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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Millimeter-wave studies of the surfaces of Mercury and Mars and the atmosphere of Venus

Disk average brightness temperatures of Mercury were obtained using a 4.6 m radio telescopes. The data was searched for periodicities which correlate with phase angle, hermocentric longitude and beat frequencies produced by modulations of various celestial mechanical parameters. Spectral line observations were made of Venus with the NRAO 11 m radio telescope. The total CO content and the CO vertical profile, and their variability were observed. Large scale thermophysical properties of the surface of Mars were studied.

Epstein, E. E.↗
DOE OSTI2024

The Most Distant H i Galaxies Discovered by the 500 m Dish FAST

Abstract Neutral hydrogen (Hi) is the primary component of the cool interstellar medium (ISM) and is the reservoir of fuel for star formation. Owing to the sensitivity of existing radio telescopes, our understanding of the evolution of the ISM in galaxies remains limited, as it is based on only a few hundred galaxies detected in Hibeyond the local Universe. With the high sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we carried out a blind Hisearch, the FAST Ultra-Deep Survey, which extends to redshifts up to 0.42 and a sensitivity of 50μJy beam −1 . Here, we report the first discovery of six galaxies in Hi atz> 0.38. For these galaxies, the FAST angular resolution of ∼4′ corresponds to a mean linear size of ∼ 1.3 h 70 − 1 Mpc. These galaxies are among the most distant Hiemission detections known, with one having the most massive Hicontent ( 10 10.93 ± 0.04 h 70 − 2 M ⊙ ). Using recent data from the DESI survey and new observations with the Hale, Big Telescope Alt-azimuth, and Keck telescopes, optical counterparts are detected for all galaxies within the 3σpositional uncertainty ( 0.5 h 70 − 1 Mpc) and 200 km s −1 in recession velocity. Assuming that the dominant source of Hiis the identified optical counterpart, we find evidence of evolution in the Hicontent of galaxies over the last 4.2 Gyr. Our new high-redshift Higalaxy sample provides the opportunity to better investigate the evolution of cool gas in galaxies. A larger sample size in the future will allow us to refine our knowledge of the formation and evolution of galaxies.

Astronomy & Astrophysics↗
NASA NTRS2010

About the Compatibility of DORIS and VLBI Observations

We investigated the compatibility of the DORIS and VLBI observations at Badary Observatory. The DORIS beacon stands at 100-m distance from the main radio telescope dish and transmits signals on two frequencies: 2036.25 MHz and 401.25 MHz. The latter frequency is modulated to send messages containing an ID number, timing information, data from the meteorological sensors, and engineering data (e.g., power). Both frequencies affect the S/X band radio telescope receivers. The parameters of the DORIS signals were measured at the outputs of the S/X band intermediate frequency amplifier. It was found that: (1) The level of RFI, produced by the DORIS beacon, practically corresponds to the level of the system (antenna plus receiver) noise signal and does not overload the S/X band receivers. (2) The DORIS 401.25 MHz signal is out of the frequency bands recorded during standard VLBI sessions. As a result, RFI from DORIS does not affect VLBI observations. This conclusion was confirmed after data correlations of actual VLBI observations that were conducted with the DORIS beacon turned on/off.

Il'in, Gennady↗
NASA NTRS1993

Radioastron flight operations

Radioastron is a space-based very-long-baseline interferometry (VLBI) mission to be operational in the mid-90's. The spacecraft and space radio telescope (SRT) will be designed, manufactured, and launched by the Russians. The United States is constructing a DSN subnet to be used in conjunction with a Russian subnet for Radioastron SRT science data acquisition, phase link, and spacecraft and science payload health monitoring. Command and control will be performed from a Russian tracking facility. In addition to the flight element, the network of ground radio telescopes which will be performing co-observations with the space telescope are essential to the mission. Observatories in 39 locations around the world are expected to participate in the mission. Some aspects of the mission that have helped shaped the flight operations concept are: separate radio channels will be provided for spacecraft operations and for phase link and science data acquisition; 80-90 percent of the spacecraft operational time will be spent in an autonomous mode; and, mission scheduling must take into account not only spacecraft and science payload constraints, but tracking station and ground observatory availability as well. This paper will describe the flight operations system design for translating the Radioastron science program into spacecraft executed events. Planning for in-orbit checkout and contingency response will also be discussed.

