Observing > Call For Proposals > Expressions of Interest in PI-led "eXtra Large Proposals" (X-proposals)

Expressions of Interest in PI-led "eXtra Large Proposals" (X-proposals)

The National Radio Astronomy Observatory (NRAO), Long Baseline Observatory (LBO), and Green Bank Observatory (GBO) invite submission of brief Expressions of Interest (EoIs) in Principal Investigator-led "eXtra Large Proposals" (X-Proposals) for the Very Large Array (VLA), Very Long Baseline Array, and Green Bank Telescope requiring 1000 hours or more of telescope time, and running over multiple semesters (and possibly multiple VLA configurations).

Responses will be used to gauge the level of community interest in such proposals, and their scientific potential. NRAO, GBO, and LBO will seek advice from their advisory committees and the joint Time Allocation Committee on the EoIs submitted. It is important to note that the observatories may not proceed to a Call for X-Proposals if, for example, there is judged to be insufficient community interest, scientific merit, or differentiation from Large Proposals.

Expressions of Interest can be submitted using the web form below.

The deadline for submissions is 31 August 2018. 

NRAO, LBO and GBO anticipate providing feedback on the outcomes of the EoI process in early 2019.

If you are considering submitting an EoI, we encourage you to pay particular attention to the following statement from the community Discussion Paper on X-Proposals: "Projects should have extraordinary scientific merit and community legacy value, and proposals for X projects must specify clearly why the science goals cannot be achieved through the standard SRP/TAC process.”

X-Proposals are expected to be resourced by the proposing team. Teams should provide sufficient information to enable NRAO/LBO/GBO to evaluate any special needs or impact on Observatory operations.

The title and PI of submitted Expressions of Interest will be made publicly available on the NRAO/LBO/GBO websites.

Expressions of Interest will be neither binding nor mandatory. No time will be allocated on the basis of an EoI alone. In the event that NRAO/LBO/GBO issues a Call for X-Proposals there will be no requirement that an EoI was submitted prior to submission of a full proposal.

If a decision is made to proceed with an X-Proposal program, then:

  • A specific Call for X-Proposals will likely occur in 2019;
  • X-Proposals will probably be assessed by a somewhat different process to that used for other VLA/VLBA/GBT proposals; and
  • X-Proposal calls will probably be repeated on a longer timescale than the usual Semester cycle. 


The Call for Proposals for the VLA, VLBA and GBT identifies a special class of “Large Proposals” defined as those that request more than 200 hours of observing time. Large Proposals are evaluated and ranked as part of the normal NRAO proposal review process and NRAO typically receives one or two large proposals per semester for the VLA. At the time of writing there are three active large proposals on the VLA. See https://science.nrao.edu/observing/proposal-types/largeproppolicy and https://science.nrao.edu/science/science-program/large-proposals for more information.

The Community Review undertaken as part of the planning for the VLA Sky Survey Project (VLASS), identified the likelihood of substantial interest and scientific merit in PI-led projects that may be substantially larger than the typical NRAO Large Project. A discussion paper from the community followed and the issue has been discussed at the 2016 and 2017 meetings of the NRAO Users Committee.

The Community Discussion paper is attached to the 2016 UC reportSee also the 2017 UC report.

VLASS observations started in September 2017 and will use ~920 hours of each B/BnA configuration, equivalent to around 13% of the total VLA time available for astronomy over a full configuration cycle. VLASS is expected to run for 7 years (Semesters 17B – 24A). 

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