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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Packet radio data link applications in the NASA Langley Research Center Transport Systems Research Vehicle

An amateur packet radio system operating in the very high frequency (VHF) range has been implemented in the Transport Systems Research Vehicle at the NASA Langley Research Center to provide an economical, bidirectional, real-time, ground-to-air data link. The packet system has been used to support flight research involving air traffic control (ATC), differential global positioning systems (DGPS), and windshear terminal doppler weather radar (TDWR). A data maximum rate of 2400 baud was used. Operational reliability of the packet system has been very good. Also, its versatility permits numerous specific configurations. These features, plus its low cost, have rendered it very satisfactory for support of data link flight experiments that do not require high data transfer rates.

Easley, Wesley C.↗
NASA NTRS2011

UAS Modeling of the Communication Links Study Results

The Federal Aviation Administration (FAA) is the authority that grants access into, and operations within, the National Airspace System (NAS) for all aircraft, including Unmanned Aircraft Systems (UAS). The safe operation of UAS in the NAS must be assured if the full potential of UAS is to be realized and supported by the public and Congress. This report analyzed the communication systems that are needed for the safe operations of UAS in the NAS. Safe operations can be defined as the availability of the required links to carry the information to control the UAS and the return links to allow controllers to know where the UAS is at any given moment as well as how it is performing. This report is the end result of work performed jointly between the FAA and National Aeronautics and Space Administration (NASA)/Kennedy Space Center (NASA KSC). The work was done in support of the Radio Technical Commission for Aeronautics (RTCA) Special Committee 203 (SC-203) Control and Communications Working Group. The RTCA is a federal advisory committee to the FAA. Though the work was not under the direction of the working group, a large part of the specific values used in the simulations came from the working group. Specifically, all of the radio links were modeled based on the formulation completed by the working group. This report analyzed three scenarios from RTCA SC-203 that represent how a UAS would operate in the NAS. Each scenario was created using the Satellite Tool Kit (STK) modeling and simulation tool. The flight paths of the UAS were generated and the UAS dynamics were likewise modeled. Then each communication asset such as transmitters, receivers, and antennas were modeled and placed on the appropriate UAS, satellite, or Control Station (CS). After that, the radio links were analyzed for signal strength and antenna blockage, and the overall link performance was analyzed in detail. The goal was to obtain 99.9% availability on all of the radio communication links. In order to ensure the 99.9% availability, certain values for the telemetry transmitter will have to be increased slightly from I watt up to about 4 watts which is reasonable. The results of this analysis show that it is possible to send commands, during the airborne segment, to the Unmanned Aircraft (UA) and have the UA send back the system health and status with high availability of at least 99.9% of the time. This 99.9% availability included the condition of heavy rain at 90 mm/hr as well as interference from adjacent satellites. The link budget values used in this report were based on the work from the working group.

Birr, Richard B.↗
NASA NTRS1999

Wireless Augmented Reality Prototype (WARP)

Initiated in January, 1997, under NASA's Office of Life and Microgravity Sciences and Applications, the Wireless Augmented Reality Prototype (WARP) is a means to leverage recent advances in communications, displays, imaging sensors, biosensors, voice recognition and microelectronics to develop a hands-free, tetherless system capable of real-time personal display and control of computer system resources. Using WARP, an astronaut may efficiently operate and monitor any computer-controllable activity inside or outside the vehicle or station. The WARP concept is a lightweight, unobtrusive heads-up display with a wireless wearable control unit. Connectivity to the external system is achieved through a high-rate radio link from the WARP personal unit to a base station unit installed into any system PC. The radio link has been specially engineered to operate within the high- interference, high-multipath environment of a space shuttle or space station module. Through this virtual terminal, the astronaut will be able to view and manipulate imagery, text or video, using voice commands to control the terminal operations. WARP's hands-free access to computer-based instruction texts, diagrams and checklists replaces juggling manuals and clipboards, and tetherless computer system access allows free motion throughout a cabin while monitoring and operating equipment.

Devereaux, A. S.↗
NASA NTRS1977

A Depolarization and Attenuation Experiment Using the CTS and COMSTAR Satellites. Mathematical Formulations and Definitions for Dual Polarized Reception of a Wave Passing Through a Depolarizing Medium (A Polarization Primer)

The theoretical fundamentals and mathematical definitions for calculations involved with dual polarized radio links are given. Detailed derivations and results are discussed for several formulations applied to a general dual polarized radio link.

Stutzman, W. L.↗
NASA NTRS1974

Simulation study of communication link for Pioneer Saturn/Uranus atmospheric entry probe

A digital simulation is presented for a candidate modem in a modeled atmospheric scintillation environment with Doppler, Doppler rate, and signal attenuation typical of the radio link conditions for an outer planets atmospheric entry probe. The results indicate that the signal acquisition characteristics and the channel error rate are acceptable for the system requirements of the radio link. The simulation also outputs data for calculating other error statistics and a quantized symbol stream from which error correction decoding can be analyzed.

Hinrichs, C. A.↗
NASA NTRS1994

Space VLBI telecommunication characteristics, protection criteria, and frequency sharing

A brief description of the technical characteristics of space VLBI is made, emphasizing the VLBI cross-correlation process. The signal-to-noise ratio of the cross-correlation process should be maintained as large as possible for the duration of the observation. Protection of this process from unwanted interference is a primary objective. The telecommunication radio links required in a space VLBI system are identified and characterized. Maximum bandwidths are suggested, as well as the minimum carrier frequencies required for the telemetering and the phase-transfer radio links. Planned space VLBI system models-Radioastron (Russia), VLBI Space Observatory Project (VSOP) (Japan), and the DSN orbiting VLBI subnet. (United States)--are taken as a baseline to determine the interference criteria. It is concluded that existing interference criteria for near-Earth research satellites are suitable for the protection of the space VLBI systems planned.

Gutierrez-Luaces, B. O.↗
NASA NTRS1977

Radio science investigations with Voyager

Radio links to and from the Voyager spacecraft will be used for occultation measurements of planetary and satellite atmospheres and ionospheres, the rings of Saturn, the solar corona, and the general-relativistic time delay for radio wave propagation through the solar gravity field. In addition, the radio link measurements may provide information on the gravity fields of the planets, the masses of the satellites, properties of the interplanetary medium, and long-wavelength gravitational radiation propagation in the solar system.

Eshleman, V. R.↗
NASA NTRS1974

A remote operation quadrupole mass spectrometer using a custom radio-frequency link approach

A commercial quadrupole mass spectrometer (residual gas analyzer, RGA) system has been modified to operate at large separations of its electronics console and sensing head. The methods implemented have made practical applications, as well as operation, of such a system possible for the first time. This advance was stimulated by a need for placing sensors at remote (45 or 60 m) chamber locations for space simulation testing of orbital flight spacecraft. Emphasis is placed on instrument functional requirements and describing the hardware changes and adjustment techniques necessary to assure operation at the extended cable lengths.

Tashbar, P. W.↗
NASA NTRS1984

Problems relevant to town incoming radio TV links

The degradations produced on the wanted TV signal by an interfering signal are examined. The TV protection ratios to be respected are also examined in case of co-channel interference and adjacent channels. Problems related to the possible disturbances produced by the interfering signal on the AGC and the squelch of the interred receiver are also taken into account. Some solutions normally adopted for the above problems are examined, including improvement of the antenna directivity, suitable filtering, and polarization discrimination. Finally, some problems related to the propagation I urban areas for what concerns the possible distortions on a color TV signal are examined.

Tomati, L.↗
NASA NTRS2013

Unmanned Aviation Systems Models of the Radio Communications Links: Study Results - Appendices Annex 2. Volume 1 and Volume 2

This report describes the analysis of communications between the Control Station and an Unmanned Aircraft (UA) flying in the National Airspace System (NAS). This work is based on the RTCA SC-203 Operational Services and Environment Description (OSED). The OSED document seeks to characterize the highly different attributes of all UAs navigating the airspace and define their relationship to airspace users, air traffic services, and operating environments of the NAS. One goal of this report is to lead to the development of Minimum Aviation System Performance Standards for Control and Communications. This report takes the nine scenarios found in the OSED and analyzes the communication links.

Birr, Richard B.↗
NASA NTRS2012

Closed-Loop Analysis of Soft Decisions for Serial Links

Modern receivers are providing soft decision symbol synchronization as radio links are challenged to push more data and more overhead through noisier channels, and software-defined radios use error-correction techniques that approach Shannon s theoretical limit of performance. The authors describe the benefit of closed-loop measurements for a receiver when paired with a counterpart transmitter and representative channel conditions. We also describe a real-time Soft Decision Analyzer (SDA) implementation for closed-loop measurements on single- or dual- (orthogonal) channel serial data communication links. The analyzer has been used to identify, quantify, and prioritize contributors to implementation loss in real-time during the development of software defined radios.

