Sander Weinreb (Caltech)

Sander Weinreb Colloquium: Future of the VLA

Marsfield Lecture Theatre

Abstract

The concept of a large cm-wave imaging array started in the early 1960’s based upon ground-breaking interferometer observations at Caltech, the UK, and Australia. This led to a $52M proposal in 1967 for a 36x25m continuum only array with 2.7 and 8.1 GHz room-temperature degenerate paramp receivers with 100K system noise. This was a time period for rapid development of radio astronomy receivers including cooled receivers, digital signal processing, and circular waveguide long-distance transmission systems. . This led to the construction of the VLA in 1973-1980 with a digital spectral line correlator, 4 cooled transistor amplifier receivers for 1.4 GHz, 5 GHz, 15, and 22 GHz with system temperatures in the 50K range, at a cost of $73M. For many years the VLA was the premier instrument in radio astronomy with more publications per year of any astronomical instrument other than the space telescope. For 30 years there was only incremental improvements in the system until approximately 2012 when the processed bandwidth was increased from 100 MHz to 8000 MHz with a new correlator, fiber optic data transmission, and new receivers with near continuous coverage from 1 to 50 GHz.
The question now is “What it the future of the VLA beyond 2030 in the light of the SKA, ALMA, ASKAP, and other instruments?” This question was posed by the NRAO director, Tony Beasley, at a recent workshop in Green Bank on US/China collaboration. Judged from the VLA past history the first stages of this development should begin in 2015 and lead to a proposal in 2019 for construction in the 2023 to 2030 era. My suggestion for the new instrument, the Northern Hemisphere Array (NHA), is for a 256 x 18m array covering 10 to 100 GHz in one feed and receiver, 90 GHz bandwidth correlation, and 100 km baselines. This array would have order of magnitude improvements in sensitivity, resolution, and survey speed in the frequency gap between SKA and ALMA. These goals are challenging but I believe are achievable at a cost capped at under $800M. A development program including the science applications, feed, LNA, data transmission, and correlator is required and will be discussed in my presentation.



Brief Biography of Sander Weinreb
Sander Weinreb is presently a Principal Scientist at JPL and a Sr. Faculty Associate at Caltech. He received the B.S.E.E. and Ph.D. degrees from M.I.T. in 1958 and 1963 respectively. Most of his career has been in the administration or development of instrumentation in radio astronomy. From 1966 to 1988 he led the Electronic Division of National Radio Astronomy Observatory where he was responsible for the design of all electronics for the Very Large Array and all other telescopes operated by the observatory. He has had interim teaching positions at UC Berkeley, U. of Virginia, and U. of Massachusetts before joining JPL and Caltech in 1999. He has over 200 publications and has received 4 awards including the 2014 American Astronomical Award for contributions to astronomy. At JPL he has worked on the development of millimeter wave radiometers, an array approach for up-grading the DSN, and on various review boards. He presently spends most of his time on contract to Caltech for mentoring of students and development of very low noise cryogenic microwave amplifiers for radio astronomy and laboratory experiments in the quantum computing area.