in the field.

Rector, R. C.↗
NASA NTRS1981

Spaceborne bistatic synthetic aperture imaging radar

The properties of two configurations for a spaceborne bistatic SAR are examined and compared with the properties of a monostatic SAR. The two bistatic configurations considered are a system consisting of an orbiting spaceborne transmitter and a ground receiver and a system consisting of a transmitter on a geostationary satellite and a receiver or receivers on an airborne platform. The properties discussed or analyzed include imaging coordinate system, azimuth and range resolution, azimuth and range ambiguities, and swath width.

Elachi, C.↗
NASA NTRS1982

Propagation effects on radio range and noise in earth-space telecommunications

Attention is given to the propagation effects on radio range and noise in earth-space telecommunications. The use of higher frequencies minimizes ionospheric effects on propagation, but tropospheric effects often increase or dominate. For paths of geostationary satellites, and beyond, the excess range delay caused by the ionosphere and plasmasphere is proportional to the total electron content along the path and inversely proportional to frequency squared. The delay due to dry air is usually of the order of a few meters while the delay due to water vapor (a few tens of centimeters) is responsible for most of the temporal variation in the range delay for clean air. For systems such as that of the Voyager spacecraft, and for attenuation values up to about 10 dB, increased sky noise degrades the received signal-to-noise ratio more than does the reduction in signal level due to attenuation.

Flock, W. L.↗
NASA NTRS1981

Visible and infrared spin scanning radiometer /VISSR/ atmospheric sounder /VAS/ ground data system

The interactive system developed at NASA/Goddard Space Flight Center to receive data from the infrared radiometer on GOES-4 in near real time and to perform interactive display and analysis of the 12-channel infrared imagery is described. The system is minicomputer based and uses a menu approach in guiding the analyst through spacecraft instrument programming, area and band selection, image acquisition, enhancement, analysis, and presentation of results. The system is linked by dual port disks to Goddard's Atmospheric and Oceanographic Information Processing System for comparing the sounding results with parameters derived from conventional data and from time lapse analysis of visible and IR imagery from other geostationary satellites. It is pointed out that the system hardware and software are being expanded to add capabilities for the integration and assimilation of VAS data with data from other sources, the comparison of severe storm observations from space with special ground network data, and the development of diagnostic models.

Dalton, J. T.↗
NASA NTRS1982

Delineation of cold-prone areas using nighttime SMS/GOES thermal data Effects of soils and water

Infrared digital data from geostationary satellites were used to demonstrate the usefulness of remotely sensed surface temperature data to delineate microscale and mesoscale climates. Nocturnal winter data (December-February) from 1976-77 to 1978-79 over Florida revealed noticeable contrasts in surface temperature patterns. Colder areas were associated with low soil moisture content in the upper layers of excessively drained and well drained sandy soils, whereas warmer areas were associated with bodies of water, wetlands, or poorly drained soils. An unexpected surface temperature pattern for one night where the north-central Florida climatic zone was colder than the north Florida climatic zone was found to be caused by differences in antecedent frontal rainfall. Differences in surface radiant energy fluxes over these two areas at 0200 EST 20 December 1977, based on average satellite-sensed surface temperatures, were compared with differences in soil heat fluxes that were computed from 1.5 m climatological temperatures and soil thermal properties by use of a simplified surface energy balance equation.

Chen, E.↗
NASA NTRS1981

Techniques for low sidelobe, high efficiency offset dual reflector antennas

Antennas with very low sidelobe levels and high aperture efficiencies are employed in satellite communications for both ground and satellite borne systems to reduce microwave interference due to traffic congestion to and from the geostationary satellite orbit. Multiple beam antennas with sidelobes 30 to 40 dB below main beam peaks are required with aperture efficiencies approaching 80%. In the present investigation techniques are presented which make it possible to obtain multibeam patterns with the required characteristics. The considered limited scanned antennas have applications to military and commercial radars as well as to space communications. It is pointed out that offset dual reflector antennas designed according to Japanese tilt criteria offer attractive solutions because optimum aperture distributions can be realized without aperture blocking. Attention is given to ideal aperture distributions, corrugated conical horn design, and subreflector design.

