Planetary radio astronomy: Earth, giant planets, and beyond

NASA Astrophysics Data System (ADS)

Rucker, H. O.; Panchenko, M.; Weber, C.

2014-11-01

The magnetospheric phenomenon of non-thermal radio emission is known since the serendipitous discovery of Jupiter as radio planet in 1955, opening the new field of "Planetary Radio Astronomy". Continuous ground-based observations and, in particular, space-borne measurements have meanwhile produced a comprehensive picture of a fascinating research area. Space missions as the Voyagers to the Giant Planets, specifically Voyager 2 further to Uranus and Neptune, Galileo orbiting Jupiter, and now Cassini in orbit around Saturn since July 2004, provide a huge amount of radio data, well embedded in other experiments monitoring space plasmas and magnetic fields. The present paper as a condensation of a presentation at the Kleinheubacher Tagung 2013 in honour of the 100th anniversary of Prof. Karl Rawer, provides an introduction into the generation mechanism of non-thermal planetary radio waves and highlights some new features of planetary radio emission detected in the recent past. As one of the most sophisticated spacecraft, Cassini, now in space for more than 16 years and still in excellent health, enabled for the first time a seasonal overview of the magnetospheric variations and their implications for the generation of radio emission. Presently most puzzling is the seasonally variable rotational modulation of Saturn kilometric radio emission (SKR) as seen by Cassini, compared with early Voyager observations. The cyclotron maser instability is the fundamental mechanism under which generation and sufficient amplification of non-thermal radio emission is most likely. Considering these physical processes, further theoretical investigations have been started to investigate the conditions and possibilities of non-thermal radio emission from exoplanets, from potential radio planets in extrasolar systems.

Review of Space VLBI RadioAstron studies of AGN

NASA Astrophysics Data System (ADS)

Gurvits, Leonid; Kovalev, Yuri

2016-07-01

Space VLBI offers an unrivalled resolution in studies of the AGN phenomena. Since 2011, the Russia-led SVLBI mission RadioAstron conducts observations at 92, 18, 6 and 1.3 cm with baselines an order of magnitude longer than the Earth diameter, therefore offering an order of magnitude "sharper" view at the brightest radio sources than achieved with Earth-based VLBI systems. In our presentation we will review the current status of the RadioAstron's scientific programme. Over the first 4.5 years of the in-orbit operations, the mission achieved successful VLBI detections of extragalactic continuum radio sources at all four observing bands. To date, detections on SVLBI baselines have been obtained for more than 150 AGN's at projected baselines up to 350 000 km (about 28 Earth diameters, ED). The highest resolution achieved is 14 microarcscends from 1.3 cm observations. RadioAstron is an international project; it conducts observations with up to 30 Earth-based radio telescopes located on different continents. We will review results of total intensity and polarisation imaging with extreme angular resolution of blazars and nearby active galaxies. We will also discuss typical and maximum brightness temperatures of blazar cores from the AGN Survey obtained with RadioAstron. Physical implications for the AGN jets formation, magnetic field and emission mechanism will be discussed on the basis of the results obtained to date.

Wave optics-based LEO-LEO radio occultation retrieval

NASA Astrophysics Data System (ADS)

Benzon, Hans-Henrik; Høeg, Per

2016-06-01

This paper describes the theory for performing retrieval of radio occultations that use probing frequencies in the XK and KM band. Normally, radio occultations use frequencies in the L band, and GPS satellites are used as the transmitting source, and the occultation signals are received by a GPS receiver on board a Low Earth Orbit (LEO) satellite. The technique is based on the Doppler shift imposed, by the atmosphere, on the signal emitted from the GPS satellite. Two LEO satellites are assumed in the occultations discussed in this paper, and the retrieval is also dependent on the decrease in the signal amplitude caused by atmospheric absorption. The radio wave transmitter is placed on one of these satellites, while the receiver is placed on the other LEO satellite. One of the drawbacks of normal GPS-based radio occultations is that external information is needed to calculate some of the atmospheric products such as the correct water vapor content in the atmosphere. These limitations can be overcome when a proper selected range of high-frequency waves are used to probe the atmosphere. Probing frequencies close to the absorption line of water vapor have been included, thus allowing the retrieval of the water vapor content. Selecting the correct probing frequencies would make it possible to retrieve other information such as the content of ozone. The retrieval is performed through a number of processing steps which are based on the Full Spectrum Inversion (FSI) technique. The retrieval chain is therefore a wave optics-based retrieval chain, and it is therefore possible to process measurements that include multipath. In this paper simulated LEO to LEO radio occultations based on five different frequencies are used. The five frequencies are placed in the XK or KM frequency band. This new wave optics-based retrieval chain is used on a number of examples, and the retrieved atmospheric parameters are compared to the parameters from a global European Centre for Medium

Microsat and Lunar-Based Imaging of Radio Bursts

NASA Technical Reports Server (NTRS)

MacDowall, R. J.; Gopalswamy, N.; Kaiser, M. L.; Demaio, L. D.; Bale, S. D.; Kasper, J. C.; Lazarus, A. J.; Howard, R. E.; Jones, D. L.; Reiner, M. J.;

Tracking Solar Type II Bursts with Space Based Radio Interferometers

NASA Astrophysics Data System (ADS)

Hegedus, Alexander M.; Kasper, Justin C.; Manchester, Ward B.

2018-06-01

The Earth’s Ionosphere limits radio measurements on its surface, blocking out any radiation below 10 MHz. Valuable insight into many astrophysical processes could be gained by having a radio interferometer in space to image the low frequency window for the first time. One application is observing type II bursts tracking solar energetic particle acceleration in Coronal Mass Ejections (CMEs). In this work we create a simulated data processing pipeline for several space based radio interferometer (SBRI) concepts and evaluate their performance in the task of localizing these type II bursts.Traditional radio astronomy software is hard coded to assume an Earth based array. To circumvent this, we manually calculate the antenna separations and insert them along with the simulated visibilities into a CASA MS file for analysis. To create the realest possible virtual input data, we take a 2-temperature MHD simulation of a CME event, superimpose realistic radio emission models from the CME-driven shock front, and propagate the signal through simulated SBRIs. We consider both probabilistic emission models derived from plasma parameters correlated with type II bursts, and analytical emission models using plasma emission wave interaction theory.One proposed SBRI is the pathfinder mission SunRISE, a 6 CubeSat interferometer to circle the Earth in a GEO graveyard orbit. We test simulated trajectories of SunRISE and image what the array recovers, comparing it to the virtual input. An interferometer on the lunar surface would be a stable alternative that avoids noise sources that affect orbiting arrays, namely the phase noise from positional uncertainty and atmospheric 10s-100s kHz noise. Using Digital Elevation Models from laser altimeter data, we test different sets of locations on the lunar surface to find near optimal configurations for tracking type II bursts far from the sun. Custom software is used to model the response of different array configurations over the lunar year

Very long baseline interferometry using a radio telescope in Earth orbit

NASA Technical Reports Server (NTRS)

Ulvestad, J. S.; Edwards, C. D.; Linfield, R. P.

1987-01-01

Successful Very Long Baseline Interferometry (VLBI) observations at 2.3 GHz were made using an antenna aboard an Earth-orbiting spacecraft as one of the receiving telescopes. These observations employed the first deployed satellite (TDRSE-E for East) of the NASA Tracking and Data Relay Satellite System (TDRSS). Fringes were found for 3 radio sources on baselines between TDRSE and telescopes in Australia and Japan. The purpose of this experiment and the characteristics of the spacecraft that are related to the VLBI observations are described. The technical obstacles to maintaining phase coherence between the orbiting antenna and the ground stations, as well as the calibration schemes for the communication link between TDRSE and its ground station at White Sands, New Mexico are explored. System coherence results and scientific results for the radio source observations are presented. Using all available calibrations, a coherence of 84% over 700 seconds was achieved for baselines to the orbiting telescope.

Radio Astronomers Lift "Fog" on Milky Way's Dark Heart: Black Hole Fits Inside Earth's Orbit

NASA Astrophysics Data System (ADS)

2004-04-01

-emitting object would fit neatly just inside the path of the Earth's orbit around the Sun, the astronomers said. The black hole itself, they calculate, is about 14 million miles across, and would fit easily inside the orbit of Mercury. Black holes are concentrations of matter so dense that not even light can escape their powerful gravity. The new VLBA observations provided astronomers their best look yet at a black hole system. "We are much closer to seeing the effects of a black hole on its environment here than anywhere else," Bower said. The Milky Way's central black hole, like its more-massive cousins in more-active galactic nuclei, is believed to be drawing in material from its surroundings, and in the process powering the emission of the radio waves. While the new VLBA observations have not provided a final answer on the nature of this process, they have helped rule out some theories, Bower said. Based on the latest work, he explained, the top remaining theories for the nature of the radio- emitting object are jets of subatomic particles, similar to those seen in radio galaxies; and some theories involving matter being accelerated near the edge of the black hole. As the astronomers studied Sagittarius A* at higher and higher radio frequencies, the apparent size of the object became smaller. This fact, too, Bower said, helped rule out some ideas of the object's nature. The decrease in observed size with increasing frequency, or shorter wavelength, also gives the astronomers a tantalizing target. "We think we can eventually observe at short enough wavelengths that we will see a cutoff when we reach the size of the black hole itself," Bower said. In addition, he said, "in future observations, we hope to see a 'shadow' cast by a gravitational lensing effect of the very strong gravity of the black hole." In 2000, Falcke and his colleagues proposed such an observation on theoretical grounds, and it now seems feasible. "Imaging the shadow of the black hole's event horizon is now

Concept and Analysis of a Satellite for Space-Based Radio Detection of Ultra-High Energy Cosmic Rays

NASA Astrophysics Data System (ADS)

Romero-Wolf, Andrew; Gorham, P.; Booth, J.; Chen, P.; Duren, R. M.; Liewer, K.; Nam, J.; Saltzberg, D.; Schoorlemmer, H.; Wissel, S.; Zairfian, P.

2014-01-01

We present a concept for on-orbit radio detection of ultra-high energy cosmic rays (UHECRs) that has the potential to provide collection rates of ~100 events per year for energies above 10^20 eV. The synoptic wideband orbiting radio detector (SWORD) mission's high event statistics at these energies combined with the pointing capabilities of a space-borne antenna array could enable charged particle astronomy. The detector concept is based on ANITA's successful detection UHECRs where the geosynchrotron radio signal produced by the extended air shower is reflected off the Earth's surface and detected in flight.

Radio studies of the magnetic connection between solar particle acceleration sites and the Earth

NASA Astrophysics Data System (ADS)

Klein, Karl-Ludwig

The magnetic connection from the Sun to the Earth is a crucial problem of SEP propagation in space. While the Parker spiral often provides a plausible configuration, there are also examples where simple impulsive SEP events are observed at Earth even when the parent active region is several tens of degrees in heliographic longitude away from the root of the nominal Parker spiral. In previous work radio spectrography and imaging, together with PFSS magnetic field extrapolations from photospheric measurements, have been shown to provide a consistent ex-planation of this observation in terms of open flux tubes that rapidly fan out with inceasing height and connect the root of the Parker spiral at the source surface to the remote solar active region. Other work, however, has challenged this view and concluded that PFSS models often do not provide adequate connections. The problem is re-examined in this contribution. It is shown that at least in several cases the claimed failure of the PFSS model is in fact due to the assumption that high-latitude active regions must connect to the Parker spiral in the ecliptic plane in order that the SEP be able to reach Earth. This means that the PFSS field lines have to care for the particle transport from high to low heliographic latitudes in these events. However, this contribution presents evidence from radio observations from metre to kilometre wavelengths that even when particles leave the Sun towards high ecliptic latitudes, interplan-etary field lines may bend down to the ecliptic between a few solar radii and 1 AU and guide the particles to the vicinity of the Earth.

Sporadic radio emission connected with a definite manifestation of solar activity in the near Earth space

NASA Technical Reports Server (NTRS)

Dudnic, A. V.; Zaljubovski, I. I.; Kartashev, V. M.; Shmatko, E. S.

1985-01-01

Sporadic radio emission of near Earth space at the frequency of 38 MHz is shown to appear in the event of a rapid development of instabilities in the ionospheric plasma. The instabilities are generated due to primary ionospheric disturbances occurring under the influence of solar chromospheric flares.

Low and Mid-Latitude Ionospheric Irregularities Studies Using TEC and Radio Scintillation Data from the CITRIS Radio Beacon Receiver in Low-Earth-Orbit

NASA Astrophysics Data System (ADS)

Siefring, C. L.; Bernhardt, P. A.; Huba, J.; Krall, J.; Roddy, P. A.

2009-12-01

Unique data on ionospheric plasma irregularities from the Naval Research Laboratory (NRL) CITRIS (Scintillation and TEC Receiver in Space) instrument will be presented. CITRIS is a multi-band receiver that recorded TEC (Total Electron Content) and radio scintillations from Low-Earth Orbit (LEO) on STPSat1. The 555+/5 km altitude 35° inclination orbit covers low and mid-latitudes. The measurements require propagation from a transmitter to a receiver through the F-region plasma. CITRIS used both 1) satellite beacons in LEO, such as the NRL CERTO (Coherent Electromagnetic Radio TOmography) beacons and 2) the global network of ground-based DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) beacons. The TEC measurements allow for tracking of ionospheric disturbances and irregularities while the measurements of scintillations can simultaneously characterize their effects. CITRIS was operated in a complementary fashion with the C/NOFS (Communication/Navigations Outages Forecasting System) satellite during most of its first year of operations. C/NOFS carries a three-frequency 150/400/1067 MHz CERTO beacon and is dedicated to the study of Spread-F. In the case of Spread-F, ionospheric irregularities start with large scale size density gradients (100s of km) and cascade through complex processes to short scale sizes (10s of meters). It is typically the 100m-1km scale features that harm communication and navigation systems through scintillations. A multi-sensor approach is needed to completely understand this complex system, such as, the combination of CITRIS remote radio sensing and C/NOFS in-situ data. Several types of irregularities have been studied including Spread-F and the newly discovered dawn-side depletions. Comparisons with the physics based SAMI3 model are being performed to help our understanding of the morphology of the irregularities.

Simulation of interference between Earth stations and Earth-orbiting satellites

NASA Technical Reports Server (NTRS)

Bishop, D. F.

1994-01-01

It is often desirable to determine the potential for radio frequency interference between earth stations and orbiting spacecraft. This information can be used to select frequencies for radio systems to avoid interference or it can be used to determine if coordination between radio systems is necessary. A model is developed that will determine the statistics of interference between earth stations and elliptical orbiting spacecraft. The model uses orbital dynamics, detailed antenna patterns, and spectral characteristics to obtain accurate levels of interference at the victim receiver. The model is programmed into a computer simulation to obtain long-term statistics of interference. Two specific examples are shown to demonstrate the model. The first example is a simulation of interference from a fixed-satellite earth station to an orbiting scatterometer receiver. The second example is a simulation of interference from earth-exploration satellites to a deep-space earth station.

Provocative radio transients and base rate bias: A Bayesian argument for conservatism

NASA Astrophysics Data System (ADS)

Hair, Thomas W.

2013-10-01

Most searches for alien radio transmissions have focused on finding omni-directional or purposefully earth-directed beams of enduring duration. However, most of the interesting signals so far detected have been transient and non-repeatable in nature. These signals could very well be the first data points in an ever-growing data base of such signals used to construct a probabilistic argument for the existence of extraterrestrial intelligence. This paper looks at the effect base rate bias could have on deciding which signals to include in such an archive based upon the likely assumption that our ability to discern natural from artificial signals will be less than perfect.

New advanced netted ground based and topside radio diagnostics for Space Weather Program

NASA Astrophysics Data System (ADS)

Rothkaehl, Hanna; Krankowski, Andrzej; Morawski, Marek; Atamaniuk, Barbara; Zakharenkova, Irina; Cherniak, Iurii

2014-05-01

To give a more detailed and complete understanding of physical plasma processes that govern the solar-terrestrial space, and to develop qualitative and quantitative models of the magnetosphere-ionosphere-thermosphere coupling, it is necessary to design and build the next generation of instruments for space diagnostics and monitoring. Novel ground- based wide-area sensor networks, such as the LOFAR (Low Frequency Array) radar facility, comprising wide band, and vector-sensing radio receivers and multi-spacecraft plasma diagnostics should help solve outstanding problems of space physics and describe long-term environmental changes. The LOw Frequency ARray - LOFAR - is a new fully digital radio telescope designed for frequencies between 30 MHz and 240 MHz located in Europe. The three new LOFAR stations will be installed until summer 2015 in Poland. The LOFAR facilities in Poland will be distributed among three sites: Lazy (East of Krakow), Borowiec near Poznan and Baldy near Olsztyn. All they will be connected via PIONIER dedicated links to Poznan. Each site will host one LOFAR station (96 high-band+96 low-band antennas). They will most time work as a part of European network, however, when less charged, they can operate as a national network The new digital radio frequency analyzer (RFA) on board the low-orbiting RELEC satellite was designed to monitor and investigate the ionospheric plasma properties. This two-point ground-based and topside ionosphere-located space plasma diagnostic can be a useful new tool for monitoring and diagnosing turbulent plasma properties. The RFA on board the RELEC satellite is the first in a series of experiments which is planned to be launched into the near-Earth environment. In order to improve and validate the large scales and small scales ionospheric structures we will used the GPS observations collected at IGS/EPN network employed to reconstruct diurnal variations of TEC using all satellite passes over individual GPS stations and the

Voyager Signal Spotted By Earth Radio Telescopes

NASA Image and Video Library

2013-09-12

Radio telescopes cannot see Voyager 1 in visible light, but rather see the spacecraft signal in radio light. This image of Voyager 1 signal on Feb. 21, 2013. At the time, Voyager 1 was 11.5 billion miles 18.5 billion kilometers away.

Radiophysical methods of diagnostics the Earth's ionosphere and the underlying earth's surface by remote sensing in the short-wave range of radio waves

NASA Astrophysics Data System (ADS)

Belov, S. Yu.; Belova, I. N.

2017-11-01

Monitoring of the earth's surface by remote sensing in the short-wave band can provide quick identification of some characteristics of natural systems. This band range allows one to diagnose subsurface aspects of the earth, as the scattering parameter is affected by irregularities in the dielectric permittivity of subsurface structures. This method based on the organization of the monitoring probe may detect changes in these environments, for example, to assess seismic hazard, hazardous natural phenomena such as earthquakes, as well as some man-made hazards and etc. The problem of measuring and accounting for the scattering power of the earth's surface in the short-range of radio waves is important for a number of purposes, such as diagnosing properties of the medium, which is of interest for geological, environmental studies. In this paper, we propose a new method for estimating the parameters of incoherent signal/noise ratio. The paper presents the results of comparison of the measurement method from the point of view of their admissible relative analytical errors. The new method is suggested. Analysis of analytical error of estimation of this parameter allowed to recommend new method instead of standard method. A comparative analysis and shows that the analytical (relative) accuracy of the determination of this parameter new method on the order exceeds the widely-used standard method.

Through-the-earth radio

DOEpatents

Reagor, David; Vasquez-Dominguez, Jose

2006-12-12

A through-the-earth communication system that includes a digital signal input device; a transmitter operating at a predetermined frequency sufficiently low to effectively penetrate useful distances through-the earth; a data compression circuit that is connected to an encoding processor; an amplifier that receives encoded output from the encoding processor for amplifying the output and transmitting the data to an antenna; and a receiver with an antenna, a band pass filter, a decoding processor, and a data decompressor.

Low-Frequency Radio Bursts and Space Weather

NASA Technical Reports Server (NTRS)

Gopalswamy, N.

2016-01-01

Low-frequency radio phenomena are due to the presence of nonthermal electrons in the interplanetary (IP) medium. Understanding these phenomena is important in characterizing the space environment near Earth and other destinations in the solar system. Substantial progress has been made in the past two decades, because of the continuous and uniform data sets available from space-based radio and white-light instrumentation. This paper highlights some recent results obtained on IP radio phenomena. In particular, the source of type IV radio bursts, the behavior of type III storms, shock propagation in the IP medium, and the solar-cycle variation of type II radio bursts are considered. All these phenomena are closely related to solar eruptions and active region evolution. The results presented were obtained by combining data from the Wind and SOHO missions.

Radio Astronomy on and Around the Moon

NASA Astrophysics Data System (ADS)

Falcke, Heino; Klein Wolt, Mark; Ping, Jinsong; Chen, Linjie

2018-06-01

The exploration of remote places on other planets has now become a major goal in current space flight scenarios. On the other hand, astronomers have always sought the most remote and isolated sites to place their observatories and to make their most precise and most breath taking discoveries. Especially for radio astronomy, lunar exploration offers a complete new window to the universe. The polar region and the far-side of the moon are acknowledged as unique locations for a low-frequency radio telescope providing scientific data at wavelengths that cannot be obtained from the Earth nor from single satellites. Scientific areas to be covered range from radio surveys, to solar-system studies, exo-planet detection, and astroparticle physics. The key science area, however, is the detection and measurement of cosmological 21 cm hydrogen emission from the still unexplored dark ages of the universe. Developing a lunar radio facility can happen in steps and may involve small satellites, rover-based radio antennas, of free- flying constellations around the moon. A first such step could be the Netherlands-Chinese Long Wavelength Explorer (NCLE), which is supposed to be launched in 2018 as part of the ChangE’4 mission to the moon-earth L2 point.

Exploring earth's atmosphere with radio occultation: contributions to weather, climate and space weather

NASA Astrophysics Data System (ADS)

Anthes, R. A.

2011-01-01

The launch of the proof-of-concept mission GPS/MET in 1995 began a revolution in profiling earth's atmosphere through radio occultation (RO). GPS/MET; subsequent single-satellite missions CHAMP, SAC-C, GRACE, METOP-A, and TerraSAR-X; and the six-satellite constellation, FORMOSAT-3/COSMIC, have proven the theoretical capabilities of RO to provide accurate and precise profiles of electron density in the ionosphere and refractivity, containing information on temperature and water vapor, in the stratosphere and troposphere. This paper summarizes results from these RO missions and the applications of RO observations to atmospheric research and operational weather analysis and prediction.

The Radio Jove Project

NASA Technical Reports Server (NTRS)

Thieman, J. R.

2010-01-01

The Radio love Project is a hands-on education and outreach project in which students, or any other interested individuals or groups build a radio telescope from a kit, operate the radio telescope, transmit the resulting signals through the internet if desired, analyze the results, and share the results with others through archives or general discussions among the observers. Radio love is intended to provide an introduction to radio astronomy for the observer. The equipment allows the user to observe radio signals from Jupiter, the Sun, the galaxy, and Earth-based radiation both natural and man-made. The project was started through a NASA Director's Discretionary Fund grant more than ten years ago. it has continued to be carried out through the dedicated efforts of a group of mainly volunteers. Dearly 1500 kits have been distributed throughout the world. Participation can also be done without building a kit. Pre-built kits are available. Users can also monitor remote radio telescopes through the internet using free downloadable software available through the radiosky.com website. There have been many stories of prize-winning projects, inspirational results, collaborative efforts, etc. We continue to build the community of observers and are always open to new thoughts about how to inspire the observers to still greater involvement in the science and technology associated with Radio Jove.

Project Radio JOVE: Hands-On Radio Astronomy for the Classroom

NASA Astrophysics Data System (ADS)

Thieman, J. R.; Higgins, C. A.

2000-10-01

Radio Jove is a relatively new educational project to involve secondary school students in collecting and analyzing observations of the natural radio emissions of the planet Jupiter and the Sun. Participating students get hands-on experience in gathering and working with space science data. They obtain the data by either building a radio receiver and antenna and making observations with their equipment, or by remotely using professional radio telescopes through the web. They can then compare their results with other schools who had also observed and come to conclusions concerning the nature of the radio sources and how the radio waves propagate to Earth. Thus, they fully follow the method of scientific inquiry used by radio astronomers to study our solar system. (National Science Content Standard A: Science as Inquiry) More than 200 kits have been distributed thus far to schools and individuals as a result of the project. With the coming Cassini flyby of Jupiter we will be advocating a campaign in which many of the schools involved in the project will be observing at times of scientific interest. While Galileo and Cassini are monitoring Jovian radio emissions at lower frequencies, the schools will be observing at frequencies of 20.1 MHz (kit-based observations) or the frequencies available through the professional radio telescopes connected on-line. The aim will be to get a thorough picture of the levels of activity at Jupiter during the flyby period and how the radio signals are received at different observing stations around the world. An archive of observations submitted by the schools will be maintained at Goddard Space Flight Center and there will also be an archive of the professional telescopes data at the University of Florida. We hope that many students will have the feeling of being a part of the planetary exploration program as a result.

Wave propagation and earth satellite radio emission studies

NASA Technical Reports Server (NTRS)

Yeh, K. C.; Liu, C. H.; Flaherty, B. J.

1974-01-01

Radio propagation studies of the ionosphere using satellite radio beacons are described. The ionosphere is known as a dispersive, inhomogeneous, irregular and sometimes even nonlinear medium. After traversing through the ionosphere the radio signal bears signatures of these characteristics. A study of these signatures will be helpful in two areas: (1) It will assist in learning the behavior of the medium, in this case the ionosphere. (2) It will provide information of the kind of signal characteristics and statistics to be expected for communication and navigational satellite systems that use the similar geometry.

From COST 271 to 296 EU actions on ionospheric monitoring and modelling for terrestrial and Earth space radio systems

NASA Astrophysics Data System (ADS)

Zolesi, B.; Cander, Lj. R.; Altadill, D.

The ionospheric community has long been aware that co-operative research on an international basis is essential to deal with temporal and spatial changes in the ionosphere that influence the performance of terrestrial and Earth-space radio systems. The EU COST (Co-operation in the field of Scientific and Technical Research) 271 Action on "Effects of the Upper Atmosphere on Terrestrial and Earth-space Communications" has had during the period of October 2000-August 2004 the following main objectives: (1) to evaluate the influence of upper atmospheric conditions on terrestrial and Earth-space communications, (2) to develop methods and techniques to improve ionospheric models over Europe for telecommunication and navigation applications and (3) to transfer the results to the appropriate radiocommunication study groups of the International Telecommunication Union (ITU-R) and other national and international organizations dealing with the modern communication systems. At the beginning of 2005 the new 296 Action in the COST Telecommunications, Information Science and Technology domain on "Mitigation of Ionospheric Effects on Radio Systems (MIERS)" was approved for the period 2005-2009. The main objectives of the MIERS are: (a) to support and enhanced the existing European facilities for historical and real-time digital ionospheric data collection and exchange; (b) to develop an integrated approach to ionospheric modelling, create the mechanism needed to ingest processed data into models, extend and develop suitable mitigation models and define the protocols needed to link models together; and (c) to strengthen the areas of expertise that already exist by stimulating closer cooperation between scientists and users, focusing the scope of all the previous COST ionospheric related studies to the mitigation of ionospheric effects on radio systems. This paper summarises briefly how the major objectives of the COST271 Action have been achieved and what are the most important

Mobile radio interferometric geodetic systems

NASA Technical Reports Server (NTRS)

Macdoran, P. F.; Niell, A. E.; Ong, K. M.; Resch, G. M.; Morabito, D. D.; Claflin, E. S.; Lockhart, T. G.

1978-01-01

Operation of the Astronomical Radio Interferometric Earth Surveying (ARIES) in a proof of concept mode is discussed. Accuracy demonstrations over a short baseline, a 180 km baseline, and a 380 km baseline are documented. Use of ARIES in the Sea Slope Experiment of the National Geodetic Survey to study the apparent differences between oceanographic and geodetic leveling determinations of the sea surface along the Pacific Coast is described. Intergration of the NAVSTAR Global Positioning System and a concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) is briefly reviewed.

The effect of solar radio bursts on the GNSS radio occultation signals

NASA Astrophysics Data System (ADS)

Yue, Xinan; Schreiner, William S.; Kuo, Ying-Hwa; Zhao, Biqiang; Wan, Weixing; Ren, Zhipeng; Liu, Libo; Wei, Yong; Lei, Jiuhou; Solomon, Stan; Rocken, Christian

2013-09-01

radio burst (SRB) is the radio wave emission after a solar flare, covering a broad frequency range, originated from the Sun's atmosphere. During the SRB occurrence, some specific frequency radio wave could interfere with the Global Navigation Satellite System (GNSS) signals and therefore disturb the received signals. In this study, the low Earth orbit- (LEO-) based high-resolution GNSS radio occultation (RO) signals from multiple satellites (COSMIC, CHAMP, GRACE, SAC-C, Metop-A, and TerraSAR-X) processed in University Corporation for Atmospheric Research (UCAR) were first used to evaluate the effect of SRB on the RO technique. The radio solar telescope network (RSTN) observed radio flux was used to represent SRB occurrence. An extreme case during 6 December 2006 and statistical analysis during April 2006 to September 2012 were studied. The LEO RO signals show frequent loss of lock (LOL), simultaneous decrease on L1 and L2 signal-to-noise ratio (SNR) globally during daytime, small-scale perturbations of SNR, and decreased successful retrieval percentage (SRP) for both ionospheric and atmospheric occultations during SRB occurrence. A potential harmonic band interference was identified. Either decreased data volume or data quality will influence weather prediction, climate study, and space weather monitoring by using RO data during SRB time. Statistically, the SRP of ionospheric and atmospheric occultation retrieval shows ~4% and ~13% decrease, respectively, while the SNR of L1 and L2 show ~5.7% and ~11.7% decrease, respectively. A threshold value of ~1807 SFU of 1415 MHz frequency, which can result in observable GNSS SNR decrease, was derived based on our statistical analysis.

Estimation of High-Frequency Earth-Space Radio Wave Signals via Ground-Based Polarimetric Radar Observations

NASA Technical Reports Server (NTRS)

Bolen, Steve; Chandrasekar, V.

2002-01-01

Expanding human presence in space, and enabling the commercialization of this frontier, is part of the strategic goals for NASA's Human Exploration and Development of Space (HEDS) enterprise. Future near-Earth and planetary missions will support the use of high-frequency Earth-space communication systems. Additionally, increased commercial demand on low-frequency Earth-space links in the S- and C-band spectra have led to increased interest in the use of higher frequencies in regions like Ku and Ka-band. Attenuation of high-frequency signals, due to a precipitating medium, can be quite severe and can cause considerable disruptions in a communications link that traverses such a medium. Previously, ground radar measurements were made along the Earth-space path and compared to satellite beacon data that was transmitted to a ground station. In this paper, quantitative estimation of the attenuation along the propagation path is made via inter-comparisons of radar data taken from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and ground-based polarimetric radar observations. Theoretical relationships between the expected specific attenuation (k) of spaceborne measurements with ground-based measurements of reflectivity (Zh) and differential propagation phase shift (Kdp) are developed for various hydrometeors that could be present along the propagation path, which are used to estimate the two-way path-integrated attenuation (PIA) on the PR return echo. Resolution volume matching and alignment of the radar systems is performed, and a direct comparison of PR return echo with ground radar attenuation estimates is made directly on a beam-by-beam basis. The technique is validated using data collected from the TExas and Florida UNderflights (TEFLUN-B) experiment and the TRMM large Biosphere-Atmosphere experiment in Amazonia (LBA) campaign. Attenuation estimation derived from this method can be used for strategiC planning of communication systems for

Propagation effects on radio range and noise in earth-space telecommunications

NASA Technical Reports Server (NTRS)

Flock, W. L.; Slobin, S. D.; Smith, E. K.

1982-01-01

Attention is given to the propagation effects on radio range and noise in earth-space telecommunications. The use of higher frequencies minimizes ionospheric effects on propagation, but tropospheric effects often increase or dominate. For paths of geostationary satellites, and beyond, the excess range delay caused by the ionosphere and plasmasphere is proportional to the total electron content along the path and inversely proportional to frequency squared. The delay due to dry air is usually of the order of a few meters while the delay due to water vapor (a few tens of centimeters) is responsible for most of the temporal variation in the range delay for clean air. For systems such as that of the Voyager spacecraft, and for attenuation values up to about 10 dB, increased sky noise degrades the received signal-to-noise ratio more than does the reduction in signal level due to attenuation.

Finite-difference time-domain modelling of through-the-Earth radio signal propagation

NASA Astrophysics Data System (ADS)

Ralchenko, M.; Svilans, M.; Samson, C.; Roper, M.

2015-12-01

This research seeks to extend the knowledge of how a very low frequency (VLF) through-the-Earth (TTE) radio signal behaves as it propagates underground, by calculating and visualizing the strength of the electric and magnetic fields for an arbitrary geology through numeric modelling. To achieve this objective, a new software tool has been developed using the finite-difference time-domain method. This technique is particularly well suited to visualizing the distribution of electromagnetic fields in an arbitrary geology. The frequency range of TTE radio (400-9000 Hz) and geometrical scales involved (1 m resolution for domains a few hundred metres in size) involves processing a grid composed of millions of cells for thousands of time steps, which is computationally expensive. Graphics processing unit acceleration was used to reduce execution time from days and weeks, to minutes and hours. Results from the new modelling tool were compared to three cases for which an analytic solution is known. Two more case studies were done featuring complex geologic environments relevant to TTE communications that cannot be solved analytically. There was good agreement between numeric and analytic results. Deviations were likely caused by numeric artifacts from the model boundaries; however, in a TTE application in field conditions, the uncertainty in the conductivity of the various geologic formations will greatly outweigh these small numeric errors.

Cognitive radio based optimal channel sensing and resources allocation

NASA Astrophysics Data System (ADS)

Vijayasarveswari, V.; Khatun, S.; Fakir, M. M.; Nayeem, M. N.; Kamarudin, L. M.; Jakaria, A.

2017-03-01

Cognitive radio (CR) is the latest type of wireless technoloy that is proposed to mitigate spectrum saturation problem. İn cognitve radio, secondary user will use primary user's spectrum during primary user's absence without interupting primary user's transmission. This paper focuses on practical cognitive radio network development process using Android based smart phone for the data transmission. Energy detector based sensing method was proposed and used here because it doesnot require primary user's information. Bluetooth and Wi-fi are the two available types of spectrum that was sensed for CR detection. Simulation showed cognitive radio network can be developed using Android based smart phones. So, a complete application was developed using Java based Android Eclipse program. Finally, the application was uploaded and run on Android based smart phone to form and verify CR network for channel sensing and resource allocation. The observed efficiency of the application was around 81%.

Web-based Teaching Radio Interferometer for Africa

NASA Astrophysics Data System (ADS)

Carignan, Claude

2015-08-01

Practical training for the future use of the African VLBI Network (AVN) or any VLBI experiment starts by understanding the basic principles of radio observations and radio interferometry. The aim of this project is to build a basic interferometer that could be used remotely via a web interface from any country on the African continent. This should turn out as a much less expensive and much more efficient way to train AVN researchers from SKA partner countries to the principles of radio astronomy and to interferometric data analysis. The idea is based on the very successful EUHOU (European Hands-On Universe) already very successful in Europe. The former EUHOU manager, Dr Yannick Liebert, arrived for a 3 years postdoc with Prof Claude Carignan at the University of Cape Town to implement the same project on the African continent (AHI: African Hands-on Interferometry). Besides the use of AHI for the AVN researchers, this web-based system could be used be any undergraduate program on radio astronomical techniques across the African continent as the EUHOU is used all across Europe.

The Deep Space Network: An instrument for radio astronomy research

NASA Technical Reports Server (NTRS)

Renzetti, N. A.; Levy, G. S.; Kuiper, T. B. H.; Walken, P. R.; Chandlee, R. C.

1988-01-01

The NASA Deep Space Network operates and maintains the Earth-based two-way communications link for unmanned spacecraft exploring the solar system. It is NASA's policy to also make the Network's facilities available for radio astronomy observations. The Network's microwave communication systems and facilities are being continually upgraded. This revised document, first published in 1982, describes the Network's current radio astronomy capabilities and future capabilities that will be made available by the ongoing Network upgrade. The Bibliography, which includes published papers and articles resulting from radio astronomy observations conducted with Network facilities, has been updated to include papers to May 1987.

A demonstration of an independent-station radio interferometry system with 4-cm precision on a 16-km base line. [for geodesy

NASA Technical Reports Server (NTRS)

Thomas, J. B.; Fanselow, J. L.; Macdoran, P. F.; Skjerve, L. J.; Spitzmesser, D. J.; Fliegel, H. F.

1976-01-01

Radio interferometry promises eventually to measure directly, with accuracies of a few centimeters, both whole earth motions and relative crustal motions with respect to an 'inertial' reference frame. Interferometry measurements of arbitrarily long base lines require, however, the development of new techniques for independent-station observation. In connection with the development of such techniques, a series of short base line demonstration experiments has been conducted between two antennas. The experiments were related to a program involving the design of independent-station instrumentation capable of making three-dimensional earth-fixed base line measurements with an accuracy of a few centimeters. Attention is given to the instrumentation used in the experiments, aspects of data analysis, and the experimental results.

Through-the-earth radio

DOEpatents

Reagor, David [Los Alamos, NM; Vasquez-Dominguez, Jose [Los Alamos, NM

2006-05-09

A method and apparatus for effective through-the-earth communication involves a signal input device connected to a transmitter operating at a predetermined frequency sufficiently low to effectively penetrate useful distances through-the earth, and having an analog to digital converter receiving the signal input and passing the signal input to a data compression circuit that is connected to an encoding processor, the encoding processor output being provided to a digital to analog converter. An amplifier receives the analog output from the digital to analog converter for amplifying said analog output and outputting said analog output to an antenna. A receiver having an antenna receives the analog output passes the analog signal to a band pass filter whose output is connected to an analog to digital converter that provides a digital signal to a decoding processor whose output is connected to an data decompressor, the data decompressor providing a decompressed digital signal to a digital to analog converter. An audio output device receives the analog output form the digital to analog converter for producing audible output.

Polarimetric mountain based radio-occultation for rain detection: The ROHP-PAZ ground campaign

NASA Astrophysics Data System (ADS)

Padulles, Ramon; Cardellach, Estel; Tomas, Sergio; de la Torre, Manuel; Turk, Joe

2014-05-01

The Radio Occultation and Heavy Precipitation experiment aboard the PAZ Low Earth Orbiter (ROHP-PAZ) is a mission of opportunity: The Spanish Ministry of Science and Innovation (MICINN) approved in 2009 a proposal to include a polarimetric Global Navigation Satellite System (GNSS) Radio-Occultation (RO) payload on board of the Spanish Earth Observation satellite PAZ. This will be a new technique that has never been tested before, that aims to improve the knowledge of precipitation through simultaneous thermodynamic and vertical rain profiles. Prior to the launch of the satellite, expected for 2014, a ground experimental campaign is being conducted with the goal of starting the process of identifying and understanding all the factors that might affect the polarimetric RO observables. The campaign is being carried out at the top of Puig Sesolles, a 1667m peak in the Natural Park of Montseny (41º46'24 N, 2º26'17 E), 50 km N-NE from Barcelona, with clear views over the horizon to the South (East to West) direction, an area in which intense precipitation events tend to occur a few times per year. The campaign uses a ICE-CSIC/IEEC's GOLD-RTR open-loop receiver initially designed for collecting GNSS signals reflected off the sea surface. The receiver has been adjusted to track occulting GNSS radio-links. A double polarization (H and V) GNSS antenna has been designed and manufactured by the Polytechnic University of Barcelona (UPC) team for this particular ground-based experiment. The antenna is a phase-array made of 7 elements, each of them being a square patch built using a Rogers 4003 substrate, and symmetrically fed by four probes. It provides a pattern of 12.9 dB peak gain, 45 degrees half-power beam-width, and <-35 dB cross-polar isolation at the peak (better than -30 dB in the main lobe). The preliminary results show that not only precipitation, but also other factors are affecting the GNSS signal, wich means that the polarimetric signal is richer than expected

A New Generation of Telecommunications for Mars: The Reconfigurable Software Radio

NASA Technical Reports Server (NTRS)

Adams, J.; Horne, W.

2000-01-01

Telecommunications is a critical component for any mission at Mars as it is an enabling function that provides connectivity back to Earth and provides a means for conducting science. New developments in telecommunications, specifically in software - configurable radios, expand the possible approaches for science missions at Mars. These radios provide a flexible and re-configurable platform that can evolve with the mission and that provide an integrated approach to communications and science data processing. Deep space telecommunication faces challenges not normally faced by terrestrial and near-earth communications. Radiation, thermal, highly constrained mass, volume, packaging and reliability all are significant issues. Additionally, once the spacecraft leaves earth, there is no way to go out and upgrade or replace radio components. The reconfigurable software radio is an effort to provide not only a product that is immediately usable in the harsh space environment but also to develop a radio that will stay current as the years pass and technologies evolve.

Near Earth Network (NEN) CubeSat Communications

NASA Technical Reports Server (NTRS)

Schaire, Scott

2017-01-01

The NASA Near Earth Network (NEN) consists of globally distributed tracking stations, including NASA, commercial, and partner ground stations, that are strategically located to maximize the coverage provided to a variety of orbital and suborbital missions, including those in LEO (Low Earth Orbit), GEO (Geosynchronous Earth Orbit), HEO (Highly Elliptical Orbit), lunar and L1-L2 orbits. The NEN's future mission set includes and will continue to include CubeSat missions. The first NEN-supported CubeSat mission will be the Cubesat Proximity Operations Demonstration (CPOD) launching into LEO in 2017. The majority of the CubeSat missions destined to fly on EM-1, launching in late 2018, many in a lunar orbit, will communicate with ground-based stations via X-band and will utilize the NASA Jet Propulsion Laboratory (JPL)-developed IRIS (Satellite Communication for Air Traffic Management) radio. The NEN recognizes the important role CubeSats are beginning to play in carrying out NASAs mission and is therefore investigating the modifications needed to provide IRIS radio compatibility. With modification, the NEN could potentially expand support to the EM-1 (Exploration Mission-1) lunar CubeSats. The NEN could begin providing significant coverage to lunar CubeSat missions utilizing three to four of the NEN's mid-latitude sites. This coverage would supplement coverage provided by the JPL Deep Space Network (DSN). The NEN, with smaller apertures than DSN, provides the benefit of a larger beamwidth that could be beneficial in the event of uncertain ephemeris data. In order to realize these benefits the NEN would need to upgrade stations targeted based on coverage ability and current configuration ease of upgrade, to ensure compatibility with the IRIS radio. In addition, the NEN is working with CubeSat radio developers to ensure NEN compatibility with alternative CubeSat radios for Lunar and L1-L2 CubeSats. The NEN has provided NEN compatibility requirements to several radio

Low-frequency Radio Observatory on the Lunar Surface (LROLS)

NASA Astrophysics Data System (ADS)

MacDowall, Robert; Network for Exploration and Space Science (NESS)

2018-06-01

A radio observatory on the lunar surface will provide the capability to image solar radio bursts and other sources. Radio burst imaging will improve understanding of radio burst mechanisms, particle acceleration, and space weather. Low-frequency observations (less than ~20 MHz) must be made from space, because lower frequencies are blocked by Earth’s ionosphere. Solar radio observations do not mandate an observatory on the farside of the Moon, although such a location would permit study of less intense solar bursts because the Moon occults the terrestrial radio frequency interference. The components of the lunar radio observatory array are: the antenna system consisting of 10 – 100 antennas distributed over a square kilometer or more; the system to transfer the radio signals from the antennas to the central processing unit; electronics to digitize the signals and possibly to calculate correlations; storage for the data until it is down-linked to Earth. Such transmission requires amplification and a high-gain antenna system or possibly laser comm. For observatories on the lunar farside a satellite or other intermediate transfer system is required to direct the signal to Earth. On the ground, the aperture synthesis analysis is completed to display the radio image as a function of time. Other requirements for lunar surface systems include the power supply, utilizing solar arrays with batteries to maintain the system at adequate thermal levels during the lunar night. An alternative would be a radioisotope thermoelectric generator requiring less mass. The individual antennas might be designed with their own solar arrays and electronics to transmit data to the central processing unit, but surviving lunar night would be a challenge. Harnesses for power and data transfer from the central processing unit to the antennas are an alternative, but a harness-based system complicates deployment. The concept of placing the antennas and harnesses on rolls of polyimide and

Direct Communication to Earth from Probes

NASA Technical Reports Server (NTRS)

Bolton, Scott J.; Folkner, William M.; Abraham, Douglas S.

2005-01-01

A viewgraph presentation on outer planetary probe communications to Earth is shown. The topics include: 1) Science Rational for Atmospheric Probes to the Outer Planets; 2) Controlling the Scientific Appetite; 3) Learning more about Jupiter before we send more probes; 4) Sample Microwave Scan From Juno; 5) Jupiter s Deep Interior; 6) The Square Kilometer Array (SKA): A Breakthrough for Radio Astronomy; 7) Deep Space Array-based Network (DSAN); 8) Probe Direct-to-Earth Data Rate Calculations; 9) Summary; and 10) Enabling Ideas.

Radio detection of extensive air showers

NASA Astrophysics Data System (ADS)

Huege, Tim

2017-12-01

Radio detection of extensive air showers initiated in the Earth's atmosphere has made tremendous progress in the last decade. Today, radio detection is routinely used in several cosmic-ray observatories. The physics of the radio emission in air showers is well-understood, and analysis techniques have been developed to determine the arrival direction, the energy and an estimate for the mass of the primary particle from the radio measurements. The achieved resolutions are competitive with those of more traditional techniques. In this article, I shortly review the most important achievements and discuss the potential for future applications.

Radio-planetary from tie from Phobos-2 VLBI data

NASA Technical Reports Server (NTRS)

Hildebrand, C. E.; Iijima, B. A.; Kroger, P. M.; Folkner, W. M.; Edwards, C. D.

1994-01-01

In an ongoing effort to improve the knowledge of the relative orientation (the 'frame tie') of the planetary ephemeris reference frame used in deep navigation and a second reference frame that is defined by the coordinates of a set of extragalactic radio sources, VLBI observations of the Soviet Phobos-2 spacecraft and nearby (in angle) radio sources were obtained at two epochs in 1989, shortly after the spacecraft entered orbit about Mars. The frame tie is an important systematic error source affecting both interplanetary navigation and the process of improving the theory of the Earth's orientation. The data from a single Phobos-2 VLBI session measure one component of the direction vector from Earth to Mars in the frame of the extragalactic radio sources (the 'radio frame'). The radio frame has been shown to be stable and internally consistent with an accuracy of 5 nrad. The planetary ephemeris reference frame has an internal consistency of approximately 15 nrad. The planetary and radio source reference frames were aligned prior to 1989 and measurements of occulations of the radio source 3C273 by the Moon. The Phobos-2 VLBI measurements provide improvement in the accuracy of two of the three angles describing a general rotation between the planetary and radio reference frames. A complete set of measurements is not available because data acquisition was terminated prematurely by loss of spacecraft. The analysis of the two Phobos-2 VLBI data sets indicates that, in the directions of the two rotation components determined by these data, the JPL planetary ephemeris DE200 is aligned with the radio frame as adopted by the International Earth Rotation Service within an accuracy of 20-40 nrad, depending on direction. The limiting errors in the solutions for these offsets are spacecraft trajectory (20 nrad), instrumental biases (19 nrad), and dependence of quasar coordinates on observing frequency (24 nrad).

A Radio-Map Automatic Construction Algorithm Based on Crowdsourcing

PubMed Central

Yu, Ning; Xiao, Chenxian; Wu, Yinfeng; Feng, Renjian

2016-01-01

Traditional radio-map-based localization methods need to sample a large number of location fingerprints offline, which requires huge amount of human and material resources. To solve the high sampling cost problem, an automatic radio-map construction algorithm based on crowdsourcing is proposed. The algorithm employs the crowd-sourced information provided by a large number of users when they are walking in the buildings as the source of location fingerprint data. Through the variation characteristics of users’ smartphone sensors, the indoor anchors (doors) are identified and their locations are regarded as reference positions of the whole radio-map. The AP-Cluster method is used to cluster the crowdsourced fingerprints to acquire the representative fingerprints. According to the reference positions and the similarity between fingerprints, the representative fingerprints are linked to their corresponding physical locations and the radio-map is generated. Experimental results demonstrate that the proposed algorithm reduces the cost of fingerprint sampling and radio-map construction and guarantees the localization accuracy. The proposed method does not require users’ explicit participation, which effectively solves the resource-consumption problem when a location fingerprint database is established. PMID:27070623

Low Frequency Radio Experiment (LORE)

NASA Astrophysics Data System (ADS)

Manoharan, P. K.; Naidu, Arun; Joshi, B. C.; Roy, Jayashree; Kate, G.; Pethe, Kaiwalya; Galande, Shridhar; Jamadar, Sachin; Mahajan, S. P.; Patil, R. A.

2016-03-01

In this paper, we present a case study of Low Frequency Radio Experiment (LORE) payload to probe the corona and the solar disturbances at solar offsets greater than 2 solar radii, i.e., at frequencies below 30 MHz. The LORE can be complimentary to the planned Indian solar mission, “Aditya-L1” and its other payloads as well as synergistic to ground-based interplanetary scintillation (IPS) observations, which are routinely carried out by the Ooty Radio Telescope. We discuss the baseline design and technical details of the proposed LORE and its particular suitability for providing measurements on the detailed time and frequency structure of fast drifting type-III and slow drifting type-II radio bursts with unprecedented time and frequency resolutions. We also brief the gonio-polarimetry, which is possible with better-designed antennas and state-of-the-art electronics, employing FPGAs and an intelligent data management system. These would enable us to make a wide range of studies, such as nonlinear plasma processes in the Sun-Earth distance, in-situ radio emission from coronal mass ejections (CMEs), interplanetary CME driven shocks, nature of ICMEs driving decelerating IP shocks and space weather effects of solar wind interaction regions.

A demonstration of a transportable radio interferometric surveying system with 3-cm accuracy on a 307-m base line

NASA Technical Reports Server (NTRS)

Ong, K. M.; Macdoran, P. F.; Thomas, J. B.; Fliegel, H. F.; Skjerve, L. J.; Spitzmesser, D. J.; Batelaan, P. D.; Paine, S. R.; Newsted, M. G.

1976-01-01

A precision geodetic measurement system (Aries, for Astronomical Radio Interferometric Earth Surveying) based on the technique of very long base line interferometry has been designed and implemented through the use of a 9-m transportable antenna and the NASA 64-m antenna of the Deep Space Communications Complex at Goldstone, California. A series of experiments designed to demonstrate the inherent accuracy of a transportable interferometer was performed on a 307-m base line during the period from December 1973 to June 1974. This short base line was chosen in order to obtain a comparison with a conventional survey with a few-centimeter accuracy and to minimize Aries errors due to transmission media effects, source locations, and earth orientation parameters. The base-line vector derived from a weighted average of the measurements, representing approximately 24 h of data, possessed a formal uncertainty of about 3 cm in all components. This average interferometry base-line vector was in good agreement with the conventional survey vector within the statistical range allowed by the combined uncertainties (3-4 cm) of the two techniques.

The Determination of Earth Orientation by VLBI and GNSS: Principles and Results

NASA Astrophysics Data System (ADS)

Capitaine, Nicole

2017-10-01

The Earth Orientation Parameters (EOP) connect the International Terrestrial Reference System (ITRS) to the Geocentric Celestial Reference System (GCRS). These parameters, i.e., Universal Time, UT1, and pole coordinates in the ITRS and in the GCRS, describe the irregularities of the Earth's rotation. They are mainly determined by two modern astro-geodetic techniques, VLBI (Very Long Baseline Radio Interferometry) on extragalactic radio sources, which is used to realize and maintain the International Celestial Reference System (ICRS), and Global Navigation Satellite System (GNSS), especially GPS (Global Positioning System), which has an important contribution to the realization of the ITRS. The aim of this presentation is twofold: to present the modern bases for the consider- ation of Earth orientation and to discuss how the principles of VLBI and GPS give access to the measure of different components of the EOP variations, especially UT1. The accuracy that can be achieved is based on the improved concepts, definitions, and models that have been adopted by IAU/IUGG resolutions on reference systems and Earth's rotation, as well as on the refined strategy of the observations.

Need a Classroom Stimulus? Introduce Radio Astronomy

ERIC Educational Resources Information Center

Derman, Samuel

2010-01-01

Silently, invisibly, ceaselessly, our planet Earth is showered by radio waves from every direction and from every region of space. This radio energy originates in our solar system, throughout the Milky Way galaxy, and far beyond, out to the remotest reaches of the universe. Detecting and unraveling the origins of these invisible signals is what…

Discovering the Highest Energy Neutrinos Using a Radio Phased Array

NASA Astrophysics Data System (ADS)

Vieregg, Abigail

2018-06-01

The detection of high energy neutrinos is an important step toward understanding the most energetic cosmic accelerators and would enable tests of fundamental physics at energy scales that cannot easily be achieved on Earth. IceCube has detected astrophysical neutrinos at lower energies, and at higher energies the best limits to date on the flux comes from IceCube and the ANITA experiment, a NASA balloon-borne radio telescope designed to detect coherent radio Cherenkov emission from cosmogenic ultra-high energy neutrinos. I will discuss a new radio phased array design that will push the achievable sensitivity and lower the energy threshold. I will discuss the initial deployment and performance of an 8-channel system in a ground-based experiment at the South Pole (ARA), and the plans for scaling to O(100) channels and lowering the power consumption for future balloon-borne and ground-based applications.

Utilization-Based Modeling and Optimization for Cognitive Radio Networks

NASA Astrophysics Data System (ADS)

Liu, Yanbing; Huang, Jun; Liu, Zhangxiong

The cognitive radio technique promises to manage and allocate the scarce radio spectrum in the highly varying and disparate modern environments. This paper considers a cognitive radio scenario composed of two queues for the primary (licensed) users and cognitive (unlicensed) users. According to the Markov process, the system state equations are derived and an optimization model for the system is proposed. Next, the system performance is evaluated by calculations which show the rationality of our system model. Furthermore, discussions among different parameters for the system are presented based on the experimental results.

The Spectrum Landscape: Prospects for Terrestrial Radio Astronomy

NASA Astrophysics Data System (ADS)

Liszt, Harvey Steven

2018-01-01

Radio astronomers work within broad constraints imposed by commercial and other non-astronomical uses of the radio spectrum, somewhat modified to accommodate astronomy’s particular needs through the provision of radio quiet zones, radio frequency allocations, coordination agreements and other devices of spectrum management. As radio astronomers increase the instantaneous bandwidth, frequency coverage and sensitivity of their instruments, these external constraints, and not the limitations of their own instruments, will increasingly be the greatest obstacles to radio astronomy’s ability to observe the cosmos from the surface of the Earth. Therefore, prospects for future radio astronomy operations are contingent on situational awareness and planning for the impact of non-astronomical uses of the radio frequency spectrum. New radio astronomy instruments will have to incorporate adaptive reactions to external developments, and radio astronomers should be encouraged to think in untraditional ways. Increased attention to spectrum management is one of these. In this talk I’ll recap some recent developments such as the proliferation of 76 – 81 GHz car radar and orbiting earth-mapping radars, either of which can burn out a radio astronomy receiver. I’ll summarize present trends for non-astronomical radio spectrum use that will be coming to fruition in the next decade or so, categorized into terrestrial fixed and mobile, airborne and space-borne uses, sub-divided by waveband from the cm to the sub-mm. I’ll discuss how they will impact terrestrial radio astronomy and the various ways in which radio astronomy should be prepared to react. Protective developments must occur both within radio astronomy’s own domain – designing, siting and constructing its instruments and mitigating unavoidable RFI – and facing outward toward the community of other spectrum users. Engagement with spectrum management is no panacea but it is an important means, and perhaps the only

Echo power analysis and simulation of low altitude radio fuze

NASA Astrophysics Data System (ADS)

Chen, Xiaolu; Chen, Biao; Xu, Tao; Xu, Suqin

2013-01-01

The echo power from the earth gound which was received by fuze plays an important role in aerial defense missile, especially when the fuze is working in the look down mode. It is necessary to analyze and even simulate the echo power signals to enhance the missile's anti-jamming ability. In this paper, the quantity of echo power from the earth ground of low altitude radio fuze was analyzed in detail. Three boundary equations of area irradiated by electromagnetic beams were presented, which include two equidistant curve equations and one equal-Doppler curve equation. The relationship between the working mode and the critical height was analyzed. The calculating formula of echo power waveform was derived. And based on the derived formula, the correlation between the maximal echo power and the incident height was given and simulated, which would be helpful for the further researches of low altitude radio fuze.

Developing Benchmarks for Solar Radio Bursts

NASA Astrophysics Data System (ADS)

Biesecker, D. A.; White, S. M.; Gopalswamy, N.; Black, C.; Domm, P.; Love, J. J.; Pierson, J.