Lansdowne, Chatwin A.↗
NASA NTRS1994

A teleoperated system for remote site characterization

The detection and characterization of buried objects and materials is an important step in the restoration of burial sites containing chemical and radioactive waste materials at Department of Energy (DOE) and Department of Defense (DOD) facilities. By performing these tasks with remotely controlled sensors, it is possible to obtain improved data quality and consistency as well as enhanced safety for on-site workers. Therefore, the DOE Office of Technology Development and the US Army Environmental Center have jointly supported the development of the Remote Characterization System (RCS). One of the main components of the RCS is a small remotely driven survey vehicle that can transport various combinations of geophysical and radiological sensors. Currently implemented sensors include ground-penetrating radar, magnetometers, an electromagnetic induction sensor, and a sodium iodide radiation detector. The survey vehicle was constructed predominantly of non-metallic materials to minimize its effect on the operation of its geophysical sensors. The system operator controls the vehicle from a remote, truck-mounted, base station. Video images are transmitted to the base station by a radio link to give the operator necessary visual information. Vehicle control commands, tracking information, and sensor data are transmitted between the survey vehicle and the base station by means of a radio ethernet link. Precise vehicle tracking coordinates are provided by a differential Global Positioning System (GPS).

Sandness, Gerald A.↗
NASA NTRS2023

Optimal Estimation Inversion of Ionospheric Electron Density from GNSS-POD Limb Measurements: Part I-Algorithm and Morphology

GNSS-LEO radio links from Precise Orbital Determination (POD) and Radio Occultation (RO) antennas have been used increasingly in characterizing the global 3D distribution and variability of ionospheric electron density (N e ). In this study, we developed an optimal estimation (OE) method to retrieve N e profiles from the slant total electron content (hTEC) measurements acquired by the GNSS-POD links at negative elevation angles (ε < 0°). Although both OE and onion-peeling (OP) methods use the Abel weighting function in the N e inversion, they are significantly different in terms of performance in the lower ionosphere. The new OE results can overcome the large N e oscillations, sometimes negative values, seen in the OP retrievals in the E-region ionosphere. In the companion paper in this Special Issue, the HmF2 and NmF2 from the OE retrieval are validated against ground-based ionosondes and radar observations, showing generally good agreements in NmF2 from all sites. Nighttime hmF2 measurements tend to agree better than the daytime when the ionosonde heights tend to be slightly lower. The OE algorithm has been applied to all GNSS-POD data acquired from the COSMIC-1 (2006–2019), COSMIC-2 (2019–present), and Spire (2019–present) constellations, showing a consistent ionospheric N e morphology. The unprecedented spatiotemporal sampling of the ionosphere from these constellations now allows a detailed analysis of the frequency–wavenumber spectra for the N e variability at different heights. In the lower ionosphere (~150 km), we found significant spectral power in DE1, DW6, DW4, SW5, and SE4 wave components, in addition to well-known DW1, SW2, and DE3 waves. In the upper ionosphere (~450 km), additional wave components are still present, including DE4, DW4, DW6, SE4, and SW4. The co-existence of eastward- and westward-propagating wave4 components implies the presence of a stationary wave4 (SPW4), as suggested by other earlier studies. Further improvements to the OE method are proposed, including a tomographic inversion technique that leverages the asymmetric sampling about the tangent point associated with GNSS-LEO links.

GNSS constellation↗
NASA NTRSDate not supplied

Global Ionospheric Electron Density from GNSS-POD Limb Measurements

GNSS-LEO radio links from Precise Orbital Determination (POD) and Radio Occultation (RO) antennas have been used increasingly in studying and monitoring the global ionospheric electron density (Ne). In this study we developed an optimal estimation (OE) method to retrieve Ne profiles from the slant total electron content (hTEC) measurements acquired by the GNSS-POD links at negative elevation angles. The hmF2 and NmF2 from the OE retrieval are validated against ground-based ionosondes and radar observations, showing generally good agreements in NmF2 from all sites. Nighttime hmF2 measurements tend to agree better than the daytime when the ionosonde heights tend to be slightly lower. The OE algorithm has been applied to all GNSS-POD data acquired from the COSMIC-1 (2006-2019), COSMIC-2 (2019-present), and Spire (2019-present) constellations, showing a consistent ionospheric Ne morphology. A detailed analysis of the frequency-wavenumber spectra is made for the Ne variability at different heights. In the lower ionosphere (~150 km) we found significant spectral power in DE1, DW6, DW4, SW5, and SE4 wave components, in addition to well-known DW1, SW2 and DE3 waves. In the upper ionosphere (~450 km), additional wave components are still present, including DE4, DW4, DW6, SE4 and SW4. The co-exist of eastward and westward propagating WN4 components implies the presence of a stationary planetary wave4 (sPW4), as suggested by other earlier studies.

