First Results with the Next Generation Geodetic VLBI System
Abstract
The next generation geodetic VLBI instrument is being developed with a goal of 1 mm position uncertainty in twenty-four hours. The broadband signal chain, which is essential for obtaining the required delay accuracy from a network of relatively small antennas, has been implemented on the 12 meter antenna at Goddard Space Flight Center, Maryland, USA, and on the 18 meter Westford antenna at Haystack Observatory, Massachusetts, USA. The first geodetic-style observing session has been completed. Data were recorded from four 512 MHz bands spanning the range 3.2 to 9.9 GHz at a total rate of 8 Gigabits/second. The signal chain was composed of commercially available broadband feeds, low noise amplifiers, digital back ends, and recorders. The six hour session demonstrated that the broadband hardware performs as expected, achieving delay precisions of a few picoseconds. The position uncertainties for the 12m antenna of ~9mm in vertical and 2mm in horizontal, obtained in a preliminary analysis from only 100 30-second observations, are probably dominated by incomplete modeling of the atmosphere. A potentially serious conflict of the broadband VLBI frequency coverage with the SLR aircraft-avoidance radars, which transmit at 9.4 GHz, and with the DORIS transmission near 2 GHz has become apparent during the implementation and testing of the VLBI2010 system. Mitigation efforts are being studied, but for this initial geodetic session, 20 percent of scheduled observations had to be dropped to avoid potential damage from the SLR radar.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.G52B..05N
- Keywords:
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- 1294 GEODESY AND GRAVITY / Instruments and techniques;
- 1295 GEODESY AND GRAVITY / Integrations of techniques