Preparing a Proposal

After composing the scientific justification and identifying the desired VLBI target source(s), select an appropriate VLBI array. Possibilities include:

1. The VLBA alone (SC, HN, NL, FD, LA, PT, KP, OV, BR, and MK). Proposal deadlines are February 1, June 1, and October 1. (Deadlines are delayed until the following Monday if one of these dates falls on Saturday or Sunday.) Observing periods for such programs are identical to those for the VLA and are advertised in the NRAO Newsletter at http://www.nrao.edu/news/newsletters/ . Time allocation is described at http://www.aoc.nrao.edu/epo/ad/scheduling.shtml and referee guidelines may be found at
   http://www.nrao.edu/administration/directors_office/refguide. Approved VLBA programs are scheduled by the VLBA schedulers (see Section 28.3), who may be contacted at schedsoc@nrao.edu. Ulvestad (2004) provides a short guide to using the VLBA, aimed specifically at inexperienced users but also useful to fill in knowledge gaps for more experienced users.

2. The VLBA (SC, HN, NL, FD, LA, PT, KP, OV, BR, and MK), with the additional inclusion of the VLA, the GBT, Effelsberg, and/or Arecibo. Observing time of up to 100 hours per trimester has been reserved for a ``High Sensitivity Array'' consisting of the VLBA, VLA, GBT, Effelsberg, and (when possible) Arecibo; this opportunity, including the specification of the High Sensitivity Array on the proposal cover sheet, is described at http://www.nrao.edu/HSA/ . Antennas from this set also may be requested individually, though priority will be given to proposals for the High Sensitivity Array. In addition, the VLA can be requested in either phased array or single antenna mode (Wrobel & Taylor 2002); the single VLA antenna generally is most useful if one needs short baselines to sample properly extended structure in the target source. All deadlines and procedures are the same as for the VLBA alone.

3. The European VLBI Network (EVN). The EVN consists of a VLBI network of antennas operated by an international consortium of institutes (Schilizzi 1995). The EVN home page at
   http://www.evlbi.org provides access to the ``EVN User Guide.'' That guide includes the ``EVN Status Table,'' giving details of current observing capabilities of all EVN antennas; and the ``EVN Call for Proposals,'' describing how to apply for observing time on the EVN. The EVN handles the proposing, refereeing, and scheduling mechanisms for such programs, which must all be run during a regular VLBI Network session. EVN proposal deadlines are February 1, June 1, and October 1, with no allowance made for weekends. VLBI Network session dates and wavelengths are given in the ``EVN Call for Proposals'' and in the NRAO Newsletter at http://www.nrao.edu/news/newsletters/ . Observing time is allocated by the EVN Program Committee. Approved EVN programs are scheduled by the EVN scheduler. Any EVN proposal requesting the VLBA or two or more of the non-EVN VLBA affiliates identified in Item 5 below constitutes a global proposal, and must be submitted to both the VLBA and the EVN.

4. The Global 3 mm Array. This array consists of the VLBA antennas outfitted at 3 mm, together with Effelsberg, Pico Veleta, Plateau de Bure, Onsala, and Metsähovi. Procedures are similar to those for the EVN, although the European part of the 3 mm Array is operated by the Max Planck Institut für Radioastronomie. For more details, see http://www.mpifr-bonn.mpg.de/index_e.html .

5. VLBA affiliates in addition to the VLA, the GBT, and Arecibo currently include Effelsberg and the Deep Space Network. A VLBA proposal requesting such affiliates is handