Calls for Proposals

Proposals are due by 2018 February 1, 17:00 US EST (22:00 UT).

This deadline applies to the following proposal types:

• Very Long Baseline Array (VLBA) and High Sensitivity Array (HSA) proposals requesting time in Semester 2018B (2018 August 1 - 2019 January 31) or multi-semester proposals.
• Global mm VLBI Array (GMVA) proposals for 2018 Session II  (Sep 27 - Oct 2), or later sessions.

Required proposal submission mechanisms are detailed in individual sections below.

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.

For Semester 2018B, we expect no significant GST-related pressure on available VLBA observing time.

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.

High Sensitivity Array (HSA)

The HSA comprises the VLBA, phased VLA, GBT, Effelsberg, and Arecibo telescopes.  We fully expect normal scientific observations, including HSA VLBI observations, to be available at Arecibo for semester 2018B.  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 2018B, in the D, C, and B configurations.  High frequencies (at receiver bands 22 GHz and above) have better phasing at more compact configurations.

Observing with a single VLA antenna (Y1) in conjunction with the VLBA will only be available through the VLBA Resident Shared Risk Observing program.

• The Green Bank Telescope, like the VLBA, 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 telescope supports both the PFB and DDC observing systems available on the VLBA.

• The Arecibo 305-m telescope is currently available only with the PFB observing system.  An RSRO project is encouraged to help qualify the 4-channel DDC observing system at Arecibo.

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

GMVA proposals submitted by the 2018 February deadline will be considered for scheduling in 2018 Session II  (Sep 27 - Oct 02), 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 GMVA stations should be quantitatively justified in the proposal.  ALMA and/or the KVN must be specified by entering "ALMA" or "KVN" as "Other" entries in the PST.

Another opportunity to propose VLBI observations using the phased ALMA telescope will be available at this Call for GMVA proposals:

It is expected that phased ALMA will participate in some GMVA observations during ALMA Cycle 6 (Oct 2018 - Sept 2019;  see the ALMA Cycle 6 Pre-announcement).   The number of ALMA dishes possible in the phased array is likely to be ~43).  ALMA will not be in a configuration suitable for VLBI during GMVA Session II 2018.  GMVA session dates during Cycle 6 are not yet fixed but Session I in 2019, which is likely to be in the period March - May, should provide an opportunity for GMVA + ALMA observing.   GMVA Session II in fall 2019 may also overlap in Cycle 6 with ALMA in a configuration suitable for VLBI.

Any GMVA proposal requesting phased ALMA during Cycle 6 must be submitted via the NRAO PST at the February 1, 2018 deadline.

Proposers should:

• specify "ALMA" in the Other Stations text field in the PST
• select the default GMVA 3mm observing mode of 2 Gbps, dual polarization
• specify the amount of time and GST range(s) needed for ALMA separately, either in Session Constraints or Comments, or in the Technical Justification.

A separate proposal to ALMA must also be submitted at the deadline for ALMA Cycle 6 proposals in April 2018.  For this, all proposers (PI and Co-I's) must be registered ALMA users (see:  http://www.almascience.org).

Restrictions on GMVA+ALMA proposal in Cycle 6:

• GMVA observations with ALMA will be limited to a fixed, continuum-only, mode, which will provide 2 Gbps on all baselines.  The KVN will not be available in this mode.
• Due to the need to phase up on the target source, only sources with correlated flux densities >0.5 Jy in intra-ALMA baselines out to 1 km may be proposed for observation.  Only ALMA antennas within the 1 km radius will be part of the phased sum.
• In order to make a clean linear-to-circular transformation of ALMA recordings, any target source must be observed for a duration of at least 3 hours (breaks for calibrators permitted) to sample a range of parallactic angles.
• Large Programs (>50 hours of observing time) are not permitted because phased ALMA is a non-standard mode.
• No long-term programs may be proposed, and no proposals will be carried over into the next cycle.
• There is a cap for VLBI of 5% of ALMA Cycle 6 observing time.  As time for GMVA observations will thus be scarce, proposals should include a quantitative justification as to why ALMA is essential for the goals of the project.

 Resubmission of ALMA Cycle 5 proposals:

The outcome of scheduled GMVA+ALMA Cycle 5 observations in April 2018 is unlikely to be known until after the ALMA Cycle 6 proposal deadline. If the PI wishes to mitigate against the possibility that these observations are not completed successfully, the proposal must be resubmitted to ALMA by the Cycle 6 proposal deadline and undergo a new review. The proposal does not need to be resubmitted to the GMVA in this case.  Observations in Cycle 6 will only occur if the April 2018 observations are not completed successfully and the ALMA Cycle 6 proposal is ranked high enough for scheduling.

However, if the PI wishes to obtain a second epoch of GMVA+ALMA observations, even if the April 2018 observations are successful, a new proposal must be submitted to both the GMVA and ALMA by their respective proposal deadlines.