Introduction

NRAO and GBO invites submissions of Extra-Large observing proposals (X-proposals for short) for the 1 August proposal submission deadline. This opportunity is open for observers seeking to use the VLA, VLBA and/or GBT. Extra-Large proposals are defined as those requesting a total of more than 1000 hours of telescope time and/or extending over four or more observing semesters (see below for capabilities and restrictions).  Note that the earliest that successful Extra-Large projects could be scheduled is the start of Semester 2020B in August 2020. The opportunity to submit Extra-Large proposals will likely not be repeated for at least three years.  A joint proposal with external facilities (e.g., HST) may be included in an Extra-Large proposal, but the total time available for the external facility is limited (see the Joint Proposals page for details).

Regular and Large proposals continue to be encouraged for Semesters 2020A and beyond. At least 50% of open skies science time on each of the VLA, VLBA and GBT will continue to be made available for Regular and Large proposals from Semester 2020B. (The maximum amount of time that can be requested through a Large proposal will be capped at 1000 hours starting from Semester 2020B.)

To be accepted, Extra-Large proposals should demonstrate outstanding science impact, a high level of scientific and technical readiness, and excellent legacy science value (the potential to generate high science impact from community use of archival data and data products).

The scientific review process for Extra-Large proposals will be different from the normal NRAO Science Review Panel (SRP) / Time Allocation Committee (TAC) process. The Science Review Panels will assess the scientific potential of each Extra-Large proposal in their science area, providing comments and a coarse grading. A new X-Proposal Science Assessment Committee (XSAC) appointed by the NRAO and GBO Directors will assess the Extra-Large proposals for their scientific merit and likely legacy science value, taking into account the initial assessments from the SRPs. Observatory staff will assess each proposal for technical readiness, and the final selection of proposals will involve a face to face scientific, technical, and operations readiness review in Spring 2020.

Preference will be given to proposals which demonstrate substantial engagement with astronomers at U.S. institutions. Preference may be given to proposals with lower requirements for observatory support, and lower operational impact. The progress of Extra-Large projects that are accepted will be monitored through NRAO Program Management Department processes.

The deadline for submissions is 1 August 2019, the same as for Semester 2020A regular and large proposals. The announcement of successful Extra-Large proposals is anticipated to occur in July 2020.

Proposal Submission

Submission of Extra-Large proposals will be via the usual NRAO Proposal Submission Tool (PST) with the same 10-page limit for the Scientific Justification as for Large proposals. There is no "Extra-Large" option for proposal type so instead please just select "Large". To distinguish Extra-Large proposals from Large proposals the text "X-Proposal" must be included at the end of the title. Extra-Large proposals may request time on one or more of the VLA, VLBA, and GBT telescopes. Proposals requesting more than one telescope should submit the same scientific justification to each telescope through the PST, but include telescope-specific resources, sources, and sessions with each submission. A representative set of sources/resources/sessions should be entered into the PST with the correct total time and LST range, but a complete source list is not required at this stage.

The following additional material is also required for Extra-Large proposals and should be submitted by emailing a PDF file to x-proposals@nrao.edu by the same 1 August deadline:

• Data Management: The data management and delivery plan, including computing resource requirements.
• Project Schedule: A set of major project milestones and schedule.
• Team Resources: The team resources (including plans for resident scientists at the Observatory).

Proposers are also encouraged to address the following:

• Project Feasibility: The demonstrated feasibility of the project (strongly suggested).
• Special Requirements: Any special requirements (such as scheduling, calibration, scanning, data processing).

• Community Engagement: How the U.S. astronomical community will be engaged in this project.
• Observing Plan: A detailed observing plan.

The ability of the proposing team to execute the data management plan, as well as the feasibility for NRAO to accommodate any requests made of it in the data management plan, will be evaluated as part of the review process. Information that assists Observatory staff to assess likely operational and NRAO/GBO support implications will be welcomed as part of the additional material. This will be the focus of the final face to face technical and operations readiness reviews with the highest ranked proposal teams.

Capabilities and restrictions for Extra-Large proposals requesting VLA time

Extra-Large proposals requesting VLA time may request a subset of VLA General Observing capabilities,
with the following restrictions:

• No Shared Risk or Resident Shared Risk capabilities.
• Maximum number of triggers per year, per proposal: 50
• Minimum response time for triggers or coordinated observations: 1 week
• Minimum cadence for monitoring: 2 weeks, with a flexibility of at least 1 week on individual observations
• Maximum correlator output data rate: 25MB/s
• Minimum scan length: 10s
• No moving sources (including Solar and planetary observations).
• No fixed date observing.
• No phased array for VLBI.
• No pulsar modes.
• No subarrays.
• No mixed 3/8-bit samplers.
• No On-The-Fly mosaicing.
• Proposers should plan a science program that can be successfully executed with 85% of the full correlator (54 baseline board pairs).
• It must be possible to complete all projects within 2 configuration cycles (32 months).
• The availability of observing time will be limited by the constraint that at least 50% of the open science time will remain available for Regular and Large proposals, also taking into account ongoing observing for the VLA Sky Survey, and the amount of good weather available for Ku-band and higher frequencies. Over two configuration cycles the total number of hours available for Extra-Large proposals is 5900. Of those 5900 hours, the number of hours for which the observing conditions are expected to be suitable for the following bands is as follows:

• Extra-Large proposal observations at Ku through Q band may only be carried out at night. Proposers aiming to use these bands should take care to evaluate whether their targets are night-time targets in the configuration(s) needed to execute their science goals. The number of hours per LST hour (number of passes) for which the observing conditions are expected to be suitable for the following bands in each of the A,B,C,D configurations over 2 configuration cycles is as follows:

Capabilities and restrictions for Extra-Large proposals requesting VLBA time

Extra-Large proposals requesting VLBA time may request a subset of VLBA General Observing capabilities,
with the following restrictions:

• No Shared Risk or Resident Shared Risk capabilities.
• Maximum number of triggers per year, per proposal: 50
• Minimum response time for triggers or coordinated observations: 1 week
• Minimum cadence for monitoring: 2 weeks, with a flexibility of at least 1 week on individual observations
• Maximum number of correlator passes: 2
• Maximum number of phase centers per correlator pass: 100
• Maximum number of source changes per hour: 200
• Maximum number of observing modes per scheduling block: 4
• Maximum correlator output data rate: 25MB/s
• No moving sources.
• No fixed date observing.
• No High Sensitivity Array observing.
• No 3mm observing.
• The availability of observing time will be limited by the constraint that at least 50% of the open science time will remain available for Regular and Large proposals, and the amount of good weather at 2cm, 1cm and 7mm. The total number of hours available for Extra-Large proposals per semester will be 650. Of those 650 hours, the number of hours for which the observing conditions are suitable for the following bands is as follows:

• PIs of Extra-Large proposals should note the availability of 4Gbps advertised for semester 2020A. At present the media pool supports only a limited number of hours at 4Gbps, so 2Gbps should be assumed when writing Extra-Large proposals. However, proposers may indicate how their science goals or observing strategy would change if 4Gbps were available for their project.

Capabilities and restrictions for Extra-large proposals requesting GBT time

Please see the GBO Call for Proposals for the GBT capabilities and restrictions for Extra-Large proposals.