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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

System Design for a Spaceborne Cloud Rada

This paper presents some crucial design parameters and a strawman system design for a nadir-looking, 94-GHz spaceborne cloud profiling radar. This sensor is expected to provide cloud measurements at vertical resolution of 500 m and with a minimum detectable cloud reflectivity of slightly better than -30 dBZ. The radar design is intended to be accommodated by a spacecraft with limited resources. It uses a 2-m antenna and an extended interaction amplifier (EIA) that are readily available in either ground-based and airborne applications. For space application, improvements in the EIA lifetime and space qualification will be required. For various reasons, the spaceborne cloud radar system development is expected to be greatly benefited by the implementation of an aircraft cloud radar instrument.

Cloud Measurement Spaceborne Cloud↗
NASA NTRS2004

System engineering for spaceborne optical interferometers

This paper is based on a collection of lessons-learned based on related missions including StarLight, a formation-flying stellar interferometry mission that merged with the Terrestrial Planet Finder technology development program just prior to entering phase C/D, the Space Interferometry Mission (currently in phase A), and the Shuttle Radar Topography Misssion of 2000.

system↗
NASA NTRS1984

Simulation Experiments on the Relative Accuracy of Inferred Atmospheric States from Idealized Wind and Temperature Profiling Systems

The First GARP Global Experiment (FGGE) led to the planning, design and implementation of a global observing system. Technologies as coherent CO2 LIDAR systems and highly sensitive IR detectors offer the potential of more accurate global spaceborne observation systems. The advent of super computers allows general circulation modeling and more sophisticated data analysis schemes. The consideration of advanced spaceborne systems better suited to meet the new emerging requirements are suggested. The Global Weather Experiment provides us with a new baseline to assess data accuracy and forecasting capabilities which is used for study of the incremental performance.

Halem, M.↗
NASA NTRS2008

Spaceborne Hybrid-FPGA System for Processing FTIR Data

Progress has been made in a continuing effort to develop a spaceborne computer system for processing readout data from a Fourier-transform infrared (FTIR) spectrometer to reduce the volume of data transmitted to Earth. The approach followed in this effort, oriented toward reducing design time and reducing the size and weight of the spectrometer electronics, has been to exploit the versatility of recently developed hybrid field-programmable gate arrays (FPGAs) to run diverse software on embedded processors while also taking advantage of the reconfigurable hardware resources of the FPGAs.

Bekker, Dmitriy↗
NASA NTRS2008

Reducing Spaceborne-Doppler-Radar Rainfall-Velocity Error

A combined frequency-time (CFT) spectral moment estimation technique has been devised for calculating rainfall velocity from measurement data acquired by a nadir-looking spaceborne Doppler weather radar system. Prior spectral moment estimation techniques used for this purpose are based partly on the assumption that the radar resolution volume is uniformly filled with rainfall. The assumption is unrealistic in general but introduces negligible error in application to airborne radar systems. However, for spaceborne systems, the combination of this assumption and inhomogeneities in rainfall [denoted non-uniform beam filling (NUBF)] can result in velocity measurement errors of several meters per second. The present CFT spectral moment estimation technique includes coherent processing of a series of Doppler spectra generated in a standard manner from data over measurement volumes that are partially overlapping in the along-track direction. Performance simulation of this technique using high-resolution data from an airborne rain-mapping radar shows that a spaceborne Ku-band Doppler radar operating at signal-to-noise ratios greater than 10 dB can achieve root-mean-square accuracy between 0.5 and 0.6 m/s in vertical-velocity estimates.

Tanelli, Simone↗
NASA NTRS1977

Synthesis and analysis of precise spaceborne laser ranging systems, volume 1

Measurement accuracy goals of 2 cm rms range estimation error and 0.003 cm/sec rms range rate estimation error, with no more than 1 cm (range) static bias error are requirements for laser measurement systems to be used in planned space-based earth physics investigations. Constraints and parameters were defined for links between a high altitude, transmit/receive satellite (HATRS), and one of three targets: a low altitude target satellite, passive (LATS), and active low altitude target, and a ground-based target, as well as with operations with a primary transmit/receive terminal intended to be carried as a shuttle payload, in conjunction with the Spacelab program.

