VLBI proposals for observing at 3mm wavelength (86 GHz) using: the VLBA, APEX, GBT*, EFFELSBERG, IRAM-30m, NOEMA, ONSALA, METSAEHOVI, YEBES and KVN telescopes should be submitted using the NRA Porposa Submission Tool (PST) by 04 FEBRUARY 2026 (UT 22:00)Successful proposals will be considered for scheduling in GMVA Session II 2026 (24-29 September) or in a later session (for 2027, those will be the dates: I – April 22-27, and II – October 14-18. SEE ALSO THE SECTION BELOW REGARDING PROPOSALS FOR GMVA OBSERVATIONS TOGETHER WITH PHASED-ALMA IN ALMA CYCLE 13
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.
* If a proposal provides a sufficiently compelling justification, GMVA observations may include the GBT. This will be only possible for observations between November and April (i.e., not possible for the usual Session II of the year). For this reason, approved proposals that include GBT observations will be carried over to 2027/I
ALMA and the KVN can be selected using the “Other Stations” text field in the PST.
The GMVA may include the Greenland Telescope (GLT) in its observations, if requested in the ‘Other Stations’ field and if feasible.
For further details on the proposal preparation, including the possibility of observations at 7mm (43 GHz; either as dedicated joint observations with ALMA/Band 1, see ALMA section below, or as interleaved scans for a subset of antennas during the 3mm observations), please consult the administrative and technical information hosted at the MPIfR here. Additional information is available at the VLBA, HSA, and GMVA proposal Guide of the NRAO under the link.
Detailed sensitivity calculations can also be performed using the GMVAsensitivity calculator, which can be found next to the EVN sensitivity calculator on the GMVA website under the Sensitivities panel here: http://www3.mpifr-bonn.mpg.de/div/vlbi/globalmm/sensi.html
Depending on antenna selection, the typical imaging sensitivities range between 0.08 – 0.5 mJy/hour (3 sigma).
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PARTICIPATION OF ALMA IN GMVA OBSERVATIONS IN ALMA CYCLE 13
It is expected that phased ALMA will participate in some GMVA observations during ALMA Cycle 13 (Oct. 2026 – Sept. 2027).
There are likely to be ~43 ALMA antennas available in Cycle-13 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-13 will only be possible in Session 2027/I, to be scheduled on April 22-27.
ALMA will support 3mm and 7mm observations in Cycle 13. Additionally,spectral line VLBI will be supported at both wavelengths, allowing for the proposal of GMVA + ALMA spectral line observations.
* Any new GMVA proposal requesting phased ALMA during Cycle 13 must be submitted via the NRAO PST at the 04 February 2026 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 must also be submitted to ALMA by the deadline for ALMA Cycle 13 proposals, which is planned for 23 April 2026. While the text of this proposal does not need to be identical to that of the GMVA, the overall scientific justification should remain the same. Please note that the ALMA proposal must be anonymised due to its dual-anonymous refereeing procedure. Please check here for any updates
Restrictions on GMVA+ALMA proposals in ALMA Cycle 13
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 >130mJy and >180mJy, respectively. Direct phasing-up on the target source (“active” phasing) thus limits the strength of the target.
For weaker sources with a flux density of less than 130 mJy or 180 mJy, ALMA offers the option of ‘passive’ phasing. In this mode, the ALMA array is periodically phased up on a bright calibrator source that is close in angular distance to the science target. For science targets, passive phasing is used, except for SNR considerations on VLBI baselines. However, the phasing calibrator must still meet the same criteria as for actively phased observations. It is recommended that the phasing calibrator is located within a certain angular separation, which should not exceed 6 degrees (3mm) or 10 degrees (7mm). Tests are continously being carried out at ALMA to improve the phasing. Please check the ALMA website for any updates on these figures (flux density limit and distance limit).
Proposers must specify any such calibrator in their proposal; consult the ALMA calibrator catalogue
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.
Please note that full-track 7mm observations with ALMA are made on a best-effort basis and the GMVA cannot support the addition of antennas other than those that are signatories to the GMVA Memorandum of Understanding. Media, planning and scheduling coordination of any other antenna is the responsibility of the PI proposing the observation.
As the 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.