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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Radar derived spatial statistics of summer rain. Volume 1: Experiment description

An experiment was performed at Wallops Island, Virginia, to obtain a statistical description of summer rainstorms. Its purpose was to obtain information needed for design of earth and space communications systems in which precipitation in the earth's atmosphere scatters or attenuates the radio signal. Rainstorms were monitored with the high resolution SPANDAR radar and the 3-dimensional structures of the storms were recorded on digital tape. The equipment, the experiment, and tabulated data obtained during the experiment are described.

Katz, I.↗
NASA NTRS1991

STS-37 Space Shuttle mission report

The STS-37 Space Shuttle Program Mission Report contains a summary of the vehicle subsystem activities during this thirty-ninth flight of the Space Shuttle and the eighth flight of the Orbiter Vehicle Atlantis (OV-104). In addition to the Atlantis vehicle, the flight vehicle consisted of the following: an External Tank (ET) (designated as ET-37/LWT-30); three Space Shuttle main engines (SSME's) (serial numbers 2019, 2031, and 2107 in positions 1, 2, and 3, respectively); and two Solid Rocket Boosters (SRB's) designated as BI-042. The primary objective of this flight was to successfully deploy the Gamma Ray Observatory (GRO) payload. The secondary objectives were to successfully perform all operations necessary to support the requirements of the Protein Crystal Growth (PCG) Block 2 version, Radiation Monitoring Experiment-3 (RME-3), Ascent Particle Monitor (APM), Shuttle Amateur Radio Experiment-2 (SAREX-2), Air Force Maui Optical Site Calibration Test (AMOS), Bioserve Instrumentation Technology Associates Materials Dispersion Apparatus (BIMDA), and the Crew and Equipment Transfer Aids (CETA) payloads.

Fricke, Robert W.↗
NASA NTRS2005

Stability-Augmentation Devices for Miniature Aircraft

Non-aerodynamic mechanical devices are under consideration as means to augment the stability of miniature autonomous and remotely controlled aircraft. Such aircraft can be used for diverse purposes, including military reconnaissance, radio communications, and safety-related monitoring of wide areas. The need for stability-augmentation devices arises because adverse meteorological conditions generally affect smaller aircraft more strongly than they affect larger aircraft: Miniature aircraft often become uncontrollable under conditions that would not be considered severe enough to warrant grounding of larger aircraft. The need for the stability-augmentation devices to be non-aerodynamic arises because there is no known way to create controlled aerodynamic forces sufficient to counteract the uncontrollable meteorological forces on miniature aircraft. A stability-augmentation device of the type under consideration includes a mass pod (a counterweight) at the outer end of a telescoping shaft, plus associated equipment to support the operation of the aircraft. The telescoping shaft and mass pod are stowed in the rear of the aircraft. When deployed, they extend below the aircraft. Optionally, an antenna for radio communication can be integrated into the shaft. At the time of writing this article, the deployment of the telescoping shaft and mass pod was characterized as passive and automatic, but information about the deployment mechanism(s) was not available. The feasibility of this stability-augmentation concept was demonstrated in flights of hand-launched prototype aircraft.

Wood, RIchard M.↗
NASA NTRS2005

Space Shuttle and Space Station Radio Frequency (RF) Exposure Analysis

This paper outlines the modeling techniques and important parameters to define a rigorous but practical procedure that can verify the compliance of RF exposure to the NASA standards for astronauts and electronic equipment. The electromagnetic modeling techniques are applied to analyze RF exposure in Space Shuttle and Space Station environments with reasonable computing time and resources. The modeling techniques are capable of taking into account the field interactions with Space Shuttle and Space Station structures. The obtained results illustrate the multipath effects due to the presence of the space vehicle structures. It's necessary to include the field interactions with the space vehicle in the analysis for an accurate assessment of the RF exposure. Based on the obtained results, the RF keep out zones are identified for appropriate operational scenarios, flight rules and necessary RF transmitter constraints to ensure a safe operating environment and mission success.

Hwu, Shian U.↗
NASA NTRS1985

Storm severity detection (RF)

Atmospheric electrical emissions occurring in association with Hurricane Alicia were observed by two crossed baseline phase linear interferometers. The sensors were located in San Antonio, Texas, and at Marshall Space Flight Center (MSFC), Huntsville, Alabama. An analysis of the data has indicated that the direction finding (DF) performance of the San Antonio site was extremely good while the DF performance at the MSFC site evidenced erratic behavior. A check of the data acquisition hardware revealed an intermitted problem in one of the radio receiver channels. Since the system has experienced several lightning strikes during the early spring of 1984, it was necessary to ship the entire rack of equipment back to SwRI for refurbishment. Analysis of the DF data from the interferometer site at San Antonio is being done. A limited subset of the MSFC data acquired during Hurricane Alicia has been found to be valid. These were data which satisfied the phase linearity criteria. Approximately 2,000 location estimates have been produced on the valid data. The results of the DF analysis and the location data are being correlated with the McIDAS data base at Marshall Space Flight Center, and with the radar summary data provided by the Hurricane Research Division using the National weather Service radar Facility at Galveston, Texas.

