Claire Chandler, VLASS Project Director
The Very Large Array Sky Survey (VLASS) will be a three-epoch (32-month cadence), all-sky, S-band (2-4 GHz) continuum polarimetry survey with 2.5-arcsecond spatial resolution. The survey will span seven years and six VLA configuration cycles, and will begin in 2017, pending successful achievement of the design phase milestones. The total VLA telescope time required for the survey is ~5400 hours, or ~900 hours per configuration cycle.
With the decision to proceed with the VLASS (see 17 Dec 2015 e-News), a 200-hr pilot in the recently commenced VLA B-configuration of semester 2016A has been approved, with the first observations starting June 2016. This pilot survey will inform VLASS implementation and operational issues associated with the full survey as input to design reviews, while at the same time providing the community with early VLASS-type data products. The pilot will be observed in as similar a mode to the full VLASS as possible, including:
S-band (2-4 GHz), 1024 x 2 MHz channels
VLA B-configuration, 2.5-arcsec resolution
On-The-Fly (OTF) mosaics scanning at 3.31 arcmin/sec in right ascension, at constant declination
Net mapping speed ~20 deg2/hr, 4-hr scheduling blocks covering 80 deg2 (10o x 8o tiles)
Some areas will be covered with three passes to provide a similar sensitivity as that expected from three epochs of the full VLASS (70 microJy/beam), while others will be observed with a single pass (120 microJy/beam) to maximize sky coverage. The pilot will cover key galactic and extragalactic fields that have good multi-wavelength ancillary data, as well as covering areas of sky with good prior radio observations for technical validation of the OTF mosaicking observing mode. The total area to be covered will be ~2500 deg2, and will include:
VLASS Pilot Fields, 3 passes (70 microJy/beam):
Galactic Plane fields: Galactic Center, Cygnus, Cepheus
Extragalactic fields: Cosmological Evolution Survey, Sloane Digital Sky Survey (SDSS) Stripe 82, Chandra Deep Field South
VLASS Pilot Fields, 1 pass (120 microJy/beam):
SDSS South Galactic Cap / FIRST southern sky for declination > 0 deg
SDSS North Galactic Cap fields: Great Observatories Origins Deep Survey – North, Elais-N1, Lockman Hole, H-ATLAS North, Bootes
Raw visibility data will be immediately available through the NRAO archive under project code TVPILOT. Data products (calibrated visibility data, images) will be made available after undergoing quality assurance.
At this time, we encourage community participation in various Science Working Groups as we define and refine the operational aspects of the pilot survey:
Extragalactic Working Group
Galactic Working Group
Transients Working Group
Polarization Working Group
EPO Working Group
Survey Implementation Working Group
NRAO Data Products, Archiving and Enhanced Data Products Working Group
A Google Group has been set up to facilitate discussion and communication within the working groups, please visit to sign up.
See the full article here .
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The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Long Baseline Array (VLBA)*.
The NRAO is building two new major research facilities in partnership with the international community that will soon open new scientific frontiers: the Atacama Large Millimeter/submillimeter Array (ALMA), and the Expanded Very Large Array (EVLA). Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).
*The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!
Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.