Paddon, E. A.↗
NASA NTRS1978

A proposed test area for the spaceborne geodynamic ranging system

Precise geodetic measurements are proposed in which an orbiting laser obtains intersite distance between retroreflectors 25 to 100 km apart on the ground. The recommended area is a rectangle 200 by 400 km in southern California and adjacent Nevada, trending northeast. It includes the entire width of the San Andreas fault zone, the Garlock fault, the thrust faults of the Transverse Ranges, and the active strike-slip faults of the Mojave Desert.

Lowman, P. D., Jr.↗
NASA NTRS1978

Determining crustal strain rates with spaceborne geodynamics ranging system data. 1: Baseline analysis

A satellite-borne laser ranging system is proposed that is capable of making highly precise geodetic measurements over baselines ranging from a few tens of kilometers to several hundred kilometers. The precision with which crustal strain rates are derived from measurements made with this system is analyzed by using simple site configurations, intersite distances of about 25-70 kilometers, and measurement programs ranging from a few years to fifteen years. It is concluded that precisions of several parts in 10 to the 9th power per year are achievable. Compared to the expected shear strain rates of about 7 x 10 to the minus 7th power yr/1, this produces very favorable signal-to-noise ratios.

Cohen, S. C.↗
NASA NTRS1979

Nd:YAG development for spaceborne laser ranging system

The results of the development of a unique modelocked laser device to be utilized in future NASA space-based, ultraprecision laser ranger systems are summarized. The engineering breadboard constructed proved the feasibility of the pump-pulsed, actively modelocked, PTM Q-switched Nd:YAG laser concept for the generation of subnanosecond pulses suitable for ultra-precision ranging. The laser breadboard also included a double-pass Nd:YAG amplifier and provision for a Type II KD*P frequency doubler. The specific technical accomplishment was the generation of single 150 psec, 20-mJ pulses at 10 pps at a wavelength of 1.064 micrometers with 25 dB suppression of pre-and post-pulses.

Harper, L. L.↗
NASA NTRS1982

Spaceborne scanner imaging system errors

The individual sensor system design elements which are the priori components in the registration and rectification process, and the potential impact of error budgets on multitemporal registration and side-lap registration are analyzed. The properties of scanner, MLA, and SAR imaging systems are reviewed. Each sensor displays internal distortion properties which to varying degrees make it difficult to generate on orthophoto projection of the data acceptable for multiple pass registration or meeting national map accuracy standards and is also affected to varying degrees by relief displacements in moderate to hilly terrain. Nonsensor related distortions, associated with the accuracy of ephemeris determination and platform stability, have a major impact on local geometric distortions. Platform stability improvements expected from the new multi mission spacecraft series and improved ephemeris and ground control point determination from the NAVSTAR/global positioning satellite systems are reviewed.

Prakash, A.↗
NASA NTRS1985

Topex - A spaceborne ocean observing system

The key to the ocean's influence on life is its general circulation. For the study of this circulation, geostrophic currents at the sea surface can be mapped from space with the aid of satellite altimeters, which measure the height of the sea surface and its variations in time and space. In view of the usefulness of satellite altimetry, the European Space Agency, Japan, France, and the United State have plans to launch Seasat-class altimeters. The similarity between the U.S. and the French programs and goals for satellite altimetry has led the respective agencies to study the possibility of combining NASA's Ocean Topography Experiment Topex with CNES's Poseidon Project. The objectives of the combined Topex/Poseidon mission involve an enhancement of the understanding of ocean dynamics on the basis of precise and accurate observations of the oceanic topography for a period of three years. The mission is to provide the foundation for a continuing program concerned with long-term observations of oceanic circulation.

Born, G. H.↗
NASA NTRS1988

Technology forecast and applications for autonomous, intelligent systems

Significant research products which have emerged from the core program of NASA's Office of Aeronautics and Space Technology (OAST) are discussed. The Space Station Thermal Control System, the Space Shuttle Integrated Communications Officer Station, the Launch Processing System, the Expert Scheduling System for Pioneer Venus Spacecraft, a Bayesian classification system, and a spaceborne multiprocessor system are included. The technology trends which led to these results are discussed and future developments in technology are forecasted.