Johnson, R. L.↗
NASA NTRS1988

Space Shuttle Main Engine radio frequency emissions

Several approaches to develop a diagnostics system for monitoring the operational health of the Space Shuttle Main Engine (SSME) are being evaluated. The ultimate goal is providing protection for the SSME as well as improving ground and flight test techniques. One scenario with some potential is measuring radio frequency (RF) emissions (if present) in the exhaust plume and correlating the data to engine health. An RF emissions detection system was therefore designed, the equipment leased, and the components integrated and checked out to conduct a quick-look investigation of RF emissions in the SSME exhaust plume. The system was installed on the A-1 Test Stand at Stennis Space Center, MS, and data were successfully acquired during SSME firings from May 3 to September 15, 1988. The experiments indicated that emitted radiation in the RF (20 to 470 MHz) spectrum definitely exists in the SSME exhaust plume, and is of such magnitude that it can be distinguished during the firing from background noise. Although additional efforts are necessary to assess the merit of this approach as a health monitoring technique, the potential is significant, and additional studies are recommended.

Rester, A. W.↗
DOE OSTI2022

Additively Manufactured Tamper Evident Container (TEC)

The protection of sensitive data, proprietary information, and physical assets from adversarial disclosure is a high priority in today’s environment of government and industrial espionage. Furthermore, knowledge of the security history and monitoring for potential acquisition or disclosure of the protected assets from oppositional sources is equally important. In 2016, as part of an LANL Institute for Materials Science (IMS) rapid response research initiative, the investigators of this technology demonstration project developed the concept of an additively manufactured tamper resistant container that possessed tamper evident features. Tamper evident seals and detection technologies have a long history in protecting consumers from product tampering, recording the installation and activation of mechanical safety panels and fasteners on dangerous electro-mechanical systems, and serving as a warranty void indicator on expensive electronic equipment. Examples of such tamper evident seals range from “no-tech” versions, e.g., the paper seals under medicine caps, to “high-tech” seals that are radio frequency-active and include encryption capabilities used by the International Atomic Energy Agency (IAEA) to monitor stored nuclear materials in support of safeguards missions. The tamper evident container (TEC) technology would have many uses.

36 MATERIALS SCIENCE↗
NASA NTRS1983

Mobile radio alternative systems study. Volume 2: Terrestrial

Terrestrial systems for satisfying the markets for mobile radio services in non-urban areas of the United States in the years from 185 to 2000 were investigated. Present day mobile communication technologies, systems and equipment are described for background in evaluating the concepts generated. Average propagation ranges are calculated for terrestrial installations in each of seven physiographic areas of the contiguous states to determine the number of installations that would be required for nationwide coverage. Four system concepts are defined and analyzed to determine how well terrestrial systems can fulfill the requirements at acceptable costs. Nationwide dispatch, telephone and data services would require terrestrial installations in many locations where they would be used infrequently and would not recover their investment. Access to a roaming vehicle requires that the vehicle location be known within the range limit of the terrestrial installation in which the vehicle is present at the time of the call. Access to that installation must be made through the public switched telephone network, usually involving a long-distance toll charge, and requiring costly means to track or locate the vehicle as it moved through the network of installations.