Altunin, V. I.↗
NASA NTRS1983

Very-long-baseline radio interferometry - The Mark III system for geodesy, astrometry, and aperture synthesis

Up to 112 megabit/sec from each radio telescope of an interferometric array can be recorded and processed by the Mark III VLBI system. Sample results are given for baseline lengths between three antennas in the U.S. and three in Europe, as well as for the arc lengths between the positions of six extragalactic radio sources. No significant change is detected in any of these quantities. Signals of a given polarization or of pairs of orthogonal polarizations may be recorded in up to 28 contiguous bands, each nearly 2 MHz wide, for mapping the brightness distribution of compact radio sources. The demonstrated ability to record large bandwidths, and to link many large radio telescopes, allows compact sources with flux densities below 1 millijansky to be detected and studied.

Rogers, A. E. E.↗
NASA NTRS1973

Polarization of solar active regions at 3.5 millimeter wavelength

A study of the circular polarization structure of solar active regions has been made from data obtained at 3.5 mm wavelength, using the 36-ft-diam radio telescope of the National Radio Astronomy Observatory at Kitt Peak, Arizona. The angular resolution of the telescope at this wavelength is 1.2 min. All important active regions observed at 3.5 mm are bipolar in nature; the degree of polarization ranges from 1 to about 2%. These oppositely polarized components correspond with the Mt. Wilson magnetic regions of opposite polarity; the line of zero polarization delineates the neutral line between the regions of opposite polarity on magnetograms. The longitudinal magnetic fields at the level of 3.5-mm emission computed from the degree of polarization are found to be several hundred gauss.

Kundu, M. R.↗
NASA NTRS1988

Ionospheric wave and irregularity measurements using passive radio astronomy techniques

The observation of midlatitude structures using passive radio astronomy techniques is discussed, with particular attention being given to the low-frequency radio telescope at the Clark Lake Radio Observatory. The present telescope operates in the 10-125-MHz frequency range. Observations of the ionosphere at separations of a few kilometers to a few hundreds of kilometers by the lines of sight to sources are possible, allowing the determination of the amplitude, wavelength, direction of propagation, and propagation speed of ionospheric waves. Data are considered on large-scale ionospheric gradients and the two-dimensional shapes and sizes of ionospheric irregularities.

Erickson, W. C.↗
NASA NTRS1977

An upper limit for the 34.3-MHz synchrotron flux from Uranus

The 34.3-MHz Cocoa Cross radio telescope at Clark Lake Radio Observatory has been used to search for synchrotron radiation from Uranus between November 27, 1974, and May 13, 1975. Inspection of daily chart records for 69 observations during this time period provides a conservative upper limit to the synchrotron flux of 8 Jy. No Uranian bursts were observed. This result is compared with the kilometric burst observations of Brown (1976) as well as with models for burst and possible synchrotron emission from Uranus.

Shawhan, S. D.↗
NASA NTRS1980

Geodetic long baseline interferometry research in Canada

The objectives and results of several studies using the Canadian long baseline interferometry system (LBI) are presented. The precision of measurements from radio telescopes at the Algonquin Radio Observatory (ARO), Lake Traverse, Ontario; the Owens Valley Radio Observatory (OVRO), Big Pine, California; and the Chilbolton Observatory (CHIL), Chilbolton, England, is discussed. Also, since LBI is insensitive to the uncertainty in the geocentric gravitational constant, it is a very useful technique for determining the scales of the coordinate systems used by other precise techniques. Beginning in May 1977, a number of LBI observing sessions were accompanied by simultaneous satellite Doppler observations. The baseline components obtained from the satellite Doppler observations were compared to the LBI values. The weighted mean scale bias of the NSWC 9Z-2 satellite Doppler coordinate system relative to the LBI system was found to be 0.42 + or - 0.05 PPM. The weighted mean difference in the origin of longitude was found to be 0.87 sec + or - 0.01 while the difference in declination origin was found to be 0.06 sec + or - 0.01.

Langley, R. B.↗
NASA NTRS1980

Radio and X-ray observations of Abell 754

The cluster of galaxies Abell 754 has been observed at 610 MHz with the Westerbork Synthesis Radio Telescope at 1420 MHz with the synthesis telescope of the Dominion Radio Astrophysical Observatory and in the interval 2-10 keV with the rotating modulation collimators on SAS-3. A complete source list for the field is given together with radio contour diagrams of extended sources associated with cluster galaxies. No X-rays were detected and a diameter of greater than 6 arcmin may be assigned to the associated source 4U 0900-09 (2A 0906-095) if a constant intensity is assumed for a single source. Upper limits to the luminosity of the cD galaxy are 2 x 10 to the 44th erg/sec in the X-ray and 5 x 10 to the 39th erg/sec in the radio.

