Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “RADIO ANTENNA”

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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Giant Molecular Clouds and High-Mass Star Formation in the Milky Way

We are conducting an extensive investigation of high-mass (OB) star formation within the dense cores of giant molecular clouds (GMCS) throughout the first Galactic quadrant of the Milky Way using enhanced resolution Infrared Astronomical Satellite (IRAS) images in combination with high-resolution ground-based observations in millimeter wave molecular transitions and radio continuum. As part of this investigation several resolution enhancement algorithms are applied to the IRAS data, including the HIgh RESolution (HIRES) algorithm developed at the IRAS Processing and Analysis Center (IPAC), as well as others ("pixon" image reconstruction). In addition, as part of a related study, we have completed a large survey of the CO emission in the first Galactic quadrant using the 15-element array detector (QUARRY) with the Five College Radio Astronomy Observatory (FCRAO) 14 m antenna, which provides sampling at an angular resolution of 50", comparable to that attained in the reprocessed IRAS data. Both of these data sets are compared with a sample of ultra-compact (UC) H II regions taken from a high-resolution multi-wavelength (6 and 20 cm) radio survey of the Galactic plane using the NRAO Very Large Array (VLA). Selected regions are observed in 1.3 mm continuum, which has proven to be particularly sensitive to the dust column density. Extensive observations of molecular clouds at high resolution in CO, CS and HCN are combined with the reprocessed IRAS high-resolution images to give a more complete picture of the physical conditions and kinematics of high-mass star forming GMCS. Our goals are to study in detail the morphology, structure, and rate of high-mass star formation within GMCs throughout the Galactic disk from the inner edge of the molecular ring to the outer Galaxy.

Source record↗
NASA NTRS2018

Radio Science System Design and Measurement Results for the NASA Deep Space Network (DSN)

Radio science measurements have been performed using the NASA Deep Space Network (DSN) with many different spacecraft over several decades. Radio science has been used for the study of planetary atmospheres, the solar corona and the search for gravity waves, among other things. The majority of these measurements are made using the X and Ka-band deep space bands. Although the primary mission for the DSN is tracking, telemetry and command (TT&C) for NASA’s many deep-space spacecraft, radio science measurements continue to be an important secondary mission. The science requirements for these measurements have resulted in stringent performance requirements for both the spacecraft and ground system equipment. In particular, the requirements for amplitude stability, phase stability (Allen deviation) and phase noise are very demanding. The system Allen deviation requirement at Ka-band is < 2.4 E-15 over 1000 seconds, while the phase noise requirement is < -50 dBc/Hz for a 1 Hz offset. Various design techniques have been used for the DSN radio frequency (RF) electronics, high power transmitters and antenna structures to meet the stringent requirements for all 3 of these parameters. Some details for the design techniques will be described in the paper. Another important consideration for a radio science system is the verification approach for components, as well as for individual subsystems and then the overall system. Phase-locked oscillators (PLOs) are one of the key component types that determine overall phase noise and Allen deviation system performance. Measurement techniques used for PLOs, as well as for the overall ground system, will be discussed. Measurement results for the 2 new DSN antennas, recently built under the DSN Aperture Enhancement Project (DAEP) will also be shown. In addition, some recent radio science measurements from the Cassini and JUNO missions, using the new antennas, will be presented.

LaBelle, Remi C.↗
NASA NTRS1993

Storm Warning Service

A Huntsville meteorologist of Baron Services, Inc. has formed a commercial weather advisory service. Weather information is based on data from Marshall Space Flight Center (MSFC) collected from antennas in Alabama and Tennessee. Bob Baron refines and enhances MSFC's real time display software. Computer data is changed to audio data for radio transmission, received by clients through an antenna and decoded by computer for display. Using his service, clients can monitor the approach of significant storms and schedule operations accordingly. Utilities and emergency management officials are able to plot a storm's path. A recent agreement with two other companies will promote continued development and marketing.

Source record↗
NASA NTRS2011

Low-Power Architectures for Large Radio Astronomy Correlators

The architecture of a cross-correlator for a synthesis radio telescope with N greater than 1000 antennas is studied with the objective of minimizing power consumption. It is found that the optimum architecture minimizes memory operations, and this implies preference for a matrix structure over a pipeline structure and avoiding the use of memory banks as accumulation registers when sharing multiply-accumulators among baselines. A straw-man design for N = 2000 and bandwidth of 1 GHz, based on ASICs fabricated in a 90 nm CMOS process, is presented. The cross-correlator proper (excluding per-antenna processing) is estimated to consume less than 35 kW.

signal processing↗
NASA NTRS1986

OH radio observations of Comet Halley

Results of OH observations of P/Halley obtained with the NRAO 43 m antenna between July 1985 and May 1986 are presented. Using Radio Model 1986a, the OH production rate derived from these data follows an rh(-2) law for heliocentric distances in the range 0.6 to 2.1 AU. Comparison of radio OH production rates to those estimated by UV techniques continues to show that the radio technique finds systematically lower production rates. Observations of the OH line shape show that the line width increases as the comet approaches perihelion, and that the broader line widths persist after perihelion out to at least rh = 1AU. Modeling of the profiles suggest that this may be accounted for through an increase in the velocity of the OH parent. The mean velocity of the OH emission (after correction for the OH Greenstein effect) is slightly blue shifted compared to the nucleus velocity and suggests that the outgassing from the nucleus is largely directed sunward.

