Search NASA⌕ Search

SEARCH · Search NASA

Results for “two-way”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Starprobe - Coronal plasma turbulence effects on tracking and telemetry

The telemetry and tracking problems expected for Starprobe, a solar flyby with a perihelion of 4 solar radii, are discussed. The Starprobe is intended to obtain measurements of the solar quadrupole moment within an accuracy of 1/100,000,000, allowing more accurate modelling of the solar interior. Obstacles are perceived for Doppler velocity measurements due to RF signal amplitude and phase scintillations created by the solar corona. Model calculations are presented for the propagation effects in the maximum disturbance area, and an open loop two-way Doppler system is described. The system comprises X-band and S-band uplinks and downlinks to eliminate the plasma-induced phase scintillations, means of correcting unfolding errors caused by S-band amplitude scintillations, and a new method of estimating the Doppler frequency.

Armstrong, J. W.↗
NASA NTRS1982

Performance of differenced range data types in Voyager navigation

Voyager radio navigation made use of differenced range data type for both Saturn encounters because of the low declination singularity of Doppler data. Nearly simultaneous two-way range from two-station baselines was explicitly differenced to produce this data type. Concurrently, a differential VLBI data type (DDOR), utilizing doubly differenced quasar-spacecraft delays, with potentially higher precision was demonstrated. Performance of these data types is investigated on the Jupiter to Saturn leg of Voyager 2. The statistics of performance are presented in terms of actual data noise comparisons and sample orbit estimates. Use of DDOR as a primary data type for navigation to Uranus is discussed.

Taylor, T. H.↗
NASA NTRS1982

Performance of differenced range data types in Voyager navigation

Voyager radio navigation made use of a differenced rage data type for both Saturn encounters because of the low declination singularity of Doppler data. Nearly simultaneous two-way range from two-station baselines was explicitly differenced to produce this data type. Concurrently, a differential VLBI data type (DDOR), utilizing doubly differenced quasar-spacecraft delays, with potentially higher precision was demonstrated. Performance of these data types is investigated on the Jupiter-to-Saturn leg of Voyager 2. The statistics of performance are presented in terms of actual data noise comparisons and sample orbit estimates. Use of DDOR as a primary data type for navigation to Uranus is discussed.

Taylor, T. H.↗
NASA NTRS1982

FORTRAN implementation of Friedman's test for several related samples

The FRIEDMAN program is a FORTRAN-coded implementation of Friedman's nonparametric test for several related samples with one observation per treatment/-block combination, or as it is sometimes called, the two-way analysis of variance by ranks. The FRIEDMAN program is described and a test data set and its results are presented to aid potential users of this program.

Davidson, S. A.↗
NASA NTRS1982

Spacecraft radio frequency subsystem

The historical background for the development of the planetary (RFS) is reviewed, and the performance capabilities of the various functional subassemblies are described. The flight radio frequency subsystem is a valid component for the three spacecraft telecommunications functions of tracking, command, and telemetry. It is the radio and the signal processing equipment residing in the spacecraft that interfaces with the control & data subsystem and performs two-way communications with the Earth-based Deep Space Network. The RFS consists of all the elements for RF reception, demodulation, modulation, and transmission, including those for command detection and telemetry modulation.

Tam, M. K.↗
NASA NTRS1983

Calculations of radar backscattering coefficient of vegetation-covered soils

A model for simulating the measured backscattering coefficient of vegetation-covered soil surfaces includes both coherent and incoherent components of the backscattered radar pulses from a rough sil surface. The effect of vegetation canopy scattering is also incorporated into the model by making the radar pulse subject to two-way attenuation and volume scattering when it passes through the vegetation layer. Model results agree well with the measured angular distributions of the radar backscattering coefficient for HH polarization at the 1.6 GHz and 4.75 GHz frequencies over grass-covered fields. It was found that the coherent scattering component is very important at angles near nadir, while the vegetation volume scattering is dominant at incident angles 30 degrees.

Mo, T.↗
NASA NTRS1983

Deep Space Navigation with Noncoherent Tracking Data

Navigation capabilities of noncoherent tracking data are evaluated for interplanetary cruise phase and planetary (Venus) flyby orbit determination. Results of a formal covariance analysis are presented which show that a combination of one-way Doppler and delta DOR yields orbit accuracies comparable to conventional two-way Doppler tracking. For the interplanetary cruise phase, a tracking cycle consisting of a 3-hour Doppler pass and delta DOR (differential one-way range) from two baselines (one observation per overlap) acquired 3 times a month results in 100-km orbit determination accuracy. For reconstruction of a Venus flyby orbit, 10 days tracking at encounter consisting of continuous one-way Doppler and delta DOR sampled at one observation per overlap is sufficient to satisfy the accuracy requirements.