2016-12-01

Solar radio bursts can interfere with radar, communication, and tracking signals. In severe cases, radio bursts can inhibit the successful use of radio communications and disrupt a wide range of systems that are reliant on Position, Navigation, and Timing services on timescales ranging from minutes to hours across wide areas on the dayside of Earth. The White House's Space Weather Action Plan has asked for solar radio burst intensity benchmarks for an event occurrence frequency of 1 in 100 years and also a theoretical maximum intensity benchmark. The solar radio benchmark team was also asked to define the wavelength/frequency bands of interest. The benchmark team developed preliminary (phase 1) benchmarks for the VHF (30-300 MHz), UHF (300-3000 MHz), GPS (1176-1602 MHz), F10.7 (2800 MHz), and Microwave (4000-20000) bands. The preliminary benchmarks were derived based on previously published work. Limitations in the published work will be addressed in phase 2 of the benchmark process. In addition, deriving theoretical maxima requires additional work, where it is even possible to, in order to meet the Action Plan objectives. In this presentation, we will present the phase 1 benchmarks and the basis used to derive them. We will also present the work that needs to be done in order to complete the final, or phase 2 benchmarks.

The Application Design of Solar Radio Spectrometer Based on FPGA

NASA Astrophysics Data System (ADS)

Du, Q. F.; Chen, R. J.; Zhao, Y. C.; Feng, S. W.; Chen, Y.; Song, Y.

2017-10-01

The Solar radio spectrometer is the key instrument to observe solar radio. By programing the computer software, we control the AD signal acquisition card which is based on FPGA to get a mass of data. The data are transferred by using PCI-E port. This program has realized the function of timing data collection, finding data in specific time and controlling acquisition meter in real time. It can also map the solar radio power intensity graph. By doing the experiment, we verify the reliability of solar radio spectrum instrument, in the meanwhile, the instrument simplifies the operation in observing the sun.

The GNSS polarimetric radio-occultation technique to sense precipitation events: a new concept to be tested aboard PAZ Low Earth Satellite

NASA Astrophysics Data System (ADS)

Tomás, Sergio; Oliveras, Santi; Cardellach, Estel; Rius, Antonio

2013-04-01

The Radio Occultation and Heavy Precipitation (ROHP) experiment, to be conducted aboard the Spanish PAZ satellite, consists of a radio occultation (RO) mission provided with dual-polarization capabilities. The research with polarimetric RO data has the goal of assessing the capabilities and limitations of this technique to infer profiles of heavy precipitation. The technique aims to provide vertical profiles of precipitation simultaneously to the vertical profiles of thermodynamic parameters (standard RO products) perfectly collocated both in space and time. If successful, the polarimetric RO will represent the first technique able to provide these complementary information on precipitation. This is a relevant input for studies on heavy and violent rainfall events, which being poorly represented by the current-generation of Numerical Weather Prediction and General Circulation Models appear to be difficult to forecast on all time-scales. The Low Earth Orbiter hosting this experiment, to be launched in 2013, will orbit at 500 km altitude in a near-Polar orbit. The Radio Occulation payload includes a RO GNSS receiver and a dual polarization (H/V) limb oriented antenna to capture the signals of setting GNSS transmitters. NOAA and UCAR participate in the ground-segment of the radiometric experiment to enable near-real time dissemination of the level-1 standard RO products. The space-based GNSS RO technique scans the atmosphere vertically at fine resolution (close to 300 meter in the troposphere) by precisely measure the delay between a GNSS transmitter and a GNSS receiver aboard a Low Earth Orbiter, when the former is setting below or rising above the Earth limb. The standard, thermodynamical, products are extracted from the excess delay induced by the atmosphere at different layers. This presentation will not focus on this well-established application, but a novel concept using polarimetry to also retrieve rain information. The precipitation-measurement principle is

Empowering file-based radio production through media asset management systems

NASA Astrophysics Data System (ADS)

Muylaert, Bjorn; Beckers, Tom

2006-10-01

In recent years, IT-based production and archiving of media has matured to a level which enables broadcasters to switch over from tape- or CD-based to file-based workflows for the production of their radio and television programs. This technology is essential for the future of broadcasters as it provides the flexibility and speed of execution the customer demands by enabling, among others, concurrent access and production, faster than real-time ingest, edit during ingest, centrally managed annotation and quality preservation of media. In terms of automation of program production, the radio department is the most advanced within the VRT, the Flemish broadcaster. Since a couple of years ago, the radio department has been working with digital equipment and producing its programs mainly on standard IT equipment. Historically, the shift from analogue to digital based production has been a step by step process initiated and coordinated by each radio station separately, resulting in a multitude of tools and metadata collections, some of them developed in-house, lacking integration. To make matters worse, each of those stations adopted a slightly different production methodology. The planned introduction of a company-wide Media Asset Management System allows a coordinated overhaul to a unified production architecture. Benefits include the centralized ingest and annotation of audio material and the uniform, integrated (in terms of IT infrastructure) workflow model. Needless to say, the ingest strategy, metadata management and integration with radio production systems play a major role in the level of success of any improvement effort. This paper presents a data model for audio-specific concepts relevant to radio production. It includes an investigation of ingest techniques and strategies. Cooperation with external, professional production tools is demonstrated through a use-case scenario: the integration of an existing, multi-track editing tool with a commercially available

MERI: an ultra-long-baseline Moon-Earth radio interferometer.

NASA Astrophysics Data System (ADS)

Burns, J. O.

Radiofrequency aperture synthesis, pioneered by Ryle and his colleagues at Cambridge in the 1960's, has evolved to ever longer baselines and larger arrays in recent years. The limiting resolution at a given frequency for modern ground-based very-long-baseline interferometry is simply determined by the physical diameter of the Earth. A second-generation, totally space-based VLB network was proposed recently by a group at the Naval Research Laboratory. The next logical extension of space-based VLBI would be a station or stations on the Moon. The Moon could serve as an outpost or even the primary correlator station for an extended array of space-based antennas.

Astronomers Win Protection for Key Part of Radio Spectrum

NASA Astrophysics Data System (ADS)

2000-06-01

International Telecommunication Union meet to painstakingly parcel out the radio frequency spectrum between radio-based applications such as personal communications, satellite broadcasting, GPS and amateur radio, and the sciences of radio astronomy, earth exploration and deep space research. The WRC also coordinates sharing between services in the same radio bands. WRC decisions are incorporated into the Radio Regulations that govern radio services worldwide. The new spectrum allocations for radio astronomy are the first since 1979. Millimeter-wave astronomy was then in its infancy and many of its needs were not yet known. As astronomers began to explore this region of the spectrum they found spectral lines from many interesting molecules in space. Many of those lines had not fallen into the areas originally set aside for astronomy, but most will be under the new allocations. "It's a win for millimeter-wave science," said Dr. John Whiteoak of the Australia Telescope National Facility, Australian delegate to WRC-00. "This secures its future." The protection is a significant step for both existing millimeter-wave telescopes and new ones such as the Atacama Large Millimeter Array (ALMA) now being planned by a U.S.-European consortium. Even at its isolated site in Chile's Atacama desert, ALMA would be vulnerable to interference from satellite emissions. Sensitive radio astronomy receivers are blinded by these emissions, just as an optical telescope would be by a searchlight. "There is more energy at millimeter and sub-millimeter wavelengths washing through the Universe than there is of light or any other kind of radiation," said ALMA Project Scientist, Dr. Al Wootten of the National Radio Astronomy Observatory. "Imaging the sources of this energy can tell us a great deal about the formation of stars and galaxies, and even planets." "But the Earth's atmosphere isn't very kind to us - it has only a few windows at these frequencies, and not very transparent ones at that. They are

Amateur Planetary Radio Data Archived for Science and Education: Radio Jove

NASA Astrophysics Data System (ADS)

Thieman, J.; Cecconi, B.; Sky, J.; Garcia, L. N.; King, T. A.; Higgins, C. A.; Fung, S. F.

2015-12-01

The Radio Jove Project is a hands-on educational activity in which students, teachers, and the general public build simple radio telescopes, usually from a kit, to observe single frequency decameter wavelength radio emissions from Jupiter, the Sun, the galaxy, and the Earth usually with simple dipole antennas. Some of the amateur observers have upgraded their receivers to spectrographs and their antennas have become more sophisticated as well. The data records compare favorably to more sophisticated professional radio telescopes such as the Long Wavelength Array (LWA) and the Nancay Decametric Array. Since these data are often carefully calibrated and recorded around the clock in widely scattered locations they represent a valuable database useful not only to amateur radio astronomers but to the professional science community as well. Some interesting phenomena have been noted in the data that are of interest to the professionals familiar with such records. The continuous monitoring of radio emissions from Jupiter could serve as useful "ground truth" data during the coming Juno mission's radio observations of Jupiter. Radio Jove has long maintained an archive for thousands of Radio Jove observations, but the database was intended for use by the Radio Jove participants only. Now, increased scientific interest in the use of these data has resulted in several proposals to translate the data into a science community data format standard and store the data in professional archives. Progress is being made in translating Radio Jove data to the Common Data Format (CDF) and also in generating new observations in that format as well. Metadata describing the Radio Jove data would follow the Space Physics Archive Search and Extract (SPASE) standard. The proposed archive to be used for long term preservation would be the Planetary Data System (PDS). Data sharing would be achieved through the PDS and the Paris Astronomical Data Centre (PADC) and the Virtual Wave Observatory (VWO

A review of ionospheric effects on Earth-space propagation

NASA Technical Reports Server (NTRS)

Klobuchar, J. A.

1984-01-01

A short description is given of each ionospheric total electron content (TEC) effect upon radio waves, along with a representative value of the magnitude of each of these effects under normal ionospheric conditions. A discussion is given of the important characteristics of average ionospheric TEC behavior and the temporal and spatial variability of TEC. Radio waves undergo several effects when they pass through the Earth's ionosphere. One of the most important of these effects is a retardation, or group delay, on the modulation or information carried on the radio wave that is due to its encounter with the free, thermal electrons in the Earth's ionosphere. Other effects the ionosphere has on radio waves include: radio frequency (RF) carrier phase advance; Doppler shift of the RF carrier of the radio wave; Faraday rotation of the plane of polarization of linearly polarized waves; angular refraction or bending of the radio wave path as it travels through the ionosphere; and amplitude and phase scintillations.

47 CFR 32.2231 - Radio systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... costs. This account shall also include the original cost of earth stations and spare parts, material or..., amplification, propagation, reception, modulation, and demodulation of radio waves in free space over which...

Thunderstorms and ground-based radio noise as observed by radio astronomy Explorer 1

NASA Technical Reports Server (NTRS)

Caruso, J. A.; Herman, J. R.

1973-01-01

Radio Astronomy Explorer (RAE) data were analyzed to determine the frequency dependence of HF terrestrial radio noise power. RAE observations of individual thunderstorms, mid-ocean areas, and specific geographic regions for which concommitant ground based measurements are available indicate that noise power is a monotonically decreasing function of frequency which conforms to expectations over the geographic locations and time periods investigated. In all cases investigated, active thunderstorm regions emit slightly higher power as contrasted to RAE observations of the region during meteorologically quiet periods. Noise levels are some 15 db higher than predicted values over mid-ocean, while in locations where ground based measurements are available a maximum deviation of 5 db occurs. Worldwide contour mapping of the noise power at 6000 km for five individual months and four observing frequencies, examples of which are given, indicate high noise levels over continental land masses with corresponding lower levels over ocean regions.

Tiny radio is based on diamond effects

NASA Astrophysics Data System (ADS)

2017-02-01

You could soon be tuning into “Diamond FM”, thanks to a new radio receiver based on atomic-scale defects in diamond, unveiled by physicists at Harvard University in the US and Element Six in the UK.

Web-based Teaching Radio Interferometer for Africa

NASA Astrophysics Data System (ADS)

Carignan, Claude; Libert, Yannick

2016-10-01

This presentation describes the web-based Teaching Radio Interferometer being built on the campus of the University of Cape Town, in South Africa, to train the future users of the African VLBI (Very Long Baseline Interferometry) Network (AVN).

Satellite observations of type III solar radio bursts at low frequencies

NASA Technical Reports Server (NTRS)

Fainberg, J.; Stone, R. G.

1974-01-01

Type III solar radio bursts have been observed from 10 MHz to 10 kHz by satellite experiments above the terrestrial plasmasphere. Solar radio emission in this frequency range results from excitation of the interplanetary plasma by energetic particles propagating outward along open field lines over distances from 5 earth radii to at least 1 AU from the sun. This review summarizes the morphology, characteristics, and analysis of individual as well as storms of bursts. Substantial evidence is available to show that the radio emission is observed at the second harmonic instead of the fundamental of the plasma frequency. This brings the density scale derived by radio observations into better agreement with direct solar wind density measurements at 1 AU and relaxes the requirement for type III propagation along large density-enhanced regions. This density scale with the measured direction of arrival of the radio burst allows the trajectory of the exciter path to be determined from 10 earth radii to 1 AU.

Radio morphing - towards a full parametrisation of the radio signal from air showers

NASA Astrophysics Data System (ADS)

Zilles, A.; Charrier, D.; Kotera, K.; Le Coz, S.; Martineau-Huynh, O.; Medina, C.; Niess, V.; Tueros, M.; de Vries, K.

2017-12-01

Over the last decades, radio detection of air showers has been established as a detection technique for ultra-high-energy cosmic-rays impinging on the Earth's atmosphere with energies far beyond LHC energies. Today’s second-generation of digital radio-detection experiments, as e.g. AERA or LOFAR, are becoming competitive in comparison to already standard techniques e.g. fluorescence light detection. Thanks to a detailed understanding of the physics of the radio emission in extensive air showers, simulations of the radio signal are already successfully tested and applied in the reconstruction of cosmic rays. However the limits of the computational power resources are easily reached when it comes to computing electric fields at the numerous positions requested by large or dense antenna arrays. In the case of mountainous areas as e.g. for the GRAND array, where 3D shower simulations are necessary, the problem arises with even stronger acuity. Therefore we developed a full parametrisation of the emitted radio signal on the basis of generic shower simulations which will reduce the simulation time by orders of magnitudes. In this talk we will present this concept after a short introduction to the concept of the radio detection of air-shower induced by cosmic rays.

A radio telescope for the calibration of radio sources at 32 gigahertz

NASA Technical Reports Server (NTRS)

Gatti, M. S.; Stewart, S. R.; Bowen, J. G.; Paulsen, E. B.

1994-01-01

A 1.5-m-diameter radio telescope has been designed, developed, and assembled to directly measure the flux density of radio sources in the 32-GHz (Ka-band) frequency band. The main goal of the design and development was to provide a system that could yield the greatest absolute accuracy yet possible with such a system. The accuracy of the measurements have a heritage that is traceable to the National Institute of Standards and Technology. At the present time, the absolute accuracy of flux density measurements provided by this telescope system, during Venus observations at nearly closest approach to Earth, is plus or minus 5 percent, with an associated precision of plus or minus 2 percent. Combining a cooled high-electron mobility transistor low-noise amplifier, twin-beam Dicke switching antenna, and accurate positioning system resulted in a state-of-the-art system at 32 GHz. This article describes the design and performance of the system as it was delivered to the Owens Valley Radio Observatory to support direct calibrations of the strongest radio sources at Ka-band.

Radio-loud CMEs from the Disk Center Lacking Shocks at 1 AU

NASA Technical Reports Server (NTRS)

Gopalswamy, N; Makela, P.; Akiyama, S.; Yashiro, S.; Xie, H.; MacDowall, R. J.; Kaiser, M. L.

2013-01-01

A coronal mass ejection (CME) associated with a type II burst and originating close to the center of the solar disk typically results in a shock at Earth in 2-3 days and hence can be used to predict shock arrival at Earth. However, a significant fraction (about 28%) of such CMEs producing type II bursts were not associated with shocks at Earth. We examined a set of 21 type II bursts observed by the Wind/WAVES experiment at decameter-hectometric (DH) wavelengths that had CME sources very close to the disk center (within a central meridian distance of 30 degrees), but did not have a shock at Earth. We find that the near-Sun speeds of these CMEs average to 644 km/s, only slightly higher than the average speed of CMEs associated with radio-quiet shocks. However, the fraction of halo CMEs is only 30%, compared to 54% for the radio-quiet shocks and 91% for all radio-loud shocks. We conclude that the disk-center radio-loud CMEs with no shocks at 1 AU are generally of lower energy and they drive shocks only close to the Sun and dissipate before arriving at Earth. There is also evidence for other possible processes that lead to the lack of shock at 1 AU: (i) overtaking CME shocks merge and one observes a single shock at Earth, and (ii) deflection by nearby coronal holes can push the shocks away from the Sun-Earth line, such that Earth misses these shocks. The probability of observing a shock at 1 AU increases rapidly above 60% when the CME speed exceeds 1000 km/s and when the type II bursts propagate to frequencies below 1 MHz.

Mars observer radio science (MORS) observations in polar regions

NASA Technical Reports Server (NTRS)

Simpson, Richard A.

1992-01-01

MORS observations will focus on two major areas of study: (1) the gravity field of Mars and its interpretation in terms of internal structure and history and (2) the structure of the atmosphere, with emphasis on both temperature-pressure profiles of the background atmosphere and small scale inhomogeneities resulting from turbulence. Scattering of cm wavelength radio signals from Mars' surface at highly oblique angles will also be studied during the primary mission; nongrazing scattering experiments may be possible during an extended mission. During the MORS primary mission, measurements of the spacecraft distance and velocity with respect to Earth based tracking stations will be used to develop models of the global gravity field. The improvement in knowledge of the gravity field will be especially evident in polar regions. The spatial and temporal coverage of atmospheric radio occultation measurements are determined by the geometry of the spacecraft orbit and the direction to the Earth. Profiles of atmospheric temperature and pressure will extend from the surface to altitudes of 50 to 70 km.

Radio Astronomy Explorer (RAE) 1 observations of terrestrial radio noise

NASA Technical Reports Server (NTRS)

Herman, J. R.; Caruso, J. A.

1971-01-01

Radio Astonomy Explorer (RAE) 1 data are analyzed to establish characteristics of HF terrestrial radio noise at an altitude of about 6000 km. Time and frequency variations in amplitude of the observed noise well above cosmic noise background are explained on the basis of temporal and spatial variations in ionospheric critical frequency coupled with those in noise source distributions. It is shown that terrestrial noise regularly breaks through the ionosphere and reaches RAE with magnitudes 15 or more db higher than cosmic noise background. Maximum terrestrial noise is observed when RAE is over the dark side of the Earth in the neighborhood of equatorial continental land masses where thunderstorms occur most frequently. The observed noise level is 30-40 db lower with RAE over oceans.

High-performance radio frequency transistors based on diameter-separated semiconducting carbon nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Yu; Che, Yuchi; Zhou, Chongwu, E-mail: chongwuz@usc.edu

In this paper, we report the high-performance radio-frequency transistors based on the single-walled semiconducting carbon nanotubes with a refined average diameter of ∼1.6 nm. These diameter-separated carbon nanotube transistors show excellent transconductance of 55 μS/μm and desirable drain current saturation with an output resistance of ∼100 KΩ μm. An exceptional radio-frequency performance is also achieved with current gain and power gain cut-off frequencies of 23 GHz and 20 GHz (extrinsic) and 65 GHz and 35 GHz (intrinsic), respectively. These radio-frequency metrics are among the highest reported for the carbon nanotube thin-film transistors. This study provides demonstration of radio frequency transistors based on carbon nanotubes with tailoredmore » diameter distributions, which will guide the future application of carbon nanotubes in radio-frequency electronics.« less

Moon-based Earth Observation for Large Scale Geoscience Phenomena

NASA Astrophysics Data System (ADS)

Guo, Huadong; Liu, Guang; Ding, Yixing

2016-07-01

The capability of Earth observation for large-global-scale natural phenomena needs to be improved and new observing platform are expected. We have studied the concept of Moon as an Earth observation in these years. Comparing with manmade satellite platform, Moon-based Earth observation can obtain multi-spherical, full-band, active and passive information,which is of following advantages: large observation range, variable view angle, long-term continuous observation, extra-long life cycle, with the characteristics of longevity ,consistency, integrity, stability and uniqueness. Moon-based Earth observation is suitable for monitoring the large scale geoscience phenomena including large scale atmosphere change, large scale ocean change,large scale land surface dynamic change,solid earth dynamic change,etc. For the purpose of establishing a Moon-based Earth observation platform, we already have a plan to study the five aspects as follows: mechanism and models of moon-based observing earth sciences macroscopic phenomena; sensors' parameters optimization and methods of moon-based Earth observation; site selection and environment of moon-based Earth observation; Moon-based Earth observation platform; and Moon-based Earth observation fundamental scientific framework.

Application of new radio tracking data types to critical spacecraft navigation problems

NASA Technical Reports Server (NTRS)

Ondrasik, V. J.; Rourke, K. H.

1972-01-01

Earth-based radio tracking data types are considered, which involve simultaneous or nearly simultaneous spacecraft tracking from widely separated tracking stations. These data types are conventional tracking instrumentation analogs of the very long baseline interferometry (VLBI) of radio astronomy-hence the name quasi-VLBI. A preliminary analysis of quasi-VLBI is presented using simplified tracking data models. The results of accuracy analyses are presented for a representative mission, Viking 1975. The results indicate that, contingent on projected tracking system accuracy, quasi-VLBI can be expected to significantly improve navigation performance over that expected from conventional tracking data types.

SArdinia Roach2-based Digital Architecture for Radio Astronomy (SARDARA)

NASA Astrophysics Data System (ADS)

Melis, A.; Concu, R.; Trois, A.; Possenti, A.; Bocchinu, A.; Bolli, P.; Burgay, M.; Carretti, E.; Castangia, P.; Casu, S.; Pestellini, C. Cecchi; Corongiu, A.; D’Amico, N.; Egron, E.; Govoni, F.; Iacolina, M. N.; Murgia, M.; Pellizzoni, A.; Perrodin, D.; Pilia, M.; Pisanu, T.; Poddighe, A.; Poppi, S.; Porceddu, I.; Tarchi, A.; Vacca, V.; Aresu, G.; Bachetti, M.; Barbaro, M.; Casula, A.; Ladu, A.; Leurini, S.; Loi, F.; Loru, S.; Marongiu, P.; Maxia, P.; Mazzarella, G.; Migoni, C.; Montisci, G.; Valente, G.; Vargiu, G.

The Sardinia Radio Telescope (SRT) is a 64-m, fully-steerable single-dish radio telescope that was recently commissioned both technically and scientifically with regard to the basic observing modes. In order to improve the scientific capability and cover all the requirements for an advanced single-dish radio telescope, we developed the SArdinia Roach2-based Digital Architecture for Radio Astronomy (SARDARA), a wide-band, multi-feed, general-purpose, and reconfigurable digital platform, whose preliminary setup was used in the early science program of the SRT in 2016. In this paper, we describe the backend both in terms of its scientific motivation and technical design, how it has been interfaced with the telescope environment during its development and, finally, its scientific commissioning in different observing modes with single-feed receivers.

Amateur Radio on the International Space Station: The First Operational Payload on the ISS

NASA Technical Reports Server (NTRS)

Bauer, Frank H.; McFadin, Lou; Steiner, Mark D.; Conley, Carolynn L.

2002-01-01

As astronauts and cosmonauts have adapted to life on the International Space Station (ISS), they have found amateur radio and its connection to life on Earth to be a important on-board companion and a substantial psychological boost. Since its first use in November 2000, the first five expedition crews have utilized the amateur radio station in the Functional Cargo Block (also referred to as the FGB or Zarya module) to talk to thousands of students in schools, to their families on Earth, and to amateur radio operators around the world. This paper will discuss the development, qualification, installation and operation of the amateur radio system. It will also discuss some of the challenges that the amateur radio international team of volunteers overcame to bring its first phase of equipment on ISS to fruition.

Cross layer optimization for cloud-based radio over optical fiber networks

NASA Astrophysics Data System (ADS)

Shao, Sujie; Guo, Shaoyong; Qiu, Xuesong; Yang, Hui; Meng, Luoming

2016-07-01

To adapt the 5G communication, the cloud radio access network is a paradigm introduced by operators which aggregates all base stations computational resources into a cloud BBU pool. The interaction between RRH and BBU or resource schedule among BBUs in cloud have become more frequent and complex with the development of system scale and user requirement. It can promote the networking demand among RRHs and BBUs, and force to form elastic optical fiber switching and networking. In such network, multiple stratum resources of radio, optical and BBU processing unit have interweaved with each other. In this paper, we propose a novel multiple stratum optimization (MSO) architecture for cloud-based radio over optical fiber networks (C-RoFN) with software defined networking. Additionally, a global evaluation strategy (GES) is introduced in the proposed architecture. MSO can enhance the responsiveness to end-to-end user demands and globally optimize radio frequency, optical spectrum and BBU processing resources effectively to maximize radio coverage. The feasibility and efficiency of the proposed architecture with GES strategy are experimentally verified on OpenFlow-enabled testbed in terms of resource occupation and path provisioning latency.

Numerical simulations of particle acceleration and low frequency radio emission in stellar environments

NASA Astrophysics Data System (ADS)

Paraskevi Moschou, Sofia; Sokolov, Igor; Cohen, Ofer; Drake, Jeremy J.; Borovikov, Dmitry; Alvarado-Gomez, Julian D.; Garraffo, Cecilia

2018-06-01

Due to their favorable atmospheric window radio waves are a useful tool for ground-based observations of astrophysical systems throughout a plethora of scales, from cosmological down to planetary ones. A wide range of physical mechanisms, from thermal processes to eruptive events linked to magnetic reconnection, can generate emission in radio frequencies. Radio waves have the distinct characteristic that they follow curved paths as they propagate in stratified environments, such as the solar corona, due to their dependence on the refraction index. Low frequency radio rays in particular are affected the most by refraction.Solar radio observations are of particular importance, since it is possible to spatially resolve the Sun and its corona and gain insights on highly dynamic and complex radio-emitting phenomena. The multi-scale problem of particle acceleration and energy partition between CMEs, flares and SEPs requires both MHD and kinetic considerations to account for the emission and mass propagation through the interplanetary space.Radio observations can play a significant role in the rapidly developing area of exoplanetary research and provide insights on the stellar environments of those systems. Even though a large number of flares has been observed for different stellar types, nevertheless there is a lack of stellar CME observations. Currently, the most promising method to incontrovertibly observe stellar CMEs is through Type II radio bursts. Low frequency radio emission can also be produced by the interaction of a magnetized planet with the stellar wind of the host star.The above mentioned characteristics of radio-waves make their integration into numerical simulations imperative for capturing and disentangling the complex radio emitting processes along the actual radio paths and provide the observers with detection limits for future Earth- and space-based missions. Radio synthetic imaging tools incorporated in realistic computational codes are already

An Evaluation of shore-based radio direction finding

DOT National Transportation Integrated Search

1978-09-30

This report describes an evaluation of Radio Direction Finding (RDF) techniques for shore-based position location performed by the Transportation Systems Center (TSC). The evaluation consisted of the following three phases: (1) A preliminary survey t...

The Sun Radio Imaging Space Experiment (SunRISE) Mission

NASA Astrophysics Data System (ADS)

Lazio, Joseph; Kasper, Justin; Maksimovic, Milan; Alibay, Farah; Amiri, Nikta; Bastian, Tim; Cohen, Christina; Landi, Enrico; Manchester, Ward; Reinard, Alysha; Schwadron, Nathan; Cecconi, Baptiste; Hallinan, Gregg; Hegedus, Alex; Krupar, Vratislav; Zaslavsky, Arnaud

2017-04-01

Radio emission from coronal mass ejections (CMEs) is a direct tracer of particle acceleration in the inner heliosphere and potential magnetic connections from the lower solar corona to the larger heliosphere. Energized electrons excite Langmuir waves, which then convert into intense radio emission at the local plasma frequency, with the most intense acceleration thought to occur within 20 RS. The radio emission from CMEs is quite strong such that only a relatively small number of antennas is required to detect and map it, but many aspects of this particle acceleration and transport remain poorly constrained. Ground-based arrays would be quite capable of tracking the radio emission associated with CMEs, but absorption by the Earth's ionosphere limits the frequency coverage of ground-based arrays (ν ≳ 15 MHz), which in turn limits the range of solar distances over which they can track the radio emission (≲ 3RS). The state-of-the-art for tracking such emission from space is defined by single antennas (Wind/WAVES, Stereo/SWAVES), in which the tracking is accomplished by assuming a frequency-to-density mapping; there has been some success in triangulating the emission between the spacecraft, but considerable uncertainties remain. We describe the Sun Radio Imaging Space Experiment (SunRISE) mission concept: A constellation of small spacecraft in a geostationary graveyard orbit designed to localize and track radio emissions in the inner heliosphere. Each spacecraft would carry a receiving system for observations below 25 MHz, and SunRISE would produce the first images of CMEs more than a few solar radii from the Sun. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

The Sun Radio Imaging Space Experiment (SunRISE) Mission

NASA Astrophysics Data System (ADS)

Kasper, J. C.; Lazio, J.; Alibay, F.; Amiri, N.; Bastian, T.; Cohen, C.; Landi, E.; Hegedus, A. M.; Maksimovic, M.; Manchester, W.; Reinard, A.; Schwadron, N.; Cecconi, B.; Hallinan, G.; Krupar, V.

2017-12-01

Radio emission from coronal mass ejections (CMEs) is a direct tracer of particle acceleration in the inner heliosphere and potential magnetic connections from the lower solar corona to the larger heliosphere. Energized electrons excite Langmuir waves, which then convert into intense radio emission at the local plasma frequency, with the most intense acceleration thought to occur within 20 R_S. The radio emission from CMEs is quite strong such that only a relatively small number of antennas is required to detect and map it, but many aspects of this particle acceleration and transport remain poorly constrained. Ground-based arrays would be quite capable of tracking the radio emission associated with CMEs, but absorption by the Earth's ionosphere limits the frequency coverage of ground-based arrays (nu > 15 MHz), which in turn limits the range of solar distances over which they can track the radio emission (< 3 R_S). The state-of-the-art for tracking such emission from space is defined by single antennas (Wind/WAVES, Stereo/SWAVES), in which the tracking is accomplished by assuming a frequency-to-density mapping; there has been some success in triangulating the emission between the spacecraft, but considerable uncertainties remain. We describe the Sun Radio Imaging Space Experiment (SunRISE) mission concept: A constellation of small spacecraft in a geostationary graveyard orbit designed to localize and track radio emissions in the inner heliosphere. Each spacecraft would carry a receiving system for observations below 25 MHz, and SunRISE would produce the first images of CMEs more than a few solar radii from the Sun. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Programmable Ultra-Lightweight System Adaptable Radio Satellite Base Station

NASA Technical Reports Server (NTRS)

Varnavas, Kosta; Sims, Herb

2015-01-01

With the explosion of the CubeSat, small sat, and nanosat markets, the need for a robust, highly capable, yet affordable satellite base station, capable of telemetry capture and relay, is significant. The Programmable Ultra-Lightweight System Adaptable Radio (PULSAR) is NASA Marshall Space Flight Center's (MSFC's) software-defined digital radio, developed with previous Technology Investment Programs and Technology Transfer Office resources. The current PULSAR will have achieved a Technology Readiness Level-6 by the end of FY 2014. The extensibility of the PULSAR will allow it to be adapted to perform the tasks of a mobile base station capable of commanding, receiving, and processing satellite, rover, or planetary probe data streams with an appropriate antenna.

Investigation of the spatial structure and developmental dynamics of near-Earth plasma perturbations under the action of powerful HF radio waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belov, A. S., E-mail: alexis-belov@yandex.ru

2015-10-15

Results of numerical simulations of the near-Earth plasma perturbations induced by powerful HF radio waves from the SURA heating facility are presented. The simulations were performed using a modified version of the SAMI2 ionospheric model for the input parameters corresponding to the series of in-situ SURA–DEMETER experiments. The spatial structure and developmental dynamics of large-scale plasma temperature and density perturbations have been investigated. The characteristic formation and relaxation times of the induced large-scale plasma perturbations at the altitudes of the Earth’s outer ionosphere have been determined.

Multi-Objective Reinforcement Learning for Cognitive Radio-Based Satellite Communications

NASA Technical Reports Server (NTRS)

Ferreira, Paulo Victor R.; Paffenroth, Randy; Wyglinski, Alexander M.; Hackett, Timothy M.; Bilen, Sven G.; Reinhart, Richard C.; Mortensen, Dale J.

2016-01-01

Previous research on cognitive radios has addressed the performance of various machine-learning and optimization techniques for decision making of terrestrial link properties. In this paper, we present our recent investigations with respect to reinforcement learning that potentially can be employed by future cognitive radios installed onboard satellite communications systems specifically tasked with radio resource management. This work analyzes the performance of learning, reasoning, and decision making while considering multiple objectives for time-varying communications channels, as well as different cross-layer requirements. Based on the urgent demand for increased bandwidth, which is being addressed by the next generation of high-throughput satellites, the performance of cognitive radio is assessed considering links between a geostationary satellite and a fixed ground station operating at Ka-band (26 GHz). Simulation results show multiple objective performance improvements of more than 3.5 times for clear sky conditions and 6.8 times for rain conditions.

Multi-Objective Reinforcement Learning for Cognitive Radio Based Satellite Communications

NASA Technical Reports Server (NTRS)

Ferreira, Paulo; Paffenroth, Randy; Wyglinski, Alexander; Hackett, Timothy; Bilen, Sven; Reinhart, Richard; Mortensen, Dale John

2016-01-01

Previous research on cognitive radios has addressed the performance of various machine learning and optimization techniques for decision making of terrestrial link properties. In this paper, we present our recent investigations with respect to reinforcement learning that potentially can be employed by future cognitive radios installed onboard satellite communications systems specifically tasked with radio resource management. This work analyzes the performance of learning, reasoning, and decision making while considering multiple objectives for time-varying communications channels, as well as different crosslayer requirements. Based on the urgent demand for increased bandwidth, which is being addressed by the next generation of high-throughput satellites, the performance of cognitive radio is assessed considering links between a geostationary satellite and a fixed ground station operating at Ka-band (26 GHz). Simulation results show multiple objective performance improvements of more than 3:5 times for clear sky conditions and 6:8 times for rain conditions.

Lunar-based Earth observation geometrical characteristics research

NASA Astrophysics Data System (ADS)

Ren, Yuanzhen; Liu, Guang; Ye, Hanlin; Guo, Huadong; Ding, Yixing; Chen, Zhaoning

2016-07-01

As is known to all, there are various platforms for carrying sensors to observe Earth, such as automobiles, aircrafts and satellites. Nowadays, we focus on a new platform, Moon, because of its longevity, stability and vast space. These advantages make it to be the next potential platform for observing Earth, enabling us to get the consistent and global measurements. In order to get a better understanding of lunar-based Earth observation, we discuss its geometrical characteristics. At present, there are no sensors on the Moon for observing Earth and we are not able to obtain a series of real experiment data. As a result, theoretical modeling and numerical calculation are used in this paper. At first, we construct an approximate geometrical model of lunar-based Earth observation, which assumes that Earth and Moon are spheres. Next, we calculate the position of Sun, Earth and Moon based on the JPL ephemeris. With the help of positions data and geometrical model, it is possible for us to decide the location of terminator and substellar points. However, in order to determine their precise position in the conventional terrestrial coordinate system, reference frames transformations are introduced as well. Besides, taking advantages of the relative positions of Sun, Earth and Moon, we get the total coverage of lunar-based Earth optical observation. Furthermore, we calculate a more precise coverage, considering placing sensors on different positions of Moon, which is influenced by its attitude parameters. In addition, different ephemeris data are compared in our research and little difference is found.

Millimetron and Earth-Space VLBI

NASA Astrophysics Data System (ADS)

Likhachev, S.

2014-01-01

The main scientific goal of the Millimetron mission operating in Space VLBI (SVLBI) mode will be the exploration of compact radio sources with extremely high angular resolution (better than one microsecond of arc). The space-ground interferometer Millimetron has an orbit around L2 point of the Earth - Sun system and allows operating with baselines up to a hundred Earth diameters. SVLBI observations will be accomplished by space and ground-based radio telescopes simultaneously. At the space telescope the received baseband signal is digitized and then transferred to the onboard memory storage (up to 100TB). The scientific and service data transfer to the ground tracking station is performed by means of both synchronization and communication radio links (1 GBps). Then the array of the scientific data is processed at the correlation center. Due to the (u,v) - plane coverage requirements for SVLBI imaging, it is necessary to propose observations at two different frequencies and two circular polarizations simultaneously with frequency switching. The total recording bandwidth (2x2x4 GHz) defines of the on-board memory size. The ground based support of the Millimetron mission in the VLBI-mode could be Atacama Large Millimeter Array (ALMA), Pico Valletta (Spain), Plateau de Bure interferometer (France), SMT telescope in the US (Arizona), LMT antenna (Mexico), SMA array, (Mauna Kea, USA), as well as the Green Bank and Effelsberg 100 m telescopes (for 22 GHz observations). We will present simulation results for Millimetron-ALMA interferometer. The sensitivity estimate of the space-ground interferometer will be compared to the requirements of the scientific goals of the mission. The possibility of multi-frequency synthesis (MFS) to obtain high quality images will also be considered.

Space Observatories RadioAstron and Millimetron: Results and Prospects

NASA Astrophysics Data System (ADS)

Kardashev, Nikolay

The Russian Academy of Sciences and Federal Space Agency, together with many international organizations, prepared the launch of the RadioAstron orbiting space observatory from the Baikonur cosmodrome on July 18, 2011. The spacecraft was launched by the Ukrainian Zenit-3F rocket with onboard 10-m reflector radio telescope, four feed and low noise receivers for operating at 1.2-1.6, 6.2, 18 and 92 cm wavelengths and both circular polarizations, a data formatter, a data transmission module and a hydrogen maser frequency standard. The orbital period in 2012-2015 will vary from 8.3 to 9.0 days, the perigee - from 7,065 km to 81,500 km, the apogee - from 280,000 to 353,000 km. Together with ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna ground-space radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than it is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include quasars (super massive black holes and relativistic jets in active galactic nuclei, pulsars (neutron stars and hypothetical quark stars), cosmic masers (regions of stars and planetary systems formation in our and other galaxies), interplanetary and interstellar plasma, and the gravitational field of the Earth. The fringes with the ground-space interferometer were founded at the baseline projections up to 25 diameters of the Earth, and corresponding models of the sources will be reported. Millimetron is the next space mission with a 10-m cooled space telescope optimized for observations in the millimeter and far infrared wavelengths. This mission will be able to contribute to the explorations of several key problems in astrophysics, such as study of formation and evolution

Nanosats for a Radio Interferometer Observatory in Space

NASA Astrophysics Data System (ADS)

Cecconi, B.; Katsanevras, S.; Puy, D.; Bentum, M.

2015-10-01

During the last decades, astronomy and space physics changed dramatically our knowledge of the evolution of the Universe. However, our view is still incomplete in the very low frequency range (1- 30 MHz), which is thus one of the last unexplored astrophysical spectral band. Below 30 MHz, ionospheric fluctuations severely perturb groundbased observations. They are impossible below 10 MHz due to the ionospheric cutoff. In addition, man made radio interferences makes it even more difficult to observe from ground at low frequencies. Deploying a radio instrument in space is the only way to open this new window on the Universe. Among the many science objectives for such type of instrumentations, we can find cosmological studies such as the Dark Ages of the Universe, the remote astrophysical objects, pulsars and fast transients, the interstellar medium. The following Solar system and Planetary objectives are also very important: - Sun-Earth Interactions: The Sun is strongly influencing the interplanetary medium (IPM) and the terrestrial geospatial environment. The evolution mechanisms of coronal mass ejections (CME) and their impact on solar system bodies are still not fully understood. This results in large inaccuracies on the eruption models and prediction tools, and their consequences on the Earth environment. Very low frequency radio imaging capabilities (especially for the Type II solar radio bursts, which are linked with interplanetary shocks) should allow the scientific community to make a big step forward in understanding of the physics and the dynamics of these phenomena, by observing the location of the radio source, how they correlate with their associated shocks and how they propagate within the IPM. - Planets and Exoplanets: The Earth and the fourgiant planets are hosting strong magnetic fields producing large magnetospheres. Particle acceleration are very efficient therein and lead to emitting intense low frequency radio waves in their auroral regions. These

47 CFR 90.656 - Responsibilities of base station licensees of Specialized Mobile Radio systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... operate mobile units on a particular Specialized Mobile Radio system will be licensed to that system. A... Specialized Mobile Radio systems. 90.656 Section 90.656 Telecommunication FEDERAL COMMUNICATIONS COMMISSION... Bands § 90.656 Responsibilities of base station licensees of Specialized Mobile Radio systems. (a) The...

Astronomers Make First Images With Space Radio Telescope

NASA Astrophysics Data System (ADS)

1997-07-01

Marking an important new milestone in radio astronomy history, scientists at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, have made the first images using a radio telescope antenna in space. The images, more than a million times more detailed than those produced by the human eye, used the new Japanese HALCA satellite, working in conjunction with the National Science Foundation's (NSF) Very Long Baseline Array (VLBA) and Very Large Array (VLA) ground-based radio telescopes. The landmark images are the result of a long-term NRAO effort supported by the National Aeronautics and Space Administration (NASA). "This success means that our ability to make detailed radio images of objects in the universe is no longer limited by the size of the Earth," said NRAO Director Paul Vanden Bout. "Astronomy's vision has just become much sharper." HALCA, launched on Feb. 11 by Japan's Institute of Space and Astronautical Science (ISAS), is the first satellite designed for radio astronomy imaging. It is part of an international collaboration led by ISAS and backed by NRAO; Japan's National Astronomical Observatory; NASA's Jet Propulsion Laboratory (JPL); the Canadian Space Agency; the Australia Telescope National Facility; the European VLBI Network and the Joint Institute for Very Long Baseline Interferometry in Europe. On May 22, HALCA observed a distant active galaxy called PKS 1519-273, while the VLBA and VLA also observed it. Data from the satellite was received by a tracking station at the NRAO facility in Green Bank, West Virginia. Tape-recorded data from the satellite and from the radio telescopes on the ground were sent to NRAO's Array Operations Center (AOC) in Socorro, NM. In Socorro, astronomers and computer scientists used a special-purpose computer to digitally combine the signals from the satellite and the ground telescopes to make them all work together as a single, giant radio telescope. This dedicated machine, the VLBA Correlator, built as

Radio Ranging System for Guidance of Approaching Spacecraft

NASA Technical Reports Server (NTRS)

Manikonda, Vikram; vanDoom, Eric

2008-01-01

A radio communication and ranging system has been proposed for determining the relative position and orientations of two approaching spacecraft to provide guidance for docking maneuvers. On Earth, the system could be used similarly for guiding approaching aircraft and for automated positioning of large, heavy objects. In principle, the basic idea is to (1) measure distances between radio transceivers on the two spacecraft and (2) compute the relative position and orientations from the measured distances.

47 CFR 90.656 - Responsibilities of base station licensees of Specialized Mobile Radio systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Responsibilities of base station licensees of... Bands § 90.656 Responsibilities of base station licensees of Specialized Mobile Radio systems. (a) The licensees of base stations that provide Specialized Mobile Radio service on a commercial basis of the use of...

Bases of Radio Direction Finding, Part II

DTIC Science & Technology

1977-12-22

of H-shaped system . Fundamental ind the equivalent diagrams of the piir of antennas are given in Fig. 7.12. For -alculation is assigned the frejuency...Geographic Names Transliteration System ......... ii Preface ...................................................... 2 Chapter 1. Problems of Radio Traffic...4 Chapter 2. Principles and Methods of Radio Traffic ......... 14 Chapter 3. Antenna Systems of Radio Direction Finders

A Visual-Based Approach for Indoor Radio Map Construction Using Smartphones.

PubMed

Liu, Tao; Zhang, Xing; Li, Qingquan; Fang, Zhixiang

2017-08-04

Localization of users in indoor spaces is a common issue in many applications. Among various technologies, a Wi-Fi fingerprinting based localization solution has attracted much attention, since it can be easily deployed using the existing off-the-shelf mobile devices and wireless networks. However, the collection of the Wi-Fi radio map is quite labor-intensive, which limits its potential for large-scale application. In this paper, a visual-based approach is proposed for the construction of a radio map in anonymous indoor environments. This approach collects multi-sensor data, e.g., Wi-Fi signals, video frames, inertial readings, when people are walking in indoor environments with smartphones in their hands. Then, it spatially recovers the trajectories of people by using both visual and inertial information. Finally, it estimates the location of fingerprints from the trajectories and constructs a Wi-Fi radio map. Experiment results show that the average location error of the fingerprints is about 0.53 m. A weighted k-nearest neighbor method is also used to evaluate the constructed radio map. The average localization error is about 3.2 m, indicating that the quality of the constructed radio map is at the same level as those constructed by site surveying. However, this approach can greatly reduce the human labor cost, which increases the potential for applying it to large indoor environments.

Astronaut William McArthur talks to students on earth using SAREX

NASA Technical Reports Server (NTRS)

1993-01-01

From the flight deck of the Earth-orbiting Space Shuttle Columbia, astronaut William S. McArthur talks to students on Earth. The mission specialist's activity was part of the Shuttle Amateur Radio Experiment (SAREX) which serves to enlighten students around the world on the topic of space travel. McArthur (call letters KC5ACR) is one of three licensed amateur radio operators on the seven-member flight.

The Radio JOVE Project: A Worldwide, Ground-Based, Amateur, Decameter-Wavelength Radio Observatory Network

NASA Astrophysics Data System (ADS)

Thieman, J.; Higgins, C.; Flagg, R.; Sky, J.

2003-05-01

The Radio JOVE project began over four years ago as an education-centered program to inspire secondary school students' interest in space science through hands-on radio astronomy. Students build a radio receiver and antenna kit capable of receiving Jovian, solar, and galactic emissions at a frequency of 20.1 MHz. More than 500 of these kits have been distributed to students and interested observers (ages 10 through adult) in 24 countries. For those who are not comfortable building their own kit, the Radio JOVE project has made it possible to monitor real-time data and streaming audio online from professional radio telescopes in Florida (http://jupiter.kochi-ct.jp) and Hawaii (http://jupiter.wcc.hawaii.edu/newradiojove/main.html). Freely downloadable software called Radio-Skypipe (http://radiosky.com) emulates a chart recorder to monitor ones own radio telescope or the telescopes of other observers worldwide who send out their data over the Internet. A built-in chat feature allows the users to discuss their observations and results in real time. New software is being developed to allow network users to interactively view a multi-frequency spectroscopic display of the Hawaii radio telescope. The Radio JOVE project is also partnering with NASA's Student Observation Network (http://sunearth.gsfc.nasa.gov/sunearthday/2003/networkintro.htm) in an effort to use online collaborations to monitor and track solar storms as a hands-on science experience for students. We believe the amateur network data to be of value to the research community and would like to have students more directly connected to ongoing research projects to enhance their interest in participating. Results of the project and plans for the future will be highlighted.

Juno: Morse code "HI" received from Earth

NASA Image and Video Library

2017-03-22

During its close flyby of Earth in 2013, NASA's Jupiter-bound Juno spacecraft listened for -- and heard -- a coordinated, global transmission from amateur radio operators using its radio and plasma wave science instrument. The message said "HI" in Morse code. More details about this sound can be found here: photojournal.jpl.nasa.gov/catalog/PIA17744

Searching for giga-Jansky fast radio bursts from the Milky Way with a global array of low-cost radio receivers

NASA Astrophysics Data System (ADS)

Maoz, Dan; Loeb, Abraham

2017-06-01

If fast radio bursts (FRBs) originate from galaxies at cosmological distances, then their all-sky rate implies that the Milky Way may host an FRB every 30-1500 yr, on average. If many FRBs persistently repeat for decades or more, a local giant FRB could be active now, with 1 GHz radio pulses of flux ˜3 × 1010 Jy, comparable with the fluxes and frequencies detectable by cellular communication devices (cell phones, Wi-Fi and GPS). We propose searching for Galactic FRBs using a global array of low-cost radio receivers. One possibility is the ˜1 GHz communication channel in cellular phones, through a Citizens-Science downloadable application. Participating phones would continuously listen for and record candidate FRBs and would periodically upload information to a central data-processing website which will identify the signature of a real, globe-encompassing, FRB from an astronomical distance. Triangulation of the GPS-based pulse arrival times reported from different Earth locations will provide the FRB sky position, potentially to arcsecond accuracy. Pulse arrival times versus frequency, from reports from phones operating at diverse frequencies, or from fast signal de-dispersion by the application, will yield the dispersion measure (DM). Compared to a Galactic DM model, it will indicate the source distance within the Galaxy. A variant approach uses the built-in ˜100 MHz FM-radio receivers present in cell phones for an FRB search at lower frequencies. Alternatively, numerous 'software-defined radio' devices, costing ˜$10 US each, could be deployed and plugged into USB ports of personal computers (particularly in radio-quiet locations) to establish the global network of receivers.

Measurement of radio emission from extensive air showers with LOPES

NASA Astrophysics Data System (ADS)

Hörandel, J. R.; Apel, W. D.; Arteaga, J. C.; Asch, T.; Badea, F.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Brüggemann, M.; Buchholz, P.; Buitink, S.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; di Pierro, F.; Doll, P.; Ender, M.; Engel, R.; Falcke, H.; Finger, M.; Fuhrmann, D.; Gemmeke, H.; Ghia, P. L.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Horneffer, A.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Kickelbick, D.; Krömer, O.; Kuijpers, J.; Lafebre, S.; Link, K.; Łuczak, P.; Ludwig, M.; Mathes, H. J.; Mayer, H. J.; Melissas, M.; Mitrica, B.; Morello, C.; Navarra, G.; Nehls, S.; Nigl, A.; Oehlschläger, J.; Over, S.; Palmieri, N.; Petcu, M.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Schröder, F.; Sima, O.; Singh, K.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Wommer, M.; Zabierowski, J.; Zensus, J. A.

2011-02-01

A new method is explored to detect extensive air showers: the measurement of radio waves emitted during the propagation of the electromagnetic shower component in the magnetic field of the Earth. Recent results of the pioneering experiment LOPES are discussed. It registers radio signals in the frequency range between 40 and 80 MHz. The intensity of the measured radio emission is investigated as a function of different shower parameters, such as shower energy, angle of incidence, and distance to shower axis. In addition, new antenna types are developed in the framework of LOPESstar and new methods are explored to realize a radio self-trigger algorithm in real time.

Earth-based remote sensing of planetary surfaces and atmospheres at radio wavelengths

NASA Technical Reports Server (NTRS)

Dickel, J. R.

1982-01-01

Two reasons for remote sensing from the Earth are given: (1) space exploration, particularly below the surfaces or underneath cloud layers, is limited to only a very few planets; and (2) a program of regular monitoring, currently impractical with a limited number of space probes, is required. Reflected solar and nonthermal radiation are discussed. Relativistic electrons, trapped in large magnetospheres on Saturn and Jupiter, are discussed. These electrons produce synchrotron radiation and also interact with the ionosphere to produce bursts of low frequency emission. Because most objects are black-bodies, continuum radiometry is emphasized. Spectroscopic techniques and the measurement of nonthermal emission are also discussed.

High Angular Resolution Imaging of Solar Radio Bursts from the Lunar Surface

NASA Technical Reports Server (NTRS)

MacDowall, Robert J.; Lazio, Joseph; Bale, Stuart; Burns, Jack O.; Farrell, William M.; Gopalswamy, Nat; Jones, Dayton L.; Kasper, Justin Christophe; Weiler, Kurt

2012-01-01

Locating low frequency radio observatories on the lunar surface has a number of advantages, including positional stability and a very low ionospheric radio cutoff. Here, we describe the Radio Observatory on the lunar Surface for Solar studies (ROLSS), a concept for a low frequency, radio imaging interferometric array designed to study particle acceleration in the corona and inner heliosphere. ROLSS would be deployed during an early lunar sortie or by a robotic rover as part of an unmanned landing. The preferred site is on the lunar near side to simplify the data downlink to Earth. The prime science mission is to image type II and type III solar radio bursts with the aim of determining the sites at and mechanisms by which the radiating particles are accelerated. Secondary science goals include constraining the density of the lunar ionosphere by measuring the low radio frequency cutoff of the solar radio emissions or background galactic radio emission, measuring the flux, particle mass, and arrival direction of interplanetary and interstellar dust, and constraining the low energy electron population in astrophysical sources. Furthermore, ROLSS serves a pathfinder function for larger lunar radio arrays. Key design requirements on ROLSS include the operational frequency and angular resolution. The electron densities in the solar corona and inner heliosphere are such that the relevant emission occurs below 10 M Hz, essentially unobservable from Earth's surface due to the terrestrial ionospheric cutoff. Resolving the potential sites of particle acceleration requires an instrument with an angular resolution of at least 2 deg at 10 MHz, equivalent to a linear array size of approximately one kilometer. The major components of the ROLSS array are 3 antenna arms, each of 500 m length, arranged in a Y formation, with a central electronics package (CEP) at their intersection. Each antenna arm is a linear strip of polyimide film (e.g., Kapton(TradeMark)) on which 16 single

Ionospheric Caustics in Solar Radio Observations

NASA Astrophysics Data System (ADS)

Koval, A.; Chen, Y.; Stanislavsky, A.

2016-12-01

The Earth ionosphere possesses by natural focusing and defocusing effects on radio waves due to presence of variable ionospheric irregularities which could act like convergent and divergent lenses on incident radiation. In particular, the focusing of emission from the Sun was firstly detected on the Nançay Decameter Array dynamic spectra in the 1980s. On time-frequency spectrograms the intensity variations form specific structures different from well-known solar radio bursts and clearly distinguishing on a background of solar radiation. Such structures have been identified as ionospheric caustics (ICs) and considered to be the result of radio waves refraction on medium scale travelling ionospheric disturbances (MSTIDs). Although nowadays the ICs are registered by different radio observatories due to augmentation of low-frequency radio telescopes, the most recent papers devoted to ICs in solar radio records date back to the 1980s. In this study, we revisit the ICs issue with some new results by conducting a statistical analysis of occurrence rate of ICs in solar dynamic spectra in meter-decameter wavelength range for long continuous period (15 years). The seasonal variations in ICs appearance have been found for the first time. Besides, we report the possible solar cycle dependence of ICs emergence. The radio waves propagation in the ionosphere comprising MSTIDs will be considered. The present research renews the subject of ICs in the low-frequency solar radio astronomy after about 35-year letup.

Instrument technology for magnetosphere plasma imaging from high Earth orbit. Design of a radio plasma sounder

NASA Technical Reports Server (NTRS)

Haines, D. Mark; Reinisch, Bodo W.

1995-01-01

The use of radio sounding techniques for the study of the ionospheric plasma dates back to G. Briet and M. A. Tuve in 1926. Ground based swept frequency sounders can monitor the electron number density (N(sub e)) as a function of height (the N(sub e) profile). These early instruments evolved into a global network that produced high-resolution displays of echo time delay vs frequency on 35-mm film. These instruments provided the foundation for the success of the International Geophysical Year (1958). The Alouette and International Satellites for Ionospheric Studies (ISIS) programs pioneered the used of spaceborne, swept frequency sounders to obtain N(sub e) profiles of the topside of the ionosphere, from a position above the electron density maximum. Repeated measurements during the orbit produced an orbital plane contour which routinely provided density measurements to within 10%. The Alouette/ISIS experience also showed that even with a high powered transmitter (compared to the low power sounder possible today) a radio sounder can be compatible with other imaging instruments on the same satellite. Digital technology was used on later spacecraft developed by the Japanese (the EXOS C and D) and the Soviets (Intercosmos 19 and Cosmos 1809). However, a full coherent pulse compression and spectral integrating capability, such as exist today for ground-based sounders (Reinisch et al., 1992), has never been put into space. NASA's 1990 Space Physics Strategy Implementation Study "The NASA Space Physics Program from 1995 to 2010" suggested using radio sounders to study the plasmasphere and the magnetopause and its boundary layers (Green and Fung, 1993). Both the magnetopause and plasmasphere, as well as the cusp and boundary layers, can be observed by a radio sounder in a high-inclination polar orbit with an apogee greater than 6 R(sub e) (Reiff et al., 1994; Calvert et al., 1995). Magnetospheric radio sounding from space will provide remote density measurements of

Nanoionics-Based Switches for Radio-Frequency Applications

NASA Technical Reports Server (NTRS)

Nessel, James; Lee, Richard

2010-01-01

Nanoionics-based devices have shown promise as alternatives to microelectromechanical systems (MEMS) and semiconductor diode devices for switching radio-frequency (RF) signals in diverse systems. Examples of systems that utilize RF switches include phase shifters for electronically steerable phased-array antennas, multiplexers, cellular telephones and other radio transceivers, and other portable electronic devices. Semiconductor diode switches can operate at low potentials (about 1 to 3 V) and high speeds (switching times of the order of nanoseconds) but are characterized by significant insertion loss, high DC power consumption, low isolation, and generation of third-order harmonics and intermodulation distortion (IMD). MEMS-based switches feature low insertion loss (of the order of 0.2 dB), low DC power consumption (picowatts), high isolation (>30 dB), and low IMD, but contain moving parts, are not highly reliable, and must be operated at high actuation potentials (20 to 60 V) generated and applied by use of complex circuitry. In addition, fabrication of MEMS is complex, involving many processing steps. Nanoionics-based switches offer the superior RF performance and low power consumption of MEMS switches, without need for the high potentials and complex circuitry necessary for operation of MEMS switches. At the same time, nanoionics-based switches offer the high switching speed of semiconductor devices. Also, like semiconductor devices, nanoionics-based switches can be fabricated relatively inexpensively by use of conventional integrated-circuit fabrication techniques. More over, nanoionics-based switches have simple planar structures that can easily be integrated into RF power-distribution circuits.