GNSS-POD↗
NASA NTRS1976

Automatic electronic fish tracking system

A newly developed electronic fish tracking system to automatically monitor the movements and migratory habits of fish is reported. The system is aimed particularly at studies of effects on fish life of industrial facilities which use rivers or lakes to dump their effluents. Location of fish is acquired by means of acoustic links from the fish to underwater Listening Stations, and by radio links which relay tracking information to a shore-based Data Base. Fish over 4 inches long may be tracked over a 5 x 5 mile area. The electronic fish tracking system provides the marine scientist with electronics which permit studies that were not practical in the past and which are cost-effective compared to manual methods.

Osborne, P. W.↗
NASA NTRS1993

Spacecraft Radio Scintillation and Solar System Exploration

When a wave propagates through a turbulent medium, scattering by the random refractive index inhomogeneities can lead to a wide variety of phenomena that have been the subject of extensive study. The observed scattering effects include amplitude or intensity scintillation, phase scintillation, angular broadening, and spectral broadening, among others. In this paper, I will refer to these scattering effects collectively as scintillation. Although the most familiar example is probably the twinkling of stars (light wave intensity scintillation by turbulence in the Earth's atmosphere), scintillation has been encountered and investigated in such diverse fields as ionospheric physics, oceanography, radio astronomy, and radio and optical communications. Ever since planetary spacecraft began exploring the solar system, scintillation has appeared during the propagation of spacecraft radio signals through planetary atmospheres, planetary ionospheres, and the solar wind. Early studies of these phenomena were motivated by the potential adverse effects on communications and navigation, and on experiments that use the radio link to conduct scientific investigations. Examples of the latter are radio occultation measurements (described below) of planetary atmospheres to deduce temperature profiles, and the search for gravitational waves. However,these concerns soon gave way to the emergence of spacecraft radio scintillation as a new scientific tool for exploring small-scale dynamics in planetary atmospheres and structure in the solar wind, complementing in situ and other remote sensing spacecraft measurements, as well as scintillation measurements using natural (celestial) radio sources. The purpose of this paper is to briefly describe and review the solar system spacecraft radio scintillation observations, to summarize the salient features of wave propagation analyses employed in interpreting them, to underscore the unique remote sensing capabilities and scientific relevance of the scintillation measurements, and to highlight some of the scientific results obtained to date. Special emphasis is placed on comparing the remote sensing features of planetary and terrestrial scintillation measurements, and on contrasting spacecraft and natural radio source scintillation measurements. I will first discuss planetary atmospheres and ionospheres, and then the solar wind.

Woo, Richard↗
NASA NTRS1983

Data analysis for dual-polarized communication link experiments

The effect of the propagation medium on the performance of dual-polarized radio links operating in the microwave and millimeter wave regions is analyzed, with particular reference to rain and ice depolarization. Three methods of displaying measured cross-polarization discrimination (XPD) versus the attenuation (A) are examined: mean, median, and equiprobable. The mean and median values are shown to be essentially the same, while equiprobable data are sensitive to many errors. Ice depolarization alone or imbedded in rain depolarization can shift the entire XPD vs A relationship for equiprobable data. It is concluded that XPD vs A sets from different experiments can be compared with confidence when mean and median values are used. However, caution must be exercised with equipotential data sets, particularly when ice effects are involved.

Stutzman, W. L.↗
NASA NTRS1990

Communicating with Voyager

The Deep Space Network for receiving Voyager 2 data is discussed. The functions of the earth-Voyager radio link are examined, including radiometrics, transmission of commands to the spacecraft, radio sciences, and the transmission of telemetry from the spacecraft to earth. The use of ranging, Doppler, and VLBI measurements to maintain position and velocity data on Voyager 2 is described. Emphasis is placed on the international tracking network for obtaining Voyager 2 data on Neptune and Triton.

Dumas, Larry N.↗