Ellis, J.↗
NASA NTRS1983

Time transfer between the Goddard Optical Research Facility and the U.S. Naval Observatory using 100 picosecond laser pulses

A horizontal two-way time comparison link in air between the University of Maryland laser ranging and time transfer equipment at the Goddard Optical Research Facility (GORF) 1.2 m telescope and the Time Services Division of the U.S. Naval Observatory (USNO) was established. Flat mirrors of 25 cm and 30 cm diameter respectively were placed on top of the Washington Cathedral and on a water tower at the Beltsville Agricultural Research Center. Two optical corner reflectors at the USNO reflect the laser pulses back to the GORF. Light pulses of 100 ps duration and an energy of several hundred microjoules are sent at the rate of 10 pulses per second. The detection at the USNO is by means of an RCA C30902E avalanche photodiode and the timing is accomplished by an HP 5370A computing counter and an HP 1000 computer with respect to a 10 pps pulse train from the Master Clock.

Alley, C. O.↗
NASA NTRS1982

The effects of rain on system performance for the NASA 30/20 GHz Experimental Satellite

A 30/20 GHz Experimental Communications Satellite System is presently under study by NASA to evaluate system technology and high data rate multi-beam communications techniques. In this paper the expected system performance for the 30/20 GHz Satellite is presented, for both trunking and customer premise service (CPS) modes, with particular emphasis on the effects of severe rain events on link reliability. A rain attenuation prediction model technique is described and path and two-way link availabilities are developed for the various modes of operation. The results indicate that acceptable link availabilities can be expected on the 30/20 GHz system for both the trunking and CPS modes, and the experimental satellite system can form the basis for verification of system performance for operational 30/20 GHz systems.

Ippolito, L. J.↗
NASA NTRS1983

Deep space optical communications experiment

An optical communications experiment between a deep space vehicle and an earth terminal is under consideration for later in this decade. The experimental link would be incoherent (direct detection) and would employ two-way cooperative pointing. The deep space optical transceiver would ride piggyback on a spacecraft with an independent scientific objective. Thus, this optical transceiver is being designed for minimum spacecraft impact - specifically, low mass and low power. The choices of laser transmitter, coding/modulation scheme, and pointing mechanization are discussed. A representative telemetry link budget is presented.

Kinman, P.↗
NASA NTRS1961

Participation of Bell Telephone Laboratories in Project Echo and Experimental Results

On August 12, 1960, Echo I, a 100-foot-diameter spherical balloon, was placed in orbit around the earth by the National Aeronautics and Space Administration. The objective was to demonstrate the feasibility of long-distance communication by microwave reflection from a satellite. A two-way coast-to-coast voice circuit was to be established between the Jet Propulsion Laboratory (JPL) facility in California and a station provided by Bell Telephone Laboratories (STL) in New Jersey. Similar tests were also planned with the Naval Research Laboratory and other stations. This paper describes the general organization and operation of the Holmdel, New Jersey, station, and discusses the results of the experiments performed between the balloon launching and March 1, 1961. Successful voice communication was achieved through a variety of modulation methods including frequency modulation with feedback, amplitude modulation, single-sideband modulation, and narrow-band phase modulation. Careful measurements were also made of the loss in the transmission path.

Jakes, William C., Jr.↗
NASA NTRS1979

Automatic Fault Protection in the Voyager Spacecraft

Due to reliability requirements placed on the Voyager spacecraft system design and a mission resulting in long two-way, light time communication links, on-board automatic fault detection and correction capabilities are a significant feature of that spacecraft's design. Most of the protection to otherwise mission-catastrophic failures is implemented in the software of the voyager's central computer, while some resides in an attitude control-dedicated processor. This paper will present the role that automatic fault protection plans in achieving Voyager's overall reliability, its design evolution, and how its design was validated during system testing. In-flight experience will also be described, and from the lessons learned there-in, conclusions and recommendations will be drawn for the benefit of future designs.

Jones, C. P.↗
NASA NTRS1982

Water Quality Monitor

An automated water quality monitoring system was developed by Langley Research Center to meet a need of the Environmental Protection Agency (EPA). Designed for unattended operation in water depths up to 100 feet, the system consists of a subsurface buoy anchored in the water, a surface control unit (SCU) and a hydrophone link for acoustic communication between buoy and SCU. Primary functional unit is the subsurface buoy. It incorporates 16 cells for water sampling, plus sensors for eight water quality measurements. Buoy contains all the electronic equipment needed for collecting and storing sensor data, including a microcomputer and a memory unit. Power for the electronics is supplied by a rechargeable nickel cadmium battery that is designed to operate for about two weeks. Through hydrophone link the subsurface buoy reports its data to the SCU, which relays it to land stations. Link allows two-way communications. If system encounters a problem, it automatically shuts down and sends alert signal. Sequence of commands sent via hydrophone link causes buoy to release from anchor and float to the surface for recovery.