Cromwell, N.↗
NASA NTRS2000

Satellite Broadcast of Graphical Weather Data Flight Tested

NASA Glenn Research Center at Lewis Field's aviation Weather Information Communications (WINCOMM) and NASA Langley Research Center's Aviation Weather Information (AWIN) programs collaborated in a flight test and evaluation of a worldwide weather data-link capability using satellites. This successful flight testing moves NASA closer to its goal of developing advanced communications and information technologies to enable high-quality and timely dissemination of aviation weather information to all relevant users on the aviation information network. Recognized as a major contributing factor in aviation accidents and incidents, weather contributes directly or indirectly to nearly 80 percent of fatal general aviation (small private aircraft) accidents. In 1997, the Aeronautics Safety Investment Strategy Team s weather team produced a prioritized list of investment areas under weather accident prevention. Weather data dissemination is the most critical and highest ranked priority on the list. NASA's Aviation Safety Program founded the Aviation Weather Information initiative to focus efforts on significantly reducing the number of weather-related aviation fatalities. Access to accurate and timely weather data could contribute to a major reduction of weather-related incidents and accidents. However, a cost-effective solution has eluded most general aviation pilots because of the high cost of onboard weather radar equipment. Rockwell Collins, through a contract with NASA and in cooperation with WorldSpace Corporation, successfully completed ground and flight testing of a receiver and antenna in Johannesburg, South Africa. This NASA/Rockwell Collins project is an evaluation of worldwide weather data-link capability using transmissions from the Satellite Digital Audio Radio Services (S DARS) AfriStar satellite. Owned and operated by WorldSpace, AfriStar is a geostationary satellite that broadcasts commercial digital audio services to stationary and mobile platforms. S DARS satellites are the most powerful communications satellites produced to date, allowing users to receive signals using simple, low-cost patch antennas instead of more expensive, beam-steered antenna arrays. Engineers connected an inexpensive, commercially available radio receiver to a laptop computer and an antenna designed and built by Rockwell Collins, enabling them to receive WorldSpace signals from the AfriStar satellite during flight tests. WorldSpace broadcast their composite color graphical weather data files, which were multiplexed with normal audio streams, to the flat patch antenna mounted on a single-engine aircraft. The aircraft was equipped with a modified commercial S-DARS receiver, a Global Positioning Satellite (GPS) receiver, and a laptop computer with color display. Continuous data reception occurred during normal aircraft maneuvers performed throughout takeoff, cruise, and landing operations. In addition, engineers monitored receiver power levels during steep turns and banks. In most instances, the receiver was able to maintain acceptable power levels during all phases of flight and to obtain weather data with little or with the successful completion of ground and flight testing of a receiver and antenna in Johannesburg, South Africa, the team has started to prepare for experiments using highspeed aircraft in areas of the world with limited access to timely weather data. NASA plans to provide a more advanced antenna design and consultation support. This successful test of real-time aviation-related weather data is a positive step toward solving communications-specific issues associated with the dissemination of weather data directly to the cockpit.

Mallasch, Paul G.↗
NASA NTRS1981

Modular reflector concept study

A study was conducted to evaluate the feasibility of space erecting a 100 meter paraboloidal radio frequency reflector by joining a number of individually deployed structural modules. Three module design concepts were considered: (1) the deployable cell module (DCM); (2) the modular paraboloidal erectable truss antenna (Mod-PETA); and (3) the modular erectable truss antenna (META). With the space shuttle (STS) as the launch system, the methodology of packaging and stowing in the orbiter, and of dispensing, deploying and joining, in orbit, were studied and the necessary support equipment identified. The structural performance of the completed reflectors was evaluated and their overall operational capability and feasibility were evaluated and compared. The potential of the three concepts to maintain stable shape in the space environment was determined. Their ability to operate at radio frequencies of 1 GHz and higher was assessed assuming the reflector surface to consist of a number of flat, hexagonal facets. A parametric study was performed to determine figure degradation as a function of reflector size, flat facet size, and f/D ratio.

Vaughan, D. H.↗
DOE OSTI2021

EMR Analysis of Vaguely Defined Commercial Systems Re: EMR Analysis of Motorola Handheld Radios APX 7000 and APX 8000 with VHF and UHF bands

Modern manufacturing requires the use of many Commercial Off-The Shelf (COTS) tools and systems on the production floor. Wireless communications is prevalent in modern COTS devices. COTS equipment come with little information regarding what EXACTLY is in the equipment. Many vendors do not even have data for what is in their equipment – built to spec. Our industry has unique requirements and very few vendors design to meet our needs.

99 GENERAL AND MISCELLANEOUS↗
NASA NTRS1973

Stanford bistatic radar experiment (S-170) on Apollos 14, 15, and 16

No special equipment was placed onboard the vehicles for the bistatic radar experiments which were carried out during the lunar orbit phases of the Apollo 14, 15, and 16 flights. Radio frequency transmissions from the orbiting command service module were directed toward the moon and received on the earth after reflection from the lunar surface. Two wavelengths, 13 cm (2287.5 MHz, S-band) and 116 cm (259.7 MHz, VHF), were used. Data were obtained at the two wavelengths simultaneously during periods when the spacecraft was maneuvered to maintain a predetermined, although changing, attitude with respect to the earth and moon. Data were also obtained at the 116 cm wavelength during periods of inertial hold and SIM bay attitude maneuvers.