Harris, D. E.↗
NASA NTRS1996

Space VLBI Co-Observing Developments in the DSN

The JPL/NASA Deep Space Network (DSN) plans to participate in the upcoming Space VLBI missions by using its 70m antenna time to co-observe with space-based radio telescopes. To enhance this support, the DSN is upgrading its radio astronomy equipment at L- and K-band, its VLBI recorders, and its computers and software for co-observing operations.

telescopes radio astronomy Jet Propulsion Laborato↗
NASA NTRS2004

The Hard X-Ray and Coordinated Multifrequency Properties of the Blazar 3C279

Upon our successful AO-1 proposal no. 120085, the quasar 3C 279 has been observed in a coordinated multiwavelength campaign, including INTEGRAL, Chandra, and ground-based radio, near-infrared, and optical observations in June 2003. INTEGRAL observed 3C279 continuously for 300 ksec in INTEGRAL AO-1 between June 1 and June 5,2003. In addition, a Chandra pointing of 5 ksec was done on June 2, the Metsiihovi radio telescope contributed high-frequency radio observations, the SEST observed the source at mm wavelengths, and the 80 cm Turola telescope at La Palma and the 2.3 m telescope at Siding Springs, Australia contributed optical observations.

Collmar, W.↗
NASA NTRS2026

The Canadian Galactic Emission Mapper (CGEM) A Cosmic Microwave Foreground Experiment

The Canadian Galactic Emission Mapper (CGEM) is a 4-meter single-dish radio telescope located at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, Canada. CGEM is designed to map polarized Galactic synchrotron emission across the entire northern sky at 8-10 GHz with 1 MHz frequency resolution and ∼ 0.5 degree angular resolution. Its goal is to obtain high-fidelity, low-noise maps of polarized Galactic synchrotron radiation, at frequencies where synchrotron dominates, in order to provide a reliable template for CMB B−mode foreground cleaning. We will show on sky performance of CGEM’s single-pixel azimuthally-symmetric telescope, its coherent, dual-polarized radiometer, and show maps made from commissioning data from the first few months of operation.

Cosmic microwave background↗
NASA NTRS1977

The 1975.9 Jovian decimetric spectrum

The Arecibo radio telescope measured the Jovian decimetric radio flux at four frequencies - 318, 430, 1415, and 2380 - on December 5 and 6, 1975. Observed flux values were obtained by comparison with the radio sources 3C18 and 3C459. The flux values were further corrected by the beaming of the Jovian emission about the xenomagnetic equator for the antenna-emission polarization angle and for the antenna-source resolution at 1415 and 2380 MHz.

Shawhan, S. D.↗
NASA NTRS1978

VLBI observations of 3C 345 and NRAO 512 in right and left circular polarization

In October 1975, the radio telescopes of the Haystack, National Radio Astronomy, and Owens Valley Radio Observatories were used as an interferometer to monitor, at 8 GHz, the right and left circularly polarized radiation emitted by the quasars 3C 345 and NRAO 512. The data for each polarization are used separately to estimate several parameters describing a model of the fine structure of the radio brightness of 3C 345 and, subsequently, the angular separation between 3C 345 and NRAO 512. The results for the two polarizations are in approximate agreement, indicating that to the limit of resolution about 0.5 milliarcsec), the fourth Stokes parameter, V, is not significantly different from zero within the compact components of these radio sources. The corresponding quantitative limits on the degree of circular polarization are 0.08 + or - 0.07 for 3C 345 and 0.01 + or - 0.08 for NRAO 512.

Menyuk, C. R.↗
NASA NTRS1986

Dark filaments observed at 8.3mm and 3.1mm wavelength

Mapping of the sun was made at 3.1mm (98 GHz) and 8.3mm (36 GHz) wavelengths with a 45m dish radio telescope at the Nobeyama Cosmic Radio Observatory. The depressions associated with large H alpha filaments are derived to be -0.2 at 8.3mm and -0.05 at 3.1mm, which are darker than the values inferred by Raoult et al. (1979)

Hiel, E.↗