Schloerb, F. Peter↗
NASA NTRS1981

Antenna feed for linear and circular polarization

Antenna system ransmits linearly-polarized microwave radio signal, yet circularly-polarized incoming signal is received without polarization-mismatch losses. Network uses only hybrid junctions, diplexer, and four-probe antenna; no waveguide switches are required. Other circuit arrangements are possible, using additional transmitters and receivers.

Bathker, D. A.↗
NASA NTRS1986

Beam steering system

A simple technique for steering the beam of a multimodule phased array MST (mesosphere, stratosphere, troposphere) radar antenna is described. It is desirable to be able to point the antenna in multiple directions, so as to derive all components of the horizontal velocity. This was done on an experimental basis by adding parallel wire line to the feed and achieving a southward tilt of the antenna. It is proved possible to steer the beam through most of the available range without adversely affecting the VSWR seen from the transmitter. Calibrating the antenna direction can be accomplished by observing radio sources, though there are an inadequate number to cover all directions. For various assumed values of the aspect sensitivity in dB/deg, and the calculated antenna pattern, it is possible to calculate the effective pointing angle of the antenna, defined as that angle which would give an identical location for the centroid of the power spectrum if aspect sensitivity were absent. Using averaged apparent steering directions, eastward and northward winds were calculated for special radar runs simultaneous with 14 balloon launches at Peoria and results are presented.

Bowhill, S. A.↗
NASA NTRS1971

Economical phased-array antenna for environmental applications

Antenna system handles data acquisition and tracking, functions as a sensitive radio telescope, and serves as a radiometer in earth atmosphere investigations. Antenna's sensitivity permits resolution of solar disk quadrants in Doppler radar observations. Antenna also serves as a planetary radar device and link to commercial aircraft.

Higgins, W. T.↗
NASA NTRS1973

Radio interferometry for international study of the earthquake mechanism

Consideration of the possibility of developing an improved technique for measuring crustal deformations over distances of hundreds to thousands of kilometers to even intercontinental distances. Attention is focused on the uses of very long baseline interferometry in the structuring of a transportable radio interferometer system capable of high-accuracy three-dimensional earth surveying. In particular, the essential elements of a system called astronomical radio interferometric earth surveying are described. This system involves the use of a pair of antennas, one fixed and one portable, which simultaneously receive random radio signals emitted from an extragalactic radio source. A combination of a readily transportable small-diameter dish for use during a limited period at a remote site with a larger-diameter antenna with a better receiver is recommended.

Macdoran, P. F.↗
NASA NTRS1982

Neutral hydrogen in elliptical galaxies with nuclear radio sources and optical emission lines

An H I detection survey of eleven elliptical galaxies with powerful nuclear radio sources was conducted, using the 305 m antenna of Arecibo Observatory, to test the hypothesis that large H I mass is conductive to the formation of nuclear radio sources in elliptical galaxies. The H I was detected in emission in UGC 09114 and was possibly detected in absorption in UGC 06671. Observations of the remaining galaxies were not sensitive enough to support or refute the hypothesis. Data was combined from other H I surveys and spectroscopic surveys to search for correlations of H I mass with other galactic properties and environmental conditions. Strong correlations of (O II) lambda 3727 emission with H I content and with nuclear radio power were found. The latter two properties may simply indicate, respectively, whether a significant amount of gas is available to be ionized and whether energy is provided by nuclear activity for ionization. No dependence of H I content on optical luminosity or on degree of isolation from other galaxies was found.

