Search NASA⌕ Search

SEARCH · Search NASA

Results for “radio detection”

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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Lightning in Jupiter's atmosphere

This paper introduces some current ideas on the dynamical structure of Jupiter's atmosphere that are likely to be important for the generation of lightning and reviews briefly the present understanding of Jovian lightning. The Galileo probe into Jupiter's atmosphere is now scheduled for a space shuttle launch in October 1989, with the probe entry into Jupiter's atmosphere to occur in December 1995. The atmospheric probe carries a radio frequency (RF) and optical lightning detection instrument to investigate the characteristics of Jovian lightning,.

Lanzerotti, L. J.↗
NASA NTRS1990

32-GHz Wideband Maser Amplifier

High-gain, wideband, microwave amplifier based on ruby cooled by liquid helium. Features include low input equivalent noise temperature and 400-MHz bandwidth. Design basically extension of previous reflected-wave masers built for frequency range of 18 to 26 GHz. Maser amplifier includes eight stages connected in reflected-wave configuration. Particularly useful for detection of weak microwave signals in radio astronomy and communications.

Shell, J. S.↗
NASA NTRS1990

Electron scattering and the distances to cluster cooling flows

Cluster cooling flows have electron-scattering optical depths which are estimated to be about 0.01. Many of the cluster-dominant galaxies centered in cluster cooling flows have active nuclei, and about 1 percent of the luminosity from the active nuclei should appear as diffuse, scattered radiation. It is shown here that detection of this scattered radiation at radio wavelengths can provide a measure of the distance to the cluster that is independent of the Hubble constant. Observations of the scattered surface brightness profile can also be used to test for clumpiness in the gas, for variations in the central radio source on time scales less than 100,000 yr, and for the degree of beaming of radiation from the central source.

Wise, Michael W.↗
NASA NTRS1992

A high-frequency survey of the southern Galactic plane for pulsars

Results of an HF survey designed to detect young, distant, and short-period pulsars are presented. The survey detected a total of 100 pulsars, 46 of which were previously unknown. The periods of the newly discovered pulsars range between 47 ms and 2.5 ms. One of the new discoveries, PSR 1259-63, is a member of a long-period binary system. At least three of the pulsars have ages less than 30,000 yr, bringing the total number of such pulsars to 12. The majority of the new discoveries are distant objects with high dispersion measures, which are difficult to detect at low frequencies. This demonstrates that the survey has reduced the severe selection effects of pulse scattering, high Galactic background temperature, and dispersion broadening, which hamper the detection of such pulsars at low radio frequencies. The pulsar distribution in the southern Galaxy is found to extend much further from the Galactic center than that in the north, probably due to two prominent spiral arms in the southern Galaxy.

Johnston, Simon↗
NASA NTRS1992

Rosat observations of PSR 0656 + 14 - A pulsating and cooling neutron star

Observations of the X-ray-emitting radio pulsar PSR 0656 + 14 with the Position Sensitive Proportional Counter on board Rosat on March 25, 1991 are reported. Pulsations at the radio period, about 0.385 s, were detected at a pulsed fraction of 14 +/-2 percent. A blackbody description yields a surface temperature of about (9.0 +/-0.4) x 10 exp 5 K, an equivalent column density of about (1.0 +/-0.2) x 10 exp 20/sq cm, and a stellar radius of 10 km under the assumption of a 500 pc source distance. A positive correlation is found to exist between the phase of the pulsed emission and the X-ray hardness, suggesting that the pulsations have their seat in a 'hot spot' on the neutron star surface. Implications of the models with regard to the cooling curve of neutron stars are discussed.

Finley, John P.↗
NASA NTRS1993

Simultaneous ROSAT, Ginga, VLA, IUE, and optical observations of the bright quasar H1821+643

Simultaneous optical, UV, and X-ray spectroscopy of the low-redshift high-luminosity QSO H1821+643 is presented in order to examine the connection between the optical UV bump and the soft X-ray excess. The correlation of the short-term variability in the optical/UV and soft X-ray band is examined, and the applicability of the accretion disk models to the simultaneous continuum energy distribution is tested. By fitting the continuum energy distribution with the thin accretion disk model, it was found that bare disk models cannot easily account for the emission in both the UV and the steep excess in the soft X-ray band. The intrinsic X-ray spectrum of H1821+643 exhibited a typical power-law slope above about 0.3 keV, as detected by ROSAT and Ginga. The first detection of H1821+643 in the radio band is reported. This radio-quiet QSO was found to have a substantial radio flux at 20 cm and a typical steep spectral slope.