Supporting Inquiry-based Earth System Science Instruction with Middle and High School Earth Science Teachers

NASA Astrophysics Data System (ADS)

Finkel, L.; Varner, R.; Froburg, E.; Smith, M.; Graham, K.; Hale, S.; Laura, G.; Brown, D.; Bryce, J.; Darwish, A.; Furman, T.; Johnson, J.; Porter, W.; von Damm, K.

2007-12-01

The Transforming Earth System Science Education (TESSE) project, a partnership between faculty at the University of New Hampshire, Pennsylvania State University, Elizabeth City State University and Dillard University, is designed to enrich the professional development of in-service and pre-service Earth science teachers. One goal of this effort is to help teachers use an inquiry-based approach to teaching Earth system science in their classrooms. As a part of the TESSE project, 42 pre-service and in-service teachers participated in an intensive two-week summer institute at UNH taught by Earth scientists and science educators from TESSE partnership institutions. The institute included instruction about a range of Earth science system topics as well as an introduction to teaching Earth science using an inquiry-based approach. In addition to providing teachers with information about inquiry-based science teaching in the form of sample lesson plans and opportunities to revise traditional lessons and laboratory exercises to make them more inquiry-based, TESSE instructors modeled an inquiry- based approach in their own teaching as much as possible. By the end of the Institute participants had developed lesson plans, units, or year-long course overviews in which they were expected to explain the ways in which they would include an inquiry-based approach in their Earth science teaching over the course of the school year. As a part of the project, graduate fellows (graduate students in the earth sciences) will work with classroom teachers during the academic year to support their implementation of these plans as well as to assist them in developing a more comprehensive inquiry-based approach in the classroom.

The Radio Frequency Environment at 240-270 MHz with Application to Signal-of-Opportunity Remote Sensing

NASA Technical Reports Server (NTRS)

Piepmeier, Jeffrey R.; Vega, Manuel; Fritts, Matthew; Du Toit, Cornelis; Knuble, Joseph; Lin, Yao-Cheng; Nold, Benjamin; Garrison, James

2017-01-01

Low frequency observations are desired for soil moisture and biomass remote sensing. Long wavelengths are needed to penetrate vegetation and Earths land surface. In addition to the technical challenges of developing Earth observing spaceflight instruments operating at low frequencies, the radio frequency spectrum allocated to remote sensing is limited. Signal-of-opportunity remote sensing offers the chance to use existing signals exploiting their allocated spectrum to make Earth science measurements. We have made observations of the radio frequency environment around 240-270 MHz and discuss properties of desired and undesired signals.

MASER: Measuring, Analysing, Simulating low frequency Radio Emissions.

NASA Astrophysics Data System (ADS)

Cecconi, B.; Le Sidaner, P.; Savalle, R.; Bonnin, X.; Zarka, P. M.; Louis, C.; Coffre, A.; Lamy, L.; Denis, L.; Griessmeier, J. M.; Faden, J.; Piker, C.; André, N.; Genot, V. N.; Erard, S.; King, T. A.; Mafi, J. N.; Sharlow, M.; Sky, J.; Demleitner, M.

2017-12-01

The MASER (Measuring, Analysing and Simulating Radio Emissions) project provides a comprehensive infrastructure dedicated to low frequency radio emissions (typically < 50 to 100 MHz). The four main radio sources observed in this frequency are the Earth, the Sun, Jupiter and Saturn. They are observed either from ground (down to 10 MHz) or from space. Ground observatories are more sensitive than space observatories and capture high resolution data streams (up to a few TB per day for modern instruments). Conversely, space-borne instruments can observe below the ionospheric cut-off (10 MHz) and can be placed closer to the studied object. Several tools have been developed in the last decade for sharing space physcis data. Data visualization tools developed by The CDPP (http://cdpp.eu, Centre de Données de la Physique des Plasmas, in Toulouse, France) and the University of Iowa (Autoplot, http://autoplot.org) are available to display and analyse space physics time series and spectrograms. A planetary radio emission simulation software is developed in LESIA (ExPRES: Exoplanetary and Planetary Radio Emission Simulator). The VESPA (Virtual European Solar and Planetary Access) provides a search interface that allows to discover data of interest for scientific users, and is based on IVOA standards (astronomical International Virtual Observatory Alliance). The University of Iowa also develops Das2server that allows to distribute data with adjustable temporal resolution. MASER is making use of all these tools and standards to distribute datasets from space and ground radio instruments available from the Observatoire de Paris, the Station de Radioastronomie de Nançay and the CDPP deep archive. These datasets include Cassini/RPWS, STEREO/Waves, WIND/Waves, Ulysses/URAP, ISEE3/SBH, Voyager/PRA, Nançay Decameter Array (Routine, NewRoutine, JunoN), RadioJove archive, swedish Viking mission, Interball/POLRAD... MASER also includes a Python software library for reading raw data.

e-POP RRI provides new opportunities for space-based, high-frequency radio science experiments

NASA Astrophysics Data System (ADS)

Burrell, Angeline G.

2017-04-01

Perry et al. (2016, https://doi.org/10.1002/2017JG003855) present the first results of the Radio Receiver Instrument (RRI), a part of the enhanced Polar Outflow Probe (e-POP) that flies on board the CAScade, Smallsat and IOnospheric Polar Explorer satellite. Using a matched filter technique, e-POP RRI was able to observe individual radio pulses transmitted by a ground-based radar. These results were used to examine the temporal variations in the dispersion, polarization, and power of the pulses, demonstrating the capacity for e-POP RRI to contribute to studies of radio propagation at high-frequency (HF) ranges. Understanding radio propagation in the presence and absence of ionospheric irregularities is crucial for ionospheric physics, as well as commercial and military radio applications. Conjunctions between e-POP RRI and ground- or space-based HF transmitters offer a new opportunity for coherent scatter experiments.

FPGA Based Wavelet Trigger in Radio Detection of Cosmic Rays

NASA Astrophysics Data System (ADS)

Szadkowski, Zbigniew; Szadkowska, Anna

2014-12-01

Experiments which show coherent radio emission from extensive air showers induced by ultra-high-energy cosmic rays are designed for a detailed study of the development of the electromagnetic part of air showers. Radio detectors can operate with 100 % up time as, e.g., surface detectors based on water-Cherenkov tanks. They are being developed for ground-based experiments (e.g., the Pierre Auger Observatory) as another type of air-shower detector in addition to fluorescence detectors, which operate with only ˜10 % of duty on dark nights. The radio signals from air showers are caused by coherent emission from geomagnetic radiation and charge-excess processes. The self-triggers in radio detectors currently in use often generate a dense stream of data, which is analyzed afterwards. Huge amounts of registered data require significant manpower for off-line analysis. Improvement of trigger efficiency is a relevant factor. The wavelet trigger, which investigates on-line the power of radio signals (˜ V2/ R), is promising; however, it requires some improvements with respect to current designs. In this work, Morlet wavelets with various scaling factors were used for an analysis of real data from the Auger Engineering Radio Array and for optimization of the utilization of the resources in an FPGA. The wavelet analysis showed that the power of events is concentrated mostly in a limited range of the frequency spectrum (consistent with a range imposed by the input analog band-pass filter). However, we found several events with suspicious spectral characteristics, where the signal power is spread over the full band-width sampled by a 200 MHz digitizer with significant contribution of very high and very low frequencies. These events may not originate from cosmic ray showers but could be the result of human contamination. The engine of the wavelet analysis can be implemented in the modern powerful FPGAs and can remove suspicious events on-line to reduce the trigger rate.

Measuring the radio emission of cosmic ray air showers with LOPES

NASA Astrophysics Data System (ADS)

Schröder, F. G.; Apel, W. D.; Arteaga, J. C.; Asch, T.; Badea, F.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Brüggemann, M.; Buchholz, P.; Buitink, S.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Falcke, H.; Finger, M.; Fuhrmann, D.; Gemmeke, H.; Ghia, P. L.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Horneffer, A.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Kickelbick, D.; Krömer, O.; Kuijpers, J.; Lafebre, S.; łuczak, P.; Ludwig, M.; Mathes, H. J.; Mayer, H. J.; Melissas, M.; Mitrica, B.; Morello, C.; Navarra, G.; Nehls, S.; Nigl, A.; Oehlschläger, J.; Over, S.; Palmieri, N.; Petcu, M.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Sima, O.; Singh, K.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Wommer, M.; Zabierowski, J.; Zensus, J. A.

2010-05-01

When ultra high energy cosmic rays hit the atmosphere, they produce a shower of millions of secondary particles. Thereby the charged particles in the shower emit a radio pulse whilst deflected in the Earth's magnetic field. LOPES is a digital antenna array measuring these radio pulses in the frequency range from 40 to 80 MHz. It is located at the site of and triggered by the air shower experiment KASCADE-Grande at Karlsruhe Institute of Technology (KIT), Germany. In its present configuration, it consists of 15 east-west-polarized and 15 north-south-polarized, absolutely calibrated short dipole antennas, as well as 10 LPDAs (with two channels each). Furthermore, it serves as a test bench for technological developments, like new antenna types or a radio-based self-triggering ( LOPESSTAR). To achieve a good angular reconstruction and to digitally form a beam into the arrival direction of the shower, it has a precise time calibration.

Providing hydrogen maser timing stability to orbiting VLBI radio telescope observations by post-measurement compensation of linked frequency standard imperfections

NASA Astrophysics Data System (ADS)

Springett, James C.

1994-05-01

Orbiting VLBI (OVLBI) astronomical observations are based upon measurements acquired simultaneously from ground-based and earth-orbiting radio telescopes. By the mid-1990s, two orbiting VLBI observatories, Russia's Radioastron and Japan's VSOP, will augment the worldwide VLBI network, providing baselines to earth radio telescopes as large as 80,000 km. The challenge for OVLBI is to effectuate space to ground radio telescope data cross-correlation (the observation) to a level of integrity currently achieved between ground radio telescopes. VLBI radio telescopes require ultrastable frequency and timing references in order that long term observations may be made without serious cross-correlation loss due to frequency source drift and phase noise. For this reason, such instruments make use of hydrogen maser frequency standards. Unfortunately, space-qualified hydrogen maser oscillators are currently not available for use on OVLBI satellites. Thus, the necessary long-term stability needed by the orbiting radio telescope may only be obtained by microwave uplinking a ground-based hydrogen maser derived frequency to the satellite. Although the idea of uplinking the frequency standard intrinsically seems simple, there are many 'contaminations' which degrade both the long and short term stability of the transmitted reference. Factors which corrupt frequency and timing accuracy include additive radio and electronic circuit thermal noise, slow or systematic phase migration due to changes of electronic circuit temporal operating conditions (especially temperature), ionosphere and troposphere induced scintillations, residual Doppler-incited components, and microwave signal multipath propagation. What is important, though, is to realize that ultimate stability does not have to be achieved in real-time. Instead, information needed to produce a high degree of coherence in the subsequent cross-correlation operation may be derived from a two-way coherent radio link, recorded and later

Providing hydrogen maser timing stability to orbiting VLBI radio telescope observations by post-measurement compensation of linked frequency standard imperfections

NASA Technical Reports Server (NTRS)

Springett, James C.

1994-01-01

Orbiting VLBI (OVLBI) astronomical observations are based upon measurements acquired simultaneously from ground-based and earth-orbiting radio telescopes. By the mid-1990s, two orbiting VLBI observatories, Russia's Radioastron and Japan's VSOP, will augment the worldwide VLBI network, providing baselines to earth radio telescopes as large as 80,000 km. The challenge for OVLBI is to effectuate space to ground radio telescope data cross-correlation (the observation) to a level of integrity currently achieved between ground radio telescopes. VLBI radio telescopes require ultrastable frequency and timing references in order that long term observations may be made without serious cross-correlation loss due to frequency source drift and phase noise. For this reason, such instruments make use of hydrogen maser frequency standards. Unfortunately, space-qualified hydrogen maser oscillators are currently not available for use on OVLBI satellites. Thus, the necessary long-term stability needed by the orbiting radio telescope may only be obtained by microwave uplinking a ground-based hydrogen maser derived frequency to the satellite. Although the idea of uplinking the frequency standard intrinsically seems simple, there are many 'contaminations' which degrade both the long and short term stability of the transmitted reference. Factors which corrupt frequency and timing accuracy include additive radio and electronic circuit thermal noise, slow or systematic phase migration due to changes of electronic circuit temporal operating conditions (especially temperature), ionosphere and troposphere induced scintillations, residual Doppler-incited components, and microwave signal multipath propagation. What is important, though, is to realize that ultimate stability does not have to be achieved in real-time. Instead, information needed to produce a high degree of coherence in the subsequent cross-correlation operation may be derived from a two-way coherent radio link, recorded and later

Sun Radio Interferometer Space Experiment (SunRISE)

NASA Astrophysics Data System (ADS)

Kasper, Justin C.; SunRISE Team

2018-06-01

The Sun Radio Interferometer Space Experiment (SunRISE) is a NASA Heliophysics Explorer Mission of Opportunity currently in Phase A. SunRISE is a constellation of spacecraft flying in a 10-km diameter formation and operating as the first imaging radio interferometer in space. The purpose of SunRISE is to reveal critical aspects of solar energetic particle (SEP) acceleration at coronal mass ejections (CMEs) and transport into space by making the first spatially resolved observations of coherent Type II and III radio bursts produced by electrons accelerated at CMEs or released from flares. SunRISE will focus on solar Decametric-Hectometric (DH, 0.1 < f < 15 MHz) radio bursts that always are detected from space before major SEP events, but cannot be seen on Earth due to ionospheric absorption. This talk will describe SunRISE objectives and implementation. Presented on behalf of the entire SunRISE team.

A novel interplanetary optical navigation algorithm based on Earth-Moon group photos by Chang'e-5T1 probe

NASA Astrophysics Data System (ADS)

Bu, Yanlong; Zhang, Qiang; Ding, Chibiao; Tang, Geshi; Wang, Hang; Qiu, Rujin; Liang, Libo; Yin, Hejun

2017-02-01

This paper presents an interplanetary optical navigation algorithm based on two spherical celestial bodies. The remarkable characteristic of the method is that key navigation parameters can be estimated depending entirely on known sizes and ephemerides of two celestial bodies, especially positioning is realized through a single image and does not rely on traditional terrestrial radio tracking any more. Actual Earth-Moon group photos captured by China's Chang'e-5T1 probe were used to verify the effectiveness of the algorithm. From 430,000 km away from the Earth, the camera pointing accuracy reaches 0.01° (one sigma) and the inertial positioning error is less than 200 km, respectively; meanwhile, the cost of the ground control and human resources are greatly reduced. The algorithm is flexible, easy to implement, and can provide reference to interplanetary autonomous navigation in the solar system.

The South Pole, Antarctica, Solar Radio Telescope (SPASRT) System

NASA Astrophysics Data System (ADS)

Gerrard, A. J.; Weatherwax, A. T.; Gary, D. E.; Kujawski, J. T.; Nita, G. M.; Melville, R.; Stillinger, A.; Jeffer, G.

2014-12-01

The study of the sun in the radio portion of the electromagnetic spectrum furthers our understanding of fundamental solar processes observed in the X-ray, UV, and visible regions of the spectrum. For example, the study of solar radio bursts, which have been shown to cause serious disruptions of technologies at Earth, are essential for advancing our knowledge and understanding of solar flares and their relationship to coronal mass ejections and solar energetic particles, as well as the underlying particle acceleration mechanisms associated with these processes. In addition, radio coverage of the solar atmosphere could yield completely new insights into the variations of output solar energy, including Alfven wave propagation through the solar atmosphere and into the solar wind, which can potentially modulate and disturb the solar wind and Earth's geospace environment. In this presentation we discuss the development, construction, and testing of the South Pole, Antarctica, Solar Radio Telescope that is planned for installation at South Pole. The system will allow for 24-hour continuous, long-term observations of the sun across the 1-18 GHz frequency band and allow for truly continuous solar observations. We show that this system will enable unique scientific investigations of the solar atmosphere.

Radio Jove: Citizen Science for Jupiter Radio Astronomy

NASA Astrophysics Data System (ADS)

Higgins, C. A.; Thieman, J.; Reyes, F. J.; Typinski, D.; Flagg, R. F.; Greenman, W.; Brown, J.; Ashcraft, T.; Sky, J.; Cecconi, B.; Garcia, L. N.

2016-12-01

The Radio Jove Project (http://radiojove.gsfc.nasa.gov) has been operating as an educational activity for 18 years to introduce radio astronomy activities to students, teachers, and the general public. Participants may build a simple radio telescope kit, make scientific observations, and interact with radio observatories in real-time over the Internet. Recently some of our dedicated citizen science observers have upgraded their systems to better study radio emission from Jupiter and the Sun by adding dual-polarization spectrographs and wide-band antennas in the frequency range of 15-30 MHz. Some of these observations are being used in conjunction with professional telescopes such as the Long Wavelength Array (LWA), the Nancay Decametric Array, and the Ukrainian URAN2 Radio Telescope. In particular, there is an effort to support the Juno Mission radio waves instrument at Jupiter by using citizen science ground-based data for comparison and polarization verification. These data will be archived through a Virtual European Solar and Planetary Access (VESPA) archive (https://voparis-radiojove.obspm.fr/radiojove/welcome) for use by the amateur and professional radio science community. We overview the program and display recent observations that will be of interest to the science community.

Using GPS radio occultation data in the study of tropical cyclogenesis

NASA Astrophysics Data System (ADS)

Didlake, A. C., Jr.; Kuo, Y. B.; Metcalfe, T.

2005-12-01

Numerous studies have examined atmospheric conditions and patterns in tropical cyclogenesis. Although much has been accomplished, a complete understanding of tropical cyclogenesis is hindered by the lack of data in the regions where formation occurs. The GPS (Global Positioning System) radio occultation technique can provide valuable data in key areas. In GPS radio occultation, GPS satellites emit radio signals through the atmosphere that are received by another satellite in a low Earth orbit. Various atmospheric properties are calculated based on the alteration of the signal. This study assessed the value of GPS radio occultation data in the study of tropical cyclogenesis by examining storms of the 2002 Western North Pacific typhoon season. The signature of precursor disturbances to tropical cyclogenesis was determined by analyzing composites of data from the NCEP Aviation (AVN) analysis over four days. Similar composites of GPS radio occultation data were produced. The AVN analysis showed strong signals of precursor disturbances in the low-level wind fields and atmospheric refractivity. The GPS radio occultation data detected similarly increased refractivity values in corresponding regions, but had sizeable measurement differences with the AVN analysis. These differences were attributed to AVN analysis error due to the lack of input observational data and the high accuracy of GPS radio occultation measurements. Further comparisons showed that with the limited quantity of data currently available, GPS radio occultation by itself was not sufficient to detect precursor disturbances. It can best be used in data assimilation to improve the analysis and forecasts of tropical storms.

The Radio JOVE Project: A Worldwide, Ground-based Amateur Decameter-Wavelength Radio Observatory Network

NASA Astrophysics Data System (ADS)

Thieman, J.; Higgins, C.; Lauffer, G.; Ulivastro, R.; Flagg, R.; Sky, J.

2003-04-01

The Radio JOVE project (http://radiojove.gsfc.nasa.gov) began over four years ago as an education-centered program to inspire secondary school students' interest in space science through hands-on radio astronomy. Students build a radio receiver and antenna kit capable of receiving Jovian, solar, and galactic emissions at a frequency of 20.1 MHz. More than 500 of these kits have been distributed to students and interested observers (ages 10 through adult) in 24 countries. Many students and teachers do not have the time or feel comfortable building a kit of their own. The Radio JOVE project has made it possible to monitor data and streaming audio from professional radio telescopes in Florida (16 element 10-40 MHz log spiral array - http://jupiter.kochi-ct.jp) and Hawaii (17-30 MHz log periodic antenna - http://jupiter.wcc.hawaii.edu/newradiojove/main.html) using standard web browsers and/or freely downloadable software. Radio-Skypipe software (http://radiosky.com) emulates a chart recorder for ones own radio telescope. It will also display the signals being received by other observers worldwide who send out their data over the Internet using the same software package. A built-in chat feature allows the users to discuss their observations and results in real time. New software is being developed to allow network users to interactively view a multi-frequency spectroscopic display of the Hawaii radio telescope. This software may also be useful for research applications. Observers in the U.S. and Europe have been contributing data to a central archive of Jupiter and Solar observations (http://jovearchive.gsfc.nasa.gov/). We believe these data to be of value to the research community and would like to have students more directly connected to ongoing research projects to enhance their interest in participating. We welcome ideas for expanding the application of these data.

Radio Searches for Signatures of Advanced Extraterrestrial Life

NASA Astrophysics Data System (ADS)

Siemion, Andrew

Over the last several decades, observational astronomy has produced a flood of discoveries that suggest that the building blocks and circumstances that gave rise to life on Earth may be the rule rather than the exception. It has now been conclusively shown that planets are common and that some 5-15% of FGKM stars host planets existing in their host star's habitable zone. Further, terrestrial biology has demonstrated that life on our own planet can thrive in extraordinarily extreme environments, dramatically extending our notion of what constitutes habitability. The deeper question, yet unanswered, is whether or not life in any form has ever existed in an environment outside of the Earth. As humans, we are drawn to an even more profound question, that of whether or not extraterrestrial life may have evolved a curiosity about the universe similar to our own and the technology with which to explore it. Radio astronomy has long played a prominent role in searches for extraterrestrial intelligence (SETI), beginning with the first suggestions by Cocconi and Morrison (1959) that narrow-band radio signals near 1420 MHz might be effective tracers of advanced technology and early experiments along these lines by Frank Drake in 1961, continuing through to more recent investigations searching for several types of coherent radio signals indicative of technology at a wider range of frequencies. The motivations for radio searches for extraterrestrial intelligence have been throughly discussed in the literature, but the salient arguments are the following: 1. coherent radio emission is commonly produced by advanced technology (judging by Earth’s technological development), 2. electromagnetic radiation can convey information at the maximum velocity currently known to be possible, 3. radio photons are energetically cheap to produce, 4. certain types of coherent radio emissions are easily distinguished from astrophysical background sources, especially within the so

The Accuracy of Radio Interferometric Measurements of Earth Rotation

NASA Technical Reports Server (NTRS)

Eubanks, T. M.; Steppe, J. A.; Spieth, M. A.

1985-01-01

The accuracy of very long base interferometry earth rotation (UT1) measurements is examined by intercomparing TEMPO and POLARIS data for 1982 and the first half of 1983. None of these data are simultaneous, and so a proper intercomparison requires accounting for the scatter introduced by the rapid, unpredictable, UT1 variations driven by exchanges of angular momentum with the atmosphere. A statistical model of these variations, based on meteorological estimates of the Atmospheric Angular Momentum is derived, and the optimal linear (Kalman) smoother for this model is constructed. The scatter between smoothed and independent raw data is consistent with the residual formal errors, which do not depend upon the actual scatter of the UT1 data. This represents the first time that an accurate prediction of the scatter between UT1 data sets were possible.

Spectrum sensing algorithm based on autocorrelation energy in cognitive radio networks

NASA Astrophysics Data System (ADS)

Ren, Shengwei; Zhang, Li; Zhang, Shibing

2016-10-01

Cognitive radio networks have wide applications in the smart home, personal communications and other wireless communication. Spectrum sensing is the main challenge in cognitive radios. This paper proposes a new spectrum sensing algorithm which is based on the autocorrelation energy of signal received. By taking the autocorrelation energy of the received signal as the statistics of spectrum sensing, the effect of the channel noise on the detection performance is reduced. Simulation results show that the algorithm is effective and performs well in low signal-to-noise ratio. Compared with the maximum generalized eigenvalue detection (MGED) algorithm, function of covariance matrix based detection (FMD) algorithm and autocorrelation-based detection (AD) algorithm, the proposed algorithm has 2 11 dB advantage.

Imaging interplanetary CMEs at radio frequency from solar polar orbit

NASA Astrophysics Data System (ADS)

Wu, Ji; Sun, Weiying; Zheng, Jianhua; Zhang, Cheng; Liu, Hao; Yan, Jingye; Wang, Chi; Wang, Chuanbing; Wang, Shui

2011-09-01

Coronal mass ejections (CMEs) represent a great concentration of mass and energy input into the lower corona. They have come to be recognized as the major driver of physical conditions change in the Sun-Earth system. Consequently, observations of CMEs are important for understanding and ultimately predicting space weather conditions. This paper discusses a proposed mission, the Solar Polar Orbit Radio Telescope (SPORT) mission, which will observe the propagation of interplanetary CMEs to distances of near 0.35 AU from the Sun. The orbit of SPORT is an elliptical solar polar orbit. The inclination angle between the orbit and ecliptic plane should be about 90°. The main payload on board SPORT will be an imaging radiometer working at the meter wavelength band (radio telescope), which can follow the propagation of interplanetary CMEs. The images that are obtained by the radio telescope embody the brightness temperature of the objectives. Due to the very large size required for the antenna aperture of the radio telescope, we adopt interferometric imaging technology to reduce it. Interferometric imaging technology is based on indirect spatial frequency domain measurements plus Fourier transformation. The SPORT spacecraft will also be equipped with a set of optical and in situ measurement instruments such as a EUV solar telescope, a solar wind ion instrument, an energetic particle detector, a magnetometer, a wave detector and a solar radio burst spectrometer.

Relativistic runaway breakdown in low-frequency radio

NASA Astrophysics Data System (ADS)

Füllekrug, Martin; Roussel-Dupré, Robert; Symbalisty, Eugene M. D.; Chanrion, Olivier; Odzimek, Anna; van der Velde, Oscar; Neubert, Torsten

2010-01-01

The electromagnetic radiation emitted by an electron avalanche beam resulting from relativistic runaway breakdown within the Earth's atmosphere is investigated. It is found from theoretical modeling with a computer simulation that the electron beam emits electromagnetic radiation which is characterized by consecutive broadband pulses in the low-frequency radio range from ˜10 to 300 kHz at a distance of ˜800 km. Experimental evidence for the existence of consecutive broadband pulses is provided by low-frequency radio observations of sprite-producing lightning discharges at a distance of ˜550 km. The measured broadband pulses occur ˜4-9 ms after the sprite-producing lightning discharge, they exhibit electromagnetic radiation which mainly spans the frequency range from ˜50 to 350 kHz, and they exhibit complex waveforms without the typical ionospheric reflection of the first hop sky wave. Two consecutive pulses occur ˜4.5 ms and ˜3 ms after the causative lightning discharge and coincide with the sprite luminosity. It is concluded that relativistic runaway breakdown within the Earth's atmosphere can emit broadband electromagnetic pulses and possibly generates sprites. The source location of the broadband pulses can be determined with an interferometric network of wideband low-frequency radio receivers to lend further experimental support to the relativistic runaway breakdown theory.

Cognitive radio adaptation for power consumption minimization using biogeography-based optimization

NASA Astrophysics Data System (ADS)

Qi, Pei-Han; Zheng, Shi-Lian; Yang, Xiao-Niu; Zhao, Zhi-Jin

2016-12-01

Adaptation is one of the key capabilities of cognitive radio, which focuses on how to adjust the radio parameters to optimize the system performance based on the knowledge of the radio environment and its capability and characteristics. In this paper, we consider the cognitive radio adaptation problem for power consumption minimization. The problem is formulated as a constrained power consumption minimization problem, and the biogeography-based optimization (BBO) is introduced to solve this optimization problem. A novel habitat suitability index (HSI) evaluation mechanism is proposed, in which both the power consumption minimization objective and the quality of services (QoS) constraints are taken into account. The results show that under different QoS requirement settings corresponding to different types of services, the algorithm can minimize power consumption while still maintaining the QoS requirements. Comparison with particle swarm optimization (PSO) and cat swarm optimization (CSO) reveals that BBO works better, especially at the early stage of the search, which means that the BBO is a better choice for real-time applications. Project supported by the National Natural Science Foundation of China (Grant No. 61501356), the Fundamental Research Funds of the Ministry of Education, China (Grant No. JB160101), and the Postdoctoral Fund of Shaanxi Province, China.

A simulation-based analytic model of radio galaxies

NASA Astrophysics Data System (ADS)

Hardcastle, M. J.

2018-04-01

I derive and discuss a simple semi-analytical model of the evolution of powerful radio galaxies which is not based on assumptions of self-similar growth, but rather implements some insights about the dynamics and energetics of these systems derived from numerical simulations, and can be applied to arbitrary pressure/density profiles of the host environment. The model can qualitatively and quantitatively reproduce the source dynamics and synchrotron light curves derived from numerical modelling. Approximate corrections for radiative and adiabatic losses allow it to predict the evolution of radio spectral index and of inverse-Compton emission both for active and `remnant' sources after the jet has turned off. Code to implement the model is publicly available. Using a standard model with a light relativistic (electron-positron) jet, subequipartition magnetic fields, and a range of realistic group/cluster environments, I simulate populations of sources and show that the model can reproduce the range of properties of powerful radio sources as well as observed trends in the relationship between jet power and radio luminosity, and predicts their dependence on redshift and environment. I show that the distribution of source lifetimes has a significant effect on both the source length distribution and the fraction of remnant sources expected in observations, and so can in principle be constrained by observations. The remnant fraction is expected to be low even at low redshift and low observing frequency due to the rapid luminosity evolution of remnants, and to tend rapidly to zero at high redshift due to inverse-Compton losses.

Factors Affecting Student Success with a Google Earth-Based Earth Science Curriculum

ERIC Educational Resources Information Center

Blank, Lisa M.; Almquist, Heather; Estrada, Jen; Crews, Jeff

2016-01-01

This study investigated to what extent the implementation of a Google Earth (GE)-based earth science curriculum increased students' understanding of volcanoes, earthquakes, plate tectonics, scientific reasoning abilities, and science identity. Nine science classrooms participated in the study. In eight of the classrooms, pre- and post-assessments…

Radio Astronomers Get Their First Glimpse of Powerful Solar Storm

NASA Astrophysics Data System (ADS)

2001-08-01

expanding set of loops similar to the loops seen at visible wavelengths. The radio loops, astronomers believe, indicate regions where electrons are being accelerated to nearly the speed of light at about the time the ejection process is getting started. The same ejection observed by the radio telescope also was observed by orbiting solar telescopes. Depending on what later radio observations show, the solar studies may reveal new insights into the physics of other astronomical phenomena. For example, shocks in the corona and the interplanetary medium accelerate electrons and ions, a process believed to occur in supernova remnants - the expanding debris from stellar explosions. The electrons also may be accelerated by processes associated with magnetic reconnection, a process that occurs in the Earth's magnetosphere. "The Sun is an excellent physics laboratory, and what it teaches us can then help us understand other astrophysical phenomena in the universe," Bastian said. The radio detection of a coronal mass ejection also means that warning of the potentially dangerous effects of these events could come from ground-based radio telescopes, rather than more-expensive orbiting observatories. "With solar radio telescopes strategically placed at three or four locations around the world, coronal mass ejections could be detected 24 hours a day to provide advance warning," Bastian said. The Nancay station for radio astronomy is a facility of the Paris Observatory. The Nancay Radioheliograph is funded by the French Ministry of Education, the Centre National de la Recherche Scientifique, and by the Region Centre. This research has also been supported by the Centre National d'Etudes Spatiales. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Li/BCX (thionyl chloride) battery for the NASA AN/PRC-112 survival radio

NASA Astrophysics Data System (ADS)

Ebel, Steven J.; Clark, W. D. K.; Eberhard, D. P.; Darcy, Eric C.

1992-02-01

As part of the NASA contingency planning related to aborting a launch after liftoff, an emergency radio is required for use by the crew when they return to Earth at some unplanned location. The power source for the radio must be able to satisfy the performance requirements for the radio's mission as well as be compatible with in-cabin storage in the space shuttle. The radio needs a base load power of about 1 W with capability to handle power spikes greater then 6.5 W. A slightly enlarged battery pack using the Li/BCX chemistry in C-size cells was developed that meets these power levels and extends the operational life of the radio by over a factor of four compared to its operation using a Li/SO2 cell battery pack. In addition, the cells meet the requirements for the Li/BCX cells used for extra-vehicular activities by the crew of the shuttle. One of the major qualifying tests is the ability of the cells to withstand exposure to high temperature (149 C) without leaking. Electrical performance and thermal abuse test data will be presented for the cells.

Li/BCX (thionyl chloride) battery for the NASA AN/PRC-112 survival radio

NASA Technical Reports Server (NTRS)

Ebel, Steven J.; Clark, W. D. K.; Eberhard, D. P.; Darcy, Eric C.

1992-01-01

As part of the NASA contingency planning related to aborting a launch after liftoff, an emergency radio is required for use by the crew when they return to Earth at some unplanned location. The power source for the radio must be able to satisfy the performance requirements for the radio's mission as well as be compatible with in-cabin storage in the space shuttle. The radio needs a base load power of about 1 W with capability to handle power spikes greater then 6.5 W. A slightly enlarged battery pack using the Li/BCX chemistry in C-size cells was developed that meets these power levels and extends the operational life of the radio by over a factor of four compared to its operation using a Li/SO2 cell battery pack. In addition, the cells meet the requirements for the Li/BCX cells used for extra-vehicular activities by the crew of the shuttle. One of the major qualifying tests is the ability of the cells to withstand exposure to high temperature (149 C) without leaking. Electrical performance and thermal abuse test data will be presented for the cells.

Harmonization based on regulatory science between scientific and commercial radio uses in a case of ultrawideband radio

NASA Astrophysics Data System (ADS)

Kohno, Ryuji; Iinatti, Jari; Sameshima, Keiko

2016-12-01

Harmonization for scientific and commercial radio uses is one of the unsolved problems in academia, industry, and regulatory bodies. The demands for commercial radio, mobile communications, and broadcasting have significantly increased over the past few decades; therefore, interference has become a major concern. There is an increasing need to prevent such interferences, for example, between commercial radio systems and other potentially sensitive radio systems such as those used for radio astronomy or studies. When discussing the fairness in resolving such conflicts, regulatory science may be a useful multidisciplinary approach as it scientifically investigates the advantages and disadvantages of a new application or technology for conflicts between different stakeholders through a mathematical analysis of risks versus benefits of the given technology. Such an analysis enables fair rules or regulations to be made. In this study, we apply the above-mentioned concept to harmonize the scientific and commercial uses of radio. After a brief introduction to regulatory science, a case study about the coexistence between ultrawideband commercial radio systems and radio astronomy is considered. Finally, a proposal by International Union of Radio Science, Japan, to the Science Council of Japan in the Cabinet Office to establish a "Center for Coexistence and Harmonization of Scientific and Commercial Uses of Radio Waves" is explained.

Radio Receiver Instrument (RRI) ePOP transionospheric observations from an HF transmitter in Ottawa (45N, 75W)

NASA Astrophysics Data System (ADS)

Hussey, G. C.; Danskin, D. W.; Gillies, R. G.; James, H. G.; Yau, A. W.; Hird, F. C.; Fairbairn, D. T.

2016-12-01

A ground-based HF transmitter operating at 10.422 MHz in Ottawa, Canada (45.4N, 75.6W) was the radio source for reception by the satellite-based Radio Receiver Instrument (RRI) for 5 passes in late April, 2016. The RRI is one of eight instruments on the enhanced Polar Outflow Probe (ePOP) scientific payload portion of the CSA (Canadian Space Agency) CASSIOPE (Cascade Demonstrator Small-Sat and Ionospheric Polar Explorer) satellite mission launched in September, 2013. The crossed-dipole configuration of the RRI allows for complete polarization observations. Initial analysis of the passes indicates reception of a highly polarized signal. South of the transmitter the signal clearly exhibits Faraday rotation of an essentially linearly polarized radio wave in agreement with modeling by Gillies et al. [2007]. This propagation is characterized as quasi-longitudinal (QL) by the Appleton-Hartree equation (electromagnetic wave propagation in a cold magnetized plasma) as the radio waves travel in a direction more along the magnetic field of the Earth. When the satellite moves north of the Ottawa transmitter the radio wave propagation transitions into quasi-transverse (QT). The data indicates favoring circular polarization dependent on the geometry with respect to the transmitter. Surprisingly the Faraday rotation effect is still very pronounced reversing in direction roughly 1000 km north of the transmitter. The model of Gillies et al. [2007] has been extended to explain these observations. This is the first direct observation, by polarimetry, of HF radio wave propagation in near-Earth space plasmas.Gillies, R.G., G.C. Hussey, H.G. James, G.J. Sofko, and D. Andre, Modelling and observation of transionospheric propagation results from ISIS II in preparation for ePOP, Ann. Geophys. 25, 87-97, 2007.

Telescopes As Big As the Earth

ERIC Educational Resources Information Center

MOSAIC, 1974

1974-01-01

Making simultaneous observations with radio antennas continents apart, astronomers are getting information from space not available before. The technique can be used to obtain information related to many problems on earth also. (RH)

The Geolocation model for lunar-based Earth observation

NASA Astrophysics Data System (ADS)

Ding, Yixing; Liu, Guang; Ren, Yuanzhen; Ye, Hanlin; Guo, Huadong; Lv, Mingyang

2016-07-01

In recent years, people are more and more aware of that the earth need to treated as an entirety, and consequently to be observed in a holistic, systematic and multi-scale view. However, the interaction mechanism between the Earth's inner layers and outer layers is still unclear. Therefore, we propose to observe the Earth's inner layers and outer layers instantaneously on the Moon which may be helpful to the studies in climatology, meteorology, seismology, etc. At present, the Moon has been proved to be an irreplaceable platform for Earth's outer layers observation. Meanwhile, some discussions have been made in lunar-based observation of the Earth's inner layers, but the geolocation model of lunar-based observation has not been specified yet. In this paper, we present a geolocation model based on transformation matrix. The model includes six coordinate systems: The telescope coordinate system, the lunar local coordinate system, the lunar-reference coordinate system, the selenocentric inertial coordinate system, the geocentric inertial coordinate system and the geo-reference coordinate system. The parameters, lncluding the position of the Sun, the Earth, the Moon, the libration and the attitude of the Earth, can be acquired from the Ephemeris. By giving an elevation angle and an azimuth angle of the lunar-based telescope, this model links the image pixel to the ground point uniquely.

Three years of RadioAstron in flight and future prospects

NASA Astrophysics Data System (ADS)

Kardashev, Nikolay

The Russian Academy of Sciences and Federal Space Agency, together with many international organizations, prepared the launch of the RadioAstron orbiting space observatory. The spacecraft was launched by the Ukranian Zenit-3F rocket with onboard 10-m reflector radio telescope (spectral bands 1.2-1.6, 6.2, 18 and 92 cm and both circular polarizations) from the Baikonur cosmodrome on July 18, 2011. The orbital period in 2012-2015 will vary from 8.3 to 9.0 days, the perigee - from 7,065 km to 81,500 km, the apogee - from 280,000 to 353,000 km. Together with ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna ground-space radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than it is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of formation of stars and planetary systems in our and other galaxies, interplanetary and interstellar plasma, and the gravitational field of the Earth. The fringes with the ground-space interferometer were founded at the baseline projections up to 25 diameters of the Earth, and corresponding models of the sources will be reported. Millimetron is the next space mission with a 10-m cooled space telescope optimized for observations in the millimeter and far infrared wavelengths. This mission will be able to contribute to the solution of several key problems in astrophysics, such as study of formation and evolution of stars and planets, galaxies, quasars and many others. The mission will have a cryogenic instruments and antenna, which will be cooled

Wearable ECG Based on Impulse-Radio-Type Human Body Communication.

PubMed

Wang, Jianqing; Fujiwara, Takuya; Kato, Taku; Anzai, Daisuke

2016-09-01

Human body communication (HBC) provides a promising physical layer for wireless body area networks (BANs) in healthcare and medical applications, because of its low propagation loss and high security characteristics. In this study, we have developed a wearable electrocardiogram (ECG) which employs impulse radio (IR)-type HBC technology for transmitting vital signals on the human body in a wearable BAN scenario. The HBC-based wearable ECG has two excellent features. First, the wideband performance of the IR scheme contributed to very low radiation power so that the transceiver is easy to satisfy the extremely weak radio laws, which does not need a license. This feature can provide big convenience in the use and spread of the wearable ECG. Second, the realization of common use of sensing and transmitting electrodes based on time sharing and capacitive coupling largely simplified the HBC-based ECG structure and contributed to its miniaturization. To verify the validity of the HBC-based ECG, we evaluated its communication performance and ECG acquisition performance. The measured bit error rate, smaller than 10 -3 at 1.25 Mb/s, showed a good physical layer communication performance, and the acquired ECG waveform and various heart-rate variability parameters in time and frequency domains exhibited good agreement with a commercially available radio-frequency ECG and a Holter ECG. These results sufficiently showed the validity and feasibility of the HBC-based ECG for healthcare applications. This should be the first time to have realized a real-time ECG transmission by using the HBC technology.

Constraints on submicrojansky radio number counts based on evolving VLA-COSMOS luminosity functions

NASA Astrophysics Data System (ADS)

Novak, M.; Smolčić, V.; Schinnerer, E.; Zamorani, G.; Delvecchio, I.; Bondi, M.; Delhaize, J.

2018-06-01

We present an investigation of radio luminosity functions (LFs) and number counts based on the Karl G. Jansky Very Large Array-COSMOS 3 GHz Large Project. The radio-selected sample of 7826 galaxies with robust optical/near-infrared counterparts with excellent photometric coverage allows us to construct the total radio LF since z 5.7. Using the Markov chain Monte Carlo algorithm, we fit the redshift dependent pure luminosity evolution model to the data and compare it with previously published VLA-COSMOS LFs obtained on individual populations of radio-selected star-forming galaxies and galaxies hosting active galactic nuclei classified on the basis of presence or absence of a radio excess with respect to the star-formation rates derived from the infrared emission. We find they are in excellent agreement, thus showing the reliability of the radio excess method in selecting these two galaxy populations at radio wavelengths. We study radio number counts down to submicrojansky levels drawn from different models of evolving LFs. We show that our evolving LFs are able to reproduce the observed radio sky brightness, even though we rely on extrapolations toward the faint end. Our results also imply that no new radio-emitting galaxy population is present below 1 μJy. Our work suggests that selecting galaxies with radio flux densities between 0.1 and 10 μJy will yield a star-forming galaxy in 90-95% of the cases with a high percentage of these galaxies existing around a redshift of z 2, thus providing useful constraints for planned surveys with the Square Kilometer Array and its precursors.

Acquisition and Development of a Cognitive Radio Based Wireless Monitoring and Surveillance Testbed for Future Battlefield Communications Research

DTIC Science & Technology

2015-03-01

for Public Release; Distribution Unlimited Final Report: Acquisition and Development of A Cognitive Radio based Wireless Monitoring and Surveillance...journals: Final Report: Acquisition and Development of A Cognitive Radio based Wireless Monitoring and Surveillance Testbed for Future Battlefield...Opeyemi Oduola, Nan Zou, Xiangfang Li, Husheng Li, Lijun Qian. Distributed Spectrum Monitoring and Surveillance using a Cognitive Radio based Testbed

Lessons from our Own Solar System: Generation Mechanisms of Radio Emissions from Earth, Saturn and Jupiter and Atmospheric Loss from Magnetized versus non-magnetized planets

NASA Astrophysics Data System (ADS)

Brandt, Pontus

2017-05-01

The understanding of the engines and mechanisms behind kilometric and decametric radio emissions from the planets in our own solar system have taken great leaps with missions such as the NASA/Cassini, IMAGE and Galileo missions. The periodic Saturn Kilometric Radiation (SKR), the Auroral Kilometric Radiation (AKR) at Earth and the periodic decametric radio emissions from Jupiter all point to the same generation mechanisms: very large-scale explosive plasma heating events in the magnetotail of each of the planets. The character and periodicity of the associated radio emissions not only tells us about the presence of a magnetic field but also about the plasma content and size of the planetary magnetosphere, and the nature of the interaction with the solar wind.The presence of a planetary magnetic field, as could be established for exoplanets by the positive detection of low-frequency exoplanetary radio emissions, has been thought to shield a planet from atmospheric loss to space. However, recent data from Mars Express, MAVEN, and Venus Express, together with the wealth of terrestrial measurements of atmospheric escape to space has brought a surprising question in to light: Does a planetary magnetic field suppress or enhance atmospheric loss? While at the non-magnetized planets such as Mars and Venus, the solar wind has a more direct access to the ionized upper atmosphere, these planets do set up self shielding currents that do limit escape. Furthermore, it is not clear if Mars have lost the majority of its atmosphere by condensation in to surface and sub-surface frost, or through atmospheric escape. At Earth, the geomagnetic field sets up a relatively large cross section to the solar wind, that allows the induced solar-wind electric field to transfer substantial energy to the upper ionosphere and atmosphere resulting in substantial loss. It is therefore not clear how a planetary magnetic field correlates to the atmospheric loss, or if it does at all.In this

Report on GMI Special Study #15: Radio Frequency Interference

NASA Technical Reports Server (NTRS)

Draper, David W.

2015-01-01

This report contains the results of GMI special study #15. An analysis is conducted to identify sources of radio frequency interference (RFI) to the Global Precipitation Measurement (GPM) Microwave Imager (GMI). The RFI impacts the 10 GHz and 18 GHz channels at both polarities. The sources of RFI are identified for the following conditions: over the water (including major inland water bodies) in the earth view, and over land in the earth view, and in the cold sky view. A best effort is made to identify RFI sources in coastal regions, with noted degradation of flagging performance due to the highly variable earth scene over coastal regions. A database is developed of such sources, including latitude, longitude, country and city of earth emitters, and position in geosynchronous orbit for space emitters. A description of the recommended approach for identifying the sources and locations of RFI in the GMI channels is given in this paper. An algorithm to flag RFI contaminated pixels which can be incorporated into the GMI Level 1Base/1B algorithms is defined, which includes Matlab code to perform the necessary flagging of RFI. A Matlab version of the code is delivered with this distribution.

[Inefficiency of electrosmog-shielding mats. Part 2: radio frequency range].

PubMed

Leitgeb, N; Cech, R

2005-09-01

It could already be shown that electromagnetic shielding mats do not reduce but even enhance electric field exposure in daily life situations. By measurements and numerical simulations the claims of manufacturers were checked who pretend that radio frequency electromagnetic fields can be shielded to 99% and more, and transferred to earth by earth cables (if attached). It could be shown that in the radio frequency range such products do not fulfil the justified expectations of customers, but in most cases even cause the opposite. The results depend on the electric properties of the material. Good electric conductivity of shielding mats even considerably increases electromagnetic field exposure. To connect the mats with earth potential by an attached cable might increase the beliefs on a protective effect, however, this is not capable to enhance the shielding effect. The investigation demonstrates that in spite of references made to experts opinions manufacturers claims about the shielding efficiency of radio frequency fields are misleading and fool clients about the real situation. Overall, acquisition and use of electrosmog shielding mats must be discouraged. If at all, shielding can be reached by placing a shielding cover between the source and the person. However, even in this case, efficiency is much lower than promised by manufacturers and decreases even more if it is taken into account that the head naturally remains uncovered and hence unshielded.

Earth-Base: A Free And Open Source, RESTful Earth Sciences Platform

NASA Astrophysics Data System (ADS)

Kishor, P.; Heim, N. A.; Peters, S. E.; McClennen, M.

2012-12-01

This presentation describes the motivation, concept, and architecture behind Earth-Base, a web-based, RESTful data-management, analysis and visualization platform for earth sciences data. Traditionally web applications have been built directly accessing data from a database using a scripting language. While such applications are great at bring results to a wide audience, they are limited in scope to the imagination and capabilities of the application developer. Earth-Base decouples the data store from the web application by introducing an intermediate "data application" tier. The data application's job is to query the data store using self-documented, RESTful URIs, and send the results back formatted as JavaScript Object Notation (JSON). Decoupling the data store from the application allows virtually limitless flexibility in developing applications, both web-based for human consumption or programmatic for machine consumption. It also allows outside developers to use the data in their own applications, potentially creating applications that the original data creator and app developer may not have even thought of. Standardized specifications for URI-based querying and JSON-formatted results make querying and developing applications easy. URI-based querying also allows utilizing distributed datasets easily. Companion mechanisms for querying data snapshots aka time-travel, usage tracking and license management, and verification of semantic equivalence of data are also described. The latter promotes the "What You Expect Is What You Get" (WYEIWYG) principle that can aid in data citation and verification.

Interplanetary Radio Transmission Through Serial Ionospheric and Material Barriers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fields, David; Kennedy, Robert G; Roy, Kenneth I

2013-01-01

A usual first principle in planning radio astronomy observations from the earth is that monitoring must be carried out well above the ionospheric plasma cutoff frequency (~5 MHz). Before space probes existed, radio astronomy was almost entirely done above 6 MHz, and this value is considered a practical lower limit by most radio astronomers. Furthermore, daytime ionization (especially D-layer formation) places additional constraints on wave propagation, and waves of frequency below 10-20 MHz suffer significant attenuation. More careful calculations of wave propagation through the earth s ionosphere suggest that for certain conditions (primarily the presence of a magnetic field) theremore » may be a transmission window well below this assumed limit. Indeed, for receiving extraterrestrial radiation below the ionospheric plasma cutoff frequency, a choice of VLF frequency appears optimal to minimize loss. The calculation, experimental validation, and conclusions are presented here. This work demonstrates the possibility of VLF transmission through the ionosphere and various subsequent material barriers. Implications include development of a new robust communications channel, communications with submerged or subterranean receivers / instruments on or offworld, and a new approach to SETI.« less

Radio frequency electromagnetic field compliance assessment of multi-band and MIMO equipped radio base stations.

PubMed

Thors, Björn; Thielens, Arno; Fridén, Jonas; Colombi, Davide; Törnevik, Christer; Vermeeren, Günter; Martens, Luc; Joseph, Wout

2014-05-01

In this paper, different methods for practical numerical radio frequency exposure compliance assessments of radio base station products were investigated. Both multi-band base station antennas and antennas designed for multiple input multiple output (MIMO) transmission schemes were considered. For the multi-band case, various standardized assessment methods were evaluated in terms of resulting compliance distance with respect to the reference levels and basic restrictions of the International Commission on Non-Ionizing Radiation Protection. Both single frequency and multiple frequency (cumulative) compliance distances were determined using numerical simulations for a mobile communication base station antenna transmitting in four frequency bands between 800 and 2600 MHz. The assessments were conducted in terms of root-mean-squared electromagnetic fields, whole-body averaged specific absorption rate (SAR) and peak 10 g averaged SAR. In general, assessments based on peak field strengths were found to be less computationally intensive, but lead to larger compliance distances than spatial averaging of electromagnetic fields used in combination with localized SAR assessments. For adult exposure, the results indicated that even shorter compliance distances were obtained by using assessments based on localized and whole-body SAR. Numerical simulations, using base station products employing MIMO transmission schemes, were performed as well and were in agreement with reference measurements. The applicability of various field combination methods for correlated exposure was investigated, and best estimate methods were proposed. Our results showed that field combining methods generally considered as conservative could be used to efficiently assess compliance boundary dimensions of single- and dual-polarized multicolumn base station antennas with only minor increases in compliance distances. © 2014 Wiley Periodicals, Inc.

Combined Radio and Space-Based Solar Observations: From Techniques to New Results - Preface

NASA Astrophysics Data System (ADS)

Kontar, Eduard P.; Nindos, Alexander

2018-06-01

The phenomena observed at the Sun have a variety of unique radio signatures that can be used to diagnose the processes in the solar atmosphere. The insights provided by radio observations are further enhanced when they are combined with observations from space-based telescopes. This Topical collection demonstrates the power of combination methodology at work and provides new results on i) type I solar radio bursts and thermal emission to study active regions; ii) type II and IV bursts to better understand the structure of coronal mass ejections; and iii) non-thermal gyro-synchrotron and/or type III bursts to improve the characterisation of particle acceleration in solar flares. The ongoing improvements in time, frequency, and spatial resolutions of ground-based telescopes reveal new levels in the complexity of solar phenomena and pose new questions.

Detection of Ultrahigh-Energy Cosmic Rays with the Auger Engineering Radio Array

NASA Astrophysics Data System (ADS)

Krause, Raphael; Pierre Auger Collaboration

2017-02-01

Ultrahigh-energy cosmic rays interact with the Earth's atmosphere and produce great numbers of secondary particles forming an extensive air shower. These air showers emit radiation in the radio frequency range which delivers important information about the processes of radio emission in extensive air showers and properties of the primary cosmic rays, e.g. arrival direction, energy and mass with a duty cycle close to 100%. The radio extension of the world's largest cosmic-ray experiment, the Pierre Auger Observatory, is called the Auger Engineering Radio Array (AERA). In addition to the particle and fluorescence detectors of the Pierre Auger Observatory, AERA investigates the electromagnetic component of extensive air showers using 153 autonomous radio stations on an area of 17km2 .

Ultra-high-energy cosmic rays from radio galaxies

NASA Astrophysics Data System (ADS)

Eichmann, B.; Rachen, J. P.; Merten, L.; van Vliet, A.; Becker Tjus, J.

2018-02-01

Radio galaxies are intensively discussed as the sources of cosmic rays observed above about 3 × 1018 eV, called ultra-high energy cosmic rays (UHECRs). We present a first, systematic approach that takes the individual characteristics of these sources into account, as well as the impact of the extragalactic magnetic-field structures up to a distance of 120 Mpc. We use a mixed simulation setup, based on 3D simulations of UHECRs ejected by observed, individual radio galaxies taken out to a distance of 120 Mpc, and on 1D simulations over a continuous source distribution contributing from beyond 120 Mpc. Additionally, we include the ultra-luminous radio galaxy Cygnus A at a distance of about 250 Mpc, as its contribution is so strong that it must be considered as an individual point source. The implementation of the UHECR ejection in our simulation setup, both that of individual radio galaxies and the continuous source function, is based on a detailed consideration of the physics of radio jets and standard first-order Fermi acceleration. This allows to derive the spectrum of ejected UHECR as a function of radio luminosity, and at the same time provides an absolute normalization of the problem involving only a small set of parameters adjustable within narrow constraints. We show that the average contribution of radio galaxies taken over a very large volume cannot explain the observed features of UHECRs measured at Earth. However, we obtain excellent agreement with the spectrum, composition, and arrival-direction distribution of UHECRs measured by the Pierre Auger Observatory, if we assume that most UHECRs observed arise from only two sources: the ultra-luminous radio galaxy Cygnus A, providing a mostly light composition of nuclear species dominating up to about 6 × 1019 eV, and the nearest radio galaxy Centaurus A, providing a heavy composition dominating above 6 × 1019 eV . Here we have to assume that extragalactic magnetic fields out to 250 Mpc, which we did not

Modelling of radio emission from cosmic ray air showers

NASA Astrophysics Data System (ADS)

Ludwig, Marianne

2011-06-01

Cosmic rays entering the Earth's atmosphere induce extensive air showers consisting of up to billions of secondary particles. Among them, a multitude of electrons and positrons are generated. These get deflected in the Earth's magnetic field, creating time-varying transverse currents. Thereby, the air shower emits coherent radiation in the MHz frequency range measured by radio antenna arrays on the ground such as LOPES at the KIT. This detection method provides a possibility to study cosmic rays with energies above 1017 eV. At this time, the radio technique undergoes the change from prototype experiments to large scale application. Thus, a detailed understanding of the radio emission process is needed more than ever. Before starting this work, different models made conflicting predictions on the pulse shape and the amplitude of the radio signal. It turned out that a radiation component caused by the variation of the number of charged particles within the air shower was missed in several models. The Monte Carlo code REAS2 superposing the radiation of the individual air shower electrons and positrons was one of those. At this time, it was not known how to take the missing component into account. For REAS3, we developed and implemented the endpoint formalism, a universal approach, to calculate the radiation from each single particle. For the first time, we achieve a good agreement between REAS3 and MGMR, an independent and completely different simulation approach. In contrast to REAS3, MGMR is based on a macroscopic approach and on parametrisations of the air shower. We studied the differences in the underlying air shower models to explain the remaining deviations. For comparisons with LOPES data, we developed a new method which allows "top-down" simulations of air showers. From this, we developed an air shower selection criterion based on the number of muons measured with KASCADE to take shower-to-shower fluctuations for a single event analysis into account. With

EarthRef.org: Exploring aspects of a Cyber Infrastructure in Earth Science and Education

NASA Astrophysics Data System (ADS)

Staudigel, H.; Koppers, A.; Tauxe, L.; Constable, C.; Helly, J.