Sletten, C. J.↗
NASA NTRS1981

Deep space optical communication via relay satellite

The application of optical communications for a deep space link via an earth-orbiting relay satellite is discussed. The system uses optical frequencies for the free-space channel and RF links for atmospheric transmission. The relay satellite is in geostationary orbit and contains the optics necessary for data processing and formatting. It returns the data to earth through the RF terrestrial link and also transmits an optical beacon to the satellite for spacecraft return pointing and for the alignment of the transmitting optics. Future work will turn to modulation and coding, pointing and tracking, and optical-RF interfacing.

Dolinar, S.↗
NASA NTRS1982

A comparison of adiabatic and kinematic vertical motions using mesoscale data

Results are compared from the adiabatic and kinematic methods of determining vertical motion during a period of severe convective storms when special meso alpha-scale rawinsonde data were available. The two procedures were tested using data from the first regional-scale day of AVE-SESAME '79 which coincided with the Red River Valley tornado outbreak of April 10-11, 1979. At 700 mb, each technique showed good agreement with the weather patterns, but the kinematic procedure gave superior results at 500 mb. The overall goodness of the adiabatic method during this particular case was not solely due to the high-resolution SESAME data since synoptic-scale mechanisms played a major role in creating a storm-conducive environment. With the advent of computer aided analysis systems such as AFOS, forecasters will have quicker access to a greater variety of information. Present results suggest that the adiabatic method can yield useful information for severe storm forecasters, especially in the lower troposphere. An interesting follow-on study would use sounding data from geostationary VAS satellites to compute adiabatic vertical motions at finer time and space resolutions than is now possible using RAOB data alone. Geostrophic winds derived from satellite thermal data probably can be used.

Fuelberg, H. E.↗
NASA NTRS1983

Low-level water vapor fields from the VISSR Atmospheric Sounder (VAS) 'split window' channels

A simple physical algorithm is presented which calculates the water vapor content of the lower troposphere from the 11 and 12 micron (split window) channels on the VISSR Atmospheric Sounder (VAS) on the Geostationary Operational Environmental Satellites. The algorithm is used to analyze a time series of VAS split window radiances observed at 15 km horizontal resolution over eastern North America during a 12 hr period on 13 July 1981. Results of the color coded images of the derived precipitable water fields are found to show vivid water vapor features whose broad structure and evolution are verified by the radiosonde and surface networks. The satellite moisture fields also show significant mesoscale features and rapid developments which are not resolved by the conventional networks. The VAS split window is determined to clearly differentiate those areas in which water vapor extends over a deep layer and is more able to support convective cells from those areas in which water vapor is confined to a shallow layer and is therefore less able to support convection. It is concluded that the VAS split windows can be used operationally to monitor mesoscale developments in the low-level moisture fields over relatively cloud-free areas of the United States.

Chesters, D.↗
NASA NTRS1983

The International Satellite Cloud Climatology Project (ISCCP) - The first project of the World Climate Research Programme

The first project of the World Climate Research Program is the International Satellite Cloud Climatology Project, (ISCCP) whose objective is the collection and analysis of satellite radiance data in order to infer the global distribution of cloud radiative properties and improve the modeling of cloud effects on climate. The operational component of ISCCP takes advantage of the global coverage provided by the current and planned international array of geostationary and polar-orbiting meteorological satellites in the 1980s. It will produce a five-year global radiance and cloud data set. The research component of ISCCP will coordinate studies to validate climatology, improve cloud analysis algorithms, improve cloud effects modelling, and investigate the role of clouds in the atmospheric radiation budget and hydrologic cycle.

Schiffer, R. A.↗
NASA NTRS1982

Launch vehicles for communications satellites

After giving brief development histories of the Delta and the Atlas Centaur launch vehicles, attention is given to the operational characteristics of the ascent, parking orbit, transfer orbit, and orbital insertion phases of the delivery of a communications satellite to a geostationary orbit by means of a Delta launch vehicle. NASA plans to employ Delta vehicles for as long as they are needed during the transition period to the Space Shuttle. NASA planning for Atlas Centaur includes launches through 1985 for INTELSAT-VA, and through 1986 for FLTSATCOM satellites.

Mahon, J. B.↗