Kolman, Michiel↗
NASA NTRS1991

Gamma-ray emission from young neutron stars

The emission models of Cheng et al. (1986) and Harding (1981) are employed to determine likely candidates for pulsed gamma-ray emission on the basis of recent radio data of pulsars. The recent detection of pulsed gamma rays from PSR 1951+32 lends observational support to the scenario of Cheng et al. which also suggests that PSR 1855+09 might be another excellent gamma-ray pulsar candidate. The possible contribution of young neutron stars to the diffuse high energy glow is also discussed.

Hartmann, Dieter H.↗
NASA NTRS1993

Fine structure of Langmuir waves produced by a solar electron event

Observations of highly structured bursts of Langmuir waves produced by energetic electrons ejected from a solar flare using wideband plasma wave measurements on the Galileo spacecraft are reported. Attention is given to the solar flare that occurred on December 10, 1990, while the spacecraft was at a radial distance of 0.98 AU from the sun. This flare emitted a stream of energetic electrons and an associated type III radio event, both of which were detected by Galileo. A large number of intense Langmuir wave bursts were detected near the local electron plasma frequency, which was about 25 kHz. The bursts, which lasted about 1.5 hr, coincided with the arrival of the solar electrons. The bursts are highly structured and consist mainly of isolated wave packets with durations as short as 1 ms and beat-type waveforms with beat frequencies ranging from 200 to 500 Hz. The highly structured envelopes of these waves are strongly suggestive of nonlinear parametric decay processes such as those predicted by various theories dealing with the saturation of beam-driven electrostatic instabilities.

Gurnett, D. A.↗
NASA NTRS2000

Could the Unidentified EGRET Sources in the Gould Belt be of Pulsar Origin?

We explore the possibility, within the polar cap model, that at least some of the recently identified new population of Energetic Gamma-Ray Experiment Telescope (EGRET) sources in the Gould Belt sources are gamma-ray pulsars, viewed at large angles to the magnetic axis, such that the line-of-sight misses both the bright gamma-ray double cone and the radio beam. We estimate that the detectability of such off-beam gamma-ray sources is about a factor of 4-5 times higher than that of the on-beam sources. The off-beam gamma-ray pulsars also have a faint, soft nature, which is consistent with the observed properties of the Gould Belt sources. We conclude that at least some of the middle latitude sources might be such off-beam gamma-ray pulsars if they are indeed in the Gould Belt.

Zhang, Bing↗
NASA NTRS2001

X-Ray Emission from the Millisecond Pulsar J1012+5307

The recently discovered 5.3 ms pulsar J1012+5307 at a distance of 520 pc is in an area of the sky which is particularly deficient in absorbing gas. The column density along the line of sight is less than 7.5 x 10(exp 19)/sq cm, which facilitates soft X-ray observations. Halpern reported a possible ROSAT PSPC detection of the pulsar in a serendipitous, off-axis observation. We have now confirmed the X-ray emission of PSR J1012+5307 in a 23 ksec observation with the ROSAT HRI. A point source is detected within 3 sec. of the radio position. Its count rate of 1.6 +/- 0.3 x 10(exp -3)/s corresponds to an unabsorbed 0.1 - 2.4 keV flux of 6.4 x 10(exp -14) ergs/sq cm s, similar to that reported previously. This counts-to-flux conversion is valid for N(sub H) = 5 x 10(exp 19)/sq cm, and either a power-law spectrum of photon index 2.5 or a blackbody of kT = 0.1 keV. The implied X-ray luminosity of 2.0 x 10(exp 30) ergs/ s is 5 x 10(exp -4) of the pulsar's spin-down power E, and similar to that of the nearest millisecond pulsar J0437-4715, which is nearly a twin of J1012+5307 in P and E. We subjected the 37 photons (and 13 background counts) within the source region to a pulsar search, but no evidence for pulsation was found. The pulsar apparently emits over a large fraction of its rotation cycle, and the absence of sharp modulation can be taken as evidence for surface thermal emission, as favored for PSR J0437-4715, rather than magnetospheric X-ray emission which is apparent in the sharp pulses of the much more energetic millisecond pulsar B1821-24. A further test of of the interpretation will be made with a longer ROSAT observation, which will increase the number of photons collected by a factor of 5, and permit a more sensitive examination of the light curve for modulation due to emission from heated polar caps. If found, such modulation will be further evidence that surface reheating by the impact of particles accelerated along open field lines operates in these approx. 10(exp 9) yr old pulsars.