2004-12-01

EarthRef.org is the common host and (co-) developer of a range of earth science databases and IT resources providing a test bed for a Cyberinfrastructure in Earth Science and Education (CIESE). EarthRef.org data base efforts include in particular the Geochemical Earth Reference Model (GERM), the Magnetics Information Consortium (MagIC), the Educational Resources for Earth Science Education (ERESE) project, the Seamount Catalog, the Mid-Ocean Ridge Catalog, the Radio-Isotope Geochronology (RiG) initiative for CHRONOS, and the Microbial Observatory for Fe oxidizing microbes on Loihi Seamount (FeMO; the most recent development). These diverse databases are developed under a single database umbrella and webserver at the San Diego Supercomputing Center. All the data bases have similar structures, with consistent metadata concepts, a common database layout, and automated upload wizards. Shared resources include supporting databases like an address book, a reference/publication catalog, and a common digital archive making database development and maintenance cost-effective, while guaranteeing interoperability. The EarthRef.org CIESE provides a common umbrella for synthesis information as well as sample-based data, and it bridges the gap between science and science education in middle and high schools, validating the potential for a system wide data infrastructure in a CIESE. EarthRef.org experiences have shown that effective communication with the respective communities is a key part of a successful CIESE facilitating both utility and community buy-in. GERM has been particularly successful at developing a metadata scheme for geochemistry and in the development of a new electronic journal (G-cubed) that has made much progress in data publication and linkages between journals and community data bases. GERM also has worked, through editors and publishers, towards interfacing databases with the publication process, to accomplish a more scholarly and database friendly data

Amateur Radio on the International Space Station - the First Operational Payload on the ISS

NASA Astrophysics Data System (ADS)

Bauer, F. H.; McFadin, L.; Steiner, M.; Conley, C. L.

2002-01-01

As astronauts and cosmonauts have adapted to life on the International Space Station (ISS), they have found Amateur Radio and its connection to life on Earth to be a constant companion and a substantial psychological boost. Since its first use in November 2000, the first five expedition crews have utilized the amateur radio station in the FGB to talk to thousands of students in schools, to their families on Earth, and to amateur radio operators around the world. Early in the development of ISS, an international organization called ARISS (Amateur Radio on the International Space Station) was formed to coordinate the construction and operation of amateur radio (ham radio) equipment on ISS. ARISS represents a melding of the volunteer teams that have pioneered the development and use of amateur radio equipment on human spaceflight vehicles. The Shuttle/Space Amateur Radio Experiment (SAREX) team enabled Owen Garriott to become the first astronaut ham to use amateur radio from space in 1983. Since then, amateur radio teams in the U.S. (SAREX), Germany, (SAFEX), and Russia (Mirex) have led the development and operation of amateur radio equipment on board NASA's Space Shuttle, Russia's Mir space station, and the International Space Station. The primary goals of the ARISS program are fourfold: 1) educational outreach through crew contacts with schools, 2) random contacts with the Amateur Radio public, 3) scheduled contacts with the astronauts' friends and families and 4) ISS-based communications experimentation. To date, over 65 schools have been selected from around the world for scheduled contacts with the orbiting ISS crew. Ten or more students at each school ask the astronauts questions, and the nature of these contacts embodies the primary goal of the ARISS program, -- to excite student's interest in science, technology and amateur radio. The ARISS team has developed various hardware elements for the ISS amateur radio station. These hardware elements have flown to ISS

The Electron Density Features Revealed by the GNSS-Based Radio Tomography in the Different Latitudinal and Longitudinal Sectors of the Ionosphere

NASA Astrophysics Data System (ADS)

Andreeva, Elena; Tereshchenko, Evgeniy; Nazarenko, Marina; Nesterov, Ivan; Kozharin, Maksim; Padokhin, Artem; Tumanova, Yulia

2016-04-01

The ionospheric radio tomography is an efficient method for electron density imaging in the different geographical regions of the world under different space weather conditions. The input for the satellite-based ionospheric radio tomography is provided by the signals that are transmitted from the navigational satellites and recorded by the chains or networks of ground receivers. The low-orbiting (LO) radio tomography employs the 150/400 MHz radio transmissions from the Earth's orbiters (like the Russian Tsikada/Parus and American Transit) flying at a height of ~1000 km above the Earth in the nearly polar orbits. The phases of the signals from a moving satellite which are recorded by the chains of ground receivers oriented along the satellite path form the families of linear integrals of electron density along the satellite-receiver rays that are used as the input data for LORT. The LO tomographic inversion of these data by phase difference method yields the 2D distributions of the ionospheric plasma in the vertical plane containing the receiving chain and the satellite path. LORT provides vertical resolution of 20-30 km and horizontal resolution of 30-40 km. The high-orbiting (HO) radio tomography employs the radio transmissions from the GPS/GLONASS satellites and enables 4D imaging of the ionosphere (3 spatial coordinates and time). HORT has a much wider spatial coverage (almost worldwide) and provides continuous time series of the reconstructions. However, the spatial resolution of HORT is lower (~100 km horizontally with a time step 60-20 min). In the regions with dense receiving networks (Europe, USA, Alaska, Japan), the resolution can be increased to 30-50 km with a time interval of 30-10 min. To date, the extensive RT data collected from the existing RT chains and networks enable a thorough analysis of both the regular and sporadic ionospheric features which are observed systematically or appear spontaneously, whose origin is fairly well understood or

Elaborate analysis and design of filter-bank-based sensing for wideband cognitive radios

NASA Astrophysics Data System (ADS)

Maliatsos, Konstantinos; Adamis, Athanasios; Kanatas, Athanasios G.

2014-12-01

The successful operation of a cognitive radio system strongly depends on its ability to sense the radio environment. With the use of spectrum sensing algorithms, the cognitive radio is required to detect co-existing licensed primary transmissions and to protect them from interference. This paper focuses on filter-bank-based sensing and provides a solid theoretical background for the design of these detectors. Optimum detectors based on the Neyman-Pearson theorem are developed for uniform discrete Fourier transform (DFT) and modified DFT filter banks with root-Nyquist filters. The proposed sensing framework does not require frequency alignment between the filter bank of the sensor and the primary signal. Each wideband primary channel is spanned and monitored by several sensor subchannels that analyse it in narrowband signals. Filter-bank-based sensing is proved to be robust and efficient under coloured noise. Moreover, the performance of the weighted energy detector as a sensing technique is evaluated. Finally, based on the Locally Most Powerful and the Generalized Likelihood Ratio test, real-world sensing algorithms that do not require a priori knowledge are proposed and tested.

Charged dust phenomena in the near-Earth space environment.

PubMed

Scales, W A; Mahmoudian, A

2016-10-01

Dusty (or complex) plasmas in the Earth's middle and upper atmosphere ultimately result in exotic phenomena that are currently forefront research issues in the space science community. This paper presents some of the basic criteria and fundamental physical processes associated with the creation, evolution and dynamics of dusty plasmas in the near-Earth space environment. Recent remote sensing techniques to probe naturally created dusty plasma regions are also discussed. These include ground-based experiments employing high-power radio wave interaction. Some characteristics of the dusty plasmas that are actively produced by space-borne aerosol release experiments are discussed. Basic models that may be used to investigate the characteristics of such dusty plasma regions are presented.

Observation of hectometric auroral radio emissions in Iceland

NASA Astrophysics Data System (ADS)

Sato, Y.; Ono, T.; Iizima, M.; Sato, N.

2006-12-01

The Earth's auroral region is an active radio source at frequencies from a few hertz to several megahertz. In the hectometric range, it was found that Terrestrial Hectometric Radiation (THR) is related to auroras by observations of the Ohzora satellite [Oya et al.(1985)]. In resent research, Shinbori et al. [2003] showed that occurrence of THR follows SC by several minutes using the Akebono satellite data. On the ground, auroral roar and MF burst were discovered by Kellogg and Monson [1979, 1984] and Weatherwax et al. [1994] in the northern Canada, respectively. Because there is not enough physical and geophysical characterization of these radio emissions, the physical mechanism of these phenomena in the auroral ionosphere has not been fully understood yet. We set up new observation system at Husafell station in Iceland in September, 2005 and have started to observe auroral radio emissions. Radio signals, which are received by the cross loop antennas, are converted into left- and right- handed polarized components within the frequency range from 1 MHz to 5 MHz. Based on the calibration of system, it was found that the possibility of occurence would be smaller than expected due to the low sensitivity because average power spectrum densities of auroral roar and MF burst are 50-100 nV/m/Hz^1/2. So, the system was planed to be upgraded in this September, which makes it possible to detect auroral roar and MF burst. It is expected that the detail physical process will be elucidated by clarifying the spectrum, polarization, dependence on the geomagnetic activity, and so on. In this presentation, we will show the improved points of the new system and preliminary observation results. There is a basic question whether auroral roar and MF burst observed on the ground are generated by the same process as THR observed by satellites. By comparing the results from the ground-based observation and the Akebono satellite observation of THR, it becomes possible to obtain a new

Ground-based observation of near-Earth asteroids

NASA Technical Reports Server (NTRS)

Gaffey, Michael J.

1992-01-01

An increased ground-based observation program is an essential component of any serious attempt to assess the resource potential of near-Earth asteroids. A vigorous search and characterization program could lead to the discovery and description of about 400 to 500 near-Earth asteroids in the next 20 years. This program, in conjunction with meteorite studies, would provide the data base to ensure that the results of a small number of asteroid-rendezvous and sample-return missions could be extrapolated with confidence into a geological base map of the Aten, Apollo, and Amor asteroids. Ground-based spectral studies of nearly 30 members of the Aten/Apollo/Amor population provide good evidence that this class includes bodies composed of silicates, metal-silicates, and carbonaceous assemblages similar to those found in meteorites. The instruments that are being used or could be used to search for near-Earth asteroids are listed. Techniques useful in characterizing asteroids and the types of information obtainable using these techniques are listed.

Giant Metrewave Radio Telescope Observations of Head–Tail Radio Galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sebastian, Biny; Lal, Dharam V.; Rao, A. Pramesh, E-mail: biny@ncra.tifr.res.in

We present results from a study of seven large known head–tail radio galaxies based on observations using the Giant Metrewave Radio Telescope at 240 and 610 MHz. These observations are used to study the radio morphologies and distribution of the spectral indices across the sources. The overall morphology of the radio tails of these sources is suggestive of random motions of the optical host around the cluster potential. The presence of multiple bends and wiggles in several head–tail sources is possibly due to the precessing radio jets. We find steepening of the spectral index along the radio tails. The prevailingmore » equipartition magnetic field also decreases along the radio tails of these sources. These steepening trends are attributed to the synchrotron aging of plasma toward the ends of the tails. The dynamical ages of these sample sources have been estimated to be ∼10{sup 8} yr, which is a factor of six more than the age estimates from the radiative losses due to synchrotron cooling.« less

Antenna design and implementation for the future space Ultra-Long wavelength radio telescope

NASA Astrophysics Data System (ADS)

Chen, Linjie; Aminaei, Amin; Gurvits, Leonid I.; Wolt, Marc Klein; Pourshaghaghi, Hamid Reza; Yan, Yihua; Falcke, Heino

2018-04-01

In radio astronomy, the Ultra-Long Wavelengths (ULW) regime of longer than 10 m (frequencies below 30 MHz), remains the last virtually unexplored window of the celestial electromagnetic spectrum. The strength of the science case for extending radio astronomy into the ULW window is growing. However, the opaqueness of the Earth's ionosphere makes ULW observations by ground-based facilities practically impossible. Furthermore, the ULW spectrum is full of anthropogenic radio frequency interference (RFI). The only radical solution for both problems is in placing an ULW astronomy facility in space. We present a concept of a key element of a space-borne ULW array facility, an antenna that addresses radio astronomical specifications. A tripole-type antenna and amplifier are analysed as a solution for ULW implementation. A receiver system with a low power dissipation is discussed as well. The active antenna is optimized to operate at the noise level defined by the celestial emission in the frequency band 1 - 30 MHz. Field experiments with a prototype tripole antenna enabled estimates of the system noise temperature. They indicated that the proposed concept meets the requirements of a space-borne ULW array facility.

Interplanetary Shocks Lacking Type 2 Radio Bursts

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Xie, H.; Maekela, P.; Akiyama, S.; Yashiro, S.; Kaiser, M. L.; Howard, R. A.; Bougeret, J.-L.

2010-01-01

We report on the radio-emission characteristics of 222 interplanetary (IP) shocks detected by spacecraft at Sun-Earth L1 during solar cycle 23 (1996 to 2006, inclusive). A surprisingly large fraction of the IP shocks (approximately 34%) was radio quiet (RQ; i.e., the shocks lacked type II radio bursts). We examined the properties of coronal mass ejections (CMEs) and soft X-ray flares associated with such RQ shocks and compared them with those of the radio-loud (RL) shocks. The CMEs associated with the RQ shocks were generally slow (average speed approximately 535 km/s) and only approximately 40% of the CMEs were halos. The corresponding numbers for CMEs associated with RL shocks were 1237 km/s and 72%, respectively. Thus, the CME kinetic energy seems to be the deciding factor in the radio-emission properties of shocks. The lower kinetic energy of CMEs associated with RQ shocks is also suggested by the lower peak soft X-ray flux of the associated flares (C3.4 versus M4.7 for RL shocks). CMEs associated with RQ CMEs were generally accelerating within the coronagraph field of view (average acceleration approximately +6.8 m/s (exp 2)), while those associated with RL shocks were decelerating (average acceleration approximately 3.5 m/s (exp 2)). This suggests that many of the RQ shocks formed at large distances from the Sun, typically beyond 10 Rs, consistent with the absence of metric and decameter-hectometric (DH) type II radio bursts. A small fraction of RL shocks had type II radio emission solely in the kilometric (km) wavelength domain. Interestingly, the kinematics of the CMEs associated with the km type II bursts is similar to those of RQ shocks, except that the former are slightly more energetic. Comparison of the shock Mach numbers at 1 AU shows that the RQ shocks are mostly subcritical, suggesting that they were not efficient in accelerating electrons. The Mach number values also indicate that most of these are quasi-perpendicular shocks. The radio-quietness is

Radio triangulation - mapping the 3D position of the solar radio emission

NASA Astrophysics Data System (ADS)

Magdalenic, Jasmina

2016-04-01

Understanding the relative position of the sources of the radio emission and the associated solar eruptive phenomena (CME and the associated shock wave) has always been a challenge. While ground-based radio interferometer observations provide us with the 2D position information for the radio emission originating from the low corona (up to 2.5 Ro), this is not the case for the radio emission originating at larger heights. The radio triangulation measurements (also referred to as direction-finding or goniopolarimetric measurements) from two or more widely separated spacecraft can provide information on the 3D positions of the sources of the radio emission. This type of interplanetary radio observations are currently performed by STEREO WAVES and WIND WAVES instruments, providing a unique possibility for up to three simultaneous radio triangulations (using up to three different pairs of spacecraft). The recent results of the radio triangulation studies bring new insight into the causal relationship of the solar radio emission and CMEs. In this presentation I will discuss some of the most intriguing results on the source positions of: a) type III radio bursts indicating propagation of the fast electrons accelerated along the open field lines, b) type II radio bursts indicating interaction of the CME-driven shocks and other coronal structures e.g. streamers and c) type IV-like radio bursts possibly associated with CME-CME interaction.

Base-level management of radio-frequency radiation-protection program. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rademacher, S.E.; Montgomery, N.D.

1989-04-01

AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation-protection program. This report supersedes USAFOEHL Report 80-42, 'A Practical R-F Guide for BEES.'

Base-level management of radio-frequency radiation-protection program. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rademacher, S.E.; Montgomery, N.D.

1989-04-01

AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation protection program. This report supersedes USAFOEHL Report 80-42, 'A practical R-F Guide for BEES.'

Ionosphere-magnetosphere studies using ground based VLF radio propagation technique: an Indian example

NASA Astrophysics Data System (ADS)

Chakravarty, Subhas

Since IGY period (1957-58), natural and artificially produced Very Low Frequency (VLF) elec-tromagnetic radiations are being recorded at large number of ground stations all over the world and on-board satellites to study various radio wave-thermal/energetic plasma interactive pro-cesses related to earth's ionosphere-plasmasphere-magnetosphere environment. The terrestrial propagation of these VLF radio waves are primarily enabled through the earth ionosphere wave guide (EIWG) mode to long horizontal distances around the globe and ducted along the ge-omagnetic field lines into the conjugate hemisphere through the plasmasphere-magnetosphere regions. The time frequency spectra of the received signals indicate presence of dispersion (wave/group velocities changing with frequency) and various cut-off frequencies based on the width of the EIWG, electron gyro and plasma frequencies etc., providing several types of received signals like whistlers, chorus, tweeks, hiss and hisslers which can be heard on loud-speakers/earphones with distinguishing audio structures. While the VLF technique has been a very effective tool for studying middle and high latitude phenomena, the importance of the similar and anomalous observations over the Indian low latitude stations provide potentially new challenges for their scientific interpretation and modelling. The ducted and non-ducted magnetospheric propagation, pro-longitudinal (PL) mode, low latitude TRIMPI/TLE (Tran-sient Luminous Emissions) or other effects of wave-particle/wave-wave interactions, effects due to ionospheric irregularities and electric fields, full wave solutions to D-region ionisation per-turbations due to solar and stellar energetic X-and γ ray emissions during normal and flaring conditions are a few problems which have been addressed in these low latitude studies over India. Since the conjugate points of Indian stations lie over the Indian oceanic region, the VLF propagation effects would be relatively free from

Estimation of ionospheric sporadic E intensities from GPS radio occultation measurements

NASA Astrophysics Data System (ADS)

Arras, C.; Wickert, J.

2018-06-01

The radio occultation experiment aboard the FORMOSAT-3/COSMIC satellites enables the observation of phenomena in Earth's ionosphere on a global scale. Numerous radio occultation profiles are used to analyse the occurrence of sporadic E layers as well as its properties. We will present a new method to approach additionally to the presence of sporadic E also its intensity which is closely related to the blanketing frequency (fbEs) provided by ionosondes. We observed that the sporadic E occurrence and its intensity show a highly developed annual cycle with high occurrence rates and intensities in the actual summer hemisphere. The global latitude/longitude distribution of both parameters is strongly related to Earth's magnetic field which is reflected by the missing of sporadic E observations along the magnetic equator.

A radio counterpart to a neutron star merger.

PubMed

Hallinan, G; Corsi, A; Mooley, K P; Hotokezaka, K; Nakar, E; Kasliwal, M M; Kaplan, D L; Frail, D A; Myers, S T; Murphy, T; De, K; Dobie, D; Allison, J R; Bannister, K W; Bhalerao, V; Chandra, P; Clarke, T E; Giacintucci, S; Ho, A Y Q; Horesh, A; Kassim, N E; Kulkarni, S R; Lenc, E; Lockman, F J; Lynch, C; Nichols, D; Nissanke, S; Palliyaguru, N; Peters, W M; Piran, T; Rana, J; Sadler, E M; Singer, L P

2017-12-22

Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy NGC 4993, at a distance of 40 megaparsecs from Earth. We report the detection of a counterpart radio source that appears 16 days after the event, allowing us to diagnose the energetics and environment of the merger. The observed radio emission can be explained by either a collimated ultrarelativistic jet, viewed off-axis, or a cocoon of mildly relativistic ejecta. Within 100 days of the merger, the radio light curves will enable observers to distinguish between these models, and the angular velocity and geometry of the debris will be directly measurable by very long baseline interferometry. Copyright © 2017, American Association for the Advancement of Science.

EVLA observations of radio-loud quasars selected to study radio orientation

NASA Astrophysics Data System (ADS)

Maithil, Jaya; Brotherton, Michael S.; Runnoe, Jessie; Wardle, John F. C.; DiPompeo, Michael; De Breuck, Carlos; Wills, Beverley J.

2018-06-01

We present preliminary work to develop an unbiased sample of radio-loud quasars to test orientation indicators. We have obtained radio data of 147 radio-loud quasars using EVLA at 10 GHz and with the A-array. With this high-resolution data we have measured the uncontaminated core flux density to determine orientation indicators based on radio core dominance. The radio cores of quasars have a flat spectrum over a broad range of frequencies, so we expect that the core flux density at the FIRST and the observed frequencies should be the same in the absence of variability. Jackson & Brown (2012) pointed out that the survey measurements of core flux density, like FIRST, often doesn't have the spatial resolution to distinguish cores from extended emission. Our measurements show that at FIRST spatial resolution, core flux measurements are indeed systematically high. Our results establish that orientation studies need high-resolution radio data as compared to survey data, and that the optical emission is a better normalization than the extended radio emission for a core dominance parameter to track orientation.

Project Explorer: Get Away Special #007. [alloy solidification, seed germination, crystal growth, and radio transmission of payload data

NASA Technical Reports Server (NTRS)

Henderson, A. J., Jr.

1984-01-01

Tentatively scheduled to fly on STS-17 (41G), this get away special aims to demonstrate amateur radio transmissions to global ground stations in the English language. Experiments No. 1, 2, and 3 use the micro-gravity of space flight to study the solidification of lead-antimony and aluminum-copper alloys, the germination of radish seeds, and the growth of potassium-tetracyanoplatinate hydrate crystals in an aqueous solution. Flight results are to be compared with Earth-based data. Experiment No. 4 (the Marshall Amateur Radio Club Experiment - MARCE) features radio transmissions and also provides timing for the start of all other experiments. A microprocessor obtains real-time data from all experiments as well as temperature and pressure measurements within the GAS canister. These data are to be transmitted on previously announced amateur radio frequencies after they are converted into the English language by a digitalker for general reception. The support structure for the G #007 experiments consists of two primary plates and four bumper assemblies.

Analysis of ELF Radio Atmospherics Radiated by Rocket-Triggered Lightning

NASA Astrophysics Data System (ADS)

Dupree, N. A.; Moore, R. C.; Pilkey, J. T.; Uman, M. A.; Jordan, D. M.; Caicedo, J. A.; Hare, B.; Ngin, T. K.

2014-12-01

Experimental observations of ELF radio atmospherics produced by rocket-triggered lightning flashes are used to analyze Earth-ionosphere waveguide excitation and propagation characteristics. Rocket-triggered lightning experiments are performed at the International Center for Lightning Research and Testing (ICLRT) located at Camp Blanding, Florida. Long-distance ELF observations are performed in California, Greenland, and Antarctica. The lightning current waveforms directly measured at the base of the lightning channel (at the ICLRT) along with pertinent Lightning Mapping Array (LMA) data are used together with the Long Wavelength Propagation Capability (LWPC) code to predict the radio atmospheric (sferic) waveform observed at the receiver locations under various ionospheric conditions. We identify fitted exponential electron density profiles that accurately describe the observed propagation delays, phase delays, and signal amplitudes. The ability to infer ionospheric characteristics using distant ELF observations greatly enhances ionospheric remote sensing capabilities, especially in regard to interpreting observations of transient luminous events (TLEs) and other ionospheric effects associated with lightning.

Radio Thermal Emission from Pluto and Charon during the New Horizons Encounter

NASA Astrophysics Data System (ADS)

Bird, Michael; Linscott, Ivan; Hinson, David; Tyler, G. L.; Strobel, Darrell F.; New Horizons Science Team

2017-10-01

As part of the New Horizons Radio-Science Experiment REX, radio thermal emission from Pluto and Charon (wavelength: 4.2 cm) was observed during the encounter on 14 July 2015. The primary REX measurement, a determination of the atmospheric height profile from the surface up to about 100 km, was conducted during an uplink radio occultation at both ingress and egress (Hinson et al., Icarus 290, 96-111, 2017). During the interval between ingress and egress, when the Earth and the REX uplink signals were occulted by the Pluto disk, the spacecraft antenna continued to point toward Earth and thus scanned diametrically across the Pluto nightside. The average diameter of the HGA 3 dB beam was ≈1100 km at the surface during this opportunity, thereby providing crudely resolved measurements of the radio brightness temperature across Pluto. The best resolution for the REX radiometry observations occurred shortly after closest approach, when the HGA was scanned twice across Pluto. These observations will be reported elsewhere (Linscott et al., Icarus, submitted, 2017). In addition to the resolved observations, full disk brightness temperature measurements of both bodies were performed during the approach (dayside) and departure (nightside) phases of the encounter. We present the results of these observations and provide a preliminary interpretation of the measured brightness temperatures.

Atmospheric Calibration for Cassini Radio Science

NASA Technical Reports Server (NTRS)

Resch, G. M.; Bar-Sever, Y.; Keihm, S.; Kroger, P.; Linfield, R.; Mahoney, M. J.; Tanner, A.; Teitelbaum, L.

1996-01-01

The signals from the Cassini spacecraft that will be affected by delay fluctuations in the Earth's atmosphere. These fluctuations are dominated by water vapor in the troposphere, and in the case of Gravitaional Wave Experiment (GWE), they are likely to be a limiting error source. A passive remote sensing system, centered around a water vapor radiometer (WVR), has been developed to provide calibrations of water vapor fluctuations during radio science experiments.

Radio-Optical Alignments in a Low Radio Luminosity Sample

NASA Technical Reports Server (NTRS)

Lacy, Mark; Ridgway, Susan E.; Wold, Margrethe; Lilje, Per B.; Rawlings, Steve

1999-01-01

We present an optically-based study of the alignment between the radio axes and the optical major axes of eight z approximately 0.7 radio galaxies in a 7C sample. The radio galaxies in this sample are approximately 20-times less radio luminous than 3C galaxies at the same redshift, and are significantly less radio-luminous than any other well-defined samples studied to date. Using Nordic Optical Telescope images taken in good seeing conditions at rest-frame wavelengths just longward of the 4000A break, we find a statistically significant alignment effect in the 7C sample. Furthermore, in two cases where the aligned components are well separated from the host we have been able to confirm spectroscopically that they are indeed at the same redshift as the radio galaxy. However, a quantitative analysis of the alignment in this sample and in a corresponding 3C sample from HST (Hubble Space Telescope) archival data indicates that the percentage of aligned flux may be lower and of smaller spatial scale in the 7C sample. Our study suggests that alignments on the 50-kpc scale are probably closely related to the radio luminosity, whereas those on the 15 kpc scale are not. We discuss these results in the context of popular models for the alignment effect.

Technique to determine location of radio sources from measurements taken on spinning spacecraft

NASA Technical Reports Server (NTRS)

Fainberg, J.

1979-01-01

The procedure developed to extract average source direction and average source size from spin-modulated radio astronomy data measured on the IMP-6 spacecraft is described. Because all measurements are used, rather than just finding maxima or minima in the data, the method is very sensitive, even in the presence of large amounts of noise. The technique is applicable to all experiments with directivity characteristics. It is suitable for onboard processing on satellites to reduce the data flow to Earth. The application to spin-modulated nonpolarized radio astronomy data is made and includes the effects of noise, background, and second source interference. The analysis was tested with computer simulated data and the results agree with analytic predictions. Applications of this method with IMP-6 radio data have led to: (1) determination of source positions of traveling solar radio bursts at large distances from the Sun; (2) mapping of magnetospheric radio emissions by radio triangulation; and (3) detection of low frequency radio emissions from Jupiter and Saturn.

Study on a novel laser target detection system based on software radio technique

NASA Astrophysics Data System (ADS)

Song, Song; Deng, Jia-hao; Wang, Xue-tian; Gao, Zhen; Sun, Ji; Sun, Zhi-hui

2008-12-01

This paper presents that software radio technique is applied to laser target detection system with the pseudo-random code modulation. Based on the theory of software radio, the basic framework of the system, hardware platform, and the implementation of the software system are detailed. Also, the block diagram of the system, DSP circuit, block diagram of the pseudo-random code generator, and soft flow diagram of signal processing are designed. Experimental results have shown that the application of software radio technique provides a novel method to realize the modularization, miniaturization and intelligence of the laser target detection system, and the upgrade and improvement of the system will become simpler, more convenient, and cheaper.

Digital Earth system based river basin data integration

NASA Astrophysics Data System (ADS)

Zhang, Xin; Li, Wanqing; Lin, Chao

2014-12-01

Digital Earth is an integrated approach to build scientific infrastructure. The Digital Earth systems provide a three-dimensional visualization and integration platform for river basin data which include the management data, in situ observation data, remote sensing observation data and model output data. This paper studies the Digital Earth system based river basin data integration technology. Firstly, the construction of the Digital Earth based three-dimensional river basin data integration environment is discussed. Then the river basin management data integration technology is presented which is realized by general database access interface, web service and ActiveX control. Thirdly, the in situ data stored in database tables as records integration is realized with three-dimensional model of the corresponding observation apparatus display in the Digital Earth system by a same ID code. In the next two parts, the remote sensing data and the model output data integration technologies are discussed in detail. The application in the Digital Zhang River basin System of China shows that the method can effectively improve the using efficiency and visualization effect of the data.

Planck intermediate results. XLV. Radio spectra of northern extragalactic radio sources

NASA Astrophysics Data System (ADS)

Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Aller, H. D.; Aller, M. F.; Arnaud, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Burigana, C.; Calabrese, E.; Catalano, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombo, L. P. L.; Couchot, F.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gruppuso, A.; Gurwell, M. A.; Hansen, F. K.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Hildebrandt, S. R.; Hobson, M.; Hornstrup, A.; Hovatta, T.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Järvelä, E.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Max-Moerbeck, W.; Meinhold, P. R.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Mingaliev, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Nati, F.; Natoli, P.; Nieppola, E.; Noviello, F.; Novikov, D.; Novikov, I.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Ramakrishnan, V.; Rastorgueva-Foi, E. A.; S Readhead, A. C.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Richards, J. L.; Ristorcelli, I.; Rocha, G.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Savelainen, M.; Savini, G.; Scott, D.; Sotnikova, Y.; Stolyarov, V.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tammi, J.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tornikoski, M.; Tristram, M.; Tucci, M.; Türler, M.; Valenziano, L.; Valiviita, J.; Valtaoja, E.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wehrle, A. E.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-12-01

Continuum spectra covering centimetre to submillimetre wavelengths are presented for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37 GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at high frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.

Regional positioning using a low Earth orbit satellite constellation

NASA Astrophysics Data System (ADS)

Shtark, Tomer; Gurfil, Pini

2018-02-01

Global and regional satellite navigation systems are constellations orbiting the Earth and transmitting radio signals for determining position and velocity of users around the globe. The state-of-the-art navigation satellite systems are located in medium Earth orbits and geosynchronous Earth orbits and are characterized by high launching, building and maintenance costs. For applications that require only regional coverage, the continuous and global coverage that existing systems provide may be unnecessary. Thus, a nano-satellites-based regional navigation satellite system in Low Earth Orbit (LEO), with significantly reduced launching, building and maintenance costs, can be considered. Thus, this paper is aimed at developing a LEO constellation optimization and design method, using genetic algorithms and gradient-based optimization. The preliminary results of this study include 268 LEO constellations, aimed at regional navigation in an approximately 1000 km × 1000 km area centered at the geographic coordinates [30, 30] degrees. The constellations performance is examined using simulations, and the figures of merit include total coverage time, revisit time, and geometric dilution of precision (GDOP) percentiles. The GDOP is a quantity that determines the positioning solution accuracy and solely depends on the spatial geometry of the satellites. Whereas the optimization method takes into account only the Earth's second zonal harmonic coefficient, the simulations include the Earth's gravitational field with zonal and tesseral harmonics up to degree 10 and order 10, Solar radiation pressure, drag, and the lunisolar gravitational perturbation.

49 CFR 220.23 - Publication of radio information.

Code of Federal Regulations, 2010 CFR

2010-10-01

... § 220.23 Publication of radio information. Each railroad shall designate where radio base stations are installed, where wayside stations may be contacted, and the appropriate radio channels used by these.... The publication shall indicate the periods during which base and wayside radio stations are...

49 CFR 220.23 - Publication of radio information.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 4 2011-10-01 2011-10-01 false Publication of radio information. 220.23 Section... § 220.23 Publication of radio information. Each railroad shall designate where radio base stations are.... The publication shall indicate the periods during which base and wayside radio stations are...

49 CFR 220.23 - Publication of radio information.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 4 2012-10-01 2012-10-01 false Publication of radio information. 220.23 Section... § 220.23 Publication of radio information. Each railroad shall designate where radio base stations are.... The publication shall indicate the periods during which base and wayside radio stations are...

Miniature interferometer terminals for earth surveying

NASA Technical Reports Server (NTRS)

Counselman, C. C., III; Shapiro, I. I.

1978-01-01

A system of miniature radio interferometer terminals was proposed for the measurement of vector baselines with uncertainties ranging from the millimeter to the centimeter level for baseline lengths ranging, respectively, from a few to a few hundred kilometers. Each terminal would have no moving parts, could be packaged in a volume of less than 0.1 cu m, and would operate unattended. These units would receive radio signals from low-power (10 w) transmitters on earth-orbiting satellites. The baselines between units could be determined virtually instantaneously and monitored continuously as long as at least four satellites were visible simultaneously.

Space-Time Localization of Plasma Turbulence Using Multiple Spacecraft Radio Links

NASA Technical Reports Server (NTRS)

Armstrong, John W.; Estabrook, Frank B.

2011-01-01

Space weather is described as the variability of solar wind plasma that can disturb satellites and systems and affect human space exploration. Accurate prediction requires information of the heliosphere inside the orbit of the Earth. However, for predictions using remote sensing, one needs not only plane-of-sky position but also range information the third spatial dimension to show the distance to the plasma disturbances and thus when they might propagate or co-rotate to create disturbances at the orbit of the Earth. Appropriately processed radio signals from spacecraft having communications lines-of-sight passing through the inner heliosphere can be used for this spacetime localization of plasma disturbances. The solar plasma has an electron density- and radio-wavelength-dependent index of refraction. An approximately monochromatic wave propagating through a thin layer of plasma turbulence causes a geometrical-optics phase shift proportional to the electron density at the point of passage, the radio wavelength, and the thickness of the layer. This phase shift is the same for a wave propagating either up or down through the layer at the point of passage. This attribute can be used for space-time localization of plasma irregularities. The transfer function of plasma irregularities to the observed time series depends on the Doppler tracking mode. When spacecraft observations are in the two-way mode (downlink radio signal phase-locked to an uplink radio transmission), plasma fluctuations have a two-pulse response in the Doppler. In the two-way mode, the Doppler time series y2(t) is the difference between the frequency of the downlink signal received and the frequency of a ground reference oscillator. A plasma blob localized at a distance x along the line of sight perturbs the phase on both the up and down link, giving rise to two events in the two-way tracking time series separated by a time lag depending the blob s distance from the Earth: T2-2x/c, where T2 is the

Interference coupling analysis based on a hybrid method: application to a radio telescope system

NASA Astrophysics Data System (ADS)

Xu, Qing-Lin; Qiu, Yang; Tian, Jin; Liu, Qi

2018-02-01

Working in a way that passively receives electromagnetic radiation from a celestial body, a radio telescope can be easily disturbed by external radio frequency interference as well as electromagnetic interference generated by electric and electronic components operating at the telescope site. A quantitative analysis of these interferences must be taken into account carefully for further electromagnetic protection of the radio telescope. In this paper, based on electromagnetic topology theory, a hybrid method that combines the Baum-Liu-Tesche (BLT) equation and transfer function is proposed. In this method, the coupling path of the radio telescope is divided into strong coupling and weak coupling sub-paths, and the coupling intensity criterion is proposed by analyzing the conditions in which the BLT equation simplifies to a transfer function. According to the coupling intensity criterion, the topological model of a typical radio telescope system is established. The proposed method is used to solve the interference response of the radio telescope system by analyzing subsystems with different coupling modes separately and then integrating the responses of the subsystems as the response of the entire system. The validity of the proposed method is verified numerically. The results indicate that the proposed method, compared with the direct solving method, reduces the difficulty and improves the efficiency of interference prediction.

Status of High Data Rate Intersatellite Laser Communication as an Enabler for Earth and Space Science

NASA Astrophysics Data System (ADS)

Heine, F.; Zech, H.; Motzigemba, M.

2017-12-01

Space based laser communication is supporting earth observation and science missions with Gbps data download capabilities. Currently the Sentinel 1 and Sentinel 2 spacecrafts from the Copernicus earth observation program of the European Commission are using the Gbps laser communication links developed by Tesat Spacecom to download low latency data products via a commercial geostationary laser relay station- the European Data Relay Service- (EDRS) as a standard data path, in parallel to the conventional radio frequency links. The paper reports on the status of high bandwidth space laser communication as an enabler for small and large space science missions ranging from cube sat applications in low earth orbit to deep space missions. Space based laser communication has left the experimental phase and will support space science missions with unprecedented data rates.

President Gerald Ford talks to ASTP crewmen via radio-telephone

NASA Technical Reports Server (NTRS)

1975-01-01

President Gerald R. Ford watches ASTP crewmen Thomas P. Stafford, Donald K. Slayton and Valeriy N. Kubasov on television as he talks to them via radio-telephone while they orbited the Earth on July 18, 1975. The American Apollo spacecraft and Soviet Soyuz spacecraft were docked.

Juno Radio Science Observations and Gravity Science Calibrations of Plasma Electron Content in Io Plasma Torus

NASA Astrophysics Data System (ADS)

Yang, Y. M.; Buccino, D.; Folkner, W. M.; Oudrhiri, K.; Phipps, P. H.; Parisi, M.; Kahan, D. S.

2017-12-01

Interplanetary and Earth ionosphere plasma electrons can have significant impacts on radio frequency signal propagation such as telecommunication between spacecraft and the Deep Space Network (DSN). On 27 August 2016, the first closest approach of The Juno spacecraft (Perijove 1) provided an opportunity to observe plasma electrons inside of the Io plasma torus using radio science measurements from Juno. Here, we report on the derivations of plasma electron content in the Io plasma torus by using two-way coherent radio science measurements made from Juno's Gravity Science Instrument and the Deep Space Network. During Perijove 1, Juno spacecraft passed through the inner region (perijove altitude of 1.06 Jovian Radii) between Jupiter and the Io plasma torus. Significant plasma electron variations of up to 30 TEC units were observed while the radio link between Juno and the DSN traveled through the Io plasma torus. In this research, we compare observations made by open-loop and closed-loop processes using different frequency radio signals, corresponding Io plasma torus model simulations, and other Earth ionosphere observations. The results of three-dimensional Io plasma model simulations are consistent with observations with some discrepancies. Results are shown to improve our understanding of the Io plasma torus effect on Juno gravity science measurements and its calibrations to reduce the corresponding (non-gravity field induced) radio frequency shift.

Spacecraft Radio Scintillation and Solar System Exploration

NASA Technical Reports Server (NTRS)

Woo, Richard

1993-01-01

When a wave propagates through a turbulent medium, scattering by the random refractive index inhomogeneities can lead to a wide variety of phenomena that have been the subject of extensive study. The observed scattering effects include amplitude or intensity scintillation, phase scintillation, angular broadening, and spectral broadening, among others. In this paper, I will refer to these scattering effects collectively as scintillation. Although the most familiar example is probably the twinkling of stars (light wave intensity scintillation by turbulence in the Earth's atmosphere), scintillation has been encountered and investigated in such diverse fields as ionospheric physics, oceanography, radio astronomy, and radio and optical communications. Ever since planetary spacecraft began exploring the solar system, scintillation has appeared during the propagation of spacecraft radio signals through planetary atmospheres, planetary ionospheres, and the solar wind. Early studies of these phenomena were motivated by the potential adverse effects on communications and navigation, and on experiments that use the radio link to conduct scientific investigations. Examples of the latter are radio occultation measurements (described below) of planetary atmospheres to deduce temperature profiles, and the search for gravitational waves. However,these concerns soon gave way to the emergence of spacecraft radio scintillation as a new scientific tool for exploring small-scale dynamics in planetary atmospheres and structure in the solar wind, complementing in situ and other remote sensing spacecraft measurements, as well as scintillation measurements using natural (celestial) radio sources. The purpose of this paper is to briefly describe and review the solar system spacecraft radio scintillation observations, to summarize the salient features of wave propagation analyses employed in interpreting them, to underscore the unique remote sensing capabilities and scientific relevance of

Space Telecommunications Radio System STRS Cognitive Radio

NASA Technical Reports Server (NTRS)

Briones, Janette C.; Handler, Louis M.

2013-01-01

Radios today are evolving from awareness toward cognition. A software defined radio (SDR) provides the most capability for integrating autonomic decision making ability and allows the incremental evolution toward a cognitive radio. This cognitive radio technology will impact NASA space communications in areas such as spectrum utilization, interoperability, network operations, and radio resource management over a wide range of operating conditions. NASAs cognitive radio will build upon the infrastructure being developed by Space Telecommunication Radio System (STRS) SDR technology. This paper explores the feasibility of inserting cognitive capabilities in the NASA STRS architecture and the interfaces between the cognitive engine and the STRS radio. The STRS architecture defines methods that can inform the cognitive engine about the radio environment so that the cognitive engine can learn autonomously from experience, and take appropriate actions to adapt the radio operating characteristics and optimize performance.

Lunar Radio Telescopes: A Staged Approach for Lunar Science, Heliophysics, Astrobiology, Cosmology, and Exploration

NASA Technical Reports Server (NTRS)

Lazio, Joseph; Bowman, Judd D.; Burns, Jack O.; Farrell, W. M.; Jones, D. L.; Kasper, J. C.; MacDowall, R. J.; Stewart, K. P.; Weiler, K.

2012-01-01

Observations with radio telescopes address key problems in cosmology, astrobiology, heliophysics, and planetary science including the first light in the Universe (Cosmic Dawn), magnetic fields of extrasolar planets, particle acceleration mechanisms, and the lunar ionosphere. The Moon is a unique science platform because it allows access to radio frequencies that do not penetrate the Earth's ionosphere and because its far side is shielded from intense terrestrial emissions. The instrument packages and infrastructure needed for radio telescopes can be transported and deployed as part of Exploration activities, and the resulting science measurements may inform Exploration (e.g., measurements of lunar surface charging). An illustrative roadmap for the staged deployment of lunar radio telescopes

Reconfigurable radio-over-fiber system based on optical switch and tunable filter

NASA Astrophysics Data System (ADS)

Li, Xiao; Yin, Rui; Ji, Wei; Sun, Kai; Zhang, Shicheng

2017-09-01

As the best candidate for wireless-access networks, radio-over-fiber (RoF) technology can carry a variety of business. It is necessary to provide differentiated services for different users, so the network needs to produce signals with different modulation formats and different frequencies. A reconfigurable RoF system based on a switch and tunable optical filter that can realize modulation format conversion and multiple frequency signal switching functions is designed. It has a good performance in terms of bit error rate and an eye diagram. The design can help to use radio frequency resources efficiently and make dynamic bandwidth resources controllable.

Planck intermediate results: XLV. Radio spectra of northern extragalactic radio sources

DOE PAGES

Ade, P. A. R.; Aghanim, N.; Aller, H. D.; ...

2016-12-12

Continuum spectra covering centimetre to submillimetre wavelengths are presented in this paper for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37 GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at highmore » frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Finally, variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.« less

Planck intermediate results: XLV. Radio spectra of northern extragalactic radio sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ade, P. A. R.; Aghanim, N.; Aller, H. D.

Continuum spectra covering centimetre to submillimetre wavelengths are presented in this paper for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37 GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at highmore » frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Finally, variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.« less

Cen A Radio Optical Gamma Composite

NASA Image and Video Library

2017-12-08

NASA release April 1, 2010 It takes the addition of radio data (orange) to fully appreciate the scale of Cen A's giant radio-emitting lobes, which stretch more than 1.4 million light-years. Gamma-rays from Fermi's Large Area Telescope (purple) and an image of the galaxy in visible light are also included in this composite. Credit: NASA/DOE/Fermi LAT Collaboration, Capella Observatory, and Ilana Feain, Tim Cornwell, and Ron Ekers (CSIRO/ATNF), R. Morganti (ASTRON), and N. Junkes (MPIfR) To learn more about these images go to: www.nasa.gov/mission_pages/GLAST/news/smokestack-plumes.html NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

Rare-earth-free high energy product manganese-based magnetic materials.

PubMed

Patel, Ketan; Zhang, Jingming; Ren, Shenqiang

2018-06-14

The constant drive to replace rare-earth metal magnets has initiated great interest in an alternative. Manganese (Mn) has emerged to be a potential candidate as a key element in rare-earth-free magnets. Its five unpaired valence electrons give it a large magnetocrystalline energy and the ability to form several intermetallic compounds. These factors have led Mn-based magnets to be a potential replacement for rare-earth permanent magnets for several applications, such as efficient power electronics, energy generators, magnetic recording and tunneling applications, and spintronics. For past few decades, Mn-based magnets have been explored in many different forms, such as bulk magnets, thin films, and nanoparticles. Here, we review the recent progress in the synthesis and structure-magnetic property relationships of Mn-based rare-earth-free magnets (MnBi, MnAl and MnGa). Furthermore, we discuss their potential to replace rare-earth magnetic materials through the control of their structure and composition to achieve the theoretically predicted magnetic properties.

Determining Thunderstorm Electric Fields using Radio Emission from Cosmic-Ray Air Showers

NASA Astrophysics Data System (ADS)

Hare, B.; Scholten, O.; Trinh, G. T. N.; Ebert, U.; Rutjes, C.

2017-12-01

We report on a novel non-intrusive way to investigate electric fields in thunderclouds.Energetic cosmic rays penetrating the atmosphere create a particle avalanche called an extensive air shower. The front of the shower is a plasma cloud that contains 10^6 or more free electrons and positrons moving towards the Earth's surface at the speed of light. The electric fields that exists in thunderclouds induces electric currents in the plasma cloud that emit radio waves. The radio footprint for intensity, linear and circular polarization thus contains the finger print of the atmospheric electric fields along the path of the air shower.Here we report on the analysis of many cosmic-ray radio footprints as have been measured at LOFAR, a dense array of simple radio antennas (several thousands of dual-polarized antennas) primarily developed for radio-astronomy observations. We show that this method can be used to determine the charge structure in thunderclouds and discuss the accuracy of the method. We have observed seasonal dependencies.

Astronaut Linenger uses SAREX to communicate with students on Earth

NASA Image and Video Library

1994-09-12

STS064-20-026 (9-20 Sept. 1994) --- Astronaut Jerry M. Linenger, STS-64 mission specialist, uses the Shuttle Amateur Radio Experiment (SAREX) to communicate with students on Earth. Various members of the crew made contact with a number of other "hams" around the world during the almost 11-day mission in Earth orbit. Photo credit: NASA or National Aeronautics and Space Administration

Radio Galaxies.

ERIC Educational Resources Information Center

Downes, Ann

1986-01-01

Provides background information on radio galaxies. Topic areas addressed include: what produces the radio emission; radio telescopes; locating radio galaxies; how distances to radio galaxies are found; physics of radio galaxies; computer simulations of radio galaxies; and the evolution of radio galaxies with cosmic time. (JN)

A “Cosmic Comb” Model of Fast Radio Bursts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Bing

2017-02-20

Recent observations of fast radio bursts (FRBs) indicate a perplexing, inconsistent picture. We propose a unified scenario to interpret diverse FRBs observed. A regular pulsar, otherwise unnoticeable at a cosmological distance, may produce a bright FRB if its magnetosphere is suddenly “combed” by a nearby, strong plasma stream toward the anti-stream direction. If the Earth is to the night side of the stream, the combed magnetic sheath would sweep across the direction of Earth and make a detectable FRB. The stream could be an AGN flare, a GRB or supernova blastwave, a tidal disruption event, or even a stellar flare.more » Since it is the energy flux received by the pulsar rather than the luminosity of the stream origin that defines the properties of the FRB, this model predicts a variety of counterparts of FRBs, including a possible connection between FRB 150418 and an AGN flare, a possible connection between FRB 131104 and a weak GRB, a steady radio nebula associated with the repeating FRB 121102, and probably no bright counterparts for some FRBs.« less

Optical Tunable-Based Transmitter for Multiple Radio Frequency Bands

NASA Technical Reports Server (NTRS)

Nguyen, Hung (Inventor); Simons, Rainee N. (Inventor); Wintucky, Edwin G. (Inventor); Freeman, Jon C. (Inventor)

2016-01-01

An optical tunable transmitter is used to transmit multiple radio frequency bands on a single beam. More specifically, a tunable laser is configured to generate a plurality of optical wavelengths, and an optical tunable transmitter is configured to modulate each of the plurality of optical wavelengths with a corresponding radio frequency band. The optical tunable transmitter is also configured to encode each of the plurality of modulated optical wavelengths onto a single laser beam for transmission of a plurality of radio frequency bands using the single laser beam.

NASA Near Earth Network (NEN) Support for Lunar and L1/L2 CubeSats

NASA Technical Reports Server (NTRS)

Schaire, Scott H.

2017-01-01

The NASA Near Earth Network (NEN) consists of globally distributed tracking stations, including NASA, commercial, and partner ground stations, that are strategically located to maximize the coverage provided to a variety of orbital and suborbital missions, including those in LEO, GEO, HEO, lunar and L1/L2 orbits. The NENs future mission set includes and will continue to include CubeSat missions. The first NEN supported CubeSat mission will be the Cubesat Proximity Operations Demonstration (CPOD) launching into low earth orbit (LEO) in early 2017. The majority of the CubeSat missions destined to fly on EM-1, launching in late 2018, many in a lunar orbit, will communicate with ground based stations via X-band and will utilize the NASA Jet Propulsion Laboratory (JPL) developed IRIS radio. The NEN recognizes the important role CubeSats are beginning to play in carrying out NASAs mission and is therefore investigating the modifications needed to provide IRIS radio compatibility. With modification, the NEN could potentially expand support to the EM-1 lunar CubeSats. The NEN could begin providing significant coverage to lunar CubeSat missions utilizing three to four of the NENs mid-latitude sites. This coverage would supplement coverage provided by the JPL Deep Space Network (DSN). The NEN, with smaller apertures than DSN, provides the benefit of a larger beamwidth that could be beneficial in the event of uncertain ephemeris data. In order to realize these benefits the NEN would need to upgrade stations targeted based on coverage ability and current configurationease of upgrade, to ensure compatibility with the IRIS radio.In addition, the NEN is working with CubeSat radio developers to ensure NEN compatibility with alternative CubeSat radios for Lunar and L1/L2 CubeSats. The NEN has provided NEN compatibility requirements to several radio developers who are developing radios that offer lower cost and, in some cases, more capabilities with fewer constraints. The NEN is

JPL Big Data Technologies for Radio Astronomy

NASA Astrophysics Data System (ADS)

Jones, Dayton L.; D'Addario, L. R.; De Jong, E. M.; Mattmann, C. A.; Rebbapragada, U. D.; Thompson, D. R.; Wagstaff, K.

2014-04-01

During the past three years the Jet Propulsion Laboratory has been working on several technologies to deal with big data challenges facing next-generation radio arrays, among other applications. This program has focused on the following four areas: 1) We are investigating high-level ASIC architectures that reduce power consumption for cross-correlation of data from large interferometer arrays by one to two orders of magnitude. The cost of operations for the Square Kilometre Array (SKA), which may be dominated by the cost of power for data processing, is a serious concern. A large improvement in correlator power efficiency could have a major positive impact. 2) Data-adaptive algorithms (machine learning) for real-time detection and classification of fast transient signals in high volume data streams are being developed and demonstrated. Studies of the dynamic universe, particularly searches for fast (<< 1 second) transient events, require that data be analyzed rapidly and with robust RFI rejection. JPL, in collaboration with the International Center for Radio Astronomy Research in Australia, has developed a fast transient search system for eventual deployment on ASKAP. In addition, a real-time transient detection experiment is now running continuously and commensally on NRAO's Very Long Baseline Array. 3) Scalable frameworks for data archiving, mining, and distribution are being applied to radio astronomy. A set of powerful open-source Object Oriented Data Technology (OODT) tools is now available through Apache. OODT was developed at JPL for Earth science data archives, but it is proving to be useful for radio astronomy, planetary science, health care, Earth climate, and other large-scale archives. 4) We are creating automated, event-driven data visualization tools that can be used to extract information from a wide range of complex data sets. Visualization of complex data can be improved through algorithms that detect events or features of interest and autonomously

The New Horizons Bistatic Radio Science Experiment to Measure Pluto's Surface Properties

NASA Astrophysics Data System (ADS)

Linscott, I.; Hinson, D. P.; Tyler, G. L.; Vincent, M.

2014-12-01

The New Horizons (NH) payload includes a Radio Science Experiment (REX) for principally occultation and radiometric measurement of Pluto and Charon during the flyby in July 2015. The REX subsystem is contained, together with the NH X-Band radio, in the Integrated Electronics Module (IEM) in the New Horizons spacecraft. REX samples and records in two polarizations both total RF power in a 4.5 MHz bandwidth, and radio signal waveforms in a narrow, 1.25 kHz band. During the encounter, and at closest approach to Pluto, the spacecraft's high gain antenna (HGA) will scan Pluto's equatorial latitudes, intercepting the specular zone, a region near Pluto's limb that geometrically favors reflection from the earth's direction. At the same time, a powerful 80 kW uplink beacon will have been transmitted from earth by the DSN to arrive at Pluto during spacecraft closest approach. Reflection from the specular zone is expected to be sufficiently strong to observe the bistatic uplink in the REX narrowband record. Measurements in both polarizations will then be combined to yield surface reflectivity, roughness and limits on the dielectric constant in the specular zone.

Radio Jove: Jupiter Radio Astronomy for Citizens

NASA Astrophysics Data System (ADS)

Higgins, Charles; Thieman, J. R.; Flagg, R.; Reyes, F. J.; Sky, J.; Greenman, W.; Brown, J.; Typinski, D.; Ashcraft, T.; Mount, A.

2014-01-01

Radio JOVE is a hands-on educational activity that brings the radio sounds of the Sun, Jupiter, the Milky Way Galaxy, and terrestrial radio noise to students, teachers, and the general public. Participants may build a simple radio telescope kit, make scientific observations, and interact with professional radio observatories in real-time over the Internet. Our website (http://radiojove.gsfc.nasa.gov) includes science information, construction manuals, observing guides, and education resources for teachers and students. Radio Jove is continually expanding its participants with over 1800 kits sold to more than 70 countries worldwide. Recently some of our most dedicated observers have upgraded their Radio Jove antennas to semi-professional observatories. We have spectrographs and wide band antennas, some with 8 MHz bandwidth and some with dual polarization capabilities. In an effort to add to the science literature, these observers are coordinating their efforts to pursue some basic questions about Jupiter’s radio emissions (radio source locations, spectral structure, long term changes, etc.). We can compare signal and ionosphere variations using the many Radio Jove observers at different locations. Observers are also working with members of the Long Wavelength Array Station 1 (LWA1) radio telescope to coordinate observations of Jupiter; Radio Jove is planning to make coordinated observations while the Juno Mission is active beginning in 2015. The Radio Jove program is overviewed, its hardware and software are highlighted, recent sample observations are shown, and we demonstrate that we are capable of real citizen science.

An adaptive software defined radio design based on a standard space telecommunication radio system API

NASA Astrophysics Data System (ADS)

Xiong, Wenhao; Tian, Xin; Chen, Genshe; Pham, Khanh; Blasch, Erik

2017-05-01

Software defined radio (SDR) has become a popular tool for the implementation and testing for communications performance. The advantage of the SDR approach includes: a re-configurable design, adaptive response to changing conditions, efficient development, and highly versatile implementation. In order to understand the benefits of SDR, the space telecommunication radio system (STRS) was proposed by NASA Glenn research center (GRC) along with the standard application program interface (API) structure. Each component of the system uses a well-defined API to communicate with other components. The benefit of standard API is to relax the platform limitation of each component for addition options. For example, the waveform generating process can support a field programmable gate array (FPGA), personal computer (PC), or an embedded system. As long as the API defines the requirements, the generated waveform selection will work with the complete system. In this paper, we demonstrate the design and development of adaptive SDR following the STRS and standard API protocol. We introduce step by step the SDR testbed system including the controlling graphic user interface (GUI), database, GNU radio hardware control, and universal software radio peripheral (USRP) tranceiving front end. In addition, a performance evaluation in shown on the effectiveness of the SDR approach for space telecommunication.

Observing Solar Radio Bursts from the Lunar Surface

NASA Technical Reports Server (NTRS)

MacDowall, R. J.; Lazio, T. J.; Bale, S. D.; Burns, J.; Gopalswamy, N.; Jones, D. L.; Kaiser, M. L.; Kasper, J.; Weiler, K. W.

2010-01-01

Locating low frequency radio observatories on the lunar surface has a number of advantages. Here, we describe the Radio Observatory for Lunar Sortie Science (ROLSS), a concept for a low frequency, radio imaging interferometric array designed to study particle acceleration in the corona and inner heliosphere. ROLSS would be deployed during an early lunar sortie or by a robotic rover as part of an unmanned landing. The prime science mission is to image type II and type III solar radio bursts with the aim of determining the sites at and mechanisms by which the radiating particles are accelerated. Secondary science goals include constraining the density of the lunar ionosphere by searching for a low radio frequency cutoff of the solar radio emissions and constraining the low energy electron population in astrophysical sources. Furthermore, ROLSS serves a pathfinder function for larger lunar radio arrays. Key design requirements on ROLES include the operational frequency and angular resolution. The electron densities in the solar corona and inner heliosphere are such that the relevant emission occurs below 10 MHz, essentially unobservable from Earth's surface due to the terrestrial ionospheric cutoff. Resolving the potential sites of particle acceleration requires an instrument with an angular resolution of at least 2 deg, equivalent to a linear array size of approximately 500 meters. Operations would consist of data acquisition during the lunar day, with regular data downlinks. The major components of the ROLSS array are 3 antenna arms arranged in a Y shape, with a central electronics package (CEP). Each antenna arm is a linear strip of polyimide film (e.g., Kapton (TM)) on which 16 single polarization dipole antennas are located by depositing a conductor (e.g., silver). The arms also contain transmission lines for carrying the radio signals from the science antennas to the CEP.

