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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

QUASAT: An orbiting very long baseline interferometer program using large space antenna systems

QUASAT, which stands for QUASAR SATELLITE, is the name given to a new mission being studied by NASA. The QUASAT mission concept involves a free flying Earth orbiting large radio telescope, which will observe astronomical radio sources simultaneously with ground radio telescopes. The primary goal of QUASAT is to provide a system capable of collecting radio frequency data which will lead to a better understanding of extremely high energy events taking place in a variety of celestial objects including quasars, galactic nuclei, interstellar masers, radio stars and pulsars. QUASAT's unique scientific contribution will be the increased resolution in the emission brightness profile maps of the celestial objects.

Jordan, J. F.↗
NASA NTRS1986

Geodesy by radio interferometry - Evidence for contemporary plate motion

Analysis of 211 very long baseline interferometry observing sessions carried out between November 1979 and August 1984 has yielded estimates of the distances between various radio telescopes located in North America and Europe. The average rate of change of the distances between four radio telescopes in North America (Haystack Observatory, Massachusetts; Westford Radio Telescope, Massachusetts; George R. Agassiz Station, Texas; and Owens Valley Radio Observatory, California) and one in Europe (Onsala Space Observatory, Sweden) obtained from the analysis of these data is 19 + or 10 mm/yr, where the (68 percent confidence interval) standard deviation is for the estimate of the rate of change of the Haystack-Onsala baseline length, the one determined most accurately from these data. This estimate of the standard deviation is dominated by the effects of correlated systematic errors due mostly to errors in the model used for the atmospheric delay which introduces errors in each baseline length estimate of 40 mm standard deviation and 60 days correlation time. (By contrast the statistical standard deviation is only 2 mm/yr). The estimated geologic rates of change of these baseline lengths, averaged over 10 to the 6th years, are 15 to 17 + or - 3 mm/yr for the various North American sites to Ondala.

Herring, T. A.↗
NASA NTRS2010

RAEGE: An Atlantic Network of Geodynamical Fundamental Stations

Project RAEGE (Red Atlantica de Estaciones Geodinamicas y Espaciales) intends to set up a Spanish-Portuguese network of four Geodetic Fundamental Stations in Yebes (1), Canary Islands (1), and A cores Islands (2), as part of the developments needed for the IVS VLBI2010 scenario. It is envisaged that each Geodetic Fundamental Station will be equipped with one radio telescope of VLBI2010 specifications (at least 12-m diameter, fast slewing speed, but also able to operate up to 40 GHz), one gravimeter, one permanent GNSS station, and, at least at the Yebes site, one SLR facility. The National Geographical Institute of Spain (IGN) has experience in VLBI, having been a member of the European VLBI Network since 1993 and being one of the founding institutions of the Joint Institute for VLBI in Europe (JIVE), and it has been participating in geodetic VLBI campaigns with the 14-m radio telescope in Yebes since 1995. A new 40-m radio telescope has been built and was recently put into operation. It regularly participates in IVS sessions. There is infrastructure available for the new stations at Yebes and the Canary Islands. An agreement between IGN, the Portuguese Geographical Institute (IGP), and the Regional Government of the A cores ensures that the RAEGE project can become a reality by 2013.

Gonzalez, Jesus Gomez↗
NASA NTRS2013

Goddard Geophysical and Astronomical Observatory

This report summarizes the technical parameters and the technical staff of the VLBI system at the fundamental station GGAO. It also gives an overview about the VLBI activities during the report year. The Goddard Geophysical and Astronomical Observatory (GGAO) consists of a 5-meter radio telescope for VLBI, a new 12-meter radio telescope for VLBI2010 development, a 1-meter reference antenna for microwave holography development, an SLR site that includes MOBLAS-7, the NGSLR development system, and a 48" telescope for developmental two-color Satellite Laser Ranging, a GPS timing and development lab, a DORIS system, meteorological sensors, and a hydrogen maser. In addition, we are a fiducial IGS site with several IGS/IGSX receivers. GGAO is located on the east coast of the United States in Maryland. It is approximately 15 miles NNE of Washington, D.C. in Greenbelt, Maryland.