Halpern, Jules P.↗
NASA NTRS2004

To Boldly Go: America's Next Era in Space. Living Places in Other Solar Systems

Dr. Sargent noted that evidence of other solar systems that might sustain life, particularly human life, is being sought. Protoplanetary (or debris) disks have been observed and are considered evidence that other solar systems exist or are being formed. Also observed is a wobble which is seen as evidence of circulation around a celestial body and gaps that are created by the potential planet. One indicator of life may be these rings or disks of debris around stars. Interferometers, which are telescopic devices that consist of multiple lenses, are being developed in order to better see celestial objects and what may be found around them. Other methods for improving celestial viewing capabilities are also under development. She spoke of particularly looking for wobble and gaps and debris disks where new planets are being formed in an effort to discover another planet that might sustain life as we know it. The next speaker, Dr. Chris McKay, is a planetary scientist at NASA Ames. He talked about the possibility of life on Mars or in some other solar system. He commented on the sameness of the origin of all life, and of the origin of, and the need for, oxygen and water. He believes that water originally came to Earth from comets. At least that is a viable possible source. Water might also have come to Earth via asteroids. Dr. McKay also postulates that there can be no water on Mars because Mars has no plate tectonic system, which he believes is an essential for recycling water. . Dr. Wes Huntress, NASA s Associate Administrator for Space Science, and Dr. Barbara Stone, also from NASA Headquarters, joined Drs. Cordova, Sargent and McKay in the question and answer period following the presentations. (Mr. Goldin was excused to keep an appointment with the President.) The discussion included the following statements and questions: The more missions that there are, the more technology is developed. We need to study our solar system to have something to which we can compare other systems. Before we send people to distant places or to other planets, we need to study the psychological and biological problems that are created by going away from Earth for a long period of time. Pulsars appear to have planets rotating around them. This is of interest and should be studied further. Looking back in time, is there any thought to seeing the development of life? How long did it take for oxygen to rise on the Earth? Do debris disks around the stars provide velocity patterns? To detect life scientists are listening for radio signals, looking for oxygen or ozone, and looking for liquid water. On Earth liquid water is the defining ecological parameter for life. This means that operationally the search for life elsewhere is primarily a search for liquid water.

Source record↗
NASA NTRS2007

Lightning: Nature's Probe of Severe Weather for Research and Operations

Lightning, the energetic and broadband electrical discharge produced by thunderstorms, provides a natural remote sensing signal for the study of severe storms and related phenomena on global, regional and local scales. Using this strong signal- one of nature's own probes of severe weather -lightning measurements prove to be straightforward and take advantage of a variety of measurement techniques that have advanced considerably in recent years. We briefly review some of the leading lightning detection systems including satellite-based optical detectors such as the Lightning Imaging Sensor, and ground-based radio frequency systems such as Vaisala's National Lightning Detection Network (NLDN), long range lightning detection systems, and the Lightning Mapping Array (LMA) networks. In addition, we examine some of the exciting new research results and operational capabilities (e.g., shortened tornado warning lead times) derived from these observations. Finally we look forward to the next measurement advance - lightning observations from geostationary orbit.