Deep Interior Mission: Imaging the Interior of Near-Earth Asteroids Using Radio Reflection Tomography

NASA Technical Reports Server (NTRS)

Safaeinili, A.; Asphaug, E.; Rodriquez, E.; Gurrola, E.; Belton, M.; Klaasen, K.; Ostro, S.; Plaut, J.; Yeomans, D.

2005-01-01

Near-Earth asteroids are important exploration targets since they provide clues to the evolution of the solar system. They are also of interest since they present a clear danger to Earth. Our mission objective is to image the internal structure of two NEOs using radio reflection tomography (RRT) in order to explore the record of asteroid origin and impact evolution, and to test the fundamental hypothesis that some NEOs are rubble piles rather than consolidated bodies. Our mission s RRT technique is analogous to doing a CAT scan of the asteroid from orbit. Closely sampled radar echoes are processed to yield volumetric maps of mechanical and compositional boundaries, and to measure interior material dielectric properties. The RRT instrument is a radar that operates at 5 and 15 MHz with two 30-m (tip-to-tip) dipole antennas that are used in a cross-dipole configuration. The radar transmitter and receiver electronics have heritage from JPL's MARSIS contribution to Mars Express, and the antenna is similar to systems used in IMAGE and LACE missions. The 5-MHz channel is designed to penetrate greater than 1 km of basaltic rock, and 15-MHz penetrates a few hundred meters or more. In addition to RRT volumetric imaging, we use redundant color cameras to explore the surface expressions of unit boundaries, in order to relate interior radar imaging to what is observable from spacecraft imaging and from Earth. The camera also yields stereo color imaging for geology and RRT-related compositional analysis. Gravity and high fidelity geodesy are used to explore how interior structure is expressed in shape, density, mass distribution and spin. Ion thruster propulsion is utilized by Deep Interior to enable tomographic radar mapping of multiple asteroids. Within the Discovery AO scheduling parameters we identify two targets, S-type 1999 ND43 (approximately 500 m diameter) and V-type 3908 Nyx (approximately 1 km), asteroids whose compositions bracket the diversity of solar system

Radio Telescopes Will Add to Cassini-Huygens Discoveries

NASA Astrophysics Data System (ADS)

2004-12-01

poorly understood. Predictions of where the Huygens probe will land range from nearly 250 miles east to nearly 125 miles west of the point where its parachute first deploys, depending on which wind model is used. What actually happens to the probe as it makes its parachute descent through Titan's atmosphere will give scientists their best-ever opportunity to learn about Titan's winds. During its descent, Huygens will transmit data from its onboard sensors to Cassini, the "mother ship" that brought it to Titan. Cassini will then relay the data back to Earth. However, the large radio telescopes will be able to receive the faint (10-watt) signal from Huygens directly, even at a distance of nearly 750 million miles. This will not be done to duplicate the data collection, but to generate new data about Huygens' position and motions through direct measurement. Measurements of the Doppler shift in the frequency of Huygens' radio signal made from the Cassini spacecraft, in an experiment led by Mike Bird of the University of Bonn, will largely give information about the speed of Titan's east-west winds. A team led by scientists at NASA's Jet Propulsion Laboratory in Pasadena, CA, will measure the Doppler shift in the probe's signal relative to Earth. These additional Doppler measurements from the Earth-based radio telescopes will provide important data needed to learn about the north-south winds. "Adding the ground-based telescopes to the experiment will not only help confirm the data we get from the Cassini orbiter but also will allow us to get a much more complete picture of the winds on Titan," said William Folkner, a JPL scientist. The VLBA The VLBA CREDIT: NRAO/AUI/NSF (Click on image for VLBA gallery) Another team, led by scientists from the Joint Institute for Very Long Baseline Interferometry in Europe (JIVE), in Dwingeloo, The Netherlands, will use a world-wide network of radio telescopes, including the NRAO telescopes, to track the probe's trajectory with unprecedented

47 CFR 25.226 - Blanket licensing provisions for domestic, U.S. Vehicle-Mounted Earth Stations (VMESs) receiving...

Code of Federal Regulations, 2010 CFR

2010-10-01

... of VMESs in the 14.47-14.5 GHz (Earth-to-space) frequency band in the vicinity of radio astronomy... location, and the applicable coordination zone. Table 1—Applicable Radio Astronomy Service (RAS) Facilities... Astronomical Research Institute, Rosman, NC 35°11′59″ 82°52′19″ 160. U of Michigan Radio Astronomy Observatory...

47 CFR 25.226 - Blanket licensing provisions for domestic, U.S. Vehicle-Mounted Earth Stations (VMESs) receiving...

Code of Federal Regulations, 2012 CFR

2012-10-01

... of VMESs in the 14.47-14.5 GHz (Earth-to-space) frequency band in the vicinity of radio astronomy... location, and the applicable coordination zone. Table 1—Applicable Radio Astronomy Service (RAS) Facilities... Astronomical Research Institute, Rosman, NC 35°11′59″ 82°52′19″ 160. U of Michigan Radio Astronomy Observatory...

47 CFR 25.226 - Blanket Licensing provisions for domestic, U.S. Vehicle-Mounted Earth Stations (VMESs) receiving...

Code of Federal Regulations, 2014 CFR

2014-10-01

... in the 14.47-14.5 GHz (Earth-to-space) frequency band in the vicinity of radio astronomy service (RAS... coordination zone. Table 1—Applicable Radio Astronomy Service (RAS) Facilities and Associated Coordination..., Rosman, NC 35°11′59″ 82°52′19″ 160. U of Michigan Radio Astronomy Observatory, Stinchfield Woods, MI 42...

47 CFR 25.226 - Blanket licensing provisions for domestic, U.S. Vehicle-Mounted Earth Stations (VMESs) receiving...

Code of Federal Regulations, 2011 CFR

2011-10-01

... of VMESs in the 14.47-14.5 GHz (Earth-to-space) frequency band in the vicinity of radio astronomy... location, and the applicable coordination zone. Table 1—Applicable Radio Astronomy Service (RAS) Facilities... Astronomical Research Institute, Rosman, NC 35°11′59″ 82°52′19″ 160. U of Michigan Radio Astronomy Observatory...

Graphene electrostatic microphone and ultrasonic radio

PubMed Central

Zhou, Qin; Zheng, Jinglin; Onishi, Seita; Crommie, M. F.; Zettl, Alex K.

2015-01-01

We present a graphene-based wideband microphone and a related ultrasonic radio that can be used for wireless communication. It is shown that graphene-based acoustic transmitters and receivers have a wide bandwidth, from the audible region (20∼20 kHz) to the ultrasonic region (20 kHz to at least 0.5 MHz). Using the graphene-based components, we demonstrate efficient high-fidelity information transmission using an ultrasonic band centered at 0.3 MHz. The graphene-based microphone is also shown to be capable of directly receiving ultrasound signals generated by bats in the field, and the ultrasonic radio, coupled to electromagnetic (EM) radio, is shown to function as a high-accuracy rangefinder. The ultrasonic radio could serve as a useful addition to wireless communication technology where the propagation of EM waves is difficult. PMID:26150483

Cross stratum resources protection in fog-computing-based radio over fiber networks for 5G services

NASA Astrophysics Data System (ADS)

Guo, Shaoyong; Shao, Sujie; Wang, Yao; Yang, Hui

2017-09-01

In order to meet the requirement of internet of things (IoT) and 5G, the cloud radio access network is a paradigm which converges all base stations computational resources into a cloud baseband unit (BBU) pool, while the distributed radio frequency signals are collected by remote radio head (RRH). A precondition for centralized processing in the BBU pool is an interconnection fronthaul network with high capacity and low delay. However, it has become more complex and frequent in the interaction between RRH and BBU and resource scheduling among BBUs in cloud. Cloud radio over fiber network has been proposed in our previous work already. In order to overcome the complexity and latency, in this paper, we first present a novel cross stratum resources protection (CSRP) architecture in fog-computing-based radio over fiber networks (F-RoFN) for 5G services. Additionally, a cross stratum protection (CSP) scheme considering the network survivability is introduced in the proposed architecture. The CSRP with CSP scheme can effectively pull the remote processing resource locally to implement the cooperative radio resource management, enhance the responsiveness and resilience to the dynamic end-to-end 5G service demands, and globally optimize optical network, wireless and fog resources. The feasibility and efficiency of the proposed architecture with CSP scheme are verified on our software defined networking testbed in terms of service latency, transmission success rate, resource occupation rate and blocking probability.

Optimization-based channel constrained data aggregation routing algorithms in multi-radio wireless sensor networks.

PubMed

Yen, Hong-Hsu

2009-01-01

In wireless sensor networks, data aggregation routing could reduce the number of data transmissions so as to achieve energy efficient transmission. However, data aggregation introduces data retransmission that is caused by co-channel interference from neighboring sensor nodes. This kind of co-channel interference could result in extra energy consumption and significant latency from retransmission. This will jeopardize the benefits of data aggregation. One possible solution to circumvent data retransmission caused by co-channel interference is to assign different channels to every sensor node that is within each other's interference range on the data aggregation tree. By associating each radio with a different channel, a sensor node could receive data from all the children nodes on the data aggregation tree simultaneously. This could reduce the latency from the data source nodes back to the sink so as to meet the user's delay QoS. Since the number of radios on each sensor node and the number of non-overlapping channels are all limited resources in wireless sensor networks, a challenging question here is to minimize the total transmission cost under limited number of non-overlapping channels in multi-radio wireless sensor networks. This channel constrained data aggregation routing problem in multi-radio wireless sensor networks is an NP-hard problem. I first model this problem as a mixed integer and linear programming problem where the objective is to minimize the total transmission subject to the data aggregation routing, channel and radio resources constraints. The solution approach is based on the Lagrangean relaxation technique to relax some constraints into the objective function and then to derive a set of independent subproblems. By optimally solving these subproblems, it can not only calculate the lower bound of the original primal problem but also provide useful information to get the primal feasible solutions. By incorporating these Lagrangean multipliers

Precession, Nutation and Wobble of the Earth

NASA Astrophysics Data System (ADS)

Dehant, V.; Mathews, P. M.

2015-04-01

Covering both astronomical and geophysical perspectives, this book describes changes in the Earth's orientation, specifically precession and nutation, and how they are observed and computed in terms of tidal forcing and models of the Earth's interior. Following an introduction to key concepts and elementary geodetic theory, the book describes how precise measurements of the Earth's orientation are made using observations of extra-galactic radio-sources by Very Long Baseline Interferometry techniques. It demonstrates how models are used to accurately pinpoint the location and orientation of the Earth with reference to the stars and how to determine variations in its rotation speed. A theoretical framework is also presented that describes the role played by the structure and properties of the Earth's deep interior. Incorporating suggestions for future developments in nutation theory for the next generation models, this book is ideal for advanced-level students and researche! rs in solid Earth geophysics, planetary science and astronomy.

An Overview of Geodetic and Astrometric VLBI at the Hartebeesthoek Radio Astronomy Observatory

NASA Astrophysics Data System (ADS)

de Witt, A.; Gaylard, M.; Quick, J.; Combrinck, L.

2013-08-01

For astronomical Very Long Baseline Interferometry (VLBI), the Hartebeesthoek Radio Astronomy Observatory (HartRAO), in South Africa operates as part of a number of networks including the European and Australian VLBI networks, global arrays and also space VLBI. HartRAO is the only African representative in the international geodetic VLBI network and participates in regular astrometric and geodetic VLBI programmes. HartRAO will play a major role in the realization of the next generation full-sky celestial reference frame, especially the improvement of the celestial reference frame in the South. The observatory also provides a base for developing the African VLBI Network (AVN), a project to convert redundant satellite Earth-station antennas across Africa to use for radio astronomy. The AVN would greatly facilitate VLBI observations of southern objects. We present an overview of the current capabilities as well as future opportunities for astrometric and geodetic VLBI at HartRAO.

Problem-Based Learning and Earth System Science - The ESSEA High School Earth System Science Online Course

NASA Astrophysics Data System (ADS)

Myers, R.; Botti, J.

2002-12-01

The high school Earth system science course is web based and designed to meet the professional development needs of science teachers in grades 9-12. Three themes predominate this course: Earth system science (ESS) content, collaborative investigations, and problem-based learning (PBL) methodology. PBL uses real-world contexts for in-depth investigations of a subject matter. Participants predict the potential impacts of the selected event on Earth's spheres and the subsequent feedback and potential interactions that might result. PBL activities start with an ill-structured problem that serves as a springboard to team engagement. These PBL scenarios contain real-world situations. Teams of learners conduct an Earth system science analysis of the event and make recommendations or offer solutions regarding the problem. The course design provides an electronic forum for conversations, debate, development, and application of ideas. Samples of threaded discussions built around ESS thinking in science and PBL pedagogy will be presented.

Problem-Based Learning and Earth System Science - The ESSEA High School Earth System Science Online Course

NASA Astrophysics Data System (ADS)

Myers, R. J.; Botti, J. A.

2001-12-01

The high school Earth system science course is web based and designed to meet the professional development needs of science teachers in grades 9-12. Three themes predominate this course: Earth system science (ESS) content, collaborative investigations, and problem-based learning (PBL) methodology. PBL uses real-world contexts for in-depth investigations of a subject matter. Participants predict the potential impacts of the selected event on Earth's spheres and the subsequent feedback and potential interactions that might result. PBL activities start with an ill-structured problem that serves as a springboard to team engagement. These PBL scenarios contain real-world situations. Teams of learners conduct an Earth system science analysis of the event and make recommendations or offer solutions regarding the problem. The course design provides an electronic forum for conversations, debate, development, and application of ideas. Samples of threaded discussions built around ESS thinking in science and PBL pedagogy will be presented.

Dispersive heterodyne probing method for laser frequency stabilization based on spectral hole burning in rare-earth doped crystals.

PubMed

Gobron, O; Jung, K; Galland, N; Predehl, K; Le Targat, R; Ferrier, A; Goldner, P; Seidelin, S; Le Coq, Y

2017-06-26

Frequency-locking a laser to a spectral hole in rare-earth doped crystals at cryogenic temperature has been shown to be a promising alternative to the use of high finesse Fabry-Perot cavities when seeking a very high short term stability laser (M. J. Thorpe et al., Nature Photonics 5, 688 (2011)). We demonstrate here a novel technique for achieving such stabilization, based on generating a heterodyne beat-note between a master laser and a slave laser whose dephasing caused by propagation near a spectral hole generate the error signal of the frequency lock. The master laser is far detuned from the center of the inhomogeneous absorption profile, and therefore exhibits only limited interaction with the crystal despite a potentially high optical power. The demodulation and frequency corrections are generated digitally with a hardware and software implementation based on a field-programmable gate array and a Software Defined Radio platform, making it straightforward to address several frequency channels (spectral holes) in parallel.

Features of HF Radio Wave Attenuation in the Midlatitude Ionosphere Near the Skip Zone Boundary

NASA Astrophysics Data System (ADS)

Denisenko, P. F.; Skazik, A. I.

2017-06-01

We briefly describe the history of studying the decameter radio wave attenuation by different methods in the midlatitude ionosphere. A new method of estimating the attenuation of HF radio waves in the ionospheric F region near the skip zone boundary is presented. This method is based on an analysis of the time structure of the interference field generated by highly stable monochromatic X-mode radio waves at the observation point. The main parameter is the effective electron collision frequency νeff, which allows for all energy losses in the form of equivalent heat loss. The frequency νeff is estimated by matching the assumed (model) and the experimentally observed structures. Model calculations are performed using the geometrical-optics approximation. The spatial attenuation caused by the influence of the medium-scale traveling ionospheric disturbances is taken into account. Spherical shape of the ionosphere and the Earth's magnetic field are roughly allowed for. The results of recording of the level of signals from the RWM (Moscow) station at a frequency of 9.996 MHz at point Rostov are used.

Earth-Affecting Solar Causes Observatory (EASCO): A Potential International Living with a Star Mission from Sun-Earth L5

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Davila, J. M.; St Cyr, O. C.; Sittler, E. C.; Auchere, F.; Duvall, Jr. T. L.; Hoeksema, J. T.; Maksimovic, M.; MacDowall, R. J.; Szabo, A.;

The radio spectral energy distribution of infrared-faint radio sources

NASA Astrophysics Data System (ADS)

Herzog, A.; Norris, R. P.; Middelberg, E.; Seymour, N.; Spitler, L. R.; Emonts, B. H. C.; Franzen, T. M. O.; Hunstead, R.; Intema, H. T.; Marvil, J.; Parker, Q. A.; Sirothia, S. K.; Hurley-Walker, N.; Bell, M.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Callingham, J. R.; Deshpande, A. A.; Dwarakanath, K. S.; For, B.-Q.; Greenhill, L. J.; Hancock, P.; Hazelton, B. J.; Hindson, L.; Johnston-Hollitt, M.; Kapińska, A. D.; Kaplan, D. L.; Lenc, E.; Lonsdale, C. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Morgan, J.; Oberoi, D.; Offringa, A.; Ord, S. M.; Prabu, T.; Procopio, P.; Udaya Shankar, N.; Srivani, K. S.; Staveley-Smith, L.; Subrahmanyan, R.; Tingay, S. J.; Wayth, R. B.; Webster, R. L.; Williams, A.; Williams, C. L.; Wu, C.; Zheng, Q.; Bannister, K. W.; Chippendale, A. P.; Harvey-Smith, L.; Heywood, I.; Indermuehle, B.; Popping, A.; Sault, R. J.; Whiting, M. T.

2016-10-01

Context. Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z ≥ 1.7) that are characterised by their relative infrared faintness, resulting in enormous radio-to-infrared flux density ratios of up to several thousand. Aims: Because of their optical and infrared faintness, it is very challenging to study IFRS at these wavelengths. However, IFRS are relatively bright in the radio regime with 1.4 GHz flux densities of a few to a few tens of mJy. Therefore, the radio regime is the most promising wavelength regime in which to constrain their nature. We aim to test the hypothesis that IFRS are young AGN, particularly GHz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that have a low frequency turnover. Methods: We use the rich radio data set available for the Australia Telescope Large Area Survey fields, covering the frequency range between 150 MHz and 34 GHz with up to 19 wavebands from different telescopes, and build radio spectral energy distributions (SEDs) for 34 IFRS. We then study the radio properties of this class of object with respect to turnover, spectral index, and behaviour towards higher frequencies. We also present the highest-frequency radio observations of an IFRS, observed with the Plateau de Bure Interferometer at 105 GHz, and model the multi-wavelength and radio-far-infrared SED of this source. Results: We find IFRS usually follow single power laws down to observed frequencies of around 150 MHz. Mostly, the radio SEDs are steep (α < -0.8; %), but we also find ultra-steep SEDs (α < -1.3; %). In particular, IFRS show statistically significantly steeper radio SEDs than the broader RL AGN population. Our analysis reveals that the fractions of GPS and CSS sources in the population of IFRS are consistent with the fractions in the broader RL AGN population. We find that at least % of IFRS contain young AGN, although the fraction might be significantly higher as suggested by

Large Diffractive Optics for GEo-Based Earth Surveillance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hyde, R A

2003-09-11

The natural vantage point for performing Earth-centric operations from space is geosynchronous orbit (GEO); a platform there moves at the same rate as the Earth's surface, so appears to continually ''hover'' over a fixed site on the Earth. Unlike spacecraft in other orbits, which rapidly fly-over targets, a GEO-based platform remains in-position all the time. In order to insure continual access to sites using low earth orbit (LEO) platforms, one needs a large enough constellation ({approx} 50) of spacecraft so that one is always overhead; in contrast, a single GEO platform provides continuous coverage over sites throughout Euro-Asia. This permanentmore » coverage comes, unfortunately, with a stiff price-tag; geosynchronous orbit is 36,000 km high, so space platforms there must operate at ranges roughly 100 times greater than ones located in LEO. For optical-based applications, this extreme range is difficult to deal with; for surveillance the price is a 100-fold loss of resolution, for laser weapons it is a 10,000-fold loss in flux-on-target. These huge performance penalties are almost always unacceptable, preventing us from successfully using GEO-based platforms. In practice, we are forced to either settle for brief, infrequent access to targets, or, if we demand continuous coverage, to invest in large, many-satellite, constellations. There is, fortunately, a way to use GEO-based optical platforms without incurring the huge, range-dependent, performance penalties; one must simply use bigger optics. As long as the aperture of a platform's optics increases as much as its operating range, then its performance (resolution and/or flux) does not suffer; the price for operating from GEO is simply 100-fold larger optics. This is, of course, a very stiff price; while meter-class optics may suffice for many low-earth-orbit applications, 100 meter apertures are needed in order to achieve similar performance from GEO. Since even the largest Earth-based telescope is only 10

DISCOVERY OF A WANDERING RADIO JET BASE AFTER A LARGE X-RAY FLARE IN THE BLAZAR MARKARIAN 421

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niinuma, K.; Kino, M.; Doi, A.

2015-07-01

We investigate the location of the radio jet bases (“radio cores”) of blazars in radio images and their stationarity by means of dense very long baseline interferometry (VLBI) observations. In order to measure the position of a radio core, we conducted a 12 epoch astrometric observation of the blazar Markarian 421 with the VLBI Exploration of Radio Astrometry at 22 GHz immediately after a large X-ray flare, which occurred in the middle of 2011 September. For the first time,we find that the radio core is not stationary but rather changes its location toward 0.5 mas downstream. This angular scale correspondsmore » to the de-projected length of a scale of 10{sup 5} Schwarzschild radii (R{sub s}) at the distance of Markarian 421. This radio-core wandering may be a new type of manifestation associated with the phenomena of large X-ray flares.« less

VLA Detects Unexplained Radio Emission From Three Brown Dwarfs

NASA Astrophysics Data System (ADS)

2005-01-01

Astronomers have discovered three brown dwarfs -- enigmatic objects that are neither stars nor planets -- emitting radio waves that scientists cannot explain. The three newly-discovered radio-emitting brown dwarfs were found as part of a systematic study of nearby brown dwarfs using the National Science Foundation's Very Large Array (VLA) radio telescope. The VLA The Very Large Array CREDIT: NRAO/AUI/NSF (Click on image for VLA gallery) Until 2001, scientists believed that brown dwarfs, which are intermediate in mass between stars and planets, could not emit detectable amounts of radio waves. That year, summer students at the VLA made the first discovery of radio emission from a brown dwarf. Subsequently, as many as a half- dozen more radio-emitting brown dwarfs were discovered. "It clearly had become time to make a systematic study and try to find out just what percentage of brown dwarfs are emitting radio waves," said Rachel Osten, an astronomer at the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia. Osten was assisted in the project in the summer of 2004 by Lynnae Quick, a student at North Carolina Agricultural and Technical State University; Tim Bastian, also an astronomer at NRAO; and Suzanne Hawley, an astronomer at the University of Washington. The research team presented their results to the American Astronomical Society's meeting in San Diego, CA. The three new detections of radio-emitting brown dwarfs are just the first results from the systematic study, which aims to observe all the known brown dwarfs within about 45 light-years of Earth. "We want to be able to say definitively just how common radio emission is among brown dwarfs," Osten explained. The study involves observing 65 individual brown dwarfs, so these new detections represent just the beginning of the results expected from the study. Brown dwarfs are too big to be planets but too small to be true stars, as they have too little mass to trigger hydrogen fusion reactions

PSR B0329+54: substructure in the scatter-broadened image discovered with RadioAstron on baselines up to 330 000 km

NASA Astrophysics Data System (ADS)

Popov, Mikhail V.; Bartel, Norbert; Gwinn, Carl R.; Johnson, Michael D.; Andrianov, Andrey; Fadeev, Evgeny; Joshi, Bhal Chandra; Kardashev, Nikolay; Karuppusamy, Ramesh; Kovalev, Yuri Y.; Kramer, Michael; Rudnitskiy, Alexey; Shishov, Vladimir; Smirnova, Tatiana; Soglasnov, Vladimir A.; Zensus, J. Anton

2017-02-01

We have resolved the scatter-broadened image of PSR B0329+54 and detected a substructure within it. These results are not influenced by any extended structure of a source but instead are directly attributed to the interstellar medium. We obtained these results at 324 MHz with the ground-space interferometer RadioAstron, which included the Space Radio Telescope, ground-based Westerbork Synthesis Radio Telescope and 64-m Kalyazin Radio Telescope on baseline projections up to 330 000 km in 2013 November 22 and 2014 January 1 to 2. At short 15 000 to 35 000 km ground-space baseline projections, the visibility amplitude decreases with baseline length, providing a direct measurement of the size of the scattering disc of 4.8 ± 0.8 mas. At longer baselines, no visibility detections from the scattering disc would be expected. However, significant detections were obtained with visibility amplitudes of 3 to 5 per cent of the maximum scattered around a mean and approximately constant up to 330 000 km. These visibilities reflect a substructure from scattering in the interstellar medium and offer a new probe of ionized interstellar material. The size of the diffraction spot near Earth is 17 000 ± 3 000 km. With the assumption of turbulent irregularities in the plasma of the interstellar medium, we estimate that the effective scattering screen is located 0.6 ± 0.1 of the distance from the Earth towards the pulsar.

Livingstone Model-Based Diagnosis of Earth Observing One Infusion Experiment

NASA Technical Reports Server (NTRS)

Hayden, Sandra C.; Sweet, Adam J.; Christa, Scott E.

2004-01-01

The Earth Observing One satellite, launched in November 2000, is an active earth science observation platform. This paper reports on the progress of an infusion experiment in which the Livingstone 2 Model-Based Diagnostic engine is deployed on Earth Observing One, demonstrating the capability to monitor the nominal operation of the spacecraft under command of an on-board planner, and demonstrating on-board diagnosis of spacecraft failures. Design and development of the experiment, specification and validation of diagnostic scenarios, characterization of performance results and benefits of the model- based approach are presented.

Lunar Radio_phase Ranging in Chinese Lunar Lander Mission for Astrometry

NASA Astrophysics Data System (ADS)

Ping, Jinsong; Meng, Qiao; Li, Wenxiao; Wang, Mingyuan; Wang, Zhen; Zhang, Tianyi; Han, Songtao

2015-08-01

The radio tracking data in lunar and planetary missions can be directly applied for scientific investigation. The variations of phase and of amplitude of the radio carrier wave signal linked between the spacecraft and the ground tracking antenna are used to deduce the planetary atmospheric and ionospheric structure, planetary gravity field, mass, ring, ephemeris, and even to test the general relativity. In the Chinese lunar missions, we developed the lunar and planetary radio science receiver to measure the distance variation between the tracking station-lander by means of open loop radio phase tracking. Using this method in Chang’E-3 landing mission, a lunar radio_phase ranging (LRR) technique was realized at Chinese deep space tracking stations and astronomical VLBI stations with H-maser clocks installed. Radio transponder and transmitter had been installed on the Chang’E-3/4. Transponder will receive the uplink S/X band radio wave transmitted from the two newly constructed Chinese deep space stations, where the high quality hydrogen maser atomic clocks have been used as local time and frequency standard. The clocks between VLBI stations and deep space stations can be synchronized to UTC standard within 20 nanoseconds using satellite common view methods. In the near future there will be a plan to improve this accuracy to 5 nanoseconds or better, as the level of other deep space network around world. In the preliminary LRR experiments of Chang'E-3, the obtained 1sps phase ranging observables have a resolution of 0.2 millimeter or better, with a fitting RMS about 2~3 millimeter, after the atmospheric and ionospheric errors removed. This method can be a new astrometric technique to measure the Earth tide and rotation, lunar orbit, tides and liberation, by means of solo observation or of working together with Lunar Laser Ranging. After differencing the ranging, we even obtained 1sps doppler series of 2-way observables with resolution of 0.07mm/second, which can

Reliable Location-Based Services from Radio Navigation Systems

PubMed Central

Qiu, Di; Boneh, Dan; Lo, Sherman; Enge, Per

2010-01-01

Loran is a radio-based navigation system originally designed for naval applications. We show that Loran-C’s high-power and high repeatable accuracy are fantastic for security applications. First, we show how to derive a precise location tag—with a sensitivity of about 20 meters—that is difficult to project to an exact location. A device can use our location tag to block or allow certain actions, without knowing its precise location. To ensure that our tag is reproducible we make use of fuzzy extractors, a mechanism originally designed for biometric authentication. We build a fuzzy extractor specifically designed for radio-type errors and give experimental evidence to show its effectiveness. Second, we show that our location tag is difficult to predict from a distance. For example, an observer cannot predict the location tag inside a guarded data center from a few hundreds of meters away. As an application, consider a location-aware disk drive that will only work inside the data center. An attacker who steals the device and is capable of spoofing Loran-C signals, still cannot make the device work since he does not know what location tag to spoof. We provide experimental data supporting our unpredictability claim. PMID:22163532

Reliable location-based services from radio navigation systems.

PubMed

Qiu, Di; Boneh, Dan; Lo, Sherman; Enge, Per

2010-01-01

Loran is a radio-based navigation system originally designed for naval applications. We show that Loran-C's high-power and high repeatable accuracy are fantastic for security applications. First, we show how to derive a precise location tag--with a sensitivity of about 20 meters--that is difficult to project to an exact location. A device can use our location tag to block or allow certain actions, without knowing its precise location. To ensure that our tag is reproducible we make use of fuzzy extractors, a mechanism originally designed for biometric authentication. We build a fuzzy extractor specifically designed for radio-type errors and give experimental evidence to show its effectiveness. Second, we show that our location tag is difficult to predict from a distance. For example, an observer cannot predict the location tag inside a guarded data center from a few hundreds of meters away. As an application, consider a location-aware disk drive that will only work inside the data center. An attacker who steals the device and is capable of spoofing Loran-C signals, still cannot make the device work since he does not know what location tag to spoof. We provide experimental data supporting our unpredictability claim.

On the Evolution of the Cores of Radio Sources and Their Extended Radio Emission

NASA Astrophysics Data System (ADS)

Yuan, Zunli; Wang, Jiancheng

2012-01-01

The work in this paper aims at determining the evolution and possible co-evolution of radio-loud active galactic nuclei (AGNs) and their cores via their radio luminosity functions (i.e., total and core RLFs, respectively). Using a large combined sample of 1063 radio-loud AGNs selected at low radio frequency, we investigate the RLF at 408 MHz of steep-spectrum radio sources. Our results support a luminosity-dependent evolution. Using core flux density data of the complete sample 3CRR, we investigate the core RLF at 5.0 GHz. Based on the combined sample with incomplete core flux data, we also estimate the core RLF using a modified factor of completeness. Both results are consistent and show that the comoving number density of radio cores displays a persistent decline with redshift, implying a negative density evolution. We find that the core RLF is obviously different from the total RLF at the 408 MHz band which is mainly contributed by extended lobes, implying that the cores and extended lobes could not be co-evolving at radio emission.

Results of Joint Observations of Jupiter's Atmosphere by Juno and a Network of Earth-Based Observing Stations

NASA Astrophysics Data System (ADS)

Orton, Glenn; Momary, Thomas; Bolton, Scott; Levin, Steven; Hansen, Candice; Janssen, Michael; Adriani, Alberto; Gladstone, G. Randall; Bagenal, Fran; Ingersoll, Andrew

2017-04-01

The Juno mission has promoted and coordinated a network of Earth-based observations, including both Earth-proximal and ground-based facilities, to extend and enhance observations made by the Juno mission. The spectral region and timeline of all of these observations are summarized in the web site: https://www.missionjuno.swri.edu/planned-observations. Among the earliest of these were observation of Jovian auroral phenomena at X-ray, ultraviolet and infrared wavelengths and measurements of Jovian synchrotron radiation from the Earth simultaneously with the measurement of properties of the upstream solar wind. Other observations of significance to the magnetosphere measured the mass loading from Io by tracking its observed volcanic activity and the opacity of its torus. Observations of Jupiter's neutral atmosphere included observations of reflected sunlight from the near-ultraviolet through the near-infrared and thermal emission from 5 μm through the radio region. The point of these measurements is to relate properties of the deep atmosphere that are the focus of Juno's mission to the state of the "weather layer" at much higher atmospheric levels. These observations cover spectral regions not included in Juno's instrumentation, provide spatial context for Juno's often spatially limited coverage of Jupiter, and they describe the evolution of atmospheric features in time that are measured only once by Juno. We will summarize the results of measurements during the approach phase of the mission that characterized the state of the atmosphere, as well as observations made by Juno and the supporting campaign during Juno's perijoves 1 (2016 August 27), 3 (2016 December 11), 4 (2017 February 2) and possibly "early" results from 5 (2017 March 27). Besides a global network of professional astronomers, the Juno mission also benefited from the enlistment of a network of dedicated amateur astronomers who provided a quasi-continuous picture of the evolution of features observed by

Learning radio astronomy by doing radio astronomy

NASA Astrophysics Data System (ADS)

Vaquerizo Gallego, J. A.

2011-11-01

PARTNeR (Proyecto Académico con el Radio Telescopio de NASA en Robledo, Academic Project with the NASA Radio Telescope at Robledo) is an educational program that allows high school and undergraduate students to control a 34 meter radio telescope and conduct radio astronomical observations via the internet. High-school teachers who join the project take a course to learn about the science of radio astronomy and how to use the antenna as an educational resource. Also, teachers are provided with learning activities they can do with their students and focused on the classroom implementation of the project within an interdisciplinary framework. PARTNeR provides students with firsthand experience in radio astronomy science. Thus, remote radio astronomical observations allow students to learn with a first rate scientific equipment the basics of radio astronomy research, aiming to arouse scientific careers and positive attitudes toward science. In this contribution we show the current observational programs and some recent results.

Correlating Type II and III Radio Bursts with Solar Energetic Particle Events

NASA Astrophysics Data System (ADS)

Ledbetter, K.; Winter, L. M.; Quinn, R. A.

2013-12-01

Solar energetic particles (SEPs) are high-energy particles, such as protons, which are accelerated at the Sun and speed outward into the solar system. If they reach Earth, they can be harmful to satellites, ionospheric communications, and humans in space or on polar airline routes. NOAA defines an SEP event as an occasion when the flux of protons with energies higher than 10 MeV exceeds 10 pfu (particle flux units) as measured by the GOES satellites in geosynchronous orbit. The most intense SEP events are associated with shocks, driven by coronal mass ejections (CMEs), which accelerate particles as they move through the corona. However, very few CMEs result in SEP events. To determine what factors are most important in distinguishing the shock waves that will result in SEP acceleration toward Earth, we take into account several variables and perform a principal component analysis (PCA) to examine their correlations. First, we examine Type II radio bursts, which are caused by electrons accelerating in the same CME-driven shocks that can accelerate SEPs. Using data from the WAVES instrument on the WIND satellite, these Type II radio bursts, as well as the Type III bursts that often accompany them, can be characterized by slope in 1/f space and by intensity. In addition, local Langmuir waves detected by WIND, which are caused by electrons speeding through the plasma surrounding the satellite, can be an indicator of the magnetic connectivity between the active region and Earth. Finally, X-ray flares directly preceding the Type II burst are also taken into consideration in the PCA analysis. The accompanying figure illustrates an example of the WAVES solar radio bursts along with the GOES solar proton flux >= 10 MeV during the SEP event on April 11, 2013. Using PCA to determine which of these factors are most relevant to the onset, intensity, and duration of SEP events will be valuable in future work to predict such events. In total, we present the analysis of all type

Record-Breaking Radio Astronomy Project to Measure Sky with Extreme Precision

NASA Astrophysics Data System (ADS)

2009-11-01

Astronomers will tie together the largest collection of the world's radio telescopes ever assembled to work as a single observing tool in a project aimed at improving the precision of the reference frame scientists use to measure positions in the sky. The National Science Foundation's Very Long Baseline Array (VLBA) will be a key part of the project, which is coordinated by the International VLBI Service for Geodesy and Astrometry. For 24 hours, starting Wednesday, November 18, and ending Thursday, November 19, 35 radio telescopes located on seven continents will observe 243 distant quasars. The quasars, galaxies with supermassive black holes at their cores, are profuse emitters of radio waves, and also are so distant that, despite their actual motions in space, they appear stationary as seen from Earth. This lack of apparent motion makes them ideal celestial landmarks for anchoring a grid system, similar to earthly latitude and longitude, used to mark the positions of celestial objects. Data from all the radio telescopes will be combined to make them work together as a system capable of measuring celestial positions with extremely high precision. The technique used, called very long baseline interferometry (VLBI), has been used for decades for both astronomical and geodetic research. However, no previous position-measuring observation has used as many radio telescopes or observed as many objects in a single session. The previous record was a 23-telescope observation. At a meeting in Brazil last August, the International Astronomical Union adopted a new reference frame for celestial positions that will be used starting on January 1. This new reference frame uses a set of 295 quasars to define positions, much like surveyor's benchmarks in a surburban subdivision. Because even with 35 radio telescopes around the world, there are some gaps in sky coverage, the upcoming observation will observe 243 of the 295. By observing so many quasars in a single observing session

Space Telecommunications Radio Architecture (STRS)

NASA Technical Reports Server (NTRS)

Reinhart, Richard C.

2006-01-01

A software defined radio (SDR) architecture used in space-based platforms proposes to standardize certain aspects of radio development such as interface definitions, functional control and execution, and application software and firmware development. NASA has charted a team to develop an open software defined radio hardware and software architecture to support NASA missions and determine the viability of an Agency-wide Standard. A draft concept of the proposed standard has been released and discussed among organizations in the SDR community. Appropriate leveraging of the JTRS SCA, OMG's SWRadio Architecture and other aspects are considered. A standard radio architecture offers potential value by employing common waveform software instantiation, operation, testing and software maintenance. While software defined radios offer greater flexibility, they also poses challenges to the radio development for the space environment in terms of size, mass and power consumption and available technology. An SDR architecture for space must recognize and address the constraints of space flight hardware, and systems along with flight heritage and culture. NASA is actively participating in the development of technology and standards related to software defined radios. As NASA considers a standard radio architecture for space communications, input and coordination from government agencies, the industry, academia, and standards bodies is key to a successful architecture. The unique aspects of space require thorough investigation of relevant terrestrial technologies properly adapted to space. The talk will describe NASA s current effort to investigate SDR applications to space missions and a brief overview of a candidate architecture under consideration for space based platforms.

Atmospheric profiles from active space-based radio measurements

NASA Technical Reports Server (NTRS)

Hardy, Kenneth R.; Hinson, David P.; Tyler, G. L.; Kursinski, E. R.

1992-01-01

The paper describes determinations of atmospheric profiles from space-based radio measurements and the retrieval methodology used, with special attention given to the measurement procedure and the characteristics of the soundings. It is speculated that reliable profiles of the terrestrial atmosphere can be obtained by the occultation technique from the surface to a height of about 60 km. With the full complement of 21 the Global Positioning System (GPS) satellites and one GPS receiver in sun synchronous polar orbit, a maximum of 42 soundings could be obtained for each complete orbit or about 670 per day, providing almost uniform global coverage.

Person-Locator System Based On Wristband Radio Transponders

NASA Technical Reports Server (NTRS)

Mintz, Frederick W.; Blaes, Brent R.; Chandler, Charles W.

1995-01-01

Computerized system based on wristband radio frequency (RF), passive transponders is being developed for use in real-time tracking of individuals in custodial institutions like prisons and mental hospitals. Includes monitoring system that contains central computer connected to low-power, high-frequency central transceiver. Transceiver connected to miniature transceiver nodes mounted unobtrusively at known locations throughout the institution. Wristband transponders embedded in common hospital wristbands. Wristbands tamperproof: each contains embedded wire loop which, when broken or torn off and discarded, causes wristband to disappear from system, thus causing alarm. Individuals could be located in a timely fashion at relatively low cost.

A Radio-Frequency-over-Fiber link for large-array radio astronomy applications

NASA Astrophysics Data System (ADS)

Mena, J.; Bandura, K.; Cliche, J.-F.; Dobbs, M.; Gilbert, A.; Tang, Q. Y.

2013-10-01

A prototype 425-850 MHz Radio-Frequency-over-Fiber (RFoF) link for the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is presented. The design is based on a directly modulated Fabry-Perot (FP) laser, operating at ambient temperature, and a single-mode fiber. The dynamic performance, gain stability, and phase stability of the RFoF link are characterized. Tests on a two-element interferometer built at the Dominion Radio Astrophysical Observatory for CHIME prototyping demonstrate that RFoF can be successfully used as a cost-effective solution for analog signal transport on the CHIME telescope and other large-array radio astronomy applications.

Earth Science

NASA Image and Video Library

1996-01-31

The Near Earth Asteroid Rendezvous (NEAR) spacecraft embarks on a journey that will culminate in a close encounter with an asteroid. The launch of NEAR inaugurates NASA's irnovative Discovery program of small-scale planetary missions with rapid, lower-cost development cycles and focused science objectives. NEAR will rendezvous in 1999 with the asteroid 433 Eros to begin the first long-term, close-up look at an asteroid's surface composition and physical properties. NEAR's science payload includes an x-ray/gamma ray spectrometer, an near-infrared spectrograph, a laser rangefinder, a magnetometer, a radio science experiment and a multi-spectral imager.

Radio continuum properties of luminous infrared galaxies. Identifying the presence of an AGN in the radio

NASA Astrophysics Data System (ADS)

Vardoulaki, E.; Charmandaris, V.; Murphy, E. J.; Diaz-Santos, T.; Armus, L.; Evans, A. S.; Mazzarella, J. M.; Privon, G. C.; Stierwalt, S.; Barcos-Muñoz, L.

2015-02-01

Context. Luminous infrared galaxies (LIRGs) are systems enshrouded in dust, which absorbs most of their optical/UV emission and radiates it again in the mid- and far-infrared. Radio observations are largely unaffected by dust obscuration, enabling us to study the central regions of LIRGs in an unbiased manner. Aims: The main goal of this project is to examine how the radio properties of local LIRGs relate to their infrared spectral characteristics. Here we present an analysis of the radio continuum properties of a subset of the Great Observatories All-sky LIRG Survey (GOALS), which consists of 202 nearby systems (z< 0.088). Our radio sample consists of 35 systems, containing 46 individual galaxies, that were observed at both 1.49 and 8.44 GHz with the VLA with a resolution of about 1 arcsec (FWHM). The aim of the project is to use the radio imagery to probe the central kpc of these LIRGs in search of active galactic nuclei (AGN). Methods: We used the archival data at 1.49 and 8.44 GHz to create radio-spectral-index maps using the standard relation between flux density Sν and frequency ν, Sν ~ ν- α, where α is the radio spectral index. By studying the spatial variations in α, we classified the objects as radio-AGN, radio-SB, and AGN/SB (a mixture). We identified the presence of an active nucleus using the radio morphology, deviations from the radio/infrared correlation, and spatially resolved spectral index maps, and then correlated this to the usual mid-infrared ([NeV]/[NeII] and [OIV]/[NeII] line ratios and equivalent width of the 6.2 μm PAH feature) and optical (BPT diagram) AGN diagnostics. Results: We find that 21 out of the 46 objects in our sample (~45%) are radio-AGN, 9 out of the 46 (~20%) are classified as starbursts (SB) based on the radio analysis, and 16 (~35%) are AGN/SB. After comparing to other AGN diagnostics we find 3 objects out of the 46 (~7%) that are identified as AGN based on the radio analysis, but are not classified as such based on

Performance evaluation of multi-stratum resources optimization with network functions virtualization for cloud-based radio over optical fiber networks.

PubMed

Yang, Hui; He, Yongqi; Zhang, Jie; Ji, Yuefeng; Bai, Wei; Lee, Young

2016-04-18

Cloud radio access network (C-RAN) has become a promising scenario to accommodate high-performance services with ubiquitous user coverage and real-time cloud computing using cloud BBUs. In our previous work, we implemented cross stratum optimization of optical network and application stratums resources that allows to accommodate the services in optical networks. In view of this, this study extends to consider the multiple dimensional resources optimization of radio, optical and BBU processing in 5G age. We propose a novel multi-stratum resources optimization (MSRO) architecture with network functions virtualization for cloud-based radio over optical fiber networks (C-RoFN) using software defined control. A global evaluation scheme (GES) for MSRO in C-RoFN is introduced based on the proposed architecture. The MSRO can enhance the responsiveness to dynamic end-to-end user demands and globally optimize radio frequency, optical and BBU resources effectively to maximize radio coverage. The efficiency and feasibility of the proposed architecture are experimentally demonstrated on OpenFlow-based enhanced SDN testbed. The performance of GES under heavy traffic load scenario is also quantitatively evaluated based on MSRO architecture in terms of resource occupation rate and path provisioning latency, compared with other provisioning scheme.

Seismo-ionospheric Precursors of the Total Electron Content Associated with Global Large Earthquakes Examined by Using Ground-based and Space-based Radio Occultation GNSS Observations

NASA Astrophysics Data System (ADS)

Liu, J. Y. G.

2017-12-01

To verify seismo-ionospheric precursors (SIPs), statistical analyses are implemented on the relationship between the total electron content (TEC) in the global ionosphere map (GIM) derived from measurements of ground-based GNSS (global navigation satellite system) receivers and worldwide M≥7.0 earthquakes during 2000-2016. A median-based method is employed to determine the characteristic of TEC anomalies related to the earthquakes. It is found that the polarity of both negative (decrease) and positive (increase) in the GIM TEC, which varies location-by location, can be observed few days before the earthquakes. In general, PEIAs with the negative polarity associated with the earthquakes are more frequently detected. Meanwhile, FORMOSAT-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) or F3/C in was launched into a circular low-Earth orbit on 15 April 2006. Six F3/C microsatellites with 72-degree inclination angle and 30-degree separation in longitude orbit at 800 km altitude, and conduct the ionospheric radio occultation (RO) observations by receiving signals from GNSS satellites and globally observing about 2500 vertical electron density profiles per day. Both ground-based and space-based RO GNSS observations are used to three dimensionally study SIPs related to the 11 March 2011 M9.0 Tohoku earthquake.

Observation duration analysis for Earth surface features from a Moon-based platform

NASA Astrophysics Data System (ADS)

Ye, Hanlin; Guo, Huadong; Liu, Guang; Ren, Yuanzhen

2018-07-01

Earth System Science is a discipline that performs holistic and comprehensive research on various components of the Earth. One of a key issue for the Earth monitoring and observation is to enhance the observation duration, the time intervals during which the Earth surface features can be observed by sensors. In this work, we propose to utilise the Moon as an Earth observation platform. Thanks to the long distance between the Earth and the Moon, and the vast space on the lunar surface which is suitable for sensor installation, this Earth observation platform could have large spatial coverage, long temporal duration, and could perform multi-layer detection of the Earth. The line of sight between a proposed Moon-based platform and the Earth will change with different lunar surface positions; therefore, in this work, the position of the lunar surface was divided into four regions, including one full observation region and three incomplete observation regions. As existing methods are not able to perform global-scale observations, a Boolean matrix method was established to calculate the necessary observation durations from a Moon-based platform. Based on Jet Propulsion Laboratory (JPL) ephemerides and Earth Orientation Parameters (EOP), a formula was developed to describe the geometrical relationship between the Moon-based platform and Earth surface features in the unified spatial coordinate system and the unified time system. In addition, we compared the observation geometries at different positions on the lunar surface and two parameters that are vital to observation duration calculations were considered. Finally, an analysis method was developed. We found that the observation duration of a given Earth surface feature shows little difference regardless of sensor position within the full observation region. However, the observation duration for sensors in the incomplete observation regions is reduced by at least half. In summary, our results demonstrate the suitability

An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks

PubMed Central

Salim, Shelly; Moh, Sangman

2016-01-01

A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead. PMID:27376290

An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks.

PubMed

Salim, Shelly; Moh, Sangman

2016-06-30

A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead.

Radio frequency detection assembly and method for detecting radio frequencies

DOEpatents

Cown, Steven H.; Derr, Kurt Warren

2010-03-16

A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

Flexible and reversibly deformable radio-frequency antenna based on stretchable SWCNTs/PANI/Lycra conductive fabric

NASA Astrophysics Data System (ADS)

Guo, Xiaohui; Huang, Ying; Wu, Can; Mao, Leidong; Wang, Yue; Xie, Zhicheng; Liu, Caixia; Zhang, Yugang

2017-10-01

We demonstrated a flexible and reversibly deformable radio-frequency antenna based on SWCNTs/PANI/Lycra conductive fabric and semipermeable film for wireless wearable communications applications. The conductive fabric fabricated by using the ‘dip and dry’ process exhibits good flexibility, electrical stability, stretchability and mechanical properties, and a high electrical conductivity (with low sheet resistance of ˜35 Ω/sq) was obtained based on the SWCNTs/PANI synergistic conductive network. The morphology of the semipermeable film was investigated to further illustrate the waterproof breathable features. Meanwhile, the modeling, fabrication procedure and radiating properties of the radio-frequency textile antenna worked at 2.45 GHz were systematically illustrated. The measured reflection coefficient, VSWR and the -10 dB bandwidth is ˜-18.6 dB, 1.58 and ˜270 MHz respectively, which agreed well with the simulation results. Furthermore, the results indicate that the design methodology for the radio-frequency textile antenna could have promising applications in flexible and reversibly deformable antennas for wearable wireless communications systems.

Space-based infrared near-Earth asteroid survey simulation

NASA Astrophysics Data System (ADS)

Tedesco, Edward F.; Muinonen, Karri; Price, Stephan D.

2000-08-01

We demonstrate the efficiency and effectiveness of using a satellite-based sensor with visual and infrared focal plane arrays to search for that subclass of Near-Earth Objects (NEOs) with orbits largely interior to the Earth's orbit. A space-based visual-infrared system could detect approximately 97% of the Atens and 64% of the IEOs (the, as yet hypothetical, objects with orbits entirely Interior to Earth's Orbit) with diameters greater than 1 km in a 5-year mission and obtain orbits, albedos and diameters for all of them; the respective percentages with diameters greater than 500 m are 90% and 60%. Incidental to the search for Atens and IEOs, we found that 70% of all Earth-Crossing Asteroids (ECAs) with diameters greater than 1 km, and 50% of those with diameters greater than 500 m, would also be detected. These are the results of a feasibility study; optimizing the concept presented would result in greater levels of completion. The cost of such a space-based system is estimated to be within a factor of two of the cost of a ground-based system capable of about 21st magnitude, which would provide only orbits and absolute magnitudes and require decades to reach these completeness levels. In addition to obtaining albedos and diameters for the asteroids discovered in the space-based survey, a space-based visual-infrared system would obtain the same information on virtually all NEOs of interest. A combined space-based and ground-based survey would be highly synergistic in that each can concentrate on what it does best and each complements the strengths of the other. The ground-based system would discover the majority of Amors and Apollos and provide long-term follow-up on all the NEOs discovered in both surveys. The space-based system would discover the majority of Atens and IEOs and provide albedos and diameters on all the NEOs discovered in both surveys and most previously discovered NEOs as well. Thus, an integrated ground- and space-based system could accomplish

49 CFR 220.23 - Publication of radio information.

Code of Federal Regulations, 2013 CFR

2013-10-01

... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD COMMUNICATIONS Radio and Wireless Communication Procedures § 220.23 Publication of radio information. Each railroad shall designate where radio base stations are... 49 Transportation 4 2013-10-01 2013-10-01 false Publication of radio information. 220.23 Section...

49 CFR 220.23 - Publication of radio information.

Code of Federal Regulations, 2014 CFR

2014-10-01

... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD COMMUNICATIONS Radio and Wireless Communication Procedures § 220.23 Publication of radio information. Each railroad shall designate where radio base stations are... 49 Transportation 4 2014-10-01 2014-10-01 false Publication of radio information. 220.23 Section...

Affirmation of triggered Jovian radio emissions and their attribution to corotating radio lasers

NASA Technical Reports Server (NTRS)

Calvert, W.

1985-01-01

It is argued that the original statistical evidence for the existence of triggered radio emissions and corotating radio lasers on Jupiter remains valid notwithstanding the critique of Desch and Kaiser (1985). The Voyager radio spectrograms used to identify the triggered emissions are analyzed and the results are discussed. It is shown that the critique by Desch and Kaiser is unjustified because it is not based on the original event criteria, i.e., the correlation between the occurrence of Jovian auroral kilometric radiation and fast-drift type III solar bursts in the same frequency.

IA-Regional-Radio - Social Network for Radio Recommendation

NASA Astrophysics Data System (ADS)

Dziczkowski, Grzegorz; Bougueroua, Lamine; Wegrzyn-Wolska, Katarzyna

This chapter describes the functions of a system proposed for the music hit recommendation from social network data base. This system carries out the automatic collection, evaluation and rating of music reviewers and the possibility for listeners to rate musical hits and recommendations deduced from auditor's profiles in the form of regional Internet radio. First, the system searches and retrieves probable music reviews from the Internet. Subsequently, the system carries out an evaluation and rating of those reviews. From this list of music hits, the system directly allows notation from our application. Finally, the system automatically creates the record list diffused each day depending on the region, the year season, the day hours and the age of listeners. Our system uses linguistics and statistic methods for classifying music opinions and data mining techniques for recommendation part needed for recorded list creation. The principal task is the creation of popular intelligent radio adaptive on auditor's age and region - IA-Regional-Radio.

Information Content in Radio Waves: Student Investigations in Radio Science

NASA Astrophysics Data System (ADS)

Jacobs, K.; Scaduto, T.

2013-12-01

We describe an inquiry-based instructional unit on information content in radio waves, created in the summer of 2013 as part of a MIT Haystack Observatory (Westford, MA) NSF Research Experiences for Teachers (RET) program. This topic is current and highly relevant, addressing science and technical aspects from radio astronomy, geodesy, and atmospheric research areas as well as Next Generation Science Standards (NGSS). Projects and activities range from simple classroom demonstrations and group investigations, to long term research projects incorporating data acquisition from both student-built instrumentation as well as online databases. Each of the core lessons is applied to one of the primary research centers at Haystack through an inquiry project that builds on previously developed units through the MIT Haystack RET program. In radio astronomy, students investigate the application of a simple and inexpensive software defined radio chip (RTL-SDR) for use in systems implementing a small and very small radio telescope (SRT and VSRT). Both of these systems allow students to explore fundamental principles of radio waves and interferometry as applied to radio astronomy. In ionospheric research, students track solar storms from the initial coronal mass ejection (using Solar Dynamics Observatory images) to the resulting variability in total electron density concentrations using data from the community standard Madrigal distributed database system maintained by MIT Haystack. Finally, students get to explore very long-baseline interferometry as it is used in geodetic studies by measuring crustal plate displacements over time. Alignment to NextGen standards is provided for each lesson and activity with emphasis on HS-PS4 'Waves and Their Applications in Technologies for Information Transfer'.

Radio frequency spectrum management

NASA Astrophysics Data System (ADS)

Sujdak, E. J., Jr.

1980-03-01

This thesis is a study of radio frequency spectrum management as practiced by agencies and departments of the Federal Government. After a brief introduction to the international agency involved in radio frequency spectrum management, the author concentrates on Federal agencies engaged in frequency management. These agencies include the National Telecommunications and Information Administration (NTIA), the Interdepartment Radio Advisory Committee (IRAC), and the Department of Defense (DoD). Based on an analysis of Department of Defense frequency assignment procedures, recommendations are given concerning decentralizing military frequency assignment by delegating broader authority to unified commanders. This proposal includes a recommendation to colocate the individual Service frequency management offices at the Washington level. This would result in reduced travel costs, lower manpower requirements, and a common tri-Service frequency management data base.

Amateur Radio On The International Space Station (ARISS) - The First Educational Outreach Program On ISS

NASA Technical Reports Server (NTRS)

Conley, Carolynn Lee; Bauer, Frank H.; Brown, Deborah A.; White, Rosalie

2002-01-01

Amateur Radio on the International Space Station (ARISS) represents the first educational outreach program that is flying on the International Space Station (ISS). The astronauts and cosmonauts will work hard on the International Space Station, but they plan to take some time off for educational activities with schools. The National Aeronautics and Space Administration s (NASA s) Education Division is a major supporter and sponsor of this student outreach activity on the ISS. This meets NASA s educational mission objective: To inspire the next generation of explorers.. .as only NASA can. The amateur radio community is helping to enrich the experience of those visiting and living on the station as well as the students on Earth. Through ARISS sponsored hardware and activities, students on Earth get a first-hand feel of what it is like to live and work in space. This paper will discuss the educational outreach accomplishments of ARISS, the school contact process, the ARISS international cooperation and volunteers, and ISS Ham radio plans for the future.

Reconfigurable radio receiver with fractional sample rate converter and multi-rate ADC based on LO-derived sampling clock

NASA Astrophysics Data System (ADS)

Park, Sungkyung; Park, Chester Sungchung

2018-03-01

A composite radio receiver back-end and digital front-end, made up of a delta-sigma analogue-to-digital converter (ADC) with a high-speed low-noise sampling clock generator, and a fractional sample rate converter (FSRC), is proposed and designed for a multi-mode reconfigurable radio. The proposed radio receiver architecture contributes to saving the chip area and thus lowering the design cost. To enable inter-radio access technology handover and ultimately software-defined radio reception, a reconfigurable radio receiver consisting of a multi-rate ADC with its sampling clock derived from a local oscillator, followed by a rate-adjustable FSRC for decimation, is designed. Clock phase noise and timing jitter are examined to support the effectiveness of the proposed radio receiver. A FSRC is modelled and simulated with a cubic polynomial interpolator based on Lagrange method, and its spectral-domain view is examined in order to verify its effect on aliasing, nonlinearity and signal-to-noise ratio, giving insight into the design of the decimation chain. The sampling clock path and the radio receiver back-end data path are designed in a 90-nm CMOS process technology with 1.2V supply.

Powerful Radio Burst Indicates New Astronomical Phenomenon

NASA Astrophysics Data System (ADS)

2007-09-01

Astronomers studying archival data from an Australian radio telescope have discovered a powerful, short-lived burst of radio waves that they say indicates an entirely new type of astronomical phenomenon. Region of Strong Radio Burst Visible-light (negative greyscale) and radio (contours) image of Small Magellanic Cloud and area where burst originated. CREDIT: Lorimer et al., NRAO/AUI/NSF Click on image for high-resolution file ( 114 KB) "This burst appears to have originated from the distant Universe and may have been produced by an exotic event such as the collision of two neutron stars or the death throes of an evaporating black hole," said Duncan Lorimer, Assistant Professor of Physics at West Virginia University (WVU) and the National Radio Astronomy Observatory (NRAO). The research team led by Lorimer consists of Matthew Bailes of Swinburne University in Australia, Maura McLaughlin of WVU and NRAO, David Narkevic of WVU, and Fronefield Crawford of Franklin and Marshall College in Lancaster, Pennsylvania. The astronomers announced their findings in the September 27 issue of the online journal Science Express. The startling discovery came as WVU undergraduate student David Narkevic re-analyzed data from observations of the Small Magellanic Cloud made by the 210-foot Parkes radio telescope in Australia. The data came from a survey of the Magellanic Clouds that included 480 hours of observations. "This survey had sought to discover new pulsars, and the data already had been searched for the type of pulsating signals they produce," Lorimer said. "We re-examined the data, looking for bursts that, unlike the usual ones from pulsars, are not periodic," he added. The survey had covered the Magellanic Clouds, a pair of small galaxies in orbit around our own Milky Way Galaxy. Some 200,000 light-years from Earth, the Magellanic Clouds are prominent features in the Southern sky. Ironically, the new discovery is not part of these galaxies, but rather is much more distant

RF Spectrum Sensing Based on an Overdamped Nonlinear Oscillator Ring for Cognitive Radios

PubMed Central

Tang, Zhi-Ling; Li, Si-Min; Yu, Li-Juan

2016-01-01

Existing spectrum-sensing techniques for cognitive radios require an analog-to-digital converter (ADC) to work at high dynamic range and a high sampling rate, resulting in high cost. Therefore, in this paper, a spectrum-sensing method based on a unidirectionally coupled, overdamped nonlinear oscillator ring is proposed. First, the numerical model of such a system is established based on the circuit of the nonlinear oscillator. Through numerical analysis of the model, the critical condition of the system’s starting oscillation is determined, and the simulation results of the system’s response to Gaussian white noise and periodic signal are presented. The results show that once the radio signal is input into the system, it starts oscillating when in the critical region, and the oscillating frequency of each element is fo/N, where fo is the frequency of the radio signal and N is the number of elements in the ring. The oscillation indicates that the spectrum resources at fo are occupied. At the same time, the sampling rate required for an ADC is reduced to the original value, 1/N. A prototypical circuit to verify the functionality of the system is designed, and the sensing bandwidth of the system is measured. PMID:27294928

RF Spectrum Sensing Based on an Overdamped Nonlinear Oscillator Ring for Cognitive Radios.

PubMed

Tang, Zhi-Ling; Li, Si-Min; Yu, Li-Juan

2016-06-09

Existing spectrum-sensing techniques for cognitive radios require an analog-to-digital converter (ADC) to work at high dynamic range and a high sampling rate, resulting in high cost. Therefore, in this paper, a spectrum-sensing method based on a unidirectionally coupled, overdamped nonlinear oscillator ring is proposed. First, the numerical model of such a system is established based on the circuit of the nonlinear oscillator. Through numerical analysis of the model, the critical condition of the system's starting oscillation is determined, and the simulation results of the system's response to Gaussian white noise and periodic signal are presented. The results show that once the radio signal is input into the system, it starts oscillating when in the critical region, and the oscillating frequency of each element is fo/N, where fo is the frequency of the radio signal and N is the number of elements in the ring. The oscillation indicates that the spectrum resources at fo are occupied. At the same time, the sampling rate required for an ADC is reduced to the original value, 1/N. A prototypical circuit to verify the functionality of the system is designed, and the sensing bandwidth of the system is measured.

Cluster based architecture and network maintenance protocol for medical priority aware cognitive radio based hospital.

PubMed

Al Mamoon, Ishtiak; Muzahidul Islam, A K M; Baharun, Sabariah; Ahmed, Ashir; Komaki, Shozo

2016-08-01

Due to the rapid growth of wireless medical devices in near future, wireless healthcare services may face some inescapable issue such as medical spectrum scarcity, electromagnetic interference (EMI), bandwidth constraint, security and finally medical data communication model. To mitigate these issues, cognitive radio (CR) or opportunistic radio network enabled wireless technology is suitable for the upcoming wireless healthcare system. The up-to-date research on CR based healthcare has exposed some developments on EMI and spectrum problems. However, the investigation recommendation on system design and network model for CR enabled hospital is rare. Thus, this research designs a hierarchy based hybrid network architecture and network maintenance protocols for previously proposed CR hospital system, known as CogMed. In the previous study, the detail architecture of CogMed and its maintenance protocols were not present. The proposed architecture includes clustering concepts for cognitive base stations and non-medical devices. Two cluster head (CH selector equations are formulated based on priority of location, device, mobility rate of devices and number of accessible channels. In order to maintain the integrity of the proposed network model, node joining and node leaving protocols are also proposed. Finally, the simulation results show that the proposed network maintenance time is very low for emergency medical devices (average maintenance period 9.5 ms) and the re-clustering effects for different mobility enabled non-medical devices are also balanced.

Space-Based Reconfigurable Software Defined Radio Test Bed Aboard International Space Station

NASA Technical Reports Server (NTRS)

Reinhart, Richard C.; Lux, James P.

2014-01-01

The National Aeronautical and Space Administration (NASA) recently launched a new software defined radio research test bed to the International Space Station. The test bed, sponsored by the Space Communications and Navigation (SCaN) Office within NASA is referred to as the SCaN Testbed. The SCaN Testbed is a highly capable communications system, composed of three software defined radios, integrated into a flight system, and mounted to the truss of the International Space Station. Software defined radios offer the future promise of in-flight reconfigurability, autonomy, and eventually cognitive operation. The adoption of software defined radios offers space missions a new way to develop and operate space transceivers for communications and navigation. Reconfigurable or software defined radios with communications and navigation functions implemented in software or VHDL (Very High Speed Hardware Description Language) provide the capability to change the functionality of the radio during development or after launch. The ability to change the operating characteristics of a radio through software once deployed to space offers the flexibility to adapt to new science opportunities, recover from anomalies within the science payload or communication system, and potentially reduce development cost and risk by adapting generic space platforms to meet specific mission requirements. The software defined radios on the SCaN Testbed are each compliant to NASA's Space Telecommunications Radio System (STRS) Architecture. The STRS Architecture is an open, non-proprietary architecture that defines interfaces for the connections between radio components. It provides an operating environment to abstract the communication waveform application from the underlying platform specific hardware such as digital-to-analog converters, analog-to-digital converters, oscillators, RF attenuators, automatic gain control circuits, FPGAs, general-purpose processors, etc. and the interconnections among

GPU-Based High-performance Imaging for Mingantu Spectral RadioHeliograph

NASA Astrophysics Data System (ADS)

Mei, Ying; Wang, Feng; Wang, Wei; Chen, Linjie; Liu, Yingbo; Deng, Hui; Dai, Wei; Liu, Cuiyin; Yan, Yihua

2018-01-01

As a dedicated solar radio interferometer, the MingantU SpEctral RadioHeliograph (MUSER) generates massive observational data in the frequency range of 400 MHz-15 GHz. High-performance imaging forms a significantly important aspect of MUSER’s massive data processing requirements. In this study, we implement a practical high-performance imaging pipeline for MUSER data processing. At first, the specifications of the MUSER are introduced and its imaging requirements are analyzed. Referring to the most commonly used radio astronomy software such as CASA and MIRIAD, we then implement a high-performance imaging pipeline based on the Graphics Processing Unit technology with respect to the current operational status of the MUSER. A series of critical algorithms and their pseudo codes, i.e., detection of the solar disk and sky brightness, automatic centering of the solar disk and estimation of the number of iterations for clean algorithms, are proposed in detail. The preliminary experimental results indicate that the proposed imaging approach significantly increases the processing performance of MUSER and generates images with high-quality, which can meet the requirements of the MUSER data processing. Supported by the National Key Research and Development Program of China (2016YFE0100300), the Joint Research Fund in Astronomy (No. U1531132, U1631129, U1231205) under cooperative agreement between the National Natural Science Foundation of China (NSFC) and the Chinese Academy of Sciences (CAS), the National Natural Science Foundation of China (Nos. 11403009 and 11463003).

The Radio JOVE Project - Shoestring Radio Astronomy

NASA Technical Reports Server (NTRS)

Thieman, J.; Flagg, R.; Greenman, W.; Higgins, C.; Reyes, F.; Sky, J.

2010-01-01

Radio JOVE is an education and outreach project intended to give students and other interested individuals hands-on experience in learning radio astronomy. They can do this through building a radio telescope from a relatively inexpensive kit that includes the parts for a receiver and an antenna as well as software for a computer chart recorder emulator (Radio Skypipe) and other reference materials

Amplitude variations of ELF radio waves in the Earth-ionosphere cavity with the day-night non-uniformity

NASA Astrophysics Data System (ADS)

Galuk, Yu P.; Nickolaenko, A. P.; Hayakawa, M.

2018-04-01

The real structure of lower ionosphere should be taken into account when modeling the sub-ionospheric radio propagation in the extremely low frequency (ELF) band and studying the global electromagnetic (Schumann) resonance of the Earth-ionosphere cavity. In the present work we use the 2D (two dimensional) telegraph equations (2DTE) for evaluating the effect of the ionosphere day-night non-uniformity on the electromagnetic field amplitude at the Schumann resonance and higher frequencies. Properties of the cavity upper boundary were taken into account by the full wave solution technique for realistic vertical profiles of atmosphere conductivity in the ambient day and ambient night conditions. We solved the electromagnetic problem in a cavity with the day-night non-uniformity by using the 2DTE technique. Initially, the testing of the 2DTE solution was performed in the model of the sharp day-night interface. The further computations were carried out in the model of the smooth day-night transition. The major attention was directed to the effects at propagation paths "perpendicular" or "parallel" to the solar terminator line. Data were computed for a series of frequencies, the comparison of the results was made and interpretation was given to the observed effects.

47 CFR 80.1087 - Ship radio equipment-Sea area A1.

Code of Federal Regulations, 2013 CFR

2013-10-01

... an INMARSAT ship earth station capable of two way communication. (b) The VHF radio installation... which the ship is normally navigated, operating either: (1) On VHF using DSC; or (2) Through the polar... voyages within coverage of MF coast stations equipped with DSC; or (4) On HF using DSC; or (5) Through the...

47 CFR 80.1087 - Ship radio equipment-Sea area A1.

Code of Federal Regulations, 2014 CFR

2014-10-01

... an INMARSAT ship earth station capable of two way communication. (b) The VHF radio installation... which the ship is normally navigated, operating either: (1) On VHF using DSC; or (2) Through the polar... voyages within coverage of MF coast stations equipped with DSC; or (4) On HF using DSC; or (5) Through the...

47 CFR 80.1087 - Ship radio equipment-Sea area A1.

Code of Federal Regulations, 2012 CFR

2012-10-01

... an INMARSAT ship earth station capable of two way communication. (b) The VHF radio installation... which the ship is normally navigated, operating either: (1) On VHF using DSC; or (2) Through the polar... voyages within coverage of MF coast stations equipped with DSC; or (4) On HF using DSC; or (5) Through the...

Radio Frequency Identification (RFID) Based Corrosion Monitoring Sensors. Part 2: Application and Testing of the Coating Materials

DTIC Science & Technology

2014-12-22

Radio frequency identification ( RFID ) based corrosion monitoring sensors: Part II Application and testing of the coating materials Youliang He1...email: yohe@nrcan.gc.ca Keywords: Corrosion monitoring; Wireless sensor; RFID ; Electromagnetic interference; Coating. Abstract Cost-effective...Radio Frequency Identification ( RFID ) transponders (tags) were investigated for wireless corrosion monitoring by applying a metal-filled conductive

Space Weather Action Plan Solar Radio Burst Phase 1 Benchmarks and the Steps to Phase 2

NASA Astrophysics Data System (ADS)

Biesecker, D. A.; White, S. M.; Gopalswamy, N.; Black, C.; Love, J. J.; Pierson, J.

2017-12-01

Solar radio bursts, when at the right frequency and when strong enough, can interfere with radar, communication, and tracking signals. In severe cases, radio bursts can inhibit the successful use of radio communications and disrupt a wide range of systems that are reliant on Position, Navigation, and Timing services on timescales ranging from minutes to hours across wide areas on the dayside of Earth. The White House's Space Weather Action Plan asked for solar radio burst intensity benchmarks for an event occurrence frequency of 1 in 100 years and also a theoretical maximum intensity benchmark. The benchmark team has developed preliminary (phase 1) benchmarks for the VHF (30-300 MHz), UHF (300-3000 MHz), GPS (1176-1602 MHz), F10.7 (2800 MHz), and Microwave (4000-20000) bands. The preliminary benchmarks were derived based on previously published work. Limitations in the published work will be addressed in phase 2 of the benchmark process. In addition, deriving theoretical maxima requires additional work, where it is even possible to, in order to meet the Action Plan objectives. In this presentation, we will present the phase 1 benchmarks, the basis used to derive them, and the limitations of that work. We will also discuss the work that needs to be done to complete the phase 2 benchmarks.

Earthquake!: An Event-Based Science Module. Teacher's Guide. Earth Science Module.

ERIC Educational Resources Information Center

Wright, Russell G.

This book is designed for middle school earth science teachers to help their students learn about earthquakes and scientific literacy through event-based science. Unlike traditional curricula, the event- based earth science module is a student-centered, interdisciplinary, inquiry-oriented program that emphasizes cooperative learning, teamwork,…

Design of fast earth-return trajectories from a lunar base

NASA Astrophysics Data System (ADS)

Anhorn, Walter

1991-09-01

The Apollo Lunar Program utilized efficient transearth trajectories which employed parking orbits in order to minimize energy requirements. This thesis concentrates on a different type of transearth trajectory. These are direct-ascent, hyperbolic trajectories which omit the parking orbits in order to achieve short flight times to and from a future lunar base. The object of the thesis is the development of a three-dimensional transearth trajectory model and associated computer program for exploring trade-offs between flight-time and energy, given various mission constraints. The program also targets the Moon with a hyperbolic trajectory, which can be used for targeting Earth impact points. The first-order model is based on an Earth-centered conic and a massless spherical Moon, using MathCAD version 3.0. This model is intended as the basis for future patched-conic formulations for the design of fast Earth-return trajectories. Applications include placing nuclear deterrent arsenals on the Moon, various space support related activities, and finally protection against Earth-threatening asteroids and comets using lunar bases.

RFI and Remote Sensing of the Earth from Space

NASA Technical Reports Server (NTRS)

Le Vine, D. M.; Johnson, J. T.; Piepmeier, J.

2016-01-01

Passive microwave remote sensing of the Earth from space provides information essential for understanding the Earth's environment and its evolution. Parameters such as soil moisture, sea surface temperature and salinity, and profiles of atmospheric temperature and humidity are measured at frequencies determined by the physics (e.g. sensitivity to changes in desired parameters) and by the availability of suitable spectrum free from interference. Interference from manmade sources (radio frequency interference) is an impediment that in many cases limits the potential for accurate measurements from space. A review is presented here of the frequencies employed in passive microwave remote sensing of the Earth from space and the associated experience with RFI.

Radio Wave Propagation Handbook for Communication on and Around Mars

NASA Technical Reports Server (NTRS)

Ho, Christian; Golshan, Nasser; Kliore, Arvydas

2002-01-01

This handbook examines the effects of the Martian environment on radio wave propagation on Mars and in the space near the planet. The environmental effects include these from the Martian atmosphere, ionosphere, global dust storms, aerosols, clouds, and geomorphologic features. Relevant Martian environmental parameters were extracted from the measurements of Mars missions during the past 30 years, especially from Mars Pathfinder and Mars Global Surveyor. The results derived from measurements and analyses have been reviewed through an extensive literature search. The updated parameters have been theoretically analyzed to study their effects on radio propagation. This handbook also provides basic information about the entire telecommunications environment on and around Mars for propagation researchers, system engineers, and link analysts. Based on these original analyses, some important recommendations have been made, including the use of the Martian ionosphere as a reflector for Mars global or trans-horizon communication between future Martian colonies, reducing dust storm scattering effects, etc. These results have extended our wave propagation knowledge to a planet other than Earth; and the tables, models, and graphics included in this handbook will benefit telecommunication system engineers and scientific researchers.

Amateur Radio Communications with a Deep Space Probe (Yes, It's Possible)

NASA Astrophysics Data System (ADS)

Cudnik, Brian; Rahman, Mahmudur; Saganti, Seth; Erickson, Gary M.; Saganti, Premkumar

2015-05-01

Prairie View A&M University through the collaboration with NASA-Johnson Space Center has partnered with the Kyushu Institute of Technology (KIT), Japan and developed a payload for the Shinen-2 spacecraft that was launched from Japan on December 3, 2014 as part of the Hayabusa2 mission. The main purpose of the Shinen-2 spacecraft is deep space communication experiment to test the feasibility of deep-space radio communications from the spacecraft to Earth without the need of the Deep Space Network (DSN) of NASA. This presents an opportunity to the wider community of amateur astronomers, ham radio operators, and other research personnel in that they will have the opportunity to work with deep space communication such as Shinen-2 spacecraft. It should be possible to detect a signal as an increased strength from Shinen-2 spacecraft at a rest frequency of 437.385 MHz, using commercially available equipment procured at low-cost, when the spacecraft approaches to within 3,000,000 km of the Earth during December 2015.

Observations of Heliospheric Faraday Rotation (FR) and Interplanetary Scintillation (IPS): Steps Towards Investigating Bz Propagation Between the Sun and the Earth

NASA Astrophysics Data System (ADS)

Bisi, Mario M.; Fallows, Richard A.; Sobey, Charlotte; Eftekhari, Tarraneh; Jensen, Elizabeth A.; Jackson, Bernard V.; Yu, Hsiu-Shan; Hick, P. Paul; Odstrcil, Dusan; Tokumaru, Munetoshi; Oyuki Chang, M. T.

2016-04-01

Space weather - analogous to terrestrial weather (describing the changing pressure, temperature, wind, and humidity conditions on Earth) - is essentially a description of the changes in velocity, density, magnetic field, high-energy particles, and radiation in the near-Earth space environment including the effects of such on the Earth. Space weather can be considered to have two main strands: (i) scientific research, and (ii) applications. The former is self-explanatory, but the latter covers operational aspects including forecasting. Understanding and forecasting space weather near the Earth is of critical importance to protecting our modern-day reliance on satellites, global-communications and navigation networks, high-altitude air travel (radiation concerns particularly on polar routes), long-distance power/oil/gas lines and piping, and for any future human exploration of space to list but a few. This includes both military and commercial considerations. Two ground-based radio-observing techniques that can add to and lead our understanding and forecasting of heliospheric space weather are those of interplanetary scintillation (IPS) and heliospheric Faraday rotation (FR). We present our latest progress using these two radio heliospheric-imaging remote-sensing techniques including the use of three-dimensional (3-D) modelling and reconstruction techniques using other, additional data as input to support and better-interpret individual case-study results.

BioRadioTransmitter: a self-powered wireless glucose-sensing system.

PubMed

Hanashi, Takuya; Yamazaki, Tomohiko; Tsugawa, Wakako; Ikebukuro, Kazunori; Sode, Koji

2011-09-01

Although an enzyme fuel cell can be utilized as a glucose sensor, the output power generated is too low to power a device such as a currently available transmitter and operating system, and an external power source is required for operating an enzyme-fuel-cell-based biosensing system. We proposed a novel biosensor that we named BioCapacitor, in which a capacitor serves as a transducer. In this study, we constructed a new BioCapacitor-based system with an added radio-transmitter circuit and a miniaturized enzyme fuel cell. A miniaturized direct-electron-transfer-type compartmentless enzyme fuel cell was constructed with flavin adenine dinucleotide-dependent glucose dehydrogenase complex-based anode and a bilirubin-oxidase-based cathode. For construction of a BioRadioTransmitter wireless sensing system, a capacitor, an ultra-low-voltage charge-pump-integrated circuit, and Hartley oscillator circuit were connected to the miniaturized enzyme fuel cell. A radio-receiver circuit, comprising two field-effect transistors and a coil as an antenna, was used to amplify the signal generated from the biofuel cells. Radio wave signals generated by the BioRadioTransmitter were received, amplified, and converted from alternate to direct current by the radio receiver. When the capacitor discharges in the presence of glucose, the BioRadioTransmitter generates a radio wave, which is monitored by a radio receiver connected wirelessly to the sensing device. Magnitude of the radio wave transmission frequency change observed at the radio receiver was correlated to glucose concentration in the fuel cells. We constructed a stand-alone, self-powered, wireless glucose-sensing system called a BioRadioTransmitter by using a radio transmitter in which the radio wave transmission frequency changes with the glucose concentration in the fuel cell. The BioRadioTransmitter is a significant advance toward construction of an implantable continuous glucose monitor. © 2011 Diabetes Technology Society.

Reflective electroabsorption modular for compact base station radio-over-fiber systems

NASA Astrophysics Data System (ADS)

Wu, Yang; Chang, Wei-Xi; Yu, Paul K. L.

2003-07-01

A Radio-over-Fiber system with simplified Base Station (BS) is proposed in which a single chip DBR Reflective Electro-absorption Modulator (REAM) serves both as an optical transceiver and as a mixer at the BS. It enables full duplex optical transmission for base band and RF band services simultaneously due to good isolation between uplink and downlink at the same chip. Grating structure is incorporated into the EA modulator for the sake of system design. It also improves yield and efficiency of high-speed devices.

Interference Information Based Power Control for Cognitive Radio with Multi-Hop Cooperative Sensing

NASA Astrophysics Data System (ADS)

Yu, Youngjin; Murata, Hidekazu; Yamamoto, Koji; Yoshida, Susumu

Reliable detection of other radio systems is crucial for systems that share the same frequency band. In wireless communication channels, there is uncertainty in the received signal level due to multipath fading and shadowing. Cooperative sensing techniques in which radio stations share their sensing information can improve the detection probability of other systems. In this paper, a new cooperative sensing scheme that reduces the false detection probability while maintaining the outage probability of other systems is investigated. In the proposed system, sensing information is collected using multi-hop transmission from all sensing stations that detect other systems, and transmission decisions are based on the received sensing information. The proposed system also controls the transmit power based on the received CINRs from the sensing stations. Simulation results reveal that the proposed system can reduce the outage probability of other systems, or improve its link success probability.

Process for preparing higher oxides of the alkali and alkaline earth metals

NASA Technical Reports Server (NTRS)

Sadhukhan, P.; Bell, A. (Inventor)

1978-01-01

High purity inorganic higher oxides of the alkali and alkaline earth metals are prepared by subjecting the hydroxide of the alkali and alkaline earth metal to a radio frequency discharge sustained in oxygen. The process is particulary adaptable to the production of high purity potassium superoxide by subjecting potassium hydroxide to glow discharge sustained in oxygen under the pressure of about 0.75 to 1.00 torr.

Amateur radio communications in a disaster preparedness simulation When all else fails . . . amateur radio.

PubMed

McCamey, Randy; Yeager, Jennifer

During natural disasters, communications can be disrupted, which negatively impacts response time of first responders thus diminishing the level of care provided to disaster victims. In the fall of 2014, as part of a larger community-based participatory research study, the Tarleton Area Amateur Radio Club (TAARC) joined the Department of Nursing, Tarleton State University, and provided amateur radio communications during a disaster preparedness simulation. The simulation was conducted to determine the ability of the university to provide rapid response and render quality, acute healthcare to its neighbors during a natural disaster. The primary goals of the TAARC were to assess the ability to quickly establish radio communications, accurately relay messages, and establish rapport and affiliation between each facility commander and the amateur radio operators. It was determined that communication was key to provide quality care, and the inclusion of amateur radio operators in the simulation helped ensure rapid response times and rapid transport of critical victims.

Software-defined Radio Based Measurement Platform for Wireless Networks

PubMed Central

Chao, I-Chun; Lee, Kang B.; Candell, Richard; Proctor, Frederick; Shen, Chien-Chung; Lin, Shinn-Yan

2015-01-01

End-to-end latency is critical to many distributed applications and services that are based on computer networks. There has been a dramatic push to adopt wireless networking technologies and protocols (such as WiFi, ZigBee, WirelessHART, Bluetooth, ISA100.11a, etc.) into time-critical applications. Examples of such applications include industrial automation, telecommunications, power utility, and financial services. While performance measurement of wired networks has been extensively studied, measuring and quantifying the performance of wireless networks face new challenges and demand different approaches and techniques. In this paper, we describe the design of a measurement platform based on the technologies of software-defined radio (SDR) and IEEE 1588 Precision Time Protocol (PTP) for evaluating the performance of wireless networks. PMID:27891210

Software-defined Radio Based Measurement Platform for Wireless Networks.

PubMed

Chao, I-Chun; Lee, Kang B; Candell, Richard; Proctor, Frederick; Shen, Chien-Chung; Lin, Shinn-Yan

2015-10-01

End-to-end latency is critical to many distributed applications and services that are based on computer networks. There has been a dramatic push to adopt wireless networking technologies and protocols (such as WiFi, ZigBee, WirelessHART, Bluetooth, ISA100.11a, etc. ) into time-critical applications. Examples of such applications include industrial automation, telecommunications, power utility, and financial services. While performance measurement of wired networks has been extensively studied, measuring and quantifying the performance of wireless networks face new challenges and demand different approaches and techniques. In this paper, we describe the design of a measurement platform based on the technologies of software-defined radio (SDR) and IEEE 1588 Precision Time Protocol (PTP) for evaluating the performance of wireless networks.

The Early Development of Indian Radio Astronomy: A Personal Perspective

NASA Astrophysics Data System (ADS)

Swarup, Govind

In this chapter I recall my initiation into the field of radio astronomy during 1953-1955 at CSIRO, Australia; the transfer of thirty-two 6-feet (1.8-m) diameter parabolic dishes from Potts Hill, Sydney, to India in 1958; and their erection at Kalyan, near Bombay (Mumbai), in 1963-1965. The Kalyan Radio Telescope was the first modern radio telescope built in India. This led to the establishment of a very active radio astronomy group at the Tata Institute of Fundamental Research, which subsequently built two world-class radio telescopes during the last 50 years and also contributed to the development of an indigenous microwave antenna industry in India. The Ooty Radio Telescope, built during 1965-1970, has an ingenious design which takes advantage of India's location near the Earth's Equator. The long axis of this 530-m × 30-m parabolic cylinder was made parallel to the Equator, by placing it on a hill with the same slope as the geographic latitude ( 11°), thus allowing it to track celestial sources continuously for 9.5 h every day. By utilizing lunar occultations, the telescope was able to measure the angular sizes of a large number of faint radio galaxies and quasars with arc-second resolution for the first time. Subsequently, during the 1990s, the group set up the Giant Metrewave Radio Telescope (GMRT) near Pune in western India, in order to investigate certain astrophysical phenomena which are best studied at decimetre and metre wavelengths. The GMRT is an array of 30 fully steerable 45-m diameter parabolic dishes, which operates at several frequencies below 1.43 GHz. These efforts have also contributed to the international proposal to construct the Square Kilometre Array (SKA). This chapter is a revised version of Swarup (Journal of Astronomical History and Heritage, 9: 21-33, 2006).

Programmable Ultra-Lightweight System Adaptable Radio

NASA Technical Reports Server (NTRS)

Werkheiser, Arthur

2015-01-01

The programmable ultra-lightweight system adaptable radio (PULSAR) is a NASA Marshall Space Flight Center transceiver designed for the CubeSat market, but has the potential for other markets. The PULSAR project aims to reduce size, weight, and power while increasing telemetry data rate. The current version of the PULSAR has a mass of 2.2 kg and a footprint of 10.8 cm2. The height depends on the specific configuration. The PULSAR S-Band Communications Subsystem is an S- and X-band transponder system comprised of a receiver/detector (receiver) element, a transmitter element(s), and related power distribution, command, control, and telemetry element for operation and information interfaces. It is capable of receiving commands, encoding and transmitting telemetry, as well as providing tracking data in a manner compatible with Earthbased ground stations, near Earth network, and deep space network station resources. The software-defined radio's (SDR's) data format characteristics can be defined and reconfigured during spaceflight or prior to launch. The PULSAR team continues to evolve the SDR to improve the performance and form factor to meet the requirements that the CubeSat market space requires. One of the unique features is that the actual radio design can change (somewhat), but not require any hardware modifications due to the use of field programmable gate arrays.

The radio sources CTA 21 and OF+247: The hot spots of radio galaxies

NASA Astrophysics Data System (ADS)

Artyukh, V. S.; Tyul'bashev, S. A.; Chernikov, P. A.

2013-06-01

The physical conditions in the radio sources CTA 21 and OF+247 are studied assuming that the low-frequency spectral turnovers are due to synchrotron self-absorption. The physical parameters of the radio sources are estimated using a technique based on a nonuniform synchrotron source model. It is shown that the magnetic-field distributions in the dominant compact components of these radio sources are strongly inhomogeneous. The magnetic fields at the center of the sources are B ˜ 10-1 G, and the fields are two to three orders of magnitude weaker at the periphery. The magnetic field averaged over the compact component is B ˜ 10-3 G, and the density of relativistic electrons is n e ˜ 10-3 cm-3. Assuming that there is equipartition of the energies of the magnetic field and relativistic particles, averaged over the source, < E H > = < E e > ˜ 10-7-10-6 erg cm-3. The energy density of the magnetic field exceeds that of the relativistic electrons at the centers of the radio sources. The derived parameters of CTA 21 and OF+247 are close to those of the hot spots in the radio galaxy Cygnus A. On this basis, it is suggested that CTA 21 and OF+247 are radio galaxies at an early stage of their evolution, when the hot spots (dominant compact radio components) have appeared, and the radio lobes (weak extended components) are still being formed.

Generation and Upper Atmospheric Propagation of Acoustic Gravity Waves according to Numerical Modeling and Radio Tomography

NASA Astrophysics Data System (ADS)

Vorontsov, Artem; Andreeva, Elena; Nesterov, Ivan; Padokhin, Artem; Kurbatov, Grigory

2016-04-01

The acoustic-gravity waves (AGW) in the upper atmosphere and ionosphere can be generated by a variety of the phenomena in the near-Earth environment and atmosphere as well as by some perturbations of the Earth's ground or ocean surface. For instance, the role of the AGW sources can be played by the earthquakes, explosions, thermal heating, seisches, tsunami waves. We present the examples of AGWs excited by the tsunami waves traveling in the ocean, by seisches, and by ionospheric heating by the high-power radio wave. In the last case, the gravity waves are caused by the pulsed modulation of the heating wave. The AGW propagation in the upper atmosphere induces the variations and irregularities in the electron density distribution of the ionosphere, whose structure can be efficiently reconstructed by the method of the ionospheric radio tomography (RT) based on the data from the global navigational satellite systems (GNSS). The input data for RT diagnostics are composed of the 150/400 MHz radio signals from the low-orbiting (LO) satellites and 1.2-1.5 GHz radio signals from the high-orbiting (HO) satellites with their orbits at ~1000 and ~20000 km above the ground, respectively. These data enable ionospheric imaging on different spatiotemporal scales with different spatiotemporal resolution and coverage, which is suitable, inter alia, for tracking the waves and wave-like features in the ionosphere. In particular, we demonstrate the maps of the ionospheric responses to the tornado at Moore (Oklahoma, USA) of May 20, 2013, which are reconstructed from the HO data. We present the examples of LORT images containing the waves and wavelike disturbances associated with various sources (e.g., auroral precipitation and high-power heating of the ionosphere). We also discuss the results of modeling the AGW generation by the surface and volumetric sources. The millihertz AGW from these sources initiate the ionospheric perturbation with a typical scale of a few hundred km at the

A FPGA-based Fast Converging Digital Adaptive Filter for Real-time RFI Mitigation on Ground Based Radio Telescopes

NASA Astrophysics Data System (ADS)

Finger, R.; Curotto, F.; Fuentes, R.; Duan, R.; Bronfman, L.; Li, D.

2018-02-01

Radio Frequency Interference (RFI) is a growing concern in the radio astronomy community. Single-dish telescopes are particularly susceptible to RFI. Several methods have been developed to cope with RF-polluted environments, based on flagging, excision, and real-time blanking, among others. All these methods produce some degree of data loss or require assumptions to be made on the astronomical signal. We report the development of a real-time, digital adaptive filter implemented on a Field Programmable Gate Array (FPGA) capable of processing 4096 spectral channels in a 1 GHz of instantaneous bandwidth. The filter is able to cancel a broad range of interference signals and quickly adapt to changes on the RFI source, minimizing the data loss without any assumption on the astronomical or interfering signal properties. The speed of convergence (for a decrease to a 1%) was measured to be 208.1 μs for a broadband noise-like RFI signal and 125.5 μs for a multiple-carrier RFI signal recorded at the FAST radio telescope.

Geophysics-based method of locating a stationary earth object

DOEpatents

Daily, Michael R [Albuquerque, NM; Rohde, Steven B [Corrales, NM; Novak, James L [Albuquerque, NM

2008-05-20

A geophysics-based method for determining the position of a stationary earth object uses the periodic changes in the gravity vector of the earth caused by the sun- and moon-orbits. Because the local gravity field is highly irregular over a global scale, a model of local tidal accelerations can be compared to actual accelerometer measurements to determine the latitude and longitude of the stationary object.

Predictions for Uranus from a radiometric Bode's law. [planetary magnetic moment estimated from radio emission flux density

NASA Technical Reports Server (NTRS)

Desch, M. D.; Kaiser, M. L.

1984-01-01

Determinations by spacecraft of the low-frequency radio spectra and radiation beam geometry of the magnetospheres of earth, Jupiter, and Saturn now permit a reliable assessment of the overall efficiency of the solar wind in stimulating intense, nonthermal radio bursts from these magnetospheres. It is found that earlier estimates of how magnetospheric radio output scales with the solar wind energy input must be greatly revised, with the result that, while the efficiency is much lower than previously thought, it is remarkably uniform from planet to planet. A 'radimetric Bode's law' is formulated from which a planet's magnetic moment can be estimated from its radio emission output. This law is applied to estimate the low-frequency radio power likely to be measured for Uranus by Voyager 2. It is shown how measurements of Uranus's radio flux can be used to estimate the planetary magnetic moment and solar wind stand-off distance before the in situ measurements.

The Giant Radio Array for Neutrino Detection

NASA Astrophysics Data System (ADS)

Martineau-Huynh, Olivier; Bustamante, Mauricio; Carvalho, Washington; Charrier, Didier; De Jong, Sijbrand; de Vries, Krijn D.; Fang, Ke; Feng, Zhaoyang; Finley, Chad; Gou, Quanbu; Gu, Junhua; Hu, Hongbo; Kotera, Kumiko; Le Coz, Sandra; Medina, Clementina; Murase, Kohta; Niess, Valentin; Oikonomou, Foteini; Timmermans, Charles; Wang, Zhen; Wu, Xiangping; Zhang, Yi

2017-03-01

The Giant Radio Array for Neutrino Detection (GRAND) is a planned array of 2·105 radio antennas deployed over 200 000 km2 in a mountainous site. It aims primarly at detecting high-energy neutrinos via the observation of extensive air showers induced by the decay in the atmosphere of taus produced by the interaction of cosmic neutrinos under the Earth surface. GRAND aims at reaching a neutrino sensitivity of 5 · 10-11 E-2 GeV-1 cm-2 s-1 sr-1 above 3 · 1016 eV. This ensures the detection of cosmogenic neutrinos in the most pessimistic source models, and 50 events per year are expected for the standard models. The instrument will also detect UHECRs and possibly FRBs. Here we show how our preliminary design should enable us to reach our sensitivity goals, and discuss the steps to be taken to achieve GRAND, while the compelling science case for GRAND is discussed in more details in [1].

The Research and Test of Fast Radio Burst Real-time Search Algorithm Based on GPU Acceleration

NASA Astrophysics Data System (ADS)

Wang, J.; Chen, M. Z.; Pei, X.; Wang, Z. Q.

2017-03-01

In order to satisfy the research needs of Nanshan 25 m radio telescope of Xinjiang Astronomical Observatory (XAO) and study the key technology of the planned QiTai radio Telescope (QTT), the receiver group of XAO studied the GPU (Graphics Processing Unit) based real-time FRB searching algorithm which developed from the original FRB searching algorithm based on CPU (Central Processing Unit), and built the FRB real-time searching system. The comparison of the GPU system and the CPU system shows that: on the basis of ensuring the accuracy of the search, the speed of the GPU accelerated algorithm is improved by 35-45 times compared with the CPU algorithm.

A search for life on Earth from the Galileo spacecraft

NASA Technical Reports Server (NTRS)

Sagan, C.; Thompson, W. R.; Carlson, R.; Gurnett, D.; Hord, C.

1993-01-01

In its December 1990 fly-by of Earth, the Galileo spacecraft found evidence of abundant gaseous oxygen, a widely distributed surface pigment with a sharp absorption edge in the red part of the visible spectrum, and atmospheric methane in extreme thermodynamic disequilibrium; together, these are strongly suggestive of life on Earth. Moreover, the presence of narrow-band, pulsed, amplitude-modulated radio transmission seems uniquely attributable to intelligence. These observations constitute a control experiment for the serach for extraterrestrial life by modern interplanetary spacecraft.

A search for life on Earth from the Galileo spacecraft.

PubMed

Sagan, C; Thompson, W R; Carlson, R; Gurnett, D; Hord, C

1993-10-21

In its December 1990 fly-by of Earth, the Galileo spacecraft found evidence of abundant gaseous oxygen, a widely distributed surface pigment with a sharp absorption edge in the red part of the visible spectrum, and atmospheric methane in extreme thermodynamic disequilibrium; together, these are strongly suggestive of life on Earth. Moreover, the presence of narrow-band, pulsed, amplitude-modulated radio transmission seems uniquely attributable to intelligence. These observations constitute a control experiment for the serach for extraterrestrial life by modern interplanetary spacecraft.

Cassini Radio Occultation by Enceladus Plume

NASA Astrophysics Data System (ADS)

Kliore, A.; Armstrong, J.; Flasar, F.; French, R.; Marouf, E.; Nagy, A.; Rappaport, N.; McGhee, C.; Schinder, P.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischman, D.; Goltz, G.; Aguilar, R.; Rochblatt, D.

2006-12-01

A fortuitous Cassini radio occultation by Enceladus plume occurs on September 15, 2006. The occultation track (the spacecraft trajectory in the plane of the sky as viewed from the Earth) has been designed to pass behind the plume (to pass above the south polar region of Enceladus) in a roughly symmetrical geometry centered on a minimum altitude above the surface of about 20 km. The minimum altitude was selected primarily to ensure probing much of the plume with good confidence given the uncertainty in the spacecraft trajectory. Three nearly-pure sinusoidal signals of 0.94, 3.6, and 13 cm-wavelength (Ka-, X-, and S-band, respectively) are simultaneously transmitted from Cassini and are monitored at two 34-m Earth receiving stations of the Deep Space Network (DSN) in Madrid, Spain (DSS-55 and DSS-65). The occultation of the visible plume is extremely fast, lasting less than about two minutes. The actual observation time extends over a much longer time interval, however, to provide a good reference baseline for potential detection of signal perturbations introduced by the tenuous neutral and ionized plume environment. Given the likely very small fraction of optical depth due to neutral particles of sizes larger than about 1 mm, detectable changes in signal intensity is perhaps unlikely. Detection of plume plasma along the radio path as perturbations in the signals frequency/phase is more likely and the magnitude will depend on the electron columnar density probed. The occultation time occurs not far from solar conjunction time (Sun-Earth-probe angle of about 33 degrees), causing phase scintillations due to the solar wind to be the primary limiting noise source. We estimate a delectability limit of about 1 to 3E16 electrons per square meter columnar density assuming about 100 seconds integration time. Potential measurement of the profile of electron columnar density along the occultation track is an exciting prospect at this time.

Case study of inclined sporadic E layers in the Earth's ionosphere observed by CHAMP/GPS radio occultations: Coupling between the tilted plasma layers and internal waves

NASA Astrophysics Data System (ADS)

Gubenko, Vladimir N.; Pavelyev, A. G.; Kirillovich, I. A.; Liou, Y.-A.

2018-04-01

We have used the radio occultation (RO) satellite data CHAMP/GPS (Challenging Minisatellite Payload/Global Positioning System) for studying the ionosphere of the Earth. A method for deriving the parameters of ionospheric structures is based upon an analysis of the RO signal variations in the phase path and intensity. This method allows one to estimate the spatial displacement of a plasma layer with respect to the ray perigee, and to determine the layer inclination and height correction values. In this paper, we focus on the case study of inclined sporadic E (Es) layers in the high-latitude ionosphere based on available CHAMP RO data. Assuming that the internal gravity waves (IGWs) with the phase-fronts parallel to the ionization layer surfaces are responsible for the tilt angles of sporadic plasma layers, we have developed a new technique for determining the parameters of IGWs linked with the inclined Es structures. A small-scale internal wave may be modulating initially horizontal Es layer in height and causing a direction of the plasma density gradient to be rotated and aligned with that of the wave propagation vector k. The results of determination of the intrinsic wave frequency and period, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase speeds, and other characteristics of IGWs under study are presented and discussed.

Infrared imaging of WENSS radio sources

NASA Astrophysics Data System (ADS)

Villani, D.; di Serego Alighieri, S.

1999-03-01

We have performed deep imaging in the IR J- and K- bands for three sub-samples of radio sources extracted from the Westerbork Northern Sky Survey, a large low-frequency radio survey containing Ultra Steep Spectrum (USS), Gigahertz Peaked Spectrum (GPS) and Flat Spectrum (FS) sources. We present the results of these IR observations, carried out with the ARcetri Near Infrared CAmera (ARNICA) at the Nordic Optical Telescope (NOT), providing photometric and morphologic information on high redshift radio galaxies and quasars. We find that the radio galaxies contained in our sample do not show the pronounced radio/IR alignment claimed for 3CR sources. IR photometric measurements of the gravitational lens system 1600+434 are also presented. % This paper is based on data obtained at the Nordic Optical Telescope on La Palma (Canary Islands).

Output power distributions of mobile radio base stations based on network measurements

NASA Astrophysics Data System (ADS)

Colombi, D.; Thors, B.; Persson, T.; Wirén, N.; Larsson, L.-E.; Törnevik, C.

2013-04-01

In this work output power distributions of mobile radio base stations have been analyzed for 2G and 3G telecommunication systems. The approach is based on measurements in selected networks using performance surveillance tools part of the network Operational Support System (OSS). For the 3G network considered, direct measurements of output power levels were possible, while for the 2G networks, output power levels were estimated from measurements of traffic volumes. Both voice and data services were included in the investigation. Measurements were conducted for large geographical areas, to ensure good overall statistics, as well as for smaller areas to investigate the impact of different environments. For high traffic hours, the 90th percentile of the averaged output power was found to be below 65% and 45% of the available output power for the 2G and 3G systems, respectively.

Firefighters' Radios

NASA Technical Reports Server (NTRS)

1976-01-01

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.

Investigation of Inter-Node B Macro Diversity for Single-Carrier Based Radio Access in Evolved UTRA Uplink

NASA Astrophysics Data System (ADS)

Kawai, Hiroyuki; Morimoto, Akihito; Higuchi, Kenichi; Sawahashi, Mamoru

This paper investigates the gain of inter-Node B macro diversity for a scheduled-based shared channel using single-carrier FDMA radio access in the Evolved UTRA (UMTS Terrestrial Radio Access) uplink based on system-level simulations. More specifically, we clarify the gain of inter-Node B soft handover (SHO) with selection combining at the radio frame length level (=10msec) compared to that for hard handover (HHO) for a scheduled-based shared data channel, considering the gains of key packet-specific techniques including channel-dependent scheduling, adaptive modulation and coding (AMC), hybrid automatic repeat request (ARQ) with packet combining, and slow transmission power control (TPC). Simulation results show that the inter-Node B SHO increases the user throughput at the cell edge by approximately 10% for a short cell radius such as 100-300m due to the diversity gain from a sudden change in other-cell interference, which is a feature specific to full scheduled-based packet access. However, it is also shown that the gain of inter-Node B SHO compared to that for HHO is small in a macrocell environment when the cell radius is longer than approximately 500m due to the gains from hybrid ARQ with packet combining, slow TPC, and proportional fairness based channel-dependent scheduling.

Antenna unit and radio base station therewith

DOEpatents

Kuwahara, Mikio; Doi, Nobukazu; Suzuki, Toshiro; Ishida, Yuji; Inoue, Takashi; Niida, Sumaru

2007-04-10

Phase and amplitude deviations, which are generated, for example, by cables connecting an array antenna of a CDMA base station and the base station, are calibrated in the baseband. The base station comprises: an antenna apparatus 1; couplers 2; an RF unit 3 that converts a receive signal to a baseband signal, converts a transmit signal to a radio frequency, and performs power control; an A/D converter 4 for converting a receive signal to a digital signal; a receive beam form unit 6 that multiplies the receive signal by semi-fixed weight; a despreader 7 for this signal input; a time-space demodulator 8 for demodulating user data; a despreader 9 for probe signal; a space modulator 14 for user data; a spreader 13 for user signal; a channel combiner 12; a Tx calibrater 11 for controlling calibration of a signal; a D/A converter 10; a unit 16 for calculation of correlation matrix for generating a probe signal used for controlling an Rx calibration system and a TX calibration system; a spreader 17 for probe signal; a power control unit 18; a D/A converter 19; an RF unit 20 for probe signal; an A/D converter 21 for signal from the couplers 2; and a despreader 22.

Conceptual Research of Lunar-based Earth Observation for Polar Glacier Motion

NASA Astrophysics Data System (ADS)

Ruan, Zhixing; Liu, Guang; Ding, Yixing

2016-07-01

The ice flow velocity of glaciers is important for estimating the polar ice sheet mass balance, and it is of great significance for studies into rising sea level under the background of global warming. However so far the long-term and global measurements of these macro-scale motion processes of the polar glaciers have hardly been achieved by Earth Observation (EO) technique from the ground, aircraft or satellites in space. This paper, facing the demand for space technology for large-scale global environmental change observation,especially the changes of polar glaciers, and proposes a new concept involving setting up sensors on the lunar surface and using the Moon as a platform for Earth observation, transmitting the data back to Earth. Lunar-based Earth observation, which enables the Earth's large-scale, continuous, long-term dynamic motions to be measured, is expected to provide a new solution to the problems mentioned above. According to the pattern and characteristics of polar glaciers motion, we will propose a comprehensive investigation of Lunar-based Earth observation with synthetic aperture radar (SAR). Via theoretical modeling and experimental simulation inversion, intensive studies of Lunar-based Earth observation for the glacier motions in the polar regions will be implemented, including the InSAR basics theory, observation modes of InSAR and optimization methods of their key parameters. It will be of a great help to creatively expand the EO technique system from space. In addition, they will contribute to establishing the theoretical foundation for the realization of the global, long-term and continuous observation for the glacier motion phenomena in the Antarctic and the Arctic.

Space-to-earth power transmission system

NASA Technical Reports Server (NTRS)

Stevens, G. H.; Schuh, R.

1976-01-01

A preliminary analysis was conducted to establish the requirements of a space-to-earth microwave power transmission system. The need for accurate phase control on the transmitter was established and methods for assessing the impact of power density and thermal constraints on system performance were demonstrated. Potential radio frequency interference was considered. The sensitivity of transmission system scale to variations in power source, transportation and orbital fabrication and assembly costs was also determined.

Geological and geophysical field investigations from a lunar base at Mare Smythii

NASA Technical Reports Server (NTRS)

Spudis, Paul D.; Hood, Lon L.

1992-01-01

Mare Smythii, located on the equator and east limb of the Moon, has a great variety of scientific and economic uses as the site for a permanent lunar base. Here a complex could be established that would combine the advantages of a nearside base (for ease of communications with Earth and normal operations) with those of a farside base (for shielding a radio astronomical observatory from the electromagnetic noise of Earth). The Mare Smythii region displays virtually the entire known range of geological processes and materials found on the Moon; from this site, a series of field traverses and investigations could be conducted that would provide data on and answers to fundamental questions in lunar geoscience. This endowment of geological materials also makes the Smythii region attractive for the mining of resources for use both on the Moon and in Earth-Moon space. We suggest that the main base complex be located at 0, 90 deg E, within the mare basalts of the Smythii basin; two additional outposts would be required, one at 0, 81 deg E to maintain constant communications with Earth, and and the other, at 0, 101 deg E on the lunar farside, to serve as a radio astronomical observatory. The bulk of lunar surface activities could be conducted by robotic teleoperations under the direct control of the human inhabitants of the base.

Radio Galaxy Zoo: A Search for Hybrid Morphology Radio Galaxies

NASA Astrophysics Data System (ADS)

Kapińska, A. D.; Terentev, I.; Wong, O. I.; Shabala, S. S.; Andernach, H.; Rudnick, L.; Storer, L.; Banfield, J. K.; Willett, K. W.; de Gasperin, F.; Lintott, C. J.; López-Sánchez, Á. R.; Middelberg, E.; Norris, R. P.; Schawinski, K.; Seymour, N.; Simmons, B.

2017-12-01

Hybrid morphology radio sources (HyMoRS) are a rare type of radio galaxy that display different Fanaroff-Riley classes on opposite sides of their nuclei. To enhance the statistical analysis of HyMoRS, we embarked on a large-scale search of these sources within the international citizen science project, Radio Galaxy Zoo (RGZ). Here, we present 25 new candidate hybrid morphology radio galaxies. Our selected candidates are moderate power radio galaxies ({L}{median}=4.7× {10}24 W Hz-1 sr-1) at redshifts 0.14< z< 1.0. Hosts of nine candidates have spectroscopic observations, of which six are classified as quasars, one as high- and two as low-excitation galaxies. Two candidate HyMoRS are giant (> 1 Mpc) radio galaxies, one resides at the center of a galaxy cluster, and one is hosted by a rare green bean galaxy. Although the origin of the hybrid morphology radio galaxies is still unclear, this type of radio source starts depicting itself as a rather diverse class. We discuss hybrid radio morphology formation in terms of the radio source environment (nurture) and intrinsically occurring phenomena (nature; activity cessation and amplification), showing that these peculiar radio galaxies can be formed by both mechanisms. While high angular resolution follow-up observations are still necessary to confirm our candidates, we demonstrate the efficacy of the RGZ in the pre-selection of these sources from all-sky radio surveys, and report the reliability of citizen scientists in identifying and classifying complex radio sources.

Radio Telescopes to Keep Sharp Eye on Mars Lander

NASA Astrophysics Data System (ADS)

2008-05-01

As NASA's Phoenix Mars Lander descends through the Red Planet's atmosphere toward its landing on May 25, its progress will be scrutinized by radio telescopes from the National Radio Astronomy Observatory (NRAO). At NRAO control rooms in Green Bank, West Virginia, and Socorro, New Mexico, scientists, engineers and technicians will be tracking the faint signal from the lander, 171 million miles from Earth. The GBT Robert C. Byrd Green Bank Telescope CREDIT: NRAO/AUI/NSF To make a safe landing, Phoenix must make a risky descent, slowing down from nearly 13,000 mph at the top of the Martian atmosphere to only 5 mph in the final seconds before touchdown. NASA officials point out that fewer than half of all Mars landing missions have been successful, but the scientific rewards of success are worth the risk. Major events in the spacecraft's atmospheric entry, descent and landing will be marked by changes in the Doppler Shift in the frequency of the vehicle's radio signal. Doppler Shift is the change in frequency caused by relative motion between the transmitter and receiver. At Green Bank, NRAO and NASA personnel will use the giant Robert C. Byrd Green Bank Telescope (GBT) to follow the Doppler changes and verify that the descent is going as planned. The radio signal from Phoenix is designed to be received by other spacecraft in Mars orbit, then relayed to Earth. However, the GBT, a dish antenna with more than two acres of collecting surface and highly-sensitive receivers, can directly receive the transmissions from Phoenix. "We'll see the frequency change as Phoenix slows down in the Martian atmosphere, then there will be a big change when the parachute deploys," said NRAO astronomer Frank Ghigo. When the spacecraft's rocket thrusters slow it down for its final, gentle touchdown, its radio frequency will stabilize, Ghigo said. "We'll have confirmation of these major events through our direct reception several seconds earlier than the controllers at NASA's Jet Propulsion

IRAS observations of radio-quiet and radio-loud quasars

NASA Technical Reports Server (NTRS)

Neugebauer, G.; Soifer, B. T.; Miley, G.; Habing, H. J.; Young, E.; Low, F. J.; Beichman, C. A.; Clegg, P. E.; Harris, S.; Rowan-Robinson, M.

1984-01-01

Observations from 12 to 100 microns are presented of two radio-quiet and three radio-loud quasars. Over this wavelength range, all five have grossly similar continuum energy distributions. The continua of the radio-loud quasars are consistent with synchrotron radiation. There is an indication, however, of excess 100 micron emission in the two radio-quiet quasars.

An astrophysical view of Earth-based metabolic biosignature gases.

PubMed

Seager, Sara; Schrenk, Matthew; Bains, William

2012-01-01

Microbial life on Earth uses a wide range of chemical and energetic resources from diverse habitats. An outcome of this microbial diversity is an extensive and varied list of metabolic byproducts. We review key points of Earth-based microbial metabolism that are useful to the astrophysical search for biosignature gases on exoplanets, including a list of primary and secondary metabolism gas byproducts. Beyond the canonical, unique-to-life biosignature gases on Earth (O(2), O(3), and N(2)O), the list of metabolic byproducts includes gases that might be associated with biosignature gases in appropriate exoplanetary environments. This review aims to serve as a starting point for future astrophysical biosignature gas research.

Physics of the Geospace Response to Powerful HF Radio Waves

DTIC Science & Technology

2012-10-31

studies of the response of the Earth’s space plasma to high-power HF radio waves from the High-frequency Active Auroral Research Program ( HAARP ...of HF heating and explored to simulate artificial ducts. DMSP- HAARP experiments revealed that HF-created ion outflows and artificial density ducts...in the topside ionosphere appeared faster than predicted by the models, pointing to kinetic (suprathermal) effects. CHAMP/GRACE- HAARP experiments

President Gerald Ford talks to ASTP crewmen via radio-telephone

NASA Image and Video Library

1975-07-18

S75-30515 (18 July 1975) --- President Gerald R. Ford watches ASTP crewmen Thomas P. Stafford, Donald K. Slayton and Valeriy N. Kubasov on television as he talks to them via radio-telephone while they orbited Earth on July 18, 1975. The American Apollo spacecraft and Soviet Soyuz spacecraft were docked. The five ASTP crewmen visited each other?s spacecraft while the Soyuz and Apollo were linked in space.

THE VLA SURVEY OF CHANDRA DEEP FIELD SOUTH. V. EVOLUTION AND LUMINOSITY FUNCTIONS OF SUB-MILLIJANSKY RADIO SOURCES AND THE ISSUE OF RADIO EMISSION IN RADIO-QUIET ACTIVE GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Padovani, P.; Mainieri, V.; Rosati, P.

