Science > Surveys > VLASS > FAQ


by Steven Myers last modified Jan 13, 2016

Frequently Asked Questions (FAQ) about the VLASS

The following are questions about the VLASS that have come up in discussions with members of the community. If you have questions not answered here, please email us at vlass AT!

  1. What was the outcome of the Community Review? A: The Community review recommended that we proceed with the ALL-SKY Survey component. See this news update and this page for more information on the review.
  2. What has happened to the DEEP Survey component? A: The review panel recommended that the DEEP Survey(s) be proposed separately as P.I. large projects. Members of the SSG are in the process of doing so. If you are interested, contact the survey at vlass AT and we will put you in contact with the appropriate P.I.
  3. What is next in 2016 for the VLASS? A: NRAO is in the process of putting together the survey team and resources to carry out the work needed to get the survey to a preliminary design review (PDR) in Q2 2016 and to carry out a Pilot Survey in May-Sep 2016. The full survey is scheduled to start in Sep 2017, unfortunately 16 months behind our originally proposed schedule.


Older FAQ (pre-review):

    1. The current call for VLASS white papers doesn't say what kinds of sky surveys are allowed. Does a "sky survey" really have to be a blind survey covering an area of sky, or can it be a directed survey pointing at a list of known targets?

    Nothing has been pre-determined for the VLASS, and therefore all options are on the table including wide-area blind surveys, targeted surveys, and even ultra-deep fields. The goal of the White Paper solicitation and the AAS Workshop is to get a wide range of possiblities on the table. The SSG will have a clean slate on which to define the VLASS.

        1. The JVLA sky surveys performance memo gives continuum survey speeds and examples of continuum surveys, and the call for white papers mentions only "commensal" spectral line observations.  Can a VLASS white paper propose spectral-line science as its primary goal?

        Yes, in that case the continuum observations (from the sum of the line channels or in extra spectral windows) would be "commensal".

            1. What are the boundary conditions on total observing time?  I seem to recall numbers in the 3-6 thousand hour range.

            No boundaries yet. We think that based on NVSS and FIRST that 3000-6000 hours is reasonable, especially if spread over a decade. Of course higher numbers would need very strong justification. It will be the job of the SSG to make the science case along with defining the survey for the proposal.

                1. What are the requirements for community involvement (e.g., number of universities, number of team members, graduate students, undergraduates, citizen science,...)?

                No "requirements" as such have been pre-determined.  The goal of setting up the SSG is to provide the mechanism for involving as wide a range of community as possible. That being said, wide participation by all the above groups would be ideal! Maybe a White Paper on this could be devised.

                    1. In the Guide to VLA Capabilities the "survey speed" SS is a property of the telescope only; it ignores the properties of radio sources. What is the survey speed realized for sources with a given power-law spectral index?

                    Good point! For sources from a population with mean spectral index <α>, where the flux at a frequency ν is proportional to να, the effective survey speed (e.g. number of sources per hour) is proportional to ν or ESS(ν) = SS(ν0)*(ν/ν0). For example, general radio sources selected at 1.5GHz around mJy levels have an average spectral index <α> ~ -0.7, therefore at 3GHz the counts at the same flux density level are only 38% of those at 1.5GHz.

                        1. The timeline mentions that a proposal will be given to the Director on Aug 1, 2014. What happens then?

                        At this time we do not know how the Director will choose to have the VLASS Proposal from the SSG reviewed, whether as part of the normal TAC process or through a special skeptical review panel. Stay tuned. Note also that the dates in the summer of 2014 are tentative, the exact schedule depends on how the SSG process proceeds in the spring.

                            1. Do I need to register for the AAS Meeting to attend the VLASS Workshop on Jan 5?

                            No, this is a public meeting alongside but not within the AAS, and thus no registration is required. You only have to show up! Note that since there is no registration, we have no idea of how many of you will attend. For our information, it would be helpful if you indicate who will attend along with your White Paper submission (a box will be provided for this soon), or just send us a note at

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