The NASA-Haystack VGOS Development Systems

Monday, 15 December 2014
Arthur E Niell1, Christopher J Beaudoin1, Roger J Cappallo1, Brian E Corey1, Steven R McWhirter1, Chester A Ruszczyk1, Jason G SooHoo1, Michael A Titus1, John M Gipson2, William Edwin Himwich2 and Sergei Bolotin2, (1)MIT Haystack Observatory, Westford, MA, United States, (2)NVI, Inc., Greenbelt, MD, United States
The first two VLBI systems that are VGOS capable, the 12-meter antenna near Washington, D. C., and the 18-meter antenna at Westford, Massachusetts, have been upgraded with improvements to the digital back ends and adoption of the Mark6 recorder. These changes are primarily of operational benefit, but they provide significant addition to station diagnostics as well as reduction in complexity. The Mark6 allows recording of all four bands of VGOS data on one recorder at rates up to 16 gigabits per second. The new firmware in the digital back end (designated RDBE-G/3.0), of which four are required per station, provides for time-keeping at the few nanosecond level and extraction of the phase calibration signal for system verification. Several observing sessions have demonstrated achievement of the expected delay precision of a few picoseconds and baseline repeatability of a few millimeters. A delay measurement system for the reference frequency cable to the phase calibrator generator, which is the final new component needed for millimeter accuracy, is being tested. Monthly observations with the two antennas are planned to begin in the autumn 2014. Other VGOS systems will be added to the observations as they become operational.