2011-10-10

We present the evolutionary properties and luminosity functions of the radio sources belonging to the Chandra Deep Field South Very Large Array survey, which reaches a flux density limit at 1.4 GHz of 43 {mu}Jy at the field center and redshift {approx}5 and which includes the first radio-selected complete sample of radio-quiet active galactic nuclei (AGNs). We use a new, comprehensive classification scheme based on radio, far- and near-IR, optical, and X-ray data to disentangle star-forming galaxies (SFGs) from AGNs and radio-quiet from radio-loud AGNs. We confirm our previous result that SFGs become dominant only below 0.1 mJy. The sub-millijanskymore » radio sky turns out to be a complex mix of SFGs and radio-quiet AGNs evolving at a similar, strong rate; non-evolving low-luminosity radio galaxies; and declining radio powerful (P {approx}> 3 x 10{sup 24} W Hz{sup -1}) AGNs. Our results suggest that radio emission from radio-quiet AGNs is closely related to star formation. The detection of compact, high brightness temperature cores in several nearby radio-quiet AGNs can be explained by the coexistence of two components, one non-evolving and AGN related and one evolving and star formation related. Radio-quiet AGNs are an important class of sub-millijansky sources, accounting for {approx}30% of the sample and {approx}60% of all AGNs, and outnumbering radio-loud AGNs at {approx}< 0.1 mJy. This implies that future, large area sub-millijansky surveys, given the appropriate ancillary multiwavelength data, have the potential of being able to assemble vast samples of radio-quiet AGNs, bypassing the problems of obscuration that plague the optical and soft X-ray bands.« less

2nd Radio and Antenna Days of the Indian Ocean (RADIO 2014)

NASA Astrophysics Data System (ADS)

2014-10-01

It was an honor and a great pleasure for all those involved in its organization to welcome the participants to the ''Radio and Antenna Days of the Indian Ocean'' (RADIO 2014) international conference that was held from 7th to 10th April 2014 at the Sugar Beach Resort, Wolmar, Flic-en-Flac, Mauritius. RADIO 2014 is the second of a series of conferences organized in the Indian Ocean region. The aim of the conference is to discuss recent developments, theories and practical applications covering the whole scope of radio-frequency engineering, including radio waves, antennas, propagation, and electromagnetic compatibility. The RADIO international conference emerged following discussions with engineers and scientists from the countries of the Indian Ocean as well as from other parts of the world and a need was felt for the organization of such an event in this region. Following numerous requests, the Island of Mauritius, worldwide known for its white sandy beaches and pleasant tropical atmosphere, was again chosen for the organization of the 2nd RADIO international conference. The conference was organized by the Radio Society, Mauritius and the Local Organizing Committee consisted of scientists from SUPELEC, France, the University of Mauritius, and the University of Technology, Mauritius. We would like to take the opportunity to thank all people, institutions and companies that made the event such a success. We are grateful to our gold sponsors CST and FEKO as well as URSI for their generous support which enabled us to partially support one PhD student and two scientists to attend the conference. We would also like to thank IEEE-APS and URSI for providing technical co-sponsorship. More than hundred and thirty abstracts were submitted to the conference. They were peer-reviewed by an international scientific committee and, based on the reviews, either accepted, eventually after revision, or rejected. RADIO 2014 brought together participants from twenty countries spanning

A Field-Based Curriculum Model for Earth Science Teacher-Preparation Programs.

ERIC Educational Resources Information Center

Dubois, David D.

1979-01-01

This study proposed a model set of cognitive-behavioral objectives for field-based teacher education programs for earth science teachers. It describes field experience integration into teacher education programs. The model is also applicable for evaluation of earth science teacher education programs. (RE)

DIFFERENCES BETWEEN RADIO-LOUD AND RADIO-QUIET γ -RAY PULSARS AS REVEALED BY FERMI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hui, C. Y.; Lee, Jongsu; Takata, J.

By comparing the properties of non-recycled radio-loud γ -ray pulsars and radio-quiet γ -ray pulsars, we have searched for the differences between these two populations. We found that the γ -ray spectral curvature of radio-quiet pulsars can be larger than that of radio-loud pulsars. Based on the full sample of non-recycled γ -ray pulsars, their distributions of the magnetic field strength at the light cylinder are also found to be different. We note that this might result from an observational bias. By reexamining the previously reported difference of γ -ray-to-X-ray flux ratios, we found that the significance can be hamperedmore » by their statistical uncertainties. In the context of the outer gap model, we discuss the expected properties of these two populations and compare with the possible differences that are identified in our analysis.« less

Amateur Radio on the International Space Station - Phase 2 Hardware System

NASA Technical Reports Server (NTRS)

Bauer, F.; McFadin, L.; Bruninga, B.; Watarikawa, H.

2003-01-01

The International Space Station (ISS) ham radio system has been on-orbit for over 3 years. Since its first use in November 2000, the first seven expedition crews and three Soyuz taxi crews have utilized the amateur radio station in the Functional Cargo Block (also referred to as the FGB or Zarya module) to talk to thousands of students in schools, to their families on Earth, and to amateur radio operators around the world. Early on, the Amateur Radio on the International Space Station (ARISS) international team devised a multi-phased hardware development approach for the ISS ham radio station. Three internal development Phases. Initial Phase 1, Mobile Radio Phase 2 and Permanently Mounted Phase 3 plus an externally mounted system, were proposed and agreed to by the ARISS team. The Phase 1 system hardware development which was started in 1996 has since been delivered to ISS. It is currently operational on 2 meters. The 70 cm system is expected to be installed and operated later this year. Since 2001, the ARISS international team have worked to bring the second generation ham system, called Phase 2, to flight qualification status. At this time, major portions of the Phase 2 hardware system have been delivered to ISS and will soon be installed and checked out. This paper intends to provide an overview of the Phase 1 system for background and then describe the capabilities of the Phase 2 radio system. It will also describe the current plans to finalize the Phase 1 and Phase 2 testing in Russia and outlines the plans to bring the Phase 2 hardware system to full operation.

Fish-Eye Observing with Phased Array Radio Telescopes

NASA Astrophysics Data System (ADS)

Wijnholds, S. J.

The radio astronomical community is currently developing and building several new radio telescopes based on phased array technology. These telescopes provide a large field-of-view, that may in principle span a full hemisphere. This makes calibration and imaging very challenging tasks due to the complex source structures and direction dependent radio wave propagation effects. In this thesis, calibration and imaging methods are developed based on least squares estimation of instrument and source parameters. Monte Carlo simulations and actual observations with several prototype show that this model based approach provides statistically and computationally efficient solutions. The error analysis provides a rigorous mathematical framework to assess the imaging performance of current and future radio telescopes in terms of the effective noise, which is the combined effect of propagated calibration errors, noise in the data and source confusion.

Digging into Inquiry-Based Earth Science Research

ERIC Educational Resources Information Center

Schultz, Bryan; Yates, Crystal; Schultz, Jayne M.

2008-01-01

To help eighth-grade students experience the excitement of Earth science research, the authors developed an inquiry-based project in which students evaluated and cataloged their campus geology and soils. Following class discussions of rock-weathering and soil-forming processes, students worked in groups to excavate multiple soil pits in the school…

SDN based millimetre wave radio over fiber (RoF) network

NASA Astrophysics Data System (ADS)

Amate, Ahmed; Milosavljevic, Milos; Kourtessis, Pandelis; Robinson, Matthew; Senior, John M.

2015-01-01

This paper introduces software-defined, millimeter Wave (mm-Wave) networks with Radio over Fiber (RoF) for the delivery of gigabit connectivity required to develop fifth generation (5G) mobile. This network will enable an effective open access system allowing providers to manage and lease the infrastructure to service providers through unbundling new business models. Exploiting the inherited benefits of RoF, complete base station functionalities are centralized at the edges of the metro and aggregation network, leaving remote radio heads (RRHs) with only tunable filtering and amplification. A Software Defined Network (SDN) Central Controller (SCC) is responsible for managing the resource across several mm-Wave Radio Access Networks (RANs) providing a global view of the several network segments. This ensures flexible resource allocation for reduced overall latency and increased throughput. The SDN based mm-Wave RAN also allows for inter edge node communication. Therefore, certain packets can be routed between different RANs supported by the same edge node, reducing latency. System level simulations of the complete network have shown significant improvement of the overall throughput and SINR for wireless users by providing effective resource allocation and coordination among interfering cells. A new Coordinated Multipoint (CoMP) algorithm exploiting the benefits of the SCC global network view for reduced delay in control message exchange is presented, accounting for a minimum packet delay and limited Channel State Information (CSI) in a Long Term Evolution-Advanced (LTE-A), Cloud RAN (CRAN) configuration. The algorithm does not require detailed CSI feedback from UEs but it rather considers UE location (determined by the eNB) as the required parameter. UE throughput in the target sector is represented using a Cumulative Distributive Function (CDF). The drawn characteristics suggest that there is a significant 60% improvement in UE cell edge throughput following the

Space Telecommunications Radio Architecture (STRS): Technical Overview

NASA Technical Reports Server (NTRS)

Reinhart, Richard C.

2006-01-01

A software defined radio (SDR) architecture used in space-based platforms proposes to standardize certain aspects of radio development such as interface definitions, functional control and execution, and application software and firmware development. NASA has charted a team to develop an open software defined radio hardware and software architecture to support NASA missions and determine the viability of an Agency-wide Standard. A draft concept of the proposed standard has been released and discussed among organizations in the SDR community. Appropriate leveraging of the JTRS SCA, OMG s SWRadio Architecture and other aspects are considered. A standard radio architecture offers potential value by employing common waveform software instantiation, operation, testing and software maintenance. While software defined radios offer greater flexibility, they also poses challenges to the radio development for the space environment in terms of size, mass and power consumption and available technology. An SDR architecture for space must recognize and address the constraints of space flight hardware, and systems along with flight heritage and culture. NASA is actively participating in the development of technology and standards related to software defined radios. As NASA considers a standard radio architecture for space communications, input and coordination from government agencies, the industry, academia, and standards bodies is key to a successful architecture. The unique aspects of space require thorough investigation of relevant terrestrial technologies properly adapted to space. The talk will describe NASA's current effort to investigate SDR applications to space missions and a brief overview of a candidate architecture under consideration for space based platforms.

NASA's SDR Standard: Space Telecommunications Radio System

NASA Technical Reports Server (NTRS)

Reinhart, Richard C.; Johnson, Sandra K.

2007-01-01

A software defined radio (SDR) architecture used in space-based platforms proposes to standardize certain aspects of radio development such as interface definitions, functional control and execution, and application software and firmware development. NASA has charted a team to develop an open software defined radio hardware and software architecture to support NASA missions and determine the viability of an Agency-wide Standard. A draft concept of the proposed standard has been released and discussed among organizations in the SDR community. Appropriate leveraging of the JTRS SCA, OMG s SWRadio Architecture and other aspects are considered. A standard radio architecture offers potential value by employing common waveform software instantiation, operation, testing and software maintenance. While software defined radios offer greater flexibility, they also poses challenges to the radio development for the space environment in terms of size, mass and power consumption and available technology. An SDR architecture for space must recognize and address the constraints of space flight hardware, and systems along with flight heritage and culture. NASA is actively participating in the development of technology and standards related to software defined radios. As NASA considers a standard radio architecture for space communications, input and coordination from government agencies, the industry, academia, and standards bodies is key to a successful architecture. The unique aspects of space require thorough investigation of relevant terrestrial technologies properly adapted to space. The talk will describe NASA s current effort to investigate SDR applications to space missions and a brief overview of a candidate architecture under consideration for space based platforms.

Imaging Interplanetary CMEs at Radio Frequency From Solar Polar Orbit

NASA Astrophysics Data System (ADS)

Wu, Ji; Sun, Weiying; Zheng, Jianhua; Zhang, Cheng; Wang, Chi; Wang, C. B.; Wang, S.

Coronal mass ejections (CMEs) are violent discharges of plasma and magnetic fields from the Sun's corona. They have come to be recognized as the major driver of physical conditions in the Sun-Earth system. Consequently, the detection of CMEs is important for un-derstanding and ultimately predicting space weather conditions. The Solar Polar Orbit Radio Telescope (SPORT) is a proposed mission to observe the propagation of interplanetary CMEs from solar polar orbit. The main payload (radio telescope) on board SPORT will be an in-terferometric imaging radiometer working at the meter wavelength band, which will follow the propagation of interplanetary CMEs from a distance of a few solar radii to near 1 AU from solar polar orbit. The SPORT spacecraft will also be equipped with a set of optical and in situ measurement instruments such as a EUV solar telescope, a solar wind plasma experiment, a solar wind ion composition instrument, an energetic particle detector, a wave detector, a mag-netometer and an interplanetary radio burst tracker. In this paper, we first describe the current shortage of interplanetary CME observations. Next, the scientific motivation and objectives of SPORT are introduced. We discuss the basic specifications of the main radio telescope of SPORT with reference to the radio emission mechanisms and the radio frequency band to be observed. Finally, we discuss the key technologies of the SPORT mission, including the con-ceptual design of the main telescope, the image retrieval algorithm and the solar polar orbit injection. Other payloads and their respective observation objectives are also briefly discussed. Key words: Interplanetary CMEs; Interferometric imaging; Solar polar orbit; Radiometer.

Variations in the rotation of the earth

NASA Astrophysics Data System (ADS)

Carter, W. E.; Robertson, D. S.; Pettey, J. E.; Tapley, B. D.; Schutz, B. E.; Eanes, R. J.; Miao, L.

Variations in the earth's rotation (UTI) and length of day have been tracked at the submillisecond level by astronomical radio interferometry and laser ranging to the LAGEOS satellite. Three years of regular measurements reveal complex patterns of variations including UTI fluctuations as large as 5 milliseconds in a few weeks. Comparison of the observed changes in length of day with variations in the global atmospheric angular momentum indicates that the dominant cause of changes in the earth's spin rate, on time scales from a week to several years, is the exchange of angular momentum between the atmosphere and the mantle. The unusually intense El Nino of 1982-1983 was marked by a strong peak in the length of day.

A modified artificial neural network based prediction technique for tropospheric radio refractivity

PubMed Central

Javeed, Shumaila; Javed, Wajahat; Atif, M.; Uddin, Mueen

2018-01-01

Radio refractivity plays a significant role in the development and design of radio systems for attaining the best level of performance. Refractivity in the troposphere is one of the features affecting electromagnetic waves, and hence the communication system interrupts. In this work, a modified artificial neural network (ANN) based model is applied to predict the refractivity. The suggested ANN model comprises three modules: the data preparation module, the feature selection module, and the forecast module. The first module applies pre-processing to make the data compatible for the feature selection module. The second module discards irrelevant and redundant data from the input set. The third module uses ANN for prediction. The ANN model applies a sigmoid activation function and a multi-variate auto regressive model to update the weights during the training process. In this work, the refractivity is predicted and estimated based on ten years (2002–2011) of meteorological data, such as the temperature, pressure, and humidity, obtained from the Pakistan Meteorological Department (PMD), Islamabad. The refractivity is estimated using the method suggested by the International Telecommunication Union (ITU). The refractivity is predicted for the year 2012 using the database of the previous ten years, with the help of ANN. The ANN model is implemented in MATLAB. Next, the estimated and predicted refractivity levels are validated against each other. The predicted and actual values (PMD data) of the atmospheric parameters agree with each other well, and demonstrate the accuracy of the proposed ANN method. It was further found that all parameters have a strong relationship with refractivity, in particular the temperature and humidity. The refractivity values are higher during the rainy season owing to a strong association with the relative humidity. Therefore, it is important to properly cater the signal communication system during hot and humid weather. Based on the

Solar rotation effects on the thermospheres of Mars and Earth.

PubMed

Forbes, Jeffrey M; Bruinsma, Sean; Lemoine, Frank G

2006-06-02

The responses of Earth's and Mars' thermospheres to the quasi-periodic (27-day) variation of solar flux due to solar rotation were measured contemporaneously, revealing that this response is twice as large for Earth as for Mars. Per typical 20-unit change in 10.7-centimeter radio flux (used as a proxy for extreme ultraviolet flux) reaching each planet, we found temperature changes of 42.0 +/- 8.0 kelvin and 19.2 +/- 3.6 kelvin for Earth and Mars, respectively. Existing data for Venus indicate values of 3.6 +/- 0.6 kelvin. Our observational result constrains comparative planetary thermosphere simulations and may help resolve existing uncertainties in thermal balance processes, particularly CO2 cooling.

The importance of Radio Quiet Zone (RQZ) for radio astronomy

NASA Astrophysics Data System (ADS)

Umar, Roslan; Abidin, Zamri Zainal; Ibrahim, Zainol Abidin

2013-05-01

Most of radio observatories are located in isolated areas. Since radio sources from the universe is very weak, astronomer need to avoid radio frequency interference (RFI) from active spectrum users and radio noise produced by human made (telecommunication, mobile phone, microwave user and many more. There are many observatories around the world are surrounded by a Radio Quiet Zone (RQZ), which is it was set up using public or state laws. A Radio Quiet Zone normally consists of two areas: an exclusive area in which totally radio emissions are forbidden, with restrictions for residents and business developments, and a larger (radius up to 100 km above) coordination area where the power of radio transmission limits to threshold levels. Geographical Information System (GIS) can be used as a powerful tool in mapping large areas with varying RQZ profiles. In this paper, we report the initial testing of the usage of this system in order to identify the areas were suitable for Radio Quiet Zone. Among the important parameters used to develop the database for our GIS are population density, information on TV and telecommunication (mobile phones) transmitters, road networks (highway), and contour shielding. We will also use other information gathered from on-site RFI level measurements on selected 'best' areas generated by the GIS. The intention is to find the best site for the purpose of establishing first radio quiet zones for radio telescope in Malaysia.

Airborne Remote Observations of L-Band Radio Frequency Interference and Implications for Satellite Missions

NASA Technical Reports Server (NTRS)

Laymon, Charles; Srinivasan, Karthik; Limaye, Ashutosh

2011-01-01

Passive remote sensing of the Earth s surface and atmosphere from space has significant importance in operational and research environmental studies, in particular for the scientific understanding, monitoring and prediction of climate change and its impacts. Passive remote sensing requires the measurement of naturally occurring radiations, usually of very low power levels, which contain essential information on the physical process under investigation. As such, these sensed radio frequency bands are a unique natural resource enabling space borne passive sensing of the atmosphere and the Earth s surface that deserves adequate allocation to the Earth Exploration Satellite Service and absolute protection from interference. Unfortunately, radio frequency interference (RFI) is an increasing problem for Earth remote sensing, particularly for passive observations of natural emissions. Because these natural signals tend to be very weak, even low levels of interference received by a passive sensor may degrade the fidelity of scientific data. The characteristics of RFI (low-level interference and radar-pulse noise) are not well known because there has been no systematic surveillance, spectrum inventory or mapping of RFI. While conducting a flight experiment over central Tennessee in May 2010, RFI, a concern for any instrument operating in the passive L band frequency, was observed across 16 subbands between 1402-1427 MHz. Such a survey provides rare characterization data from which to further develop mitigation technologies as well as to identify bandwidths to avoid in future sensor formulation.

Observing Tropospheric Water Vapor by Radio Occultation using the Global Positioning System

NASA Technical Reports Server (NTRS)

Kursinski, E. R.; Hajj, G. A.; Hardy, K. R.; Romans, L. J.; Schofield, J. T.

1995-01-01

Given the importance of water vapor to weather, climate and hydrology, global humidity observations from satellites are critical. At low latitudes, radio occultation observations of Earth's atmosphere using the Global Positioning System (GPS) satellites allow water vapor profiles to be retrieved with accuracies of 10 to 20% below 6 to 7 km altitude and approx. 5% or better within the boundary layer. GPS observations provide a unique combination of accuracy, vertical resolution (less than or equal to 1 km) and insensitivity to cloud and aerosol particles that is well suited to observations of the lower troposphere. These characteristics combined with the inherent stability of radio occultation observations make it an excellent candidate for the measurement of long term trends.

[Establishment of Oncomelania hupensis snail database based on smartphone and Google Earth].

PubMed

Wang, Wei-chun; Zhan, Ti; Zhu, Ying-fu

2015-02-01

To establish an Oncomelania hupensis snail database based on smartphone and Google Earth. The HEAD GPS software was loaded in the smartphone first. The GPS data of the snails were collected by the smartphone. The original data were exported to the computer with the format of KMIUKMZ. Then the data were converted into Excel file format by using some software. Finally, the results based on laboratory were filled, and the digital snail data were established. The data were converted into KML, and then were showed by Google Earth visually. The snail data of a 5 hm2-beach along the Yangtze River were collected and the distribution of the snails based on Google Earth was obtained. The database of the snails was built. The query function was implemented about the number of the total snails, the living snails and the schistosome infected snails of each survey frame. The digital management of the snail data is realized by using the smartphone and Google Earth.

Wavelet Based Characterization of Low Radio Frequency Solar Emissions

NASA Astrophysics Data System (ADS)

Suresh, A.; Sharma, R.; Das, S. B.; Oberoi, D.; Pankratius, V.; Lonsdale, C.

2016-12-01

Low-frequency solar radio observations with the Murchison Widefield Array (MWA) have revealed the presence of numerous short-lived, narrow-band weak radio features, even during quiet solar conditions. In their appearance in in the frequency-time plane, they come closest to the solar type III bursts, but with much shorter spectral spans and flux densities, so much so that they are not detectable with the usual swept frequency radio spectrographs. These features occur at rates of many thousand features per hour in the 30.72 MHz MWA bandwidth, and hence necessarily require an automated approach to determine robust statistical estimates of their properties, e.g., distributions of spectral widths, temporal spans, flux densities, slopes in the time-frequency plane and distribution over frequency. To achieve this, a wavelet decomposition approach has been developed for feature recognition and subsequent parameter extraction from the MWA dynamic spectrum. This work builds on earlier work by the members of this team to achieve a reliable flux calibration in a computationally efficient manner. Preliminary results show that the distribution of spectral span of these features peaks around 3 MHz, most of them last for less than two seconds and are characterized by flux densities of about 60% of the background solar emission. In analogy with the solar type III bursts, this non-thermal emission is envisaged to arise via coherent emission processes. There is also an exciting possibility that these features might correspond to radio signatures of nanoflares, hypothesized (Gold, 1964; Parker, 1972) to explain coronal heating.

rfpipe: Radio interferometric transient search pipeline

NASA Astrophysics Data System (ADS)

Law, Casey J.

2017-10-01

rfpipe supports Python-based analysis of radio interferometric data (especially from the Very Large Array) and searches for fast radio transients. This extends on the rtpipe library (ascl:1706.002) with new approaches to parallelization, acceleration, and more portable data products. rfpipe can run in standalone mode or be in a cluster environment.

Full-Wave Radio Characterization of Ionospheric Modification at HAARP

DTIC Science & Technology

2015-07-26

Full-Wave Radio Characterization of Ionospheric Modification at HAARP We have studied electrostatic and electromagnetic turbulence stimulated by...radio receivers at HAARP in Alaska, and ground-based radio receivers, incoherent scatter radars, and in-situ measurements from Canadian, ESA, and Polish...363255 San Juan, PR 00936 -3255 31-May-2015 ABSTRACT Final Report: Full-Wave Radio Characterization of Ionospheric Modification at HAARP Report Title We

Prediction of CMEs and Type II Bursts from Sun to Earth

NASA Astrophysics Data System (ADS)

Cairns, I. H.; Schmidt, J. M.; Gopalswamy, N.; van der Holst, B.

2017-12-01

Most major space weather events are due to fast CMEs and their shocks interacting with Earth's magnetosphere. SImilarly, type II solar radio bursts are well-known signatures of CMEs and their shocks moving through the corona and solar wind. The properties of the space weather events and the type II radio bursts depend sensitively on the CME velocity, shape, and evolution as functions of position and time, as well as on the magnetic field vector in the coronal and solar wind plasma, downstream of the CME shock, and inside the CME. We report simulations of CMEs and type II bursts from the Sun to Earth with the Space Weather Modelling Framework (2015 and 2016 versions), set up carefully using relevant data, and a kinetic radio emission theory. Excellent agreement between observations, simulations, and theory are found for the coronal (metric) type II burst of 7 September 2014 and associated CME, including the lack of radio emission in the solar wind beyond about 10 solar radii. Similarly, simulation of a CME and type II burst from the Sun to 1 AU over the period 29 November - 1 December 2013 yield excellent agreement for the radio burst from 10 MHz to 30 kHz for STEREO A and B and Wind, arrival of the CME at STEREO A within 1 hour reported time, deceleration of the CME in agreement with the Gopalswamy et al. [2011] observational analyses, and Bz rotations at STEREO A from upstream of the CME shock to within the CME. These results provide strong support for the type II theory and also that the Space WeatherModeling Framework can accurately predict the properties and evolution of CMEs and the interplanetary magnetic field and plasma from the Sun to 1 AU when sufficiently carefully initialized.

Clustering-based Filtering to Detect Isolated and Intermittent Pulses in Radio Astronomy Data

NASA Astrophysics Data System (ADS)

Wagstaff, Kiri; Tang, B.; Lazio, T. J.; Spolaor, S.

2013-01-01

Radio-emitting neutron stars (pulsars) produce a series of periodic pulses at radio frequencies. Dispersion, caused by propagation through the interstellar medium, delays signals at lower frequencies more than higher frequencies. This well understood effect can be reversed though de-dispersion at the appropriate dispersion measure (DM). The periodic nature of a pulsar provides multiple samples of signals at the same DM, increasing the reliability of any candidate detection. However, existing methods for pulsar detection are ineffective for many pulse-emitting phenomena now being discovered. Sources exhibit a wide range of pulse repetition rates, from highly regular canonical pulsars to intermittent and nulling pulsars to rotating radio transients (RRATs) that may emit only a few pulses per hour. Other source types may emit only a few pulses, or even only a single pulse. We seek to broaden the scope of radio signal analysis to enable the detection of isolated and intermittent pulses. Without a requirement that detected sources be periodic, we find that a typical de-dispersion search yields results that are often dominated by spurious detections from radio frequency interference (RFI). These occur across the DM range, so filtering out DM-0 signals is insufficient. We employ DBSCAN data clustering to identify groups within the de-dispersion results, using information for each candidate about time, DM, SNR, and pulse width. DBSCAN is a density-based clustering algorithm that offers two advantages over other clustering methods: 1) the number of clusters need not to be specified, and 2) there is no model of expected cluster shape (such as the Gaussian assumption behind EM clustering). Each data cluster can be selectively masked or investigated to facilitate the process of sifting through hundreds of thousands of detections to focus on those of true interest. Using data obtained by the Byrd Green Bank Telescope (GBT), we show how this approach can help separate RFI from

Planck Early Results. XV. Spectral Energy Distributions and Radio Continuum Spectra of Northern Extragalactic Radio Sources

NASA Technical Reports Server (NTRS)

Aatrokoski, J.; Ade, P. A. R.; Aghanim, N.; Aller, H. D.; Aller, M. F.; Angelakis, E.; Amaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.;

Planck early results. XV. Spectral energy distributions and radio continuum spectra of northern extragalactic radio sources

DOE PAGES

Aatrokoski, J.

2011-12-01

Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources, based on the Planck Early Release Compact Source Catalogue (ERCSC) and simultaneous multifrequency data. The nine Planck frequencies, from 30 to 857GHz, are complemented by a set of simultaneous observations ranging from radio to gamma-rays. This is the first extensive frequency coverage in the radio and millimetre domains for an essentially complete sample of extragalactic radio sources, and it shows how the individual shocks, each in their own phase of development, shape the radio spectra as they move in the relativisticmore » jet. The SEDs presented in this paper were fitted with second and third degree polynomials to estimate the frequencies of the synchrotron and inverse Compton (IC) peaks, and the spectral indices of low and high frequency radio data, including the Planck ERCSC data, were calculated. SED modelling methods are discussed, with an emphasis on proper, physical modelling of the synchrotron bump using multiple components. Planck ERCSC data also suggest that the original accelerated electron energy spectrum could be much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The implications of this are discussed for the acceleration mechanisms effective in blazar shock. Furthermore in many cases the Planck data indicate that gamma-ray emission must originate in the same shocks that produce the radio emission.« less

ULF radio monitoring network in a seismic area

NASA Astrophysics Data System (ADS)

Toader, Victorin; Moldovan, Iren-Adelina; Ionescu, Constantin; Marmureanu, Alexandru

2017-04-01

ULF monitoring is a part of a multidisciplinary network (AeroSolSys) located in Vrancea (Curvature Carpathian Mountains). Four radio receivers (100 kHz - microwave) placed on faults in a high seismic area characterized by deep earthquakes detect fairly weak radio waves. The radio power is recorded in correlation with many other parameters related to near surface low atmosphere phenomena (seismicity, solar radiation, air ionization, electromagnetic activity, radon, CO2 concentration, atmospheric pressure, telluric currents, infrasound, seismo-acoustic emission, meteorological information). We follow variations in the earth's surface propagate radio waves avoiding reflection on ionosphere. For this reason the distance between stations is less than 60 km and the main source of emission is near (Bod broadcasting transmitter for long- and medium-wave radio, next to Brasov city). In the same time tectonic stress affects the radio propagation in air and it could generates ULF waves in ground (LAI coupling). To reduce the uncertainty is necessary to monitor a location for extended periods of time to outline local and seasonal fluctuations. Solar flares do not affect seismic activity but they produce disturbances in telecommunications networks and power grids. Our ULF monitoring correlated with two local magnetometers does not indicate this so far with our receivers. Our analysis was made during magnetic storms with Kp 7 and 8 according to NOAA satellites. To correlate the results we implemented an application that monitors the satellite EUTELSAT latency compared to WiMAX land communication in the same place. ULF band radio monitoring showed that our receiver is dependent on temperature and that it is necessary to introduce a band pass filter in data analysis. ULF data acquisition is performed by Kinemetrics and National Instruments digitizers with a sampling rate of 100 Hz in Miniseed format and then converted into text files with 1 Hz rate for analysis in very low

National surveys of radiofrequency field strengths from radio base stations in Africa

PubMed Central

Joyner, Ken H.; Van Wyk, Marthinus J.; Rowley, Jack T.

2014-01-01

The authors analysed almost 260 000 measurement points from surveys of radiofrequency (RF) field strengths near radio base stations in seven African countries over two time frames from 2001 to 2003 and 2006 to 2012. The results of the national surveys were compared, chronological trends investigated and potential exposures compared by technology and with frequency modulation (FM) radio. The key findings from thes data are that irrespective of country, the year and mobile technology, RF fields at a ground level were only a small fraction of the international human RF exposure recommendations. Importantly, there has been no significant increase in typical measured levels since the introduction of 3G services. The mean levels in these African countries are similar to the reported levels for countries of Asia, Europe and North America using similar mobile technologies. The median level for the FM services in South Africa was comparable to the individual but generally lower than the combined mobile services. PMID:24044904

Rydberg-atom based radio-frequency electrometry using frequency modulation spectroscopy in room temperature vapor cells.

PubMed

Kumar, Santosh; Fan, Haoquan; Kübler, Harald; Jahangiri, Akbar J; Shaffer, James P

2017-04-17

Rydberg atom-based electrometry enables traceable electric field measurements with high sensitivity over a large frequency range, from gigahertz to terahertz. Such measurements are particularly useful for the calibration of radio frequency and terahertz devices, as well as other applications like near field imaging of electric fields. We utilize frequency modulated spectroscopy with active control of residual amplitude modulation to improve the signal to noise ratio of the optical readout of Rydberg atom-based radio frequency electrometry. Matched filtering of the signal is also implemented. Although we have reached similarly, high sensitivity with other read-out methods, frequency modulated spectroscopy is advantageous because it is well-suited for building a compact, portable sensor. In the current experiment, ∼3 µV cm^-1 Hz^-1/2 sensitivity is achieved and is found to be photon shot noise limited.

Hardware Architecture Study for NASA's Space Software Defined Radios

NASA Technical Reports Server (NTRS)

Reinhart, Richard C.; Scardelletti, Maximilian C.; Mortensen, Dale J.; Kacpura, Thomas J.; Andro, Monty; Smith, Carl; Liebetreu, John

2008-01-01

This study defines a hardware architecture approach for software defined radios to enable commonality among NASA space missions. The architecture accommodates a range of reconfigurable processing technologies including general purpose processors, digital signal processors, field programmable gate arrays (FPGAs), and application-specific integrated circuits (ASICs) in addition to flexible and tunable radio frequency (RF) front-ends to satisfy varying mission requirements. The hardware architecture consists of modules, radio functions, and and interfaces. The modules are a logical division of common radio functions that comprise a typical communication radio. This paper describes the architecture details, module definitions, and the typical functions on each module as well as the module interfaces. Trade-offs between component-based, custom architecture and a functional-based, open architecture are described. The architecture does not specify the internal physical implementation within each module, nor does the architecture mandate the standards or ratings of the hardware used to construct the radios.

Diversity of Approaches to Structuring University-Based Earth System Science Education

NASA Astrophysics Data System (ADS)

Aron, J.; Ruzek, M.; Johnson, D. R.

2004-12-01

Over the past quarter century, the "Earth system science" paradigm has emerged among the interdisciplinary science community, emphasizing interactions among components hitherto considered within separate disciplines: atmosphere (air); hydrosphere (water); biosphere (life); lithosphere (land); anthroposphere (human dimension); and exosphere (solar system and beyond). How should the next generation of Earth system scientists learn to contribute to this interdisciplinary endeavor? There is no one simple answer. The Earth System Science Education program, funded by NASA, has addressed this question by supporting faculty at U.S. universities who develop new courses, curricula and degree programs in their institutional contexts. This report demonstrates the diversity of approaches to structuring university-based Earth system science education, focusing on the 18 current grantees of the Earth System Science Education Program for the 21st Century (ESSE21). One of the most fundamental characteristics is the departmental structure for teaching Earth system science. The "home" departments of the Earth system science faculty range from Earth sciences and physics to agronomy and social work. A brand-new institution created an interdisciplinary Institute for Earth Systems Science and Policy without traditional "parent" departments. Some institutions create new degree programs as majors or as minors while others work within existing degree programs to add or revise courses. A university may also offer multiple strands, such as a degree in the Science of the Earth System and a degree in the Human Dimensions of the Earth System. Defining a career path is extremely important to students considering Earth system science programs and a major institutional challenge for all programs in Earth system science education. How will graduate programs assess prospective students? How will universities and government agencies assess prospective faculty and scientists? How will government

Radio Measurements of Air Showers with LOPES

NASA Astrophysics Data System (ADS)

Schröder, F. G.; Apel, W. D.; Arteaga-Velazquez, J. C.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Cantoni, E.; Chiavassa, A.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Falcke, H.; Fuchs, B.; Fuhrmann, D.; Gemmeke, H.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Horneffer, A.; Huber, D.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Krömer, O.; Kuijpers, J.; Link, K.; Łuczak, P.; Ludwig, M.; Mathes, H. J.; Melissas, M.; Morello, C.; Oehlschläger, J.; Palmieri, N.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Rühle, C.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Sima, O.; Toma, G.; Trinchero, G. C.; Weindl, A.; Wochele, J.; Zabierowski, J.; Zensus, J. A.

2013-02-01

LOPES is a digital antenna array for the radio measurement of cosmic-ray air showers at energies around 1017 eV. It is triggered by the KASCADE-Grande air-shower array at the Karlsruhe Institute of Technology (KIT), Germany. Because of an absolute amplitude calibration and a sophisticated data analysis, LOPES can test models for the radio emission to an up-to-now unachieved level, thus improving our understanding of the radio emission mechanisms. Recent REAS simulations of the air-shower radio emission come closer to the measurements than any previously tested simulations. We have determined the radio-reconstruction precision of interesting air-shower parameters by comparing LOPES reconstructions to both REAS simulations and KASCADE-Grande measurements, and present our latest results for the angular resolution, the energy and the Xmax reconstruction based on the radio measurement of about 500 air showers. Although the precision of LOPES is limited by the high level of anthropogenic noise at KIT, it opens a promising perspective for next-generation radio arrays in regions with a lower ambient noise level.

Student-Teachers' Use of "Google Earth" in Problem-Based Geology Learning

ERIC Educational Resources Information Center

Ratinen, Ilkka; Keinonen, Tuula

2011-01-01

Geographical Information Systems (GIS) are adequate for analyzing complex scientific and spatial phenomena in geography education. "Google Earth" is a geographic information tool for GIS-based learning. It allows students to engage in the lesson, explore the Earth, explain what they identify and evaluate the implications of what they are…

Spectrum sharing in cognitive radio networks--an auction-based approach.

PubMed

Wang, Xinbing; Li, Zheng; Xu, Pengchao; Xu, Youyun; Gao, Xinbo; Chen, Hsiao-Hwa

2010-06-01

Cognitive radio is emerging as a promising technique to improve the utilization of the radio frequency spectrum. In this paper, we consider the problem of spectrum sharing among primary (or "licensed") users (PUs) and secondary (or "unlicensed") users (SUs). We formulate the problem based on bandwidth auction, in which each SU makes a bid for the amount of spectrum and each PU may assign the spectrum among the SUs by itself according to the information from the SUs without degrading its own performance. We show that the auction is a noncooperative game and that Nash equilibrium (NE) can be its solution. We first consider a single-PU network to investigate the existence and uniqueness of the NE and further discuss the fairness among the SUs under given conditions. Then, we present a dynamic updating algorithm in which each SU achieves NE in a distributed manner. The stability condition of the dynamic behavior for this spectrum-sharing scheme is studied. The discussion is generalized to the case in which there are multiple PUs in the network, where the properties of the NE are shown under appropriate conditions. Simulations were used to evaluate the system performance and verify the effectiveness of the proposed algorithm.

Instructional Radio Reconsidered; An International Perspective.

ERIC Educational Resources Information Center

Theroux, James M.

Though the use of educational radio has fallen from fashion, for three reasons it deserves reconsideration as a valuable educational tool: 1) it is economical, costing only a fraction of the required expense to deliver the same material via television; 2) the effectiveness of radio-based instruction has been shown to be equal to that of…

Computing angle of arrival of radio signals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borchardt, John J.; Steele, David K.

Various technologies pertaining to computing angle of arrival of radio signals are described. A system that is configured for computing the angle of arrival of a radio signal includes a cylindrical sheath wrapped around a cylindrical object, where the cylindrical sheath acts as a ground plane. The system further includes a plurality of antennas that are positioned about an exterior surface of the cylindrical sheath, and receivers respectively coupled to the antennas. The receivers output measurements pertaining to the radio signal. A processing circuit receives the measurements and computes the angle of arrival of the radio signal based upon themore » measurements.« less

Type III-L Solar Radio Bursts and Solar Energetic Particle Events

NASA Astrophysics Data System (ADS)

Duffin, R. T.; White, S. M.; Ray, P. S.; Kaiser, M. L.

2015-09-01

A radio-selected sample of fast drift radio bursts with complex structure occurring after the impulsive phase of the associated flare (“Type III-L bursts”) is identified by inspection of radio dynamic spectra from 1 to 180 MHz for over 300 large flares in 2001. An operational definition that takes into account previous work on these radio bursts starting from samples of solar energetic particle (SEP) events is applied to the data, and 66 Type III-L bursts are found in the sample. In order to determine whether the presence of these radio bursts can be used to predict the occurrence of SEP events, we also develop a catalog of all SEP proton events in 2001 using data from the ERNE detector on the SOHO satellite. 68 SEP events are found, for 48 of which we can identify a solar source and hence look for associated Type III-L emission. We confirm previous work that found that most (76% in our sample) of the solar sources of SEP events exhibit radio emission of this type. However, the correlation in the opposite direction is not as strong: starting from a radio-selected sample of Type III-L events, around 64% of the bursts that occur at longitudes magnetically well-connected to the Earth, and hence favorable for detection of SEPs, are associated with SEP events. The degree of association increases when the events have durations over 10 minutes at 1 MHz, but in general Type III-L bursts do not perform any better than Type II bursts in our sample as predictors of SEP events. A comparison of Type III-L timing with the arrival of near-relativistic electrons at the ACE spacecraft is not inconsistent with a common source for the accelerated electrons in both phenomena.

Theory of Type 3 and Type 2 Solar Radio Emissions

NASA Technical Reports Server (NTRS)

Robinson, P. A.; Cairns, I. H.

2000-01-01

The main features of some current theories of type III and type II bursts are outlined. Among the most common solar radio bursts, type III bursts are produced at frequencies of 10 kHz to a few GHz when electron beams are ejected from solar active regions, entering the corona and solar wind at typical speeds of 0.1c. These beams provide energy to generate Langmuir waves via a streaming instability. In the current stochastic-growth theory, Langmuir waves grow in clumps associated with random low-frequency density fluctuations, leading to the observed spiky waves. Nonlinear wave-wave interactions then lead to secondary emission of observable radio waves near the fundamental and harmonic of the plasma frequency. Subsequent scattering processes modify the dynamic radio spectra, while back-reaction of Langmuir waves on the beam causes it to fluctuate about a state of marginal stability. Theories based on these ideas can account for the observed properties of type III bursts, including the in situ waves and the dynamic spectra of the radiation. Type 11 bursts are associated with shock waves propagating through the corona and interplanetary space and radiating from roughly 30 kHz to 1 GHz. Their basic emission mechanisms are believed to be similar to those of type III events and radiation from Earth's foreshock. However, several sub-classes of type II bursts may exist with different source regions and detailed characteristics. Theoretical models for type II bursts are briefly reviewed, focusing on a model with emission from a foreshock region upstream of the shock for which observational evidence has just been reported.

RadioAstron Science Program Five Years after Launch: Main Science Results

NASA Astrophysics Data System (ADS)

Kardashev, N. S.; Alakoz, A. V.; Andrianov, A. S.; Artyukhov, M. I.; Baan, W.; Babyshkin, V. E.; Bartel, N.; Bayandina, O. S.; Val'tts, I. E.; Voitsik, P. A.; Vorobyov, A. Z.; Gwinn, C.; Gomez, J. L.; Giovannini, G.; Jauncey, D.; Johnson, M.; Imai, H.; Kovalev, Y. Y.; Kurtz, S. E.; Lisakov, M. M.; Lobanov, A. P.; Molodtsov, V. A.; Novikov, B. S.; Pogodin, A. V.; Popov, M. V.; Privesenzev, A. S.; Rudnitski, A. G.; Rudnitski, G. M.; Savolainen, T.; Smirnova, T. V.; Sobolev, A. M.; Soglasnov, V. A.; Sokolovsky, K. V.; Filippova, E. N.; Khartov, V. V.; Churikova, M. E.; Shirshakov, A. E.; Shishov, V. I.; Edwards, P.

2017-12-01

The RadioAstron ground-space interferometer provides the highest angular resolution achieved now in astronomy. The detection of interferometric fringes from quasars with this angular resolution on baselines of 100-200 thousand km suggests the brightness temperatures which exceed the Compton limit by two orders of magnitude. Polarimetric measurements on ground-space baselines have revealed fine structure testifying to recollimation shocks on scales of 100-250 μas and a helical magnetic field near the base of radio emission in BL Lacertae. Substructure within a the scattering disk of pulsar emission on interferometer baselines (from 60000 to 250000 km) was discovered. This substructure is produced by action of the interstellar interferometer with an effective baseline of about 1 AU and the effective angular resolution of better than 1 μas. Diameters of scattering disks were measured for several pulsars, and distances to diffusing screens were evaluated. The ground-space observations of sources of the maser radiation in lines of water and hydroxyl have shown that the maser sources in star-forming regions remain unresolved on baselines, which considerably exceed the Earth diameter. These very compact and bright features with angular sizes of about 20-60 μas correspond to linear sizes of about 5-10 million km (several solar diameters).

Galaxy-wide radio-induced feedback in a radio-quiet quasar

NASA Astrophysics Data System (ADS)

Villar-Martín, M.; Emonts, B.; Cabrera Lavers, A.; Tadhunter, C.; Mukherjee, D.; Humphrey, A.; Rodríguez Zaurín, J.; Ramos Almeida, C.; Pérez Torres, M.; Bessiere, P.

2017-12-01

We report the discovery of a radio-quiet type 2 quasar (SDSS J165315.06+234943.0 nicknamed the 'Beetle' at z = 0.103) with unambiguous evidence for active galactic nucleus (AGN) radio-induced feedback acting across a total extension of ∼46 kpc and up to ∼26 kpc from the AGN. To the best of our knowledge, this is the first radio-quiet system where radio-induced feedback has been securely identified at ≫several kpc from the AGN. The morphological, ionization and kinematic properties of the extended ionized gas are correlated with the radio structures. We find along the radio axis (a) enhancement of the optical line emission at the location of the radio hotspots (b) turbulent gas kinematics (FWHM ∼ 380-470 km s-1) across the entire spatial range circumscribed by them (c) ionization minima for the turbulent gas at the location of the hot spots, (d) high temperature Te ≳ 1.9 × 104 K at the NE hotspot. Turbulent gas is also found far from the radio axis, ∼25 kpc in the perpendicular direction. We propose a scenario in which the radio structures have perforated the interstellar medium of the galaxy and escaped into the circumgalactic medium. While advancing, they have interacted with in situ gas modifying its properties. Our results show that jets of modest power can be the dominant feedback mechanism acting across huge volumes in radio-quiet systems, including highly accreting luminous AGNs, where radiative mode feedback may be expected.

Earth Adventure: Virtual Globe-based Suborbital Atmospheric Greenhouse Gases Exploration

NASA Astrophysics Data System (ADS)

Wei, Y.; Landolt, K.; Boyer, A.; Santhana Vannan, S. K.; Wei, Z.; Wang, E.

2016-12-01

The Earth Venture Suborbital (EVS) mission is an important component of NASA's Earth System Science Pathfinder program that aims at making substantial advances in Earth system science through measurements from suborbital platforms and modeling researches. For example, the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) project of EVS-1 collected measurements of greenhouse gases (GHG) on local to regional scales in the Alaskan Arctic. The Atmospheric Carbon and Transport - America (ACT-America) project of EVS-2 will provide advanced, high-resolution measurements of atmospheric profiles and horizontal gradients of CO2 and CH4.As the long-term archival center for CARVE and the future ACT-America data, the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC) has been developing a versatile data management system for CARVE data to maximize their usability. One of these efforts is the virtual globe-based Suborbital Atmospheric GHG Exploration application. It leverages Google Earth to simulate the 185 flights flew by the C-23 Sherpa aircraft in 2012-2015 for the CARVE project. Based on Google Earth's 3D modeling capability and the precise coordinates, altitude, pitch, roll, and heading info of the aircraft recorded in every second during each flight, the application provides users accurate and vivid simulation of flight experiences, with an active 3D visualization of a C-23 Sherpa aircraft in view. This application provides dynamic visualization of GHG, including CO2, CO, H2O, and CH4 captured during the flights, at the same pace of the flight simulation in Google Earth. Photos taken during those flights are also properly displayed along the flight paths. In the future, this application will be extended to incorporate more complicated GHG measurements (e.g. vertical profiles) from the ACT-America project. This application leverages virtual globe technology to provide users an integrated framework to interactively explore information

Near Earth Asteroid redirect missions based on gravity assist maneuver

NASA Astrophysics Data System (ADS)

Ledkov, Anton; Shustov, Boris M.; Eismont, Natan; Boyarsky, Michael; Nazirov, Ravil; Fedyaev, Konstantin

gravity assist maneuver near Earth resulted by following impact with dangerous asteroid. As example of the last one the Apophis was chosen. The required delta-V pulse to be applied to the candidate projectile asteroid to fulfill mentioned change of initial trajectory was confirmed to be comparatively small: not exceeding 10 m/s, and the smallest is about 2 m/s. To fulfilled this maneuver it is necessary to land and to mount on the surface of the asteroid projectile the spacecraft with sufficient amount of propellant onboard. The possible trajectories and demanded maneuvers were explored and it was confirmed that for contemporary space technology it is doable for the small asteroids belonging to the determined by our studies list of candidates supposing some reservations, namely the mass of the found asteroids. This was not considered as decisive obstacle because up to now only about 1% of small enough asteroids are included in catalogue so the list of the appropriate ones is far from to be closed. The studies have been fulfilled aimed to develop the methods to reached required accuracies of asteroid projectile trajectory parameters determination. With existing methods used for the usual spacecraft the limits of achievable accuracies demand the corrections delta-V maneuvers which may exceed the nominal ones. As a result the proposed conception of hazardous asteroids deflection becomes problematic. To overcome this obstacle in the paper new method of trajectory parameters determination is proposed and explored. Practically it is radio interferometer method when one transponder is placed on the asteroid target and two others together with the asteroid projectile form tetrahedron. This system begins to operate in vicinity of target asteroid in autonomous regime and expected to allow reaching the demanded low enough correction maneuver values. Paper gives the estimations of the accuracy of these three bodies relative motion parameters and expected limit values of correction

Integrating Research of the Sun-Earth System

DOE PAGES

Jordanova, Vania K.; Borovsky, Joseph E.; Jordanov, Valentin T.

2017-05-02

Understanding the complex interactions between the magnetic fields of the Sun and Earth remains an important challenge to space physics research. Processes that occur near the Sun at tens of thousands of kilometers from the Earth can generate geomagnetic storms that affect the entire magnetosphere, down to the upper atmosphere. These storms also threaten the ever more sophisticated technologies that we place into the space environment to sustain us, for example, GPS, the satellites we rely on to monitor our weather, and relays that guide our radio transmissions. Increasingly, we need to develop space weather models that can provide timelymore » and accurate predictions so that we can safeguard our society and the infrastructure we depend on.« less

Integrating Research of the Sun-Earth System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordanova, Vania K.; Borovsky, Joseph E.; Jordanov, Valentin T.

Understanding the complex interactions between the magnetic fields of the Sun and Earth remains an important challenge to space physics research. Processes that occur near the Sun at tens of thousands of kilometers from the Earth can generate geomagnetic storms that affect the entire magnetosphere, down to the upper atmosphere. These storms also threaten the ever more sophisticated technologies that we place into the space environment to sustain us, for example, GPS, the satellites we rely on to monitor our weather, and relays that guide our radio transmissions. Increasingly, we need to develop space weather models that can provide timelymore » and accurate predictions so that we can safeguard our society and the infrastructure we depend on.« less

On the origins of part-time radio pulsars

NASA Astrophysics Data System (ADS)

Zhang, Bing; Gil, Janusz; Dyks, Jaroslaw

2007-01-01

Growing evidence suggests that some radio pulsars only act sporadically. These `part-time' pulsars include long-term nulls, quasi-periodic radio flares in PSR B1931+24, as well as the so-called Rotating Radio Transients (RRATs). Based on the assumption that these objects are isolated neutron stars similar to conventional radio pulsars, we discuss two possible interpretations to the phenomenon. The first interpretation suggests that these objects are pulsars slightly below the radio emission `death line', which become occasionally active only when the conditions for pair production and coherent emission are satisfied. The second interpretation invokes a radio emission direction reversal in conventional pulsars, as has been introduced to interpret the peculiar mode changing phenomenon in PSR B1822-09. In this picture, our line of sight misses the main radio emission beam of the pulsar but happens to sweep the emission beam when the radio emission direction is reversed. These part-time pulsars are therefore the other half of `nulling' pulsars. We suggest that X-ray observations may provide clues to differentiate between these two possibilities.

Youngest Radio Pulsar Revealed with Green Bank Telescope

NASA Astrophysics Data System (ADS)

2002-04-01

Astronomers using the National Science Foundation's (NSF) newly commissioned Robert C. Byrd Green Bank Telescope (GBT) have detected remarkably faint radio signals from an 820 year-old pulsar, making it the youngest radio-emitting pulsar known. This discovery pushes the boundaries of radio telescope sensitivity for discovering pulsars, and will enable scientists to conduct observations that could lead to a better understanding of how these stars evolve. The Robert C. Byrd Green Bank Telescope Robert C. Byrd Green Bank Telescope "Important questions about pulsars may be answered by long-term monitoring of objects such as the one we just detected," said Fernando Camilo of Columbia University in New York City. "Young pulsars are particularly rare, and being able to study such a young one at radio wavelengths provides an outstanding opportunity to learn critical facts about their evolution and workings." The results of this research, based on observations conducted on February 22-23, 2002, were accepted for publication in the Astrophysical Journal Letters. Scientists have long suspected that a pulsar - a rapidly spinning, superdense neutron star - was born when a giant star ended its life in a cataclysmic supernova explosion observed in late summer of 1181, as suggested by Japanese and Chinese historical records. For the past 20 years, astronomers have searched this supernova remnant (3C58), located 10,000 light-years away in the constellation Cassiopeia, for the telltale pulsations of a newly born pulsar. Late in 2001, data from NASA's Chandra X-ray satellite confirmed its existence, but it remained an elusive quarry for radio telescopes. "We believed from historical records and certainly knew from recent X-ray observations that this star was there," Camilo remarked, "but despite many attempts, no one had been able to find any radio pulsations from it because the signals are, it turns out, incredibly weak." For comparison, this pulsar's radio emission is some 250

NASA Near Earth Network (NEN) Support for Lunar and L1/L2 CubeSats

NASA Technical Reports Server (NTRS)

Schaire, Scott; Altunc, Serhat; Wong, Yen; Shelton, Marta; Celeste, Peter; Anderson, Michael; Perrotto, Trish

2017-01-01

The NASA Near Earth Network (NEN) consists of globally distributed tracking stations, including NASA, commercial, and partner ground stations, that are strategically located to maximize the coverage provided to a variety of orbital and suborbital missions, including those in LEO, GEO, HEO, lunar and L1/L2 orbits. The NENs future mission set includes and will continue to include CubeSat missions. The majority of the CubeSat missions destined to fly on EM-1, launching in late 2018, many in a lunar orbit, will communicate with ground based stations via X-band and will utilize the NASA Jet Propulsion Laboratory (JPL) developed IRIS radio. The NEN recognizes the important role CubeSats are beginning to play in carrying out NASAs mission and is therefore investigating the modifications needed to provide IRIS radio compatibility. With modification, the NEN could potentially expand support to the EM-1 lunar CubeSats.The NEN could begin providing significant coverage to lunar CubeSat missions utilizing three to four of the NENs mid-latitude sites. This coverage would supplement coverage provided by the JPL Deep Space Network (DSN). The NEN, with smaller apertures than DSN, provides the benefit of a larger beamwidth that could be beneficial in the event of uncertain ephemeris data. In order to realize these benefits the NEN would need to upgrade stations targeted based on coverage ability and current configuration/ease of upgrade, to ensure compatibility with the IRIS radio. In addition, the NEN is working with CubeSat radio developers to ensure NEN compatibility with alternative CubeSat radios for Lunar and L1/L2 CubeSats. The NEN has provided NEN compatibility requirements to several radio developers who are developing radios that offer lower cost and, in some cases, more capabilities with fewer constraints. The NEN is ready to begin supporting CubeSat missions. The NEN is considering network upgrades to broaden the types of CubeSat missions that can be supported and is

Mass Determination of Pluto and Charon from New Horizon REX Radio Science Observations

NASA Astrophysics Data System (ADS)

Pätzold, M.; Andert, T. P.; Tyler, G. L.; Bird, M. K.; Hinson, D. H.; Linscott, I. R.

2013-09-01

The anticipated 14 July 2015 New Horizons flythrough of the Pluto system provides the first opportunity to determine both the total system mass and the individual masses of Pluto and Charon by direct observation. This will be accomplished by use of: i) two-way Doppler radio frequency tracking data during intervals along the fly-in and -out trajectory, and ii) one-way uplink Doppler frequency recorded by the on-board radio science instrument, REX, during the day of closest approaches to Pluto and Charon. Continuous tracking is not feasible as a result of pointing sharing with the instruments during the encounter phase. Needed radio tracking will be obtained during time slots shared with i) two-way Doppler tracking for navigation, ii) 'plasma rolls' with the spacecraft antenna pointing to Earth, and iii) during the ingress and egress phases of the occultations. Simulations of the NH encounter indicate the potential accuracies of the combined and individual mass determinations of Pluto and Charon in the order of 0.1%.

New Antennas and Methods for the Low Frequency Stellar and Planetary Radio Astronomy

NASA Astrophysics Data System (ADS)

Konovalenko, A. A.; Falkovich, I. S.; Rucker, H. O.; Lecacheux, A.; Zarka, Ph.; Koliadin, V. L.; Zakharenko, V. V.; Stanislavsky, A. A.; Melnik, V. N.; Litvinenko, G. V.; Gridin, A. A.; Bubnov, I. N.; Kalinichenko, N. N.; Reznik, A. P.; Sidorchuk, M. A.; Stepkin, S. V.; Mukha, D. V.; Nikolajenko, V. S.; Karlsson, R.; Thide, B.

According to the special Program of the National Academy of Sciences of Ukraine, creation of the new giant Ukrainian radio telescope (GURT) was started a few years ago on the UTR-2 radio telescope observatory. The main goal is to reach maximum band at the lowest frequencies (10-70 MHz), effective area (step-by-step up to 100,000 sq.m), and high interference immunity for resolving many astrophysical tasks when the sensitivity is less limited by the confusion effects. These tasks include stellar radio astronomy (the Sun, solar wind, flare stars, pulsars, transients) and planetary one (Jupiter, planetary lightnings, Earth ionosphere, the Moon, exoplanets). This array should be complementary to the LOFAR, E-LOFAR systems. The first stages of the GURT (6 x 25 cross dipole active elements) and broad-band digital registration of the impulsive and sporadic events were tested in comparison with the existing largest decameter array UTR-2.

