Proposal submission information for the following three combinations of telescopes are detailed in individual sections below:

• Very Long Baseline Array (VLBA) and High Sensitivity Array (HSA) proposals requesting time in Semester 2020A (2020 February 1 - 2020 July 31) or multi-semester proposals.
• Global mm VLBI Array (GMVA) proposals for 2020 Session I (Apr 23 - 28), or later sessions.

VLBA Proposals

The VLBA provides ultra-high angular resolution for astrophysical studies including:

• Non-thermal continuum emission, including polarimetry, from active galactic nuclei (AGN), Galactic micro-quasars, pulsars, and other sources.
• Maser emission lines of OH (1.7 and 6.0 GHz), CH₃OH (6.7 and 12.2 GHz), H₂O (22 GHz), SiO (43 and 86 GHz) and other molecules, and numerous thermal absorption lines, in a variety of Galactic and extragalatic circumstances.
• Multiple-phase-center surveys across the primary beam.
• Parallax and proper motion via differential astrometry of a variety of stars, star-forming regions, and nearby extragalactic objects, at accuracies as good as 10 microarcsec.
• Absolute astrometry at accuracies of ~200 microarcsec to expand the International Celestial Reference Frame.

Overall information about the VLBA is available in the VLBA Observational Status Summary (OSS); specific sections relevant to various proposal types are linked below.

The VLBA operates two data systems, a Polyphase Filterbank (PFB), and a Digital Downconverter (DDC).  These are described in detail in Section 5.4 of the VLBA OSS, which also includes suggestions for selecting the optimal observing system for various scientific goals.

VLBA proposals must be prepared and submitted using the NRAO Proposal Submission Tool (PST), accessible via NRAO Interactive Services.  Use of the PST requires registration by all proposers, including co-investigators, in the NRAO User Database.

Proposals requiring significant additional correlator resources, such as multiple phase centers per field or multiple pulsar phase bins, should consider mechanisms to support the correlation without adversely affecting the throughput of other projects.  These should be entered in the technical justification section of the proposal.

Approximately 1000 to 1200 hours of VLBA observing time are expected to be available for Open Skies in observing semester 2020A.  In recent semesters, there has been less pressure in the GST range 0600 - 1800 hours as compared to 1800 - 0600 GST, and we expect this trend to continue.

4096 Mbps Recording Rate to General Observing on the VLBA (only)

Beginning in 2020A, general observing (GO) on the VLBA  (not the HSA) will be offered with a maximum recording rate of 4096 Mbps.    During semester 20A we expect to be able to support 4096 Mbps recording for ~40% (~400 hours) of the open-skies observing time.  Therefore we will allocate 4096 Mbps to the most highly-ranked proposals that request it.  Your proposal should indicate whether it could be considered for allocation at 2048 Mbps, perhaps with an increased time request, or dropped from consideration altogether.

NRAO Staff Assistance with VLBA Observation Setup and Data Reduction

Beginning with the 2020A proposal call, NRAO will offer extra staff assistance with VLBA observational setups and data reduction.  For the 2020A semester, this offer will pertain to proposals which request only the VLBA (i.e. no HSA, GMVA, or cm Global proposals).   Additionally, this offer will be limited in scope to new or novice VLBA users, and will include both observing and data reduction assistance.   There will also be limitations in some capabilities which will be supported under this program, for example which bands will be allowed.  In order to request this assistance, a new checkbox/text box is available on the General page of VLBA proposals in the Proposal Submission Tool (PST), at the bottom of the page.  Please check the checkbox and provide input on your proficiency and/or specific requests in the text box.   Note  that checking the text box and providing the requested input does not automatically mean that this service will be provided for your proposal.  There will be an internal NRAO review of these requests similar to that done for RSRO proposals (see below); the proposal disposition letter will inform the proposers whether or not the service can be provided.

VLBA Filler Proposals

Filler proposals, which are scientifically useful programs which can be scheduled at a large range of GST times, with fewer than 8 stations, low-frequency weather requirements, and short (2 - 6 hours) scheduling blocks, are especially encouraged on the VLBA.  Such  projects can help to fill "gaps" in the dynamic observing schedule.

VLBA Extra-Large (X-)Proposals

NRAO and GBO will consider submissions of Extra-Large observing proposals (X-proposals for short) at the upcoming 1 August proposal submission deadline. This opportunity is open for observers seeking to use the VLA, VLBA and / or GBT. Extra-Large proposals will be defined as those requesting a total of more than 1000 hours of telescope time and / or extending over four or more observing semesters. 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.  Please see the  Announcement of Opportunity for Extra-Large Proposals in the NRAO Newsletter.  Details for proposers can be found in the Extra-Large Proposals section in the 2020A Call for Proposals.

VLBA Resident Shared Risk Observing

The VLBA Resident Shared Risk Observing (RSRO) program provides users with early access to new capabilities in exchange for a period of residency in Socorro to help commission those capabilities. For example, the phased-VLA system was developed through RSRO programs.  Users are encouraged to conceive and propose innovative ideas for new VLBA capabilities.  Some staff suggestions are  included at the VLBA RSRO program page, along with details for submitting RSRO proposals.  

Proposers should be aware that RSRO capabilities are generally not approved at priority A, owing to the level of risk associated with these observations.

High Sensitivity Array (HSA) Proposals

The HSA comprises the VLBA, phased VLA, GBT, Effelsberg, and Arecibo telescopes.   All of the HSA stations are equipped with instrumentation compatible with the VLBA observing capabilities described in Section 5.4 of the VLBA OSS.  Ongoing special considerations for the HSA telescopes are documented in OSS Section 14.2; new features and special cases are cited here.

VLBI observations combining the VLBA with any one or more of the other four HSA stations can be requested in a single HSA proposal.  However, separate proposals must be submitted for any non-VLBI use of any requested telescopes.

HSA proposals must be prepared and submitted using the NRAO Proposal Submission Tool (PST), accessible via NRAO Interactive Services.  Use of the PST requires registration by all proposers, including co-investigators, in the NRAO User Database.  The inclusion of HSA stations should be quantitatively justified in the proposal.

• The phased Very Large Array (Y27) will be available for HSA observing in Semester 2020A, in the C and B configurations.  High frequencies (at receiver bands 22 GHz and above) have better phasing in the more compact configurations (C and D).  High frequency phasing in the extended configurations in the summer can be quite difficult.

• The Green Bank Telescope (Gb), has transitioned into a new partnership arrangement, the Green Bank Observatory (GBO).  Time available for VLBI on the GBT will be reduced compared to earlier years, and only the most highly rated proposals across all GBT observation types will be awarded time.  Additionally, proposers should be aware that long scheduling blocks (more than 6 hours) will be very difficult to schedule owing to constraints coming from non-NSF GBO partners.  Proposers are encouraged to make clear in the technical justification section any constraints about how observing time could be broken into smaller pieces without adversely affecting the proposed science; include information as relevant regarding maximum elapsed time of a split schedule and minimum scheduling block lengths.

Observations using the GBT 6-cm receiver as part of the HSA must be taken, correlated, and calibrated in full Stokes mode.  Due to the large cross-talk between polarizations, only total intensity (Stokes I) data will be usable. 

• The Effelsberg (Eb) 100-m telescope supports both the PFB and DDC observing systems available on the VLBA.  Consult this web page for more detailed information about the Eb HSA station.

• The Arecibo (Ar) 305-m telescope is currently available only with the PFB observing system, but an upgrade is in progress to accommodate Mar 6 + DDC-8.  The status of this project for future calls will be available on the AO VLBI website.   The sensitivity of VLBI observations with Ar changed after the 2017 hurricanes at the station, due to flooding which altered the shape of a portion of the main reflector.  Please use the EVN Sensitivity Calculator for the most up-to-date values.

Global 3mm VLBI Array (GMVA) Proposals, including Phased ALMA

GMVA proposals submitted by the 2019 August 1 deadline will be considered for scheduling in 2020 Session I  (Apr 23 - Apr 28), or later sessions.

Complete information on the GMVA is available at the GMVA website.  Ongoing special considerations for the GMVA are documented in Section 14.3 of the VLBA OSS; new features and/or special cases are cited here.

As noted in the HSA section above, GBT time available for VLBI has been reduced due to its new partnership arrangements.

GMVA proposals must be prepared and submitted using the NRAO Proposal Submission Tool (PST), accessible via NRAO Interactive Services.  Use of the PST requires registration by all proposers, including co-investigators, in the NRAO User Database.  The inclusion of the GBT in a GMVA proposal should be quantitatively justified.  The KVN must be specified by entering "KVN" as "Other" entries in the PST.

The GMVA will record at the highest bitrate which instrumentation and resources permit. Currently all telescopes will record at 2048 Mbps. The GMVA observatories are working to increase the default recording bitrate to 4096 Mbps in the near future.

GMVA proposals requesting the phased ALMA telescope should not be submitted at the 1 Aug 2019 (semester 2020A) deadline.

Documentation and Assistance

Detailed Information about the VLBA instrument, its capabilities, observing strategies,  proposal preparation and submission, and  observation preparation, can be found in the VLBA Observational Status Summary, at the Guide to Proposing for the VLBA, and at the Guide to Observing with the VLBA. Answers to Frequently Asked Questions are contained in these proposing and observing guides. Questions may also be directed to the NRAO Helpdesk.