Source record↗
NASA NTRS1981

Space Derived Health Aids (Cardiac Pacemaker)

St. Jude Medical's Cardiac Rhythm Management Division's (formerly known as Pacesetter Systems, Inc.) pacer is a rechargeable cardiac pacemaker that eliminates the recurring need for surgery to implant a new battery. The Programalith is an advanced cardiac pacing system which permits a physician to reprogram a patient's implanted pacemaker without surgery. System consists of a pacemaker, together with a physician's console containing the programmer and a data printer. Signals are transmitted by wireless telemetry. Two-way communications, originating from spacecraft electrical power systems technology, allows physician to interrogate the pacemaker as to the status of the heart, then to fine tune the device to best suit the patient's needs.

Source record↗
NASA NTRS1976

Firefighters' Radios

Public Technology Inc. asked for NASA assistance to devise the original firefighter's radio. Good short-range radio communications are essential during a fire to coordinate hose lines, rescue victims, and otherwise increase efficiency. Useful firefighting tool is lower cost, more rugged short range two-way radio. Inductorless electronic circuit replaced inductances and coils in radio circuits with combination of transistors and other low-cost components. Substitution promises reduced circuit size and cost. Enhanced electrical performance made radio more durable and improved maintainability by incorporating modular construction.

Source record↗
NASA NTRS1978

Heart Monitoring By Satellite

The ambulance antenna shown is a specially designed system that allows satellite-relayed two-way communications between a moving emergency vehicle and a hospital emergency room. It is a key component of a demonstration program aimed at showing how emergency medical service can be provided to people in remote rural areas. Satellite communication permits immediate, hospital- guided treatment of heart attacks or other emergencies by ambulance personnel, saving vital time when the scene of the emergency is remote from the hospital. If widely adopted, the system could save tens of thousands of lives annually in the U.S. alone, medical experts say. The problem in conventional communication with rural areas is the fact that radio signals travel in line of sight. They may be blocked by tall buildings, hills and mountains, or even by the curvature of the Earth, so signal range is sharply limited. Microwave relay towers could solve the problem, but a complete network of repeater towers would be extremely expensive. The satellite provides an obstruction-free relay station in space.

Source record↗
NASA NTRS1978

Infant Transport Monitoring

The photo sequence illustrates the movement of an ill infant to a special care hospital by means of a new Pediatric Monitoring and Transport System, in which NASA technology and technical assistance are being applied to an urgent medical problem. Development of the system is a collaborative effort involving several organizations, principally, NASA Ames Research Center and Children's Hospital Medical Center, Oakland, California. Key to the system's efficacy is a custom-designed ambulance-to-hospital and hospital-to-hospital communications network, including two-way voice capability and space-derived biotelemetry; it allows a specialist at the destination hospital to monitor continuously the vital signs of the patient during transit.

Source record↗
NASA NTRS1977

Sports and Recreation

Among a number of solar energy tests being jointly conducted by NASA's Lewis Research Center and the Energy Research and Development Administration are a sun-powered refrigerator and a back-pack mounted power supply for radios. Both use solar cells, spacecraft power sources which convert sun energy into electricity. The refrigerator, which has potential utility for outdoor campers, is in operation at a trail construction camp in Isle Royale National Park, a remote wilderness in Michigan's Lake Superior where electricity is available only at park headquarters. Trail maintenance crews working in the back country get food supplies only once weekly; with refrigeration they can enjoy a more varied and nutritious diet. Solar cells provide power to run the refrigerator and to charge its batteries for an alternate power supply when sun is not available. At the request of Znyo National Forest personnel NASA-Lewis also developed a back-pack system. The lightweight solar cell pack (on the pack strap in photo) charges batteries for portable two-way radios used by trailguards, who are on patrol for as much as two weeks at a time. Guards want continuous communication with the District Station, but battery capacity precludes such operation. With the solar cell power supply, guards can use their radios 24 hours a day.A lightweight, higher-capacity oxygen bottle-derived from rocket propellant tank technology-proved an important aid in the 1976 ascent to the summit of Mt. Everest by members of the. American Bicentennial Everest Expedition.

Source record↗