Dense solar wind cloud geometries deduced from comparisons of radio signal delay and in situ plasma measurements

NASA Technical Reports Server (NTRS)

Landt, J. A.

1974-01-01

The geometries of dense solar wind clouds are estimated by comparing single-location measurements of the solar wind plasma with the average of the electron density obtained by radio signal delay measurements along a radio path between earth and interplanetary spacecraft. Several of these geometries agree with the current theoretical spatial models of flare-induced shock waves. A new class of spatially limited structures that contain regions with densities greater than any observed in the broad clouds is identified. The extent of a cloud was found to be approximately inversely proportional to its density.

A Kalman-Filter-Based Approach to Combining Independent Earth-Orientation Series

NASA Technical Reports Server (NTRS)

Gross, Richard S.; Eubanks, T. M.; Steppe, J. A.; Freedman, A. P.; Dickey, J. O.; Runge, T. F.

1998-01-01

An approach. based upon the use of a Kalman filter. that is currently employed at the Jet Propulsion Laboratory (JPL) for combining independent measurements of the Earth's orientation, is presented. Since changes in the Earth's orientation can be described is a randomly excited stochastic process, the uncertainty in our knowledge of the Earth's orientation grows rapidly in the absence of measurements. The Kalman-filter methodology allows for an objective accounting of this uncertainty growth, thereby facilitating the intercomparison of measurements taken at different epochs (not necessarily uniformly spaced in time) and with different precision. As an example of this approach to combining Earth-orientation series, a description is given of a combination, SPACE95, that has been generated recently at JPL.

Teaching radio astronomy with Affordable Small Radio Telescope (ASRT)

NASA Astrophysics Data System (ADS)

Joshi, Bhal Chandra

A simple, easy to build and portable radio telescope, called Affordable Small Radio Telescope (ASRT), has been developed by the Radio Physics Laboratory (RPL), a radio astronomy teaching unit associated with the National Centre for Radio Astrophysics (TIFR) and Inter-University Centre for Astronomy and Astrophysics (IUCAA), which are two premier astronomy institutes in India. ASRT consists of off-the-shelf available Direct to Home television dishes and is easy to assemble. Our design is scalable from simple very low cost telescope to more complex yet moderately costing instrument. ASRT provides a platform for demonstrating radio physics concepts through simple hands-on experiment as well as for carrying out solar monitoring by college/University students. The presentation will highlight the concept of ASRT and the different experiments that can be carried out using it. The solar monitoring observations will be discussed along-with details of methods for calibrating these measurements. The pedagogical usefulness of ASRT in introducing undergraduatephysics students to astrophysics, measurements and analysis methods used in radio astronomy will also be discussed. Use of ASRT in the last three years in the programs of RPL, namely the annual Radio Astronomy Winter School for College students (RAWSC) and Pulsar Observing for Students (POS) is also presented. This year a new program was initiated to form a virtual group of an ASRT community, which will not only share their measurements, but also think of improving the pedagogical usefulness of ASRT by innovative experiments. This initiative is presented with the best practices drawn from our experience in using ASRT as a tool for student training in space sciences. The talk will also point out future ideas in involving a larger body of students in simple radio astronomy experiments with the ASRT, which RPL is likely to nucleate as part of its mandate.

Galileo radio science investigations

NASA Technical Reports Server (NTRS)

Howard, H. T.; Eshleman, V. R.; Hinson, D. P.; Kliore, A. J.; Lindal, G. F.; Woo, R.; Bird, M. K.; Volland, H.; Edenhoffer, P.; Paetzold, M.

1992-01-01

Galileo radio-propagation experiments are based on measurements of absolute and differential propagation time delay, differential phase delay, Doppler shift, signal strength, and polarization. These measurements can be used to study: the atmospheric and ionospheric structure, constituents, and dynamics of Jupiter; the magnetic field of Jupiter; the diameter of Io, its ionospheric structure, and the distribution of plasma in the Io torus; the diameters of the other Galilean satellites, certain properties of their surfaces, and possibly their atmospheres and ionospheres; and the plasma dynamics and magnetic field of the solar corona. The spacecraft system provides linear rather than circular polarization on the S-band downlink signal, the capability to receive X-band uplink signals, and a differential downlink ranging mode. A highly-stable, dual-frequency, spacecraft radio system is developed that is suitable for simultaneous measurements of all the parameters normally attributed to radio waves.

Comparison of Earth Science Achievement between Animation-Based and Graphic-Based Testing Designs

ERIC Educational Resources Information Center

Wu, Huang-Ching; Chang, Chun-Yen; Chen, Chia-Li D.; Yeh, Ting-Kuang; Liu, Cheng-Chueh

2010-01-01

This study developed two testing devices, namely the animation-based test (ABT) and the graphic-based test (GBT) in the area of earth sciences covering four domains that ranged from astronomy, meteorology, oceanography to geology. Both the students' achievements of and their attitudes toward ABT compared to GBT were investigated. The purposes of…

Radio emissions from pulsar companions: a refutable explanation for galactic transients and fast radio bursts

NASA Astrophysics Data System (ADS)

Mottez, F.; Zarka, P.

2014-09-01

Context. The six known highly dispersed fast radio bursts are attributed to extragalactic radio sources that are of unknown origin but extremely energetic. We propose here a new explanation that does not require an extreme release of energy and involves a body (planet, asteroid, white dwarf) orbiting an extragalactic pulsar. Aims: We investigate a theory of radio waves associated with such pulsar-orbiting bodies. We focus our analysis on the waves emitted from the magnetic wake of the body in the pulsar wind. After deriving their properties, we compare them with the observations of various transient radio signals to determine whether they could originate from pulsar-orbiting bodies. Methods: The analysis is based on the theory of Alfvén wings: for a body immersed in a pulsar wind, a system of two stationary Alfvén waves is attached to the body, provided that the wind is highly magnetised. When they are destabilised through plasma instabilities, Alfvén wings can be the locus of strong radio sources that are convected with the pulsar wind. By assuming a cyclotron maser instability operating in the Alfvén wings, we make predictions about the shape, frequencies, and brightness of the resulting radio emissions. Results: Because of the beaming by relativistic aberration, the signal is seen only when the companion is perfectly aligned between its parent pulsar and the observer, as is the case for occultations. For pulsar winds with a high Lorentz factor (≥104), the whole duration of the radio event does not exceed a few seconds, and it is composed of one to four peaks that last a few milliseconds each and are detectable up to distances of several Mpc. The Lorimer burst, the three isolated pulses of PSR J1928+15, and the recently detected fast radio bursts are all compatible with our model. According to it, these transient signals should repeat periodically with the companion's orbital period. Conclusions: The search of pulsar-orbiting bodies could be an exploration

Occultations of Astrophysical Radio Sources as Probes of Planetary Environments: A Case Study of Jupiter and Possible Applications to Exoplanets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Withers, Paul; Vogt, Marissa F.

Properties of planetary atmospheres, ionospheres, and magnetospheres are difficult to measure from Earth. Radio occultations are a common method for measuring these properties, but they traditionally rely on radio transmissions from a spacecraft near the planet. Here, we explore whether occultations of radio emissions from a distant astrophysical radio source can be used to measure magnetic field strength, plasma density, and neutral density around planets. In a theoretical case study of Jupiter, we find that significant changes in polarization angle due to Faraday rotation occur for radio signals that pass within 10 Jupiter radii of the planet and that significantmore » changes in frequency and power occur from radio signals that pass through the neutral atmosphere. There are sufficient candidate radio sources, such as pulsars, active galactic nuclei, and masers, that occultations are likely to occur at least once per year. For pulsars, time delays in the arrival of their emitted pulses can be used to measure plasma density. Exoplanets, whose physical properties are very challenging to observe, may also occult distant astrophysical radio sources, such as their parent stars.« less

Navigating the Return Trip from the Moon Using Earth-Based Ground Tracking and GPS

NASA Technical Reports Server (NTRS)

Berry, Kevin; Carpenter, Russell; Moreau, Michael C.; Lee, Taesul; Holt, Gregg N.

2009-01-01

NASA s Constellation Program is planning a human return to the Moon late in the next decade. From a navigation perspective, one of the most critical phases of a lunar mission is the series of burns performed to leave lunar orbit, insert onto a trans-Earth trajectory, and target a precise re-entry corridor in the Earth s atmosphere. A study was conducted to examine sensitivity of the navigation performance during this phase of the mission to the type and availability of tracking data from Earth-based ground stations, and the sensitivity to key error sources. This study also investigated whether GPS measurements could be used to augment Earth-based tracking data, and how far from the Earth GPS measurements would be useful. The ability to track and utilize weak GPS signals transmitted across the limb of the Earth is highly dependent on the configuration and sensitivity of the GPS receiver being used. For this study three GPS configurations were considered: a "standard" GPS receiver with zero dB antenna gain, a "weak signal" GPS receiver with zero dB antenna gain, and a "weak signal" GPS receiver with an Earth-pointing direction antenna (providing 10 dB additional gain). The analysis indicates that with proper selection and configuration of the GPS receiver on the Orion spacecraft, GPS can potentially improve navigation performance during the critical final phases of flight prior to Earth atmospheric entry interface, and may reduce reliance on two-way range tracking from Earth-based ground stations.

Improved Wireless Security through Physical Layer Protocol Manipulation and Radio Frequency Fingerprinting

DTIC Science & Technology

2014-09-18

radios in a cognitive radio network using a radio frequency fingerprinting based method. In IEEE International Conference on Communications (ICC...IMPROVEDWIRELESS SECURITY THROUGH PHYSICAL LAYER PROTOCOL MANIPULATION AND RADIO FREQUENCY FINGERPRINTING DISSERTATION Benjamin W. Ramsey, Captain...PHYSICAL LAYER PROTOCOL MANIPULATION AND RADIO FREQUENCY FINGERPRINTING DISSERTATION Presented to the Faculty Graduate School of Engineering and

Associating Fast Radio Bursts with Extragalactic Radio Sources: General Methodology and a Search for a Counterpart to FRB 170107

NASA Astrophysics Data System (ADS)

Eftekhari, T.; Berger, E.; Williams, P. K. G.; Blanchard, P. K.

2018-06-01

The discovery of a repeating fast radio burst (FRB) has led to the first precise localization, an association with a dwarf galaxy, and the identification of a coincident persistent radio source. However, further localizations are required to determine the nature of FRBs, the sources powering them, and the possibility of multiple populations. Here we investigate the use of associated persistent radio sources to establish FRB counterparts, taking into account the localization area and the source flux density. Due to the lower areal number density of radio sources compared to faint optical sources, robust associations can be achieved for less precise localizations as compared to direct optical host galaxy associations. For generally larger localizations that preclude robust associations, the number of candidate hosts can be reduced based on the ratio of radio-to-optical brightness. We find that confident associations with sources having a flux density of ∼0.01–1 mJy, comparable to the luminosity of the persistent source associated with FRB 121102 over the redshift range z ≈ 0.1–1, require FRB localizations of ≲20″. We demonstrate that even in the absence of a robust association, constraints can be placed on the luminosity of an associated radio source as a function of localization and dispersion measure (DM). For DM ≈1000 pc cm‑3, an upper limit comparable to the luminosity of the FRB 121102 persistent source can be placed if the localization is ≲10″. We apply our analysis to the case of the ASKAP FRB 170107, using optical and radio observations of the localization region. We identify two candidate hosts based on a radio-to-optical brightness ratio of ≳100. We find that if one of these is indeed associated with FRB 170107, the resulting radio luminosity (1029‑ 4 × 1030 erg s‑1 Hz‑1, as constrained from the DM value) is comparable to the luminosity of the FRB 121102 persistent source.

Sensors Locate Radio Interference

NASA Technical Reports Server (NTRS)

2009-01-01

After receiving a NASA Small Business Innovation Research (SBIR) contract from Kennedy Space Center, Soneticom Inc., based in West Melbourne, Florida, created algorithms for time difference of arrival and radio interferometry, which it used in its Lynx Location System (LLS) to locate electromagnetic interference that can disrupt radio communications. Soneticom is collaborating with the Federal Aviation Administration (FAA) to install and test the LLS at its field test center in New Jersey in preparation for deploying the LLS at commercial airports. The software collects data from each sensor in order to compute the location of the interfering emitter.

Coping with Radio Frequency Interference

NASA Astrophysics Data System (ADS)

Lewis, B. M.

2009-01-01

The radio spectrum is a finite resource, on which humanity makes many demands. And pressure on it is ever increasing with the development of new technology and ideas for radio services. After all, we all benefit from wifi and cell phones. Radio astronomers have a small percentage of the spectrum allocated to them at octave intervals in the metre-centimetre bands, and at important frequencies, such as that of the 21cm line of HI. Signals from other services, as well as from our own poorly-engineered equipment, sometimes contaminate our bands: these signals constitute RFI. These may totally obliterate the astronomical signal, or, in the case of CLOUDSAT, may be capable of completely destroying a receiver, which introduces us to the new possibility of 'destructive interference'. A geo-stationary satellite can block access to a piece of sky from one site. Good equipment design eliminates self-inflicted interference, while physical separation often provides adequate practical mitigation at many frequencies. However, new observatories end up being located in the West Australian desert or Antarctica. In future they may be on the back side of the Moon. But there is no Earth-bound protection via physical separation against satellite signals. Some mitigation can be achieved by frequent data dumps and the excision of RFI, or by real-time detection and blanking of the receiver, or by more sophisticated algoriths. Astronomers of necessity aim to achieve mitigation via coordination, at the local level, and by participating in spectrum management at the national and international levels. This involves them spending a lot of time in Geneva at the International Telegraphic Union protecting their access to spectrum, and access to clean spectrum from the L3 point and the far side of the Moon.

A technique for measurement of earth station antenna G/T by radio stars and Applications Technology Satellites.

NASA Technical Reports Server (NTRS)

Kochevar, H. J.

1972-01-01

A new technique has been developed to accurately measure the G/T of a small aperture antenna using geostationary satellites and the well established radio star method. A large aperture antenna having the capability of accurately measuring its G/T by using a radio star of known power density is used to obtain an accurate G/T to use as a reference. The CNR of both the large and small aperture antennas are then measured using an Applications Technology Satellite (ATS). After normalizing the two C/N ratios to the large antenna system noise temperature the G/T or the gain G of the small aperture antenna can then be determined.

Simulating 3D Spacecraft Constellations for Low Frequency Radio Imaging

NASA Astrophysics Data System (ADS)

Hegedus, A. M.; Amiri, N.; Lazio, J.; Belov, K.; Kasper, J. C.

2016-12-01

Constellations of small spacecraft could be used to realize a low-frequency phased array for either heliophysics or astrophysics observations. However, there are issues that arise with an orbiting array that do not occur on the ground, thus rendering much of the existing radio astronomy software inadequate for data analysis and simulation. In this work we address these issues and consider the performance of two constellation concepts. The first is a 32-spacecraft constellation for astrophysical observations, and the second is a 5-element concept for pointing to the location of radio emission from coronal mass ejections (CMEs). For the first, we fill the software gap by extending the APSYNSIM software to simulate the aperture synthesis for a radio interferometer in orbit. This involves using the dynamic baselines from the relative motion of the individual spacecraft as well as the capability to add galactic noise. The ability to simulate phase errors corresponding to positional uncertainty of the antennas was also added. The upgraded software was then used to model the imaging of a 32 spacecraft constellation that would orbit the moon to image radio galaxies like Cygnus A at .3-30 MHz. Animated images showing the improvement of the dirty image as the orbits progressed were made. RMSE plots that show how well the dirty image matches the input image as a function of integration time were made. For the second concept we performed radio interferometric simulations of the Sun Radio Interferometer Space Experiment (SunRISE) using the Common Astronomy Software Applications (CASA) package. SunRISE is a five spacecraft phased array that would orbit Earth to localize the low frequency radio emission from CMEs. This involved simulating the array in CASA, creating truth images for the CMEs over the entire frequency band of SunRISE, and observing them with the simulated array to see how well it could localize the true position of the CME. The results of our analysis show that we

75 FR 10439 - Cognitive Radio Technologies and Software Defined Radios

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-08

... Technologies and Software Defined Radios AGENCY: Federal Communications Commission. ACTION: Final rule. SUMMARY... concerning the use of open source software to implement security features in software defined radios (SDRs... ongoing technical developments in cognitive and software defined radio (SDR) technologies. 2. On April 20...

Reproducibility of UAV-based earth surface topography based on structure-from-motion algorithms.

NASA Astrophysics Data System (ADS)

Clapuyt, François; Vanacker, Veerle; Van Oost, Kristof

2014-05-01

A representation of the earth surface at very high spatial resolution is crucial to accurately map small geomorphic landforms with high precision. Very high resolution digital surface models (DSM) can then be used to quantify changes in earth surface topography over time, based on differencing of DSMs taken at various moments in time. However, it is compulsory to have both high accuracy for each topographic representation and consistency between measurements over time, as DSM differencing automatically leads to error propagation. This study investigates the reproducibility of reconstructions of earth surface topography based on structure-from-motion (SFM) algorithms. To this end, we equipped an eight-propeller drone with a standard reflex camera. This equipment can easily be deployed in the field, as it is a lightweight, low-cost system in comparison with classic aerial photo surveys and terrestrial or airborne LiDAR scanning. Four sets of aerial photographs were created for one test field. The sets of airphotos differ in focal length, and viewing angles, i.e. nadir view and ground-level view. In addition, the importance of the accuracy of ground control points for the construction of a georeferenced point cloud was assessed using two different GPS devices with horizontal accuracy at resp. the sub-meter and sub-decimeter level. Airphoto datasets were processed with SFM algorithm and the resulting point clouds were georeferenced. Then, the surface representations were compared with each other to assess the reproducibility of the earth surface topography. Finally, consistency between independent datasets is discussed.

Radio structure effects on the optical and radio representations of the ICRF

NASA Astrophysics Data System (ADS)

Andrei, A. H.; da Silva Neto, D. N.; Assafin, M.; Vieira Martins, R.

Silva Neto et al. (2002) show that comparing the ICRF Ext.1 sources standard radio position (Ma et al. 1998) against their optical counterpart position (Zacharias et al. 1999, Monet et al., 1998), a systematic pattern appears, which depends on the radio structure index (Fey and Charlot, 2000). The optical to radio offsets produce a distribution suggestive of a coincidence of the optical and radio centroids worse for the radio extended than for the radio compact sources. On average, the coincidence between the optical and radio centroids is found 7.9±1.1 mas smaller for the compact than for the extended sources. Such an effect is reasonably large, and certainly much too large to be due to errors on the VLBI radio position. On the other hand, it is too small to be accounted to the errors on the optical position, which moreover should be independent from the radio stucture. Thus, other than a true pattern of centroids non-coincidence, the remaining explanation is of a hazard result. This paper summarizes the several statistical tests used to discard the hazard explanation.

Virtual observatory tools and amateur radio observations supporting scientific analysis of Jupiter radio emissions

NASA Astrophysics Data System (ADS)

Cecconi, Baptiste; Hess, Sebastien; Le Sidaner, Pierre; Savalle, Renaud; Stéphane, Erard; Coffre, Andrée; Thétas, Emmanuel; André, Nicolas; Génot, Vincent; Thieman, Jim; Typinski, Dave; Sky, Jim; Higgins, Chuck; Imai, Masafumi

2016-04-01

In the frame of the preparation of the NASA/JUNO and ESA/JUICE (Jupiter Icy Moon Explorer) missions, and the development of a planetary sciences virtual observatory (VO), we are proposing a new set of tools directed to data providers as well as users, in order to ease data sharing and discovery. We will focus on ground based planetary radio observations (thus mainly Jupiter radio emissions), trying for instance to enhance the temporal coverage of jovian decametric emission. The data service we will be using is EPN-TAP, a planetary science data access protocol developed by Europlanet-VESPA (Virtual European Solar and Planetary Access). This protocol is derived from IVOA (International Virtual Observatory Alliance) standards. The Jupiter Routine Observations from the Nancay Decameter Array are already shared on the planetary science VO using this protocol, as well as data from the Iitate Low Frquency Radio Antenna, in Japan. Amateur radio data from the RadioJOVE project is also available. The attached figure shows data from those three providers. We will first introduce the VO tools and concepts of interest for the planetary radioastronomy community. We will then present the various data formats now used for such data services, as well as their associated metadata. We will finally show various prototypical tools that make use of this shared datasets.

The Earth Based Ground Stations Element of the Lunar Program

NASA Technical Reports Server (NTRS)

Gal-Edd, Jonathan; Fatig, Curtis; Schier, James; Lee, Charles

2007-01-01

The Lunar Architecture Team (LAT) is responsible for developing a concept for building and supporting a lunar outpost with several exploration capabilities such as rovers, colonization, and observatories. The lunar outpost is planned to be located at the Moon's South Pole. The LAT Communications and Navigation Team (C&N) is responsible for defining the network infrastructure to support the lunar outpost. The following elements are needed to support lunar outpost activities: A Lunar surface network based on industry standard wireless 802.xx protocols, relay satellites positioned 180 degrees apart to provide South Pole coverage for the half of the lunar 28-day orbit that is obscured from Earth view, earth-based ground stations deployed at geographical locations 120 degrees apart. This paper will focus on the Earth ground stations of the lunar architecture. Two types of ground station networks are discussed. One provides Direct to Earth (DTE) support to lunar users using Kaband 23/26Giga-Hertz (GHz) communication frequencies. The second supports the Lunar Relay Satellite (LRS) that will be using Ka-band 40/37GHz (Q-band). This paper will discuss strategies to provide a robust operational network in support of various lunar missions and trades of building new antennas at non-NASA facilities, to improve coverage and provide site diversification for handling rain attenuation.

Security management based on trust determination in cognitive radio networks

NASA Astrophysics Data System (ADS)

Li, Jianwu; Feng, Zebing; Wei, Zhiqing; Feng, Zhiyong; Zhang, Ping

2014-12-01

Security has played a major role in cognitive radio networks. Numerous researches have mainly focused on attacking detection based on source localization and detection probability. However, few of them took the penalty of attackers into consideration and neglected how to implement effective punitive measures against attackers. To address this issue, this article proposes a novel penalty mechanism based on cognitive trust value. The main feature of this mechanism has been realized by six functions: authentication, interactive, configuration, trust value collection, storage and update, and punishment. Data fusion center (FC) and cluster heads (CHs) have been put forward as a hierarchical architecture to manage trust value of cognitive users. Misbehaving users would be punished by FC by declining their trust value; thus, guaranteeing network security via distinguishing attack users is of great necessity. Simulation results verify the rationality and effectiveness of our proposed mechanism.

Radio Frequency Based Programmable Logic Controller Anomaly Detection

DTIC Science & Technology

2013-09-01

include wireless radios, IEEE 802.15 Blue- tooth devices, cellular phones, and IEEE 802.11 WiFi networking devices. While wireless communication...MacKenzie, H. Shamoon Malware and SCADA Security What are the Im- pacts? . Technical Report, Tofino Security, Sep 2012. 61. Mateti,P. Hacking Techniques

Opportunistic Capacity-Based Resource Allocation for Chunk-Based Multi-Carrier Cognitive Radio Sensor Networks

PubMed Central

Huang, Jie; Zeng, Xiaoping; Jian, Xin; Tan, Xiaoheng; Zhang, Qi

2017-01-01

The spectrum allocation for cognitive radio sensor networks (CRSNs) has received considerable research attention under the assumption that the spectrum environment is static. However, in practice, the spectrum environment varies over time due to primary user/secondary user (PU/SU) activity and mobility, resulting in time-varied spectrum resources. This paper studies resource allocation for chunk-based multi-carrier CRSNs with time-varied spectrum resources. We present a novel opportunistic capacity model through a continuous time semi-Markov chain (CTSMC) to describe the time-varied spectrum resources of chunks and, based on this, a joint power and chunk allocation model by considering the opportunistically available capacity of chunks is proposed. To reduce the computational complexity, we split this model into two sub-problems and solve them via the Lagrangian dual method. Simulation results illustrate that the proposed opportunistic capacity-based resource allocation algorithm can achieve better performance compared with traditional algorithms when the spectrum environment is time-varied. PMID:28106803

Reconfigurable, Cognitive Software-Defined Radio

NASA Technical Reports Server (NTRS)

Bhat, Arvind

2015-01-01

Software-defined radio (SDR) technology allows radios to be reconfigured to perform different communication functions without using multiple radios to accomplish each task. Intelligent Automation, Inc., has developed SDR platforms that switch adaptively between different operation modes. The innovation works by modifying both transmit waveforms and receiver signal processing tasks. In Phase I of the project, the company developed SDR cognitive capabilities, including adaptive modulation and coding (AMC), automatic modulation recognition (AMR), and spectrum sensing. In Phase II, these capabilities were integrated into SDR platforms. The reconfigurable transceiver design employs high-speed field-programmable gate arrays, enabling multimode operation and scalable architecture. Designs are based on commercial off-the-shelf (COTS) components and are modular in nature, making it easier to upgrade individual components rather than redesigning the entire SDR platform as technology advances.

Prospects for the Detection of Earths Orbiting Other Stars

NASA Technical Reports Server (NTRS)

Borucki, William J.; Koch, David G.; Jenkins, Jon M.; Lissauer, Jack J.; Dunham, Edward W.

2001-01-01

Extrasolar planets have been detected by timing the radio signals from millisecond pulsars, from Doppler velocity changes in the spectra of main sequence stars, and most recently by the white-light transit of HD209458. Detection of Earth-sized planets in and near the habitable zone of main-sequence stars appears to be extremely difficult, if not impossible, from ground-based observatories because of noise introduced by scintillation and transparency changes in the Earth#s atmosphere. To overcome these difficulties, several spaceborne photometric missions have been proposed. The COROT mission is a CNES/ESA mission with a 30 cm aperture telescope that will monitor each of several star fields for five months to find short period planets. The Kepler project is a USA effort designed to monitor 100,000 solar-like stars in a single field of view for a period of four years. The long duration enables the reliable detection of planets with orbital periods from a few days to as long as two years. Thus it should be able to determine the frequency of planets in and near the habitable zone and associate them with stellar spectral types. Canadian and Scandinavian missions are also being developed. This paper compares these missions and discusses their expected contribution to our understanding of the frequency of terrestrial-sized planets around other stars.

Reconfigurable firmware-defined radios synthesized from standard digital logic cells

NASA Astrophysics Data System (ADS)

Faisal, Muhammad; Park, Youngmin; Wentzloff, David D.

2011-06-01

This paper presents recent work on reconfigurable all-digital radio architectures. We leverage the flexibility and scalability of synthesized digital cells to construct reconfigurable radio architectures that consume significantly less power than a software defined radio implementing similar architectures. We present two prototypes of such architectures that can receive and demodulate FM and FRS band signals. Moreover, a radio architecture based on a reconfigurable alldigital phase-locked loop for coherent demodulation is presented.

A Rules-Based Service for Suggesting Visualizations to Analyze Earth Science Phenomena.

NASA Astrophysics Data System (ADS)

Prabhu, A.; Zednik, S.; Fox, P. A.; Ramachandran, R.; Maskey, M.; Shie, C. L.; Shen, S.

2016-12-01

Current Earth Science Information Systems lack support for new or interdisciplinary researchers, who may be unfamiliar with the domain vocabulary or the breadth of relevant data available. We need to evolve the current information systems, to reduce the time required for data preparation, processing and analysis. This can be done by effectively salvaging the "dark" resources in Earth Science. We assert that Earth science metadata assets are dark resources, information resources that organizations collect, process, and store for regular business or operational activities but fail to utilize for other purposes. In order to effectively use these dark resources, especially for data processing and visualization, we need a combination of domain, data product and processing knowledge, i.e. a knowledge base from which specific data operations can be performed. In this presentation, we describe a semantic, rules based approach to provide i.e. a service to visualize Earth Science phenomena, based on the data variables extracted using the "dark" metadata resources. We use Jena rules to make assertions about compatibility between a phenomena and various visualizations based on multiple factors. We created separate orthogonal rulesets to map each of these factors to the various phenomena. Some of the factors we have considered include measurements, spatial resolution and time intervals. This approach enables easy additions and deletions based on newly obtained domain knowledge or phenomena related information and thus improving the accuracy of the rules service overall.

The Importance of Radio News to Listeners.

ERIC Educational Resources Information Center

Martin, Ernie

While the news is considered a vitally important aspect of most radio stations' formats, broadcasters need to determine what a listener wants from the news-listening experience and how a station can program news in the form most desirable for the listener. This study, based on a Lawrence, Kansas, telephone survey of radio listeners, found that…

Using the Earth as an Effective Model for Integrating Space Science Into Education Outreach Programs

NASA Astrophysics Data System (ADS)

Morris, P. A.; Allen, J.; Galindo, C.; McKay, G.; Obot, V.; Reiff, P.

2005-05-01

Our methods of teaching Earth and space science as two disciplines do not represent the spirit of earlier scientists such as Aristotle, da Vinci, and Galileo. We need to re-evaluate these methods and take advantage of the excitement created in the general public over the recent space science exploration programs. The information that we are obtaining from both the Mars missions and Cassini-Huygens focuses on interpreting geomorphology, mineral compositions and gas identification based on Earth as a baseline for data evaluation. This type of evaluation is an extension of Hutton's 18th century principle of Uniformitarianism, the present is the key to the past, or Earth is the key for understanding extraterrestrial bodies. Geomorphological examples are volcanic activity, meteoritic impacts, and evidence of water altering surface features. The Hawaiian, or shield, type volcanoes are analogues for Olympus Mons and the other volcanoes on Mars. Other examples include comparing sand dunes on Earth with possible Martian dunes, known stream patterns on Earth with potential stream patterns on Mars, and even comparing meteoritic impact features on Mars, the Earth, Moon and Mercury. All of these comparisons have been developed into inquiry-based activities and are available through NASA publications. Each of these activities is easily adapted to emphasize either Earth science or space science or both. Beyond geomorphology, solar storms are an excellent topic for integrating Earth and space science. Solar storms are traditionally part of space science studies, but most students do not understand their effect on Earth or the intense effects they could have on humans, whether traveling through space or exploring the surfaces of the Moon or Mars. Effects are not only limited to space travel and other planetary surfaces but also include Earth's magnetosphere, which in turn, affect radio transmission and potentially climate. Like geomorphology courses, there are extensive NASA

Probing the Innermost Regions of AGN Jets and Their Magnetic Fields with RadioAstron. I. Imaging BL Lacertae at 21 Microarcsecond Resolution

NASA Astrophysics Data System (ADS)

Gómez, José L.; Lobanov, Andrei P.; Bruni, Gabriele; Kovalev, Yuri Y.; Marscher, Alan P.; Jorstad, Svetlana G.; Mizuno, Yosuke; Bach, Uwe; Sokolovsky, Kirill V.; Anderson, James M.; Galindo, Pablo; Kardashev, Nikolay S.; Lisakov, Mikhail M.

2016-02-01

We present the first polarimetric space very long baseline interferometry (VLBI) imaging observations at 22 GHz. BL Lacertae was observed in 2013 November 10 with the RadioAstron space VLBI mission, including a ground array of 15 radio telescopes. The instrumental polarization of the space radio telescope is found to be less than 9%, demonstrating the polarimetric imaging capabilities of RadioAstron at 22 GHz. Ground-space fringes were obtained up to a projected baseline distance of 7.9 Earth diameters in length, allowing us to image the jet in BL Lacertae with a maximum angular resolution of 21 μas, the highest achieved to date. We find evidence for emission upstream of the radio core, which may correspond to a recollimation shock at about 40 μas from the jet apex, in a pattern that includes other recollimation shocks at approximately 100 and 250 μas from the jet apex. Polarized emission is detected in two components within the innermost 0.5 mas from the core, as well as in some knots 3 mas downstream. Faraday rotation analysis, obtained from combining RadioAstron 22 GHz and ground-based 15 and 43 GHz images, shows a gradient in rotation measure and Faraday-corrected polarization vector as a function of position angle with respect to the core, suggesting that the jet in BL Lacertae is threaded by a helical magnetic field. The intrinsic de-boosted brightness temperature in the unresolved core exceeds 3× {10}12 K, suggesting, at the very least, departure from equipartition of energy between the magnetic field and radiating particles.

The radio properties of infrared-faint radio sources

NASA Astrophysics Data System (ADS)

Middelberg, E.; Norris, R. P.; Hales, C. A.; Seymour, N.; Johnston-Hollitt, M.; Huynh, M. T.; Lenc, E.; Mao, M. Y.

2011-02-01

Context. Infrared-faint radio sources (IFRS) are objects that have flux densities of several mJy at 1.4 GHz, but that are invisible at 3.6 μm when using sensitive Spitzer observations with μJy sensitivities. Their nature is unclear and difficult to investigate since they are only visible in the radio. Aims: High-resolution radio images and comprehensive spectral coverage can yield constraints on the emission mechanisms of IFRS and can give hints to similarities with known objects. Methods: We imaged a sample of 17 IFRS at 4.8 GHz and 8.6 GHz with the Australia Telescope Compact Array to determine the structures on arcsecond scales. We added radio data from other observing projects and from the literature to obtain broad-band radio spectra. Results: We find that the sources in our sample are either resolved out at the higher frequencies or are compact at resolutions of a few arcsec, which implies that they are smaller than a typical galaxy. The spectra of IFRS are remarkably steep, with a median spectral index of -1.4 and a prominent lack of spectral indices larger than -0.7. We also find that, given the IR non-detections, the ratio of 1.4 GHz flux density to 3.6 μm flux density is very high, and this puts them into the same regime as high-redshift radio galaxies. Conclusions: The evidence that IFRS are predominantly high-redshift sources driven by active galactic nuclei (AGN) is strong, even though not all IFRS may be caused by the same phenomenon. Compared to the rare and painstakingly collected high-redshift radio galaxies, IFRS appear to be much more abundant, but less luminous, AGN-driven galaxies at similar cosmological distances.

The Earth rotation and revolution effect on the daily and annual variation of sporadic meteor echo

NASA Astrophysics Data System (ADS)

Ohnishi, Kouji; Hattori, Shinobu; Nishimura, Osamu; Ishikawa, Toshiyuki; Aoki, Yoshie; Iijima, Yukiko; Kobayashi, Aya; Maegawa, Kimio; Abe, Shinsuke

2001-11-01

The Earth rotation and revolution will affect the daily and annual variation of sporadic meteor echo. We try to investigate such effect using Ham-band Radio Observation (HRO). Our system is constructed with paired two-element loop antennas (F/B ratio is 10 dB) at Nagano, Japan using the beacon signals at 53.750 MHz, 50W from Sabae, Fukui, Japan. The direction of one of this paired antenna was West toward Sagae and the other was East, so that this system could be roughly detected the direction of the reflected radio echoes. Using this system, (1) The total echo rose from midnight with the peak coming at about 6:00 and decreasing to the noon. This is well known daily variation due to the Earth rotation. (2) The peak echoes time by Eastward antenna and by Westward antennas was different; Westward was at 3:00 and Eastward was at 10:00. This daily variation is interpreted as the effect of the Earth rotation and revolution and the specular reflection property of forward meteor scattering observation.

Super-Sharp Radio "Vision" Measures Galaxy's Motion in Space

NASA Astrophysics Data System (ADS)

2005-03-01

Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) have measured the motion across the sky of a galaxy nearly 2.4 million light-years from Earth. While scientists have been measuring the motion of galaxies directly toward or away from Earth for decades, this is the first time that the transverse motion (called proper motion by astronomers) has been measured for a galaxy that is not a satellite of our own Milky Way Galaxy. M33 Radio/Optical Image of M33 CREDIT: NRAO/AUI/NSF, NOAO/AURA/NSF (Click on image for more files) An international scientific team analyzed VLBA observations made over two and a half years to detect minuscule shifts in the sky position of the spiral galaxy M33. Combined with previous measurements of the galaxy's motion toward Earth, the new data allowed the astronomers to calculate M33's movement in three dimensions for the first time. "A snail crawling on Mars would appear to be moving across the surface more than 100 times faster than the motion we measured for this galaxy," said Mark Reid, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA. M33 is a satellite of the larger galaxy M31, the well-known Andromeda Galaxy that is the most distant object visible to the naked eye. Both are part of the Local Group of galaxies that includes the Milky Way. In addition to measuring the motion of M33 as a whole, the astronomers also were able to make a direct measurement of the spiral galaxy's rotation. Both measurements were made by observing the changes in position of giant clouds of molecules inside the galaxy. The water vapor in these clouds acts as a natural maser, strengthening, or amplifying, radio emission the same way that lasers amplify light emission. The natural masers acted as bright radio beacons whose movement could be tracked by the ultra-sharp radio "vision" of the VLBA. Reid and his colleagues plan to continue measuring M33's motion and also to make similar measurements of M31's motion

Increasing participation in the Earth sciences through engagement of K-12 educators in Earth system science analysis, inquiry and problem- based learning and teaching

NASA Astrophysics Data System (ADS)

Burrell, S.

2012-12-01

Given low course enrollment in geoscience courses, retention in undergraduate geoscience courses, and granting of BA and advanced degrees in the Earth sciences an effective strategy to increase participation in this field is necessary. In response, as K-12 education is a conduit to college education and the future workforce, Earth science education at the K-12 level was targeted with the development of teacher professional development around Earth system science, inquiry and problem-based learning. An NSF, NOAA and NASA funded effort through the Institute for Global Environmental Strategies led to the development of the Earth System Science Educational Alliance (ESSEA) and dissemination of interdisciplinary Earth science content modules accessible to the public and educators. These modules formed the basis for two teacher workshops, two graduate level courses for in-service teachers and two university course for undergraduate teacher candidates. Data from all three models will be presented with emphasis on the teacher workshop. Essential components of the workshop model include: teaching and modeling Earth system science analysis; teacher development of interdisciplinary, problem-based academic units for implementation in the classroom; teacher collaboration; daily workshop evaluations; classroom observations; follow-up collaborative meetings/think tanks; and the building of an on-line professional community for continued communication and exchange of best practices. Preliminary data indicate increased understanding of Earth system science, proficiency with Earth system science analysis, and renewed interest in innovative delivery of content amongst teachers. Teacher-participants reported increased student engagement in learning with the implementation of problem-based investigations in Earth science and Earth system science thinking in the classroom, however, increased enthusiasm of the teacher acted as a contributing factor. Teacher feedback on open

Looking for radio waves with a simple radio wave detector

NASA Astrophysics Data System (ADS)

Sugimoto (Stray Cats), Norihiro

2011-11-01

I created a simple device that can detect radio waves in a classroom. In physics classes I tell students that we live in a sea of radio waves. They come from TV, radio, and cell phone signals as well as other sources. Students don't realize this because those electromagnetic waves are invisible. So, I wondered if I could come up with a way to detect the waves and help students to understand them better. Electromagnetic wave meters, which measure intensity of radio waves quantitatively, are commercially available. However, to students most of these are black boxes, and at the introductory level it is more effective to detect radio waves in a simpler way. This paper describes my device and how I have used it in my classes.

Radio science electron density profiles of lunar ionosphere based on the service module of circumlunar return and reentry spacecraft

NASA Astrophysics Data System (ADS)

Wang, M.; Han, S.; Ping, J.; Tang, G.; Zhang, Q.

2017-09-01

The existence of lunar ionosphere has been under debate for a long time. Radio occultation experiments had been performed by both Luna 19/22 and SELENE missions and electron column density of lunar ionosphere was provided. The Apollo 14 mission also acquired the electron density with in situ measurements. But the results of these missions don't well-matched. In order to explore the lunar ionosphere, radio occultation with the service module of Chinese circumlunar return and reentry spacecraft has been performing. One coherent S-band and X-band radio signals were recorded by China deep space stations, and local correlation was adopted to compute carrier phases of both signals. Based on the above work, the electron density profiles of lunar ionosphere was obtained and analyzed.

Q-Learning and p-persistent CSMA based rendezvous protocol for cognitive radio networks operating with shared spectrum activity

NASA Astrophysics Data System (ADS)

Watson, Clifton L.; Biswas, Subir

2014-06-01

With an increasing demand for spectrum, dynamic spectrum access (DSA) has been proposed as viable means for providing the flexibility and greater access to spectrum necessary to meet this demand. Within the DSA concept, unlicensed secondary users temporarily "borrow" or access licensed spectrum, while respecting the licensed primary user's rights to that spectrum. As key enablers for DSA, cognitive radios (CRs) are based on software-defined radios which allow them to sense, learn, and adapt to the spectrum environment. These radios can operate independently and rapidly switch channels. Thus, the initial setup and maintenance of cognitive radio networks are dependent upon the ability of CR nodes to find each other, in a process known as rendezvous, and create a link on a common channel for the exchange of data and control information. In this paper, we propose a novel rendezvous protocol, known as QLP, which is based on Q-learning and the p-persistent CSMA protocol. With the QLP protocol, CR nodes learn which channels are best for rendezvous and thus adapt their behavior to visit those channels more frequently. We demonstrate through simulation that the QLP protocol provides a rendevous capability for DSA environments with different dynamics of PU activity, while attempting to achieve the following performance goals: (1) minimize the average time-to-rendezvous, (2) maximize system throughput, (3) minimize primary user interference, and (4) minimize collisions among CR nodes.

Synthesis and photoluminescence properties of novel Schiff base type polymer-rare earth complexes containing furfural-based bidentate Schiff base ligands

NASA Astrophysics Data System (ADS)

Gao, Baojiao; Zhang, Dandan; Li, Yanbin

2018-03-01

Luminescent polymer-rare earth complexes are an important class of photoluminescence and electroluminescence materials. Via molecular design, two furfural-based bidentate Schiff base ligands, furfural-aniline (FA) type ligand and furfural-cyclohexylamine (FC) type ligand, were bonded on the side chains of polysulfone (PSF), respectively, forming two functionalized macromolecules, PSF-FA and PSF-FC. And then through respective coordination reactions of the two functionalized macromolecules with Eu(Ⅲ) ion and Tb(Ⅲ) ion, novel luminescent binary and ternary (with 1,10-phenanthroline as the second ligand) polymer-rare earth complexes were synthesized. For these complexes, on basis of the characterization of their chemical structures, they photoluminescence properties were main researched, and the relationship between their luminescent properties and structures was explored. The experimental results show that the complexes coming from PSF-FA and Eu(Ⅲ) ion including binary and ternary complexes emit strong red luminescence, indicating that the bonded bidentate Schiff base ligand FA can sensitize the fluorescence emission of Eu(III) ion. While the complexes coming from PSF-FC and Tb(Ⅲ) ion produce green luminescence, displaying that the bonded bidentate Schiff base ligand FC can sensitize the fluorescence emission of Tb(Ⅲ) ion. The fluorescence emission intensities of the ternary complexes were stronger than that of binary complexes, reflecting the important effect of the second ligand. The fluorescence emission of the solid film of complexes is much stronger than that of the solutions of complexes. Besides, by comparison, it is found that the furfural (as a heteroaromatic compound)-based Schiff base type polymer-rare earth complexes have stronger fluorescence emission and higher energy transfer efficiency than salicylaldehyde (as a common aromatic compound)-based Schiff base type polymer-rare earth complexes.

Application of the GNU Radio platform in the multistatic radar

NASA Astrophysics Data System (ADS)

Szlachetko, Boguslaw; Lewandowski, Andrzej

2009-06-01

This document presents the application of the Software Defined Radio-based platform in the multistatic radar. This platform consists of four-sensor linear antenna, Universal Software Radio Peripheral (USRP) hardware (radio frequency frontend) and GNU-Radio PC software. The paper provides information about architecture of digital signal processing performed by USRP's FPGA (digital down converting blocks) and PC host (implementation of the multichannel digital beamforming). The preliminary results of the signal recording performed by our experimental platform are presented.

Earth Stewardship Science: International Research Networks based in Africa (Invited)

NASA Astrophysics Data System (ADS)

Gaines, S. M.

2010-12-01

The role of networking in student and early career years is critical in the development of international interdisciplinary earth system science. These networks - both peer and mentor-based - can build community, foster enthusiasm and further research applications in addition to the traditional goal of identifying and obtaining work. UNESCO has nearly 40 years of experience in building international research teams through the International Geoscience Program (IGCP) and has recently focused their attention on the status of the earth sciences in Africa. UNESCO’s Earth Science Education Initiative in Africa ran a series of regional scoping workshops around the continent in order to develop an integrated status report on the earth sciences in Africa. The results, which are globally relevant, indicate that the field is limited by the level of basic science education of incoming students and restricted laboratory facilities, but also by a lack of connectedness. This isolation relates both to the interaction between researchers within countries and around the world but also the divide between Universities and Industry and the failure of the field to communicate its relevance to the public. In a context where livelihood opportunities are the driver of study and the earth sciences provide a major source of income, practical academic ties to industry are an essential element of the attractiveness of the field to students. Actions and ideas for addressing this situation will be presented to reinforce the role of the earth sciences in improving human and environmental well-being.

Crowdsourcing-Assisted Radio Environment Database for V2V Communication.

PubMed

Katagiri, Keita; Sato, Koya; Fujii, Takeo

2018-04-12

In order to realize reliable Vehicle-to-Vehicle (V2V) communication systems for autonomous driving, the recognition of radio propagation becomes an important technology. However, in the current wireless distributed network systems, it is difficult to accurately estimate the radio propagation characteristics because of the locality of the radio propagation caused by surrounding buildings and geographical features. In this paper, we propose a measurement-based radio environment database for improving the accuracy of the radio environment estimation in the V2V communication systems. The database first gathers measurement datasets of the received signal strength indicator (RSSI) related to the transmission/reception locations from V2V systems. By using the datasets, the average received power maps linked with transmitter and receiver locations are generated. We have performed measurement campaigns of V2V communications in the real environment to observe RSSI for the database construction. Our results show that the proposed method has higher accuracy of the radio propagation estimation than the conventional path loss model-based estimation.

Radio Frequency Interference: Radio Astronomy's Biggest Enemy

NASA Astrophysics Data System (ADS)

Acevedo, F.; Ghosh, Tapasi

1997-12-01

As technology progresses, the demand for the usage of the electromagnetic spectrum increases with it. The development is so fast and prolific that clean band space for passive users such as Radio Astronomy is becoming ever so scarce. Even though, several spectral bands have been protected for Radio Astronomy by Federal Communication Commission (in the USA) under the recommendations of the International Telecommunication Union (ITU), pressure for making more spectral space commercially usable is extreme. Although these commercial usages make our modern living at all possible, often the extreme vulnerability of passive users are are not fully appreciated, resulting in unwanted emissions (RFI) in the Radio Astronomy Bands. Another source of RFI is the fact that many of the electronic devices used in the observatories themselves generate radio waves. If proper precautions are not taken, these can be received back through the Radio Telescope itself. This problem is referred to as internal RFI. The focus of this paper is the search and diminution of internal RFI in the Arecibo Observatory in Arecibo, Puerto Rico. Using a simple setup of a log-periodic antenna and a Spectrum Analyzer, spectra spanning a frequency range of 100 - 1800 MHZ were recorded in some areas of the Observatory and the new Visitor Center (AOVEF). The measurements disclosed sources of radio emission among some of the digital electronic equipment in the Equipment room and a few displays in the AOVEF. Most prominent of these was a 2.5 MHz comb spanning the entire range of the measurements emitted from the SRENDIP and AOFTM machines. The respective groups were informed and corrective shielding & isolations were implemented immediately. In AOVEF, three displays, some audio-visual equipment, and video/digital cameras used by the visitors were found to be "leaky". In future, the use of such cameras will be prohibited and the exhibits will be screened appropriately.

The High Time Resolution Radio Sky

NASA Astrophysics Data System (ADS)

Thornton, D.

2013-11-01

Pulsars are laboratories for extreme physics unachievable on Earth. As individual sources and possible orbital companions can be used to study magnetospheric, emission, and superfluid physics, general relativistic effects, and stellar and binary evolution. As populations they exhibit a wide range of sub-types, with parameters varying by many orders of magnitude signifying fundamental differences in their evolutionary history and potential uses. There are currently around 2200 known pulsars in the Milky Way, the Magellanic clouds, and globular clusters, most of which have been discovered with radio survey observations. These observations, as well as being suitable for detecting the repeating signals from pulsars, are well suited for identifying other transient astronomical radio bursts that last just a few milliseconds that either singular in nature, or rarely repeating. Prior to the work of this thesis non-repeating radio transients at extragalactic distances had possibly been discovered, however with just one example status a real astronomical sources was in doubt. Finding more of these sources was a vital to proving they were real and to open up the universe for millisecond-duration radio astronomy. The High Time Resolution Universe survey uses the multibeam receiver on the 64-m Parkes radio telescope to search the whole visible sky for pulsars and transients. The temporal and spectral resolution of the receiver and the digital back-end enable the detection of relatively faint, and distant radio sources. From the Parkes telescope a large portion of the Galactic plane can be seen, a rich hunting ground for radio pulsars of all types, while previously poorly surveyed regions away from the Galactic plane are also covered. I have made a number of pulsar discoveries in the survey, including some rare systems. These include PSR J1226-6208, a possible double neutron star system in a remarkably circular orbit, PSR J1431-471 which is being eclipsed by its companion with

A Software Defined Radio Based Airplane Communication Navigation Simulation System

NASA Astrophysics Data System (ADS)

He, L.; Zhong, H. T.; Song, D.

2018-01-01

Radio communication and navigation system plays important role in ensuring the safety of civil airplane in flight. Function and performance should be tested before these systems are installed on-board. Conventionally, a set of transmitter and receiver are needed for each system, thus all the equipment occupy a lot of space and are high cost. In this paper, software defined radio technology is applied to design a common hardware communication and navigation ground simulation system, which can host multiple airplane systems with different operating frequency, such as HF, VHF, VOR, ILS, ADF, etc. We use a broadband analog frontend hardware platform, universal software radio peripheral (USRP), to transmit/receive signal of different frequency band. Software is compiled by LabVIEW on computer, which interfaces with USRP through Ethernet, and is responsible for communication and navigation signal processing and system control. An integrated testing system is established to perform functional test and performance verification of the simulation signal, which demonstrate the feasibility of our design. The system is a low-cost and common hardware platform for multiple airplane systems, which provide helpful reference for integrated avionics design.

Earth System Science: Problem-based Learning Courses for Teachers Through ESSEA

NASA Astrophysics Data System (ADS)

Close, E.; Witiw, M. R.

2007-12-01

One method that has proven effective in the study of Earth system science is to use a problem-based and event- centered course organization. In such a course, different events that occur in the Earth system are examined and how each event influences subsequent events in each of Earth's spheres (the atmosphere, hydrosphere, biosphere and lithosphere) is studied. A course is composed of several problem-based modules, where each module is centered about a particular event or issue that is important to the Earth system. The Institute for Global Environmental Strategies (IGES) was recently awarded a grant by the National Science Foundation's Geo-Teach program to develop and implement courses for teachers in Earth system science. Through the Earth System Science Education Alliance (ESSEA), IGES subsequently made awards to a group of 24 universities. Under the ESSEA program, problem-based modules are being developed for courses for middle school and high school teachers. In a typical university schedule, each module is designed to last three weeks and includes both group work and individual assignments. In the first week ("Teacher as Problem Solver"), participants explore their own ideas concerning the event and exchange their ideas with other members of their group. In the second week ("Teacher as Scholar"), participants research the issue and become more familiar with the event and the sphere-to-sphere interactions that occur. In the last week ("Teacher as Designer"), each participant develops a lesson plan for his or her own classroom. Current ESSEA modules cover topics such as volcanoes, Brazilian deforestation, Antarctic ice sheets, coral reefs, and stratospheric ozone depletion. Many new modules are under development with topics that range from plate tectonics and tsunamis to agriculture and sustainable water systems. Seattle Pacific University, in cooperation with Seattle Public Schools, was recently awarded a three-year grant by IGES to provide Earth system

Trends in Performance and Characteristics of Ultra-Stable Oscillators for Deep Space Radio Science Experiments

NASA Technical Reports Server (NTRS)

Asmar, Sami

1997-01-01

Telecommunication systems of spacecraft on deep space missions also function as instruments for Radio Science experiments. Radio scientists utilize the telecommunication links between spacecraft and Earth to examine very small changes in the phase/frequency, amplitude, and/or polarization of radio signals to investigate a host of physical phenomena in the solar system. Several missions augmented the radio communication system with an Ultra-Stable Oscillator (USO) in order to provide a highly stable reference signal for oneway downlink. This configuration is used in order to enable better investigations of the atmospheres of the planets occulting the line-of-sight to the spacecraft; one-way communication was required and the transponders' built-in auxiliary oscillators were neither sufficiently stable nor spectrally pure for the occultation experiments. Since Radio Science instrumentation is distributed between the spacecraft and the ground stations, the Deep Space Network (DSN) is also equipped to function as a world-class instrument for Radio Science research. For a detailed account of Radio Science experiments, methodology, key discoveries, and the DSN's historical contribution to the field, see Asmar and Renzetti (1993). The tools of Radio Science can be and have also been utilized in addressing several mission engineering challenges; e.g., characterization of spacecraft nutation and anomalous motion, antenna calibrations, and communications during surface landing phases. Since the first quartz USO was flown on Voyager, the technology has advanced significantly, affording future missions higher sensitivity in reconstructing the temperature pressure profiles of the atmospheres under study as well as other physical phenomena of interest to Radio Science. This paper surveys the trends in stability and spectral purity performance, design characteristics including size and mass, as well as cost and history of these clocks in space.

Ultra High-Speed Radio Frequency Switch Based on Photonics.

PubMed

Ge, Jia; Fok, Mable P

2015-11-26

Microwave switches, or Radio Frequency (RF) switches have been intensively used in microwave systems for signal routing. Compared with the fast development of microwave and wireless systems, RF switches have been underdeveloped particularly in terms of switching speed and operating bandwidth. In this paper, we propose a photonics based RF switch that is capable of switching at tens of picoseconds speed, which is hundreds of times faster than any existing RF switch technologies. The high-speed switching property is achieved with the use of a rapidly tunable microwave photonic filter with tens of gigahertz frequency tuning speed, where the tuning mechanism is based on the ultra-fast electro-optics Pockels effect. The RF switch has a wide operation bandwidth of 12 GHz and can go up to 40 GHz, depending on the bandwidth of the modulator used in the scheme. The proposed RF switch can either work as an ON/OFF switch or a two-channel switch, tens of picoseconds switching speed is experimentally observed for both type of switches.

Silicon Carbide Mixers Demonstrated to Improve the Interference Immunity of Radio-Based Aircraft Avionics

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.

1998-01-01

Concern over the interference of stray radiofrequency (RF) emissions with key aircraft avionics is evident during takeoff and landing of every commercial flight when the flight attendant requests that all portable electronics be switched off. The operation of key radio-based avionics (such as glide-slope and localizer approach instruments) depends on the ability of front-end RF receivers to detect and amplify desired information signals while rejecting interference from undesired RF sources both inside and outside the aircraft. Incidents where key navigation and approach avionics malfunction because of RF interference clearly represent an increasing threat to flight safety as the radio spectrum becomes more crowded. In an initial feasibility experiment, the U.S. Army Research Laboratory and the NASA Lewis Research Center recently demonstrated the strategic use of silicon carbide (SiC) semiconductor components to significantly reduce the susceptibility of an RF receiver circuit to undesired RF interference. A pair of silicon carbide mixer diodes successfully reduced RF interference (intermodulation distortion) in a prototype receiver circuit by a factor of 10 (20 dB) in comparison to a pair of commercial silicon-based mixer diodes.

Monitoring Radio Frequency Interference in Southwest Virginia

NASA Astrophysics Data System (ADS)

Rapp, Steve

2010-01-01

The radio signals received from astronomical objects are extremely weak. Because of this, radio sources are easily shrouded by interference from devices such as satellites and cell phone towers. Radio astronomy is very susceptible to this radio frequency interference (RFI). Possibly even worse than complete veiling, weaker interfering signals can contaminate the data collected by radio telescopes, possibly leading astronomers to mistaken interpretations. To help promote student awareness of the connection between radio astronomy and RFI, an inquiry-based science curriculum was developed to allow high school students to determine RFI levels in their communities. The Quiet Skies Project_the result of a collaboration between the National Aeronautics and Space Administration (NASA), the National Science Foundation (NSF), and the National Radio Astronomy Observatory (NRAO)_encourages students to collect and analyze RFI data and develop conclusions as a team. Because the project focuses on electromagnetic radiation, it is appropriate for physics, physical science, chemistry, or general science classes. My class-about 50 students from 15 southwest Virginia high schools-participated in the Quiet Skies Project and were pioneers in the use of the beta version of the Quiet Skies Detector (QSD), which is used to detect RFI. Students have been involved with the project since 2005 and have collected and shared data with NRAO. In analyzing the data they have noted some trends in RFI in Southwest Virginia.