The Very Large Array Sky Survey (VLASS)

Sky surveys have been integral to astronomy for two thousand years.  As far back as the 2nd century BC, Hipparcos and astronomers of the Han dynasty observed and recorded astronomical phenomenon and seasonal celestial changes from the night sky. Sky surveys are a way to map, in a systematic way, the universe and its constituents parts, opening up the observational impact of how celestial objects, especially those beyond our solar system, change with time. Within the last century, as technology has allowed for the expansion of observations beyond the traditional visible wavelength window, sky surveys have proved to be a fundamental part of multi-wavelength astronomy.

The Very Large Array Sky Survey (VLASS) represents our third radio survey project in the last twenty years. The VLA has undergone a complete technical transformation since our last two surveys: the NRAO VLA Sky Survey (NVSS) and Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) in 1992. From 2001-2012, the original electronic system, designed and built during the 1970’s, has been replaced with state-of-the-art technology that vastly expanded the VLA’s observing capabilities. This major upgrade has transformed the VLA into a completely new scientific tool. Our next-generation sky survey will harness the tremendously improved capabilities of the VLA, resulting in a unique and extremely valuable tool for frontier research over a diverse range of scientific fields.

VLASS is designed to produce a large collection of radio data available to wide range of scientists within the astronomical community. Our science goal is to produce a radio, all-sky survey that will benefit the entire astronomical community. As VLASS completes its three scans of the sky separated by approximately 32 months, new developments in data processing techniques will allow scientists an opportunity to download data instantly on potentially millions of astronomical radio sources. This data from all three epochs will be combined to make even more detailed radio images, creating the largest-ever celestial radio census.  Scientists will be able to compare images from the individual observation cycles, allowing for the discovery of newly-appearing sources or short-lived (transient) objects.

Sorting Out the Data

One of the problems that VLASS presents is sorting through the sheer amount of data being collected. In their effort to make quicker use of this data, the Canadian Initiative for Astronomy Data Analysis (CIRADA) has developed a machine-learning method to categorize the more than 500,000 radio sources seen by VLASS. The method can organize sources into 100 different classes or ‘neurons’. This should aid astronomers in studying different types of radio sources, as well as filtering out bad data.

Fundamentally, astronomy is about exploring — making images of the sky to see what is out there — and our VLA sky survey is a new and powerful resource for this exploration.