Howard, H. T.↗
NASA NTRS1976

Satellites for distress alerting and locating: Report by Interagency Committee for Search and Rescue Ad Hoc Working Group

The background behind the congressional legislation that led to the requirement for the Emergency Locator Transmitter (ELT) and the Emergency Position-Indicating Radio Beacon (EPIRB) to be installed on certain types of aircraft and inspected marine vessels respectively is discussed. The DAL problem is discussed for existing ELT and EPIRB equipped aircraft and ships. It is recognized that the DAL requirement for CONUS and Alaska and the maritime regions are not identical. In order to address the serious DAL problem which currently exists in CONUS and Alaska, a low orbiting satellite system evolves as the most viable and cost effective alternative that satisfies the overall SAR system design requirements. A satellite system designed to meet the needs of the maritime regions could be either low orbiting or geostationary. The conclusions drawn from this report support the recommendation to proceed with the implementation of a SAR orbiting satellite system.

Ehrlich, E.↗
NASA NTRS1979

Current results and developments in astrometric VLBI at the Jet Propulsion Laboratory

The Jet Propulsion Laboratory's program of astrometric VLBI as one element of a navigation system for interplanetary spacecraft includes developing a radioastrometric source catalog, and a catalog of positions of compact extragalactic radio sources correct to about 0.01 arc sec. The three (64 m) antenna complexes of the Deep Space Network in Spain, Australia, and the U.S. are involved, each equipped to receive simultaneously at wavelengths of 13 and 3.6 cm with total system temperatures of about 20-25 K at both wavelengths. The program is to provide precise values of parameters used in navigational computations, including UT1 accurate to about 0.001s, and current values of polar motion to 30 cm. Bandwidth synthesis methods were applied to measure delays as well as rates regarding source positions derived from observations using the Mark II VLBI recording system which has a sampling rate of four million bits per second.

Purcell, G. H., Jr.↗
NASA NTRS1980

Heart rate, multiple body temperature, long-range and long-life telemetry system for free-ranging animals

The design details and rationale for a versatile, long-range, long-life telemetry data acquisition system for heart rates and body temperatures at multiple locations from free-ranging animals are presented. The design comprises an implantable transmitter for short to medium range transmission, a receiver retransmitter collar to be worn for long-range transmission, and a signal conditioner interface circuit to assist in signal discrimination and demodulation of receiver or tape-recorded audio outputs. Implanted electrodes are used to obtain an ECG, from which R-wave characteristics are selected to trigger a short RF pulse. Pulses carrying heart rate information are interrupted periodically by a series of pulse interval modulated RF pulses conveying temperature information sensed at desired locations by thermistors. Pulse duration and pulse sequencing are used to discriminate between heart rate and temperature pulses as well as radio frequency interference. The implanted transmitter may be used alone for medium and short-range tracking, or with a receiver-transmitter collar that employs commercial tracking equipment for transmissions of up to 12 km. A system prototype has been tested on a dog.

Lund, G. F.↗
NASA NTRS1995

Electromagnetic compatibility and the all-electric airplane

NASA is studying the feasibility of installing 'all-electric' controls in future commercial aircraft, replacing the current hydraulic and pneumatic systems. Planes utilizing such equipment should weigh less and be cheaper to maintain, but might also be susceptible to interference from undesired external electromagnetic fields. Possible sources of these extraneous signals include radio and television broadcasters, two-way communications stations, and radar installations of all kinds. One way to reduce the hazard would be to use fiber-optic cables to carry signals from the cockpit to the various points of use, a concept known as 'fly-by-light' or FBL. However, electrical circuits (PBW, or 'power-by-wire') would still be required at both ends of the cables to perform control functions, so the possibility of harmful interference would remain. Computer models for two different antennas were created in order to find the magnitude of the electric fields which would be generated in the airspace around them while in the transmit mode. The first antenna was a horizontal 'rhombic' used by the Voice of America (VOA) for long-distance short-wave broadcasting. The second antenna was a multi-element 'log-periodic dipole array' (LPDA) of a type often used for two-way radio communications. For each case, a specified amount of power was applied in the computer model, and the resulting electric field intensity was predicted at a variety of locations surrounding the antenna. This information will then be used to calculate the levels of interference which could occur inside an airplane flying in the vicinity of these radiation emitters.

Christman, Al↗
NASA NTRS1978

The radio telescope RATAN 600

A six-meter radio antenna having 900 reflector elements arranged on a 579 -meter diameter circle and located in the northern part of the Caucasian Mountains is described. The elements are about 7.4 m by 2 m resulting in a total reflector surface of about 10,000 sq m. Individual elements can be adjusted by changing 260 screws and can be rotated both horizontally and vertically as well as being moved translationally in the radial direction. The circular area is equipped with a grid of tracks where four asymmetric cylindrical paraboloids serving as subreflectors are located. The directional profile or observational direction of the antenna is achieved by shifting the subreflectors and changing the position of the reflecting elements with respect to the subreflectors. Different radio sources can be observed at the same time by using different subreflectors and their associated reflector sectors. Each subreflector is connected to a receiving station. Capabilities for spectroscopic observation are discussed.

Schwartz, R.↗