Dressel, L. L.↗
NASA NTRS2000

Calibration of Atmospherically Induced Delay Fluctuations Due to Water Vapor

We have completed a new generation of water vapor radiometers (WVR), the A- series, in order to support radio science experiments with the Cassini spacecraft. These new instruments sense three frequencies in the vicinity of the 22 GHz emission line of atmospheric water vapor within a 1 degree beamwidth from a clear aperture antenna that is co-pointed with the radio telescope down to 10 degree elevation. The radiometer electronics features almost an order of magnitude improvement in temperature stability compared with earlier WVR designs. For many radio science experiments, the error budget is likely to be dominated by path delay fluctuations due to variable atmospheric water vapor along the line-of-sight to the spacecraft. In order to demonstrate the performance of these new WVRs we are attempting to calibrate the delay fluctuations as seen by a radio interferometer operating over a 21 km baseline with a WVR near each antenna. The characteristics of these new WVRs will be described and the results of our preliminary analysis will be presented indicating an accuracy of 0.2 to 0.5 mm in tracking path delay fluctuations over time scales of 10 to 10,000 seconds.

Resch, George↗
NASA NTRS1974

Solar gravitational deflection of radio waves measured by very-long-baseline interferometry

Utilizing a four-antenna technique, simultaneous observations were made, at each end of an 845-km baseline, of the radio sources 3C279 and 3C273B, which are 10 deg apart in the sky. Differences in interferometric phases at 3.7-cm wavelength monitored near the time of the 1972 occultation of 3C279 by the sun, yielded a gravitational deflection of 0.99 plus or minus 0.03 times the value predicted by general relativity, corresponding to gamma = 0.98 plus or minus 0.06 (standard error).

Counselman, C. C., III↗
NASA NTRS1978

Extraterrestrial intelligence - An observational approach

The article surveys present and proposed search techniques for extraterrestrial intelligence in terms of technological requirements. It is proposed that computer systems used along with existing antennas may be utilized to search for radio signals over a broad frequency range. A general search within the electromagnetic spectrum would explore frequency, received power flux, spatial locations, and modulation. Previous SETI projects (beginning in 1960) are briefly described. An observation project is proposed in which the earth's rotational motion would scan the antenna beam along one declination circle in 24 hours. The 15 degree beam width would yield a mapping of 75% of the sky in an 8-day period if the beam were shifted 15 degrees per day. With the proposed instrument parameters, a sensitivity of about 10 to the -21 watt/sq m is achieved at a 0 degree declination and 1.5 GHz. In a second phase, a 26 m antenna would yield an HPBW of 0.8 degrees at 1 GHz and 0.03 degrees at 25 GHz. It is noted that the described technology would provide secondary benefits for radio astronomy, radio communications, and other fields.

Murray, B.↗
DOE OSTI2021

A High Gain Lens-Coupled On-Chip Antenna Module for Miniature-Sized Millimeter-Wave Wireless Transceivers

This paper presents high gain and compact Transmit/Receive (TX/RX) integrated antennas in a standard BiCMOS 130nm technology for millimeter-scale millimeter-wave (mm-wave) applications, including high data rate radios and high resolution radars. The proposed TX/RX antenna module utilizes an integrated dipole antenna for the receiver and a slot antenna for the transmitter, placed orthogonally. The achieved gain and radiation efficiency are 5.7dBi and 41.3% for the slot antenna, respectively, and 6dBi and 39% for the dipole antenna. The link budget is improved by 16dB by optimization on the geometry aswell as application of a high resistivity hemispheric silicon dielectric lens.

Engineering↗
NASA NTRS1982

An electric noise component with density 1/f identified on ISEE 3

The properties of the 1/f noise detected at the terminals of ISEE 3 antennas are described and related to the solar wind parameters. The 1/f noise was observed with the radio receivers of the three-dimensional radio mapping experiment using the S and Z dipole antennas. The noise spectra contained a negative spectral index component at frequencies lower than 0.7 of the plasma frequency, and 5-10 times the predicted thermal noise for the Z antenna. S-antenna measurements of the 1/f component revealed it to be deeply spin modulated with a minimum electric field in the direction of the solar wind. Modulation increases with increasing frequency, becomes negligible when the 1/f intensity is negligible with respect to the thermal noise, and increases with solar wind velocity. The possibilities that the noise is due either to waves or currents are discussed.

Hoang, S.↗
NASA NTRS1982

HF produced ionospheric electron density irregularities diagnosed by UHF radio star scintillations

Three observations of radio star intensity fluctuations at UHF are reported for HF ionospheric modification experiments carried out at the Arecibo Observatory. Two observations at 430 MHz and one at 1400 MHz suggest that the the thin phase screen theory is a good approximation to the observed power spectra. It is noted, however, that the theory has to be extended to include antenna filtering. This type of filtering is important for UHF radio star scintillations since the antenna usually has a narrow beamwidth. HF power densities of less than 37 microwatts/sq m incident on the ionosphere give rise to electron density irregularities larger than 13% of the ambient density (at 260 km) having scale sizes of approximately 510 m perpendicular to the geomagnetic field. The irregularities are found to form within 20-25 s after the HF power is turned on. The drift velocities of the irregularities can be estimated from the observed power spectra.

Frey, A.↗