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  • 1
    Publikationsdatum: 2019-08-13
    Beschreibung: The Ka-band radio spectrum is now being used for a wide variety of applications. This paper highlights the use of Ka-band as a frequency for precise deep space navigation based on a set of reference beacons provided by extragalactic quasars which emit broadband noise at Ka-band. This quasar-based celestial reference frame is constructed using X/Ka-band (8.4/32 GHz) from fifty-five 24-hour sessions with the Deep Space Network antennas in California, Australia, and Spain. We report on observations which have detected 464 sources covering the full 24 hours of Right Ascension and declinations down to -45 deg. Comparison of this X/Ka-band frame to the international standard S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of approximately 200 micro-arcsec in alpha cos(delta) and approximately 300 micro-arcsec in delta. There is evidence for systematic errors at the 100 micro-arcsec level. Known errors include limited SNR, lack of instrumental phase calibration, tropospheric refraction mis-modeling, and limited southern geometry. The motivation for extending the celestial reference frame to frequencies above 8 GHz is to access more compact source morphology for improved frame stability and to support spacecraft navigation for Ka-band based NASA missions.
    Schlagwort(e): Space Communications, Spacecraft Communications, Command and Tracking
    Materialart: Ka and Broadband Communications, Navigation and Earth Observation Conference; Oct 03, 2011 - Oct 05, 2011; Palermo; Italy
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2019-08-08
    Beschreibung: We present the second catalogue of accurate positions and correlated flux densities for 1100 compact extragalactic radio sources that were not observed before 2008 at high angular resolution. The catalogue spans the declination range [-90, -30] and was constructed from 19 24-h VLBI observing sessions with the Australian Long Baseline Array at 8.3 GHz. The catalogue presents the final part of the program that was started in 2008. The goals of that campaign were (1) to extend the number of compact radio sources with precise coordinates and measure their correlated flux densities, which can be used for phase referencing very long baseline interferometry (VLBI) and Atacama Large Millimeter/submillimeter Array (ALMA) observations, geodetic VLBI, search for sources with significant offsets with respect to Gaia positions, and space navigation; (2) to extend the complete flux-limited sample of compact extragalactic sources to the Southern hemisphere; and (3) to investigate the parsec-scale properties of sources from the high-frequency AT20G survey. The median uncertainty of the source positions is 3.5 mas. As a result of this VLBI campaign, the number of compact radio sources south of declination -40 that have measured VLBI-correlated flux densities and positions known to milliarcsecond accuracy has increased by over a factor of 6.
    Schlagwort(e): Space Radiation
    Materialart: GSFC-E-DAA-TN70012 , Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711) (e-ISSN 1365-2966); 485; 1; 88-101
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2019-08-07
    Beschreibung: Each of NASAs three Deep Space Network sites has multiple large antennas capable of acquiring VLBI data. The long range plan is to have four 34-meter beam waveguide antennas at each site. At present Goldstone has three, Canberra has three, and Madrid has two with two more under construction. These antennas offer the opportunity to do connected element interferometry (CEI) over the few hundred meter baselines within each complex. Given that all antennas within a site are of nominally the same structural design, are run off the same clock, observe through almost the same atmosphere, and are subject to almost the same geophysics, doing CEI experiments is an excellent way to probe the limits of VLBI accuracy and expose station-specific systematic errors. This paper will report the results of just such tests which achieved about 0.2 mm baseline precision per pass. Some stations exhibit more than 1 mm systematics. Based on this data we will discuss the implications for whether the IAGs goal of 1 mm station stability in VLBI geodesy is possible for large antennas.
    Schlagwort(e): Earth Resources and Remote Sensing; Systems Analysis and Operations Research
    Materialart: JPL-CL-CL#17-4335 , Working Meeting of the European VLBI Group; May 14, 2017 - May 19, 2017; Gothenburg; Sweden
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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