Figueroa, Ricardo↗
NASA NTRS2022

Mars 2020 Entry, Descent, and Landing as Observed by Radio Science Techniques at UHF and X-band Frequencies

On February 18, 2021, NASA’s Mars 2020 Rover “Perseverance” conducted the Entry, Descent, and Landing (EDL) sequence to land safely on the surface of Mars at Jezero Crater. Due to the criticality of the EDL sequence, redundant telecommunications strategies were utilized to observe the event. The rover transmitted an X-band (8.4 GHz) signal encoded with Multiple Frequency Shift Keying tones direct-to-Earth and a UHF (401.5 MHz) signal with 8 kbps encoded telemetry to orbiters, which relayed the signal back to Earth at X-band. NASA’s Deep Space Network complexes at Goldstone, California and Madrid, Spain received the direct-to-Earth X-band signal. Two of the largest steerable radio telescopes in the world, the 100-meter Green Bank Telescope in West Virginia and the Effelsberg 100-meter Radio Telescope in Germany also received the UHF carrier signal on Earth. During the EDL event, full spectrum recordings of the UHF and X-band signals were captured at these observatories using open-loop receivers. Real-time and post-processing signal analysis to determine power level, received frequency, and Doppler shift allowed determination of the spacecraft’s health and safety state during critical sequences, including event detection such as atmospheric entry, plasma blackouts, and parachute deployment. Simultaneous observations of the UHF and X-band radio links allow for redundancy in the event of a fault and greatly improve confidence in Doppler event detection.

Gladden, Roy↗
NASA NTRS1987

Collaborative VLBI experiments with Radioastron

The USSR is planning to launch a 10-m radio telescope into earth orbit for use in VLBI observations. This mission (Radioastron) will be the first opportunity for astronomically important VLBI experiments with baselines much longer than can be obtained between telescopes on the earth. This paper describes the potential scientific advantages of combining data from the orbiting telescope with data from some of the very sensitive radio telescopes in western Europe, Australia, Japan, and the U.S. The advantages of using NASA's Space Network telescopes to track the Radioastron spacecraft when it is not visible from Soviet tracking stations are considered.

Jones, D. L.↗
NASA NTRS1991

The great observatories for space astrophysics

The nation's strategy for astrophysics research during the rest of this century and into the next is a coordinated, multispectral examination of the universe. NASA plans to launch a family of large orbital observatories, each tuned to a different part of the electromagnetic spectrum. They are as follows: the Gamma Ray Observatory (GRO); the Advanced X Ray Astrophysics Facility (AXAF); the Hubble Space Telescope (HST); and the Space Infrared Telescope Facility (SIRTF). To complement these sensitive space telescopes, a powerful new radio observatory system is envisioned: the Very Long Baseline Array (VLBA), an intercontinental network of radio telescopes, working with radio observatories in space to perform orbiting very long baseline interferometry (OVLBI). Observing the universe across the spectrum requires different kinds of telescopes based on quite different techniques of detection. An optical telescope has little in common with a gamma ray detector; they do not look alike, nor do they operate on the same principles. No single telescope can answer all the questions or make all the discoveries that await.

Source record↗
NASA NTRS1999

Deep Space Telecommunications

The increasing load on NASA's deep Space Network, the new capabilities for deep space missions inherent in a next-generation radio telescope, and the potential of new telescope technology for reducing construction and operation costs suggest a natural marriage between radio astronomy and deep space telecommunications in developing advanced radio telescope concepts.

Deep↗
NASA NTRS1980

6 cm observations of a solar active region and bursts with approximately 6 arcsec resolution

The paper examines the solar active region located near N04E49, that was mapped at a 6 cm wavelength over a period of 12 hours, employing the Westerbork synthesis radio telescope. Two impulsive radio bursts were recorded during this time, one of which was associated with a chromospheric flare. One-dimensional fan beam scans of the burst sources were synthesized in order to display their time history with regard to intensity, polarization, position and size.

Erskine, F. T.↗
NASA NTRS2023

Radioastron Discovery of A Mini-Cocoon Around the Restarted Parsec-Scale Jet in 3C 84

We present RadioAstron space-based very long baseline interferometry (VLBI) observations of the nearby radio galaxy 3C 84 (NGC 1275) at the centre of the Perseus cluster. The observations were carried out during a perigee passage of the Spektr-R spacecraft on September 21–22, 2013 and involved a global array of 24 ground radio telescopes observing at 5 GHz and 22 GHz, together with the Space Radio Telescope (SRT). Furthermore, the Very Long Baseline Array (VLBA) and the phased Very Large Array (VLA) observed the source quasi-simultaneously at 15 GHz and 43 GHz. Fringes between the ground array and the SRT were detected on baseline lengths up to 8.1 times the Earth’s diameter, providing unprecedented resolution for 3C 84 at these wavelengths. We note that the corresponding fringe spacing is 125 μas at 5 GHz and 27 μas at 22 GHz. Our space-VLBI images reveal a previously unseen sub-structure inside the compact ∼1 pc long jet that was ejected about ten years earlier. In the 5 GHz image, we detected, for the first time, low-intensity emission from a cocoon-like structure around the restarted jet. Our results suggest that the increased power of the young jet is inflating a bubble of hot plasma as it carves its way through the ambient medium of the central region of the galaxy. Here, we estimate the minimum energy stored in the mini-cocoon, along with its pressure, volume, expansion speed, and the ratio of heavy particles to relativistic electrons, as well as the density of the ambient medium. About half of the energy delivered by the jet is dumped into the mini-cocoon and the quasi-spherical shape of the bubble suggests that this energy may be transferred to a significantly larger volume of the interstellar medium than what would be accomplished by the well-collimated jet on its own. The pressure of the hot mini-cocoon also provides a natural explanation for the almost cylindrical jet profile seen in the 22 GHz RadioAstron image.

galaxies: jets↗
NASA NTRS2000

Deep Space Telecommunications

The increasing load on NASA's deep Space Network, the new capabilities for deep space missions inherent in a next-generation radio telescope, and the potential of new telescope technology for reducing construction and operation costs suggest a natural marriage between radio astronomy and deep space telecommunications in developing advanced radio telescope concepts.

Kuiper, T. B. H.↗
NASA NTRS1994

DSN Co-Observing Operations to Support Space VLBI Missions

Reliable radio astronomy support of Space Very-Long-Baseline- Interferometry missions by ground radio telescopes is mandatory in order to achieve high scientific return from missions, The 70m DSN antennas along with other ground radio telescopes will perform as the ground segment of the Earth-space interferometer. Improvements of radio astronomy VLBI operations at the DSN to achieve higher reliability, efficiency, flexibility, and lower operations costs is a major goal in preparing for radio astronomy support of SVLBI. To help realize this goal, a remote control and monitoring mode for radio astronomy operations at the DSN is being developed.

radio↗
NASA NTRS1994

DSN co-observing operations to support space VLBI missions

Reliable radio astronomy support of space very long baseline interferometry (VLBI) missions by ground radio telescopes is mandatory in order to achieve a high scientific return from the missions. The 70 m DSN antennas along with other ground radio telescopes will perform as the ground segment of the earth-space interferometer. Improvements of radio astronomy VLBI operations at the DSN to achieve higher reliability, efficiency, flexibility, and lower operations costs is a major goal in preparing for radio astronomy support of SVLBI. To help realize this goal, a remote control and monitoring mode for radio astronomy operations at the DSN has been developed.

Altunin, Valery I.↗
NASA NTRS1986

Communications considerations of the very long baseline interferometry demonstration using the tracking and data relay satellite system

A desire for increased angular resolution at microwave frequencies has led to the development of radio telescopes with very lage effective apertures. Very long baseline interferometry (VLBI) has made it possible to synthesize telescopes with effective dimensions of a large fraction of an earth diameter. By using a satellite-borne radio telescope as part of a VLBI array, the dimensions of the earth cease to be a limitation. A demonstration was performed to show that the orbiting VLBI (OVLBI) concept is feasible. The Tracking and Data Relay Satellite System (TDRSS) was used as the orbiting element of the VLBI demonstration. Stability tests were made before the observations to determine the suitability of the TDRSS for OVLBI use. The first successful OVLBI observations were performed using the 64-m antenna observatories of NASA's Deep Space Network in Tidbinbilla, Australia, and of the Institute for Space and Astronautical Science in Usuda, Japan in conjunction with the TDRSS.

Levy, G. S.↗
NASA NTRS1997

Very Large Array and Ratan 600 Observations in Support of the Coronas I Mission

The world's two largest radio telescopes, the VLA and RATAN 600, were used to observe the Sun in support of the Terek Soft X-ray telescope aboard CORONA-1 spacecraft, thereby enhancing the scientific return of all three instruments beyond that expected from using each one alone. The large collecting areas of these radio telescopes were uniquely suited for investigating quiescent coronal structures, and they each provided unique perspectives of high spatial resolution (VLA) and high frequency resolution with polarization (RATAN 600).

Lang, Kenneth R.↗