Blakeslee, R.J.↗
NASA NTRS2010

The Spectral Energy Distribution of Fermi Bright Blazars

We have conducted a detailed investigation of the broadband spectral properties of the gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray /gamma-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. The SED of these gamma-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual log v-log v Fv representation, the typical broadband spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SED to characterize the peak intensity of both the low- and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, alpha(sub ro) , and optical to X-ray, alpha(sub ox), spectral slopes) and from the gamma-ray spectral index. Our data show that the synchrotron peak frequency (v(sup S) (sub peak)) is positioned between 10(exp 12.5) and 10(exp 14) Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 10(exp 13) and 10(exp 17) Hz in featureless BL Lacertae objects. We find that the gamma-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron-inverse Compton scenarios. However, simple homogeneous, one-zone, synchrotron self-Compton (SSC) models cannot explain most of our SED, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. More complex models involving external Compton radiation or multiple SSC components are required to reproduce the overall SED and the observed spectral variability. While more than 50% of known radio bright high energy peaked (HBL) BL Lacs are detected in the LBAS sample, only less than 13% of known bright FSRQs and LBL BL Lacs are included. This suggests that the latter sources, as a class, may be much fainter gamma-ray emitters than LBAS blazars, and could in fact radiate close to the expectations of simple SSC models. We categorized all our sources according to a new physical classification scheme based on the generally accepted paradigm for Active Galactic Nuclei and on the results of this SED study. Since the LAT detector is more sensitive to flat spectrum gamma-ray sources, the correlation between v(sup S) (sub peak) and gamma-ray spectral index strongly favors the detection of high energy peaked blazars, thus explaining the Fermi overabundance of this type of sources compared to radio and EGRET samples. This selection effect is similar to that experienced in the soft X-ray band where HBL BL Lacs are the dominant type of blazars.

Abdo, A. A.↗
NASA NTRS2014

Simulation Tools Prevent Signal Interference on Spacecraft

NASA engineers use simulation software to detect and prevent interference between different radio frequency (RF) systems on a rocket and satellite before launch. To speed up the process, Kennedy Space Center awarded SBIR funding to Champaign, Illinois-based Delcross Technologies LLC, which added a drag-and-drop feature to its commercial simulation software, resulting in less time spent preparing for the analysis.

Source record↗
NASA NTRS2023

MAXI J1848-015: The first detection of relativistically moving outflows from a globular cluster X-ray binary

Over the past decade, observations of relativistic outflows from outbursting X-ray binaries in the Galactic field have grown significantly. In this work, we present the first detection of moving and decelerating radio-emitting outflows from an X-ray binary in a globular cluster. MAXI J1848−015 is a recently discovered transient X-ray binary in the direction of the globular cluster GLIMPSE-C01. Using observations from the Karl G. Jansky Very Large Array, and a monitoring campaign with the MeerKAT observatory for 500 days, we model the motion of the outflows. This represents some of the most intensive, long-term coverage of relativistically moving X-ray binary outflows to date. We use the proper motions of the outflows from MAXI J1848−015 to constrain the component of the intrinsic jet speed along the line of sight, βint COS θejection, to be =0.19 ± 0.02. Assuming it is located in GLIMPSE-C01, at 3.4 kpc, we determine the intrinsic jet speed, βint = 0.79 ± 0.07, and the inclination angle to the line of sight, θejection = 76° ± 2°. This makes the outflows from MAXI J1848−015 somewhat slower than those seen from many other known X-ray binaries. We also constrain the maximum distance to MAXI J1848−015 to be 4.3 kpc. Finally, we discuss the implications of our findings for the nature of the compact object in this system, finding that a black hole primary is a viable (but as-of-yet unconfirmed) explanation for the observed properties of MAXI J1848−015. If future data and/or analysis provide more conclusive evidence that MAXI J1848−015 indeed hosts a black hole, it would be the first black hole X-ray binary in outburst identified in a Galactic globular cluster.

A. Bahramian↗
DOE OSTI2020

Wireless oxygen dosimeter

A tag for detecting an analyte can include a radio frequency identification tag including a sensor portion, the sensor portion configured to change resistivity when the radio frequency identification tag contacts or interacts with an analyte, whereby the resistivity change alters an output of the radio frequency identification tag, wherein the sensor portion includes a circuit, and wherein the sensor portion is configured to activate the circuit or deactivate the circuit when contacted or having interacted with the analyte, wherein the sensor portion includes a conductive material associated with a polymer complex.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