Lum, Henry, Jr.↗
NASA NTRS1988

Spaceborne VHSIC multiprocessor system for AI applications

A multiprocessor system, under design for space-station applications, makes use of the latest generation symbolic processor and packaging technology. The result will be a compact, space-qualified system two to three orders of magnitude more powerful than present-day symbolic processing systems.

Lum, Henry, Jr.↗
NASA NTRS1991

Office of Spaceflight Standard Spaceborne Global Positioning System (GPS) user equipment project

The Global Positioning System (GPS) provides the following: (1) position and velocity determination to support vehicle GN&C, precise orbit determination, and payload pointing; (2) time reference to support onboard timing systems and data time tagging; (3) relative position and velocity determination to support cooperative vehicle tracking; and (4) attitude determination to support vehicle attitude control and payload pointing.

Saunders, Penny E.↗
NASA NTRS1991

Office of Space Flight standard spaceborne Global Positioning System user equipment project

The Global Positioning System (GPS) provides users autonomous, real-time navigation capability. A vehicle equipped with GPS user equipment can receive and process signals transmitted by a constellation of GPS satellites and derive from the resulting measurements the vehicle's position and velocity. Specified accuracies range from 16 to 76 meters and 0.1 to 1.0 meters/second for position and velocity, respectively. In a rendezvous and docking scenario, the use of a technique called relative GPS can provide range and range rate accuracies on the order of 1 meter and 0.01 meters/second, respectively. Relative GPS requires both vehicles to be equipped with GPS user equipment and a data communication link for transmission of GPS data and GPS satellite selection coordination information. Through coordinated satellite selection, GPS measurement errors common to both users are cancelled and improved relative position and velocity accuracies are achieved. The background, the design approach, the expected performance and capabilities, the development plan, and the project status are described. In addition, a description of relative GPS, the possible GPS hardware and software configurations, and its application to automated rendezvous and capture are presented.

Saunders, Penny E.↗
NASA NTRS1990

Spaceborne autonomous multiprocessor systems

The goal of this task is to provide technology for the specification and integration of advanced processors into the Space Station Freedom data management system environment through computer performance measurement tools, simulators, and an extended testbed facility. The approach focuses on five categories: (1) user requirements--determine the suitability of existing computer technologies and systems for real-time requirements of NASA missions; (2) system performance analysis--characterize the effects of languages, architectures, and commercially available hardware on real-time benchmarks; (3) system architecture--expand NASA's capability to solve problems with integrated numeric and symbolic requirements using advanced multiprocessor architectures; (4) parallel Ada technology--extend Ada software technology to utilize parallel architectures more efficiently; and (5) testbed--extend in-house testbed to support system performance and system analysis studies.

Fernquist, Alan↗
NASA NTRS1997

Feasibility Study For A Spaceborne Ozone/Aerosol Lidar System

Because ozone provides a shield against harmful ultraviolet radiation, determines the temperature profile in the stratosphere, plays important roles in tropospheric chemistry and climate, and is a health risk near the surface, changes in natural ozone layers at different altitudes and their global impact are being intensively researched. Global ozone coverage is currently provided by passive optical and microwave satellite sensors that cannot deliver high spatial resolution measurements and have particular limitations in the troposphere. Vertical profiling DIfferential Absorption Lidars (DIAL) have shown excellent range-resolved capabilities, but these systems have been large, inefficient, and have required continuous technical attention for long term operations. Recently, successful, autonomous DIAL measurements have been performed from a high-altitude aircraft (LASE - Lidar Atmospheric Sensing Experiment), and a space-qualified aerosol lidar system (LITE - Laser In-space Technology Experiment) has performed well on Shuttle. Based on the above successes, NASA and the Canadian Space Agency are jointly studying the feasibility of developing ORACLE (Ozone Research with Advanced Cooperative Lidar Experiments), an autonomously operated, compact DIAL instrument to be placed in orbit using a Pegasus class launch vehicle.

Campbell, Richard E.↗