NRAO
call for proposals

"The National Radio Astronomy Observatory (NRAO) invites
scientists to participate in the Semester 2023B Call for Proposals (https://science.nrao.edu/observing/call-for-proposals) for
the Karl G. Jansky Very Large Array (VLA) and the Very Long Baseline Array
(VLBA), High Sensitivity Array (HSA), and Global 3mm VLBI Array (GMVA). The submission deadline for Semester
2023A proposals is Wednesday, 1 February 2023, at 17:00 EST (22:00
UTC). Proposal preparation and submission are via the
Proposal Submission Tool available through NRAO Interactive Services."

GMVA
call for proposals

Deadline: 1 February 2023

VLBI proposals for observing at 3mm
wavelength (86 GHz) using the VLBA, GBT*, EFFELSBERG, PICO VELETA, NOEMA,
ONSALA, METSAEHOVI, YEBES and KVN telescopes should be submitted by

1 FEBRUARY 2023 (UT 22:00)

Successful proposals will be considered for scheduling in GMVA Session II 2023
(11-16 October) or in a later session.

SEE ALSO THE SECTION BELOW REGARDING
PROPOSALS FOR GMVA OBSERVATIONS TOGETHER WITH PHASED-ALMA IN ALMA CYCLE 10, NOW
ALSO INCLUDING 7-mm OPPORTUNITY

ALL PROPOSALS SHOULD BE SUBMITTED USING

THE NRAO PROPOSAL SUBMISSION TOOL (PST):

https://my.nrao.edu

In order to maximize the sensitivity for continuum observations the GMVA will
record at the highest bitrate which instrumentation and resources permit.
Currently all telescopes will record at 4 Gbps. All data will be correlated at
the Bonn DiFX software correlator.

* The GBT may be included in GMVA
observations if a sufficiently compelling justification is given in the
proposal but the amount of time available will be reduced compared to earlier
observing semesters, and observing blocks greater than 6 hours will be very
difficult to schedule.

ALMA and the KVN can be selected
using the "Other Stations" text field in the PST. The Greenland
Telescope (GLT) may be available for some GMVA observations. If requested (in
the "Other Stations" field) it will be included in the observations
if this is possible. For further details on proposing, including the
possibility of additional support observations at 7mm (43 GHz), please consult
the administrative and technical information hosted at the MPIfR:

http://www3.mpifr-bonn.mpg.de/div/vlbi/globalmm

PARTICIPATION OF ALMA IN GMVA
OBSERVATIONS IN ALMA CYCLE 10

It is expected that phased ALMA will
participate in some GMVA observations during ALMA Cycle 10 (Oct. 2023 - Sept.
2024). Please look for the ALMA Cycle-10 pre-announcement (expected to be at
this link).

There are likely to be ~43 ALMA
antennas available in Cycle-10 but the phased sum used for VLBI will be formed
only from those that lie within a circle of radius 0.5 km (or less, depending
on atmospheric conditions).

Observations together with ALMA in
Cycle-10 will only be possible in Session 2024/I, scheduled tentatively on
April 18-23, 2024.

In ALMA Cycle 10, ALMA expects to
support both 3mm and 7mm observations. Also, spectral line VLBI in both
wavelengths is also supported, so GMVA + ALMA spectral line observations could
be proposed.

Any new GMVA proposal requesting phased ALMA during Cycle 10 must

be submitted via the NRAO PST at the 1 February 2023 deadline.

Proposers should:

• specify
  "ALMA" in the Other Stations text field in the PST


• select the default
  GMVA observing mode of 4 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 10 proposals, likely to be in
April/May 2023. The text of this proposal need not be identical to that for the
GMVA but the overall scientific justification should be the same. Note that the
ALMA proposal should be anonymized due to their dual-anonymous refereeing
procedure.

Restrictions on GMVA+ALMA proposals
in ALMA Cycle 10



GMVA observations with ALMA will be limited to a fixed recording mode, which
currently provides 4 Gbps on all baselines.

Direct phasing of the ALMA array is
limited to targets with a 7mm and 3mm correlated flux density >0.35Jy and
>0.5Jy, respectively.

Direct phasing-up on the target source ("active" phasing) thus limits
the strength of the target.

For weaker sources (<350 mJy or
<500 mJy), ALMA offers the option of "passive" phasing. In this
mode, the ALMA array is periodically phased up on a bright calibrator source
close in angular distance to the science target. There will be no restrictions
on the flux density of science targets using passive phasing (aside from SNR
considerations on VLBI baselines). However, the phasing calibrator properties
must meet the same criteria as for actively phased observations, and it is
recommended that the phasing calibrator lies within an angular separation of no
more than 6 degrees (3mm) or 10 degrees (7mm) from the science target.

Proposers must specify any such
calibrator in their proposal; consult the ALMA calibrator
catalogue.

In order to make a clean
linear-to-circular polarisation transformation of ALMA recordings, any target
source must be observed for a duration of at least 3h at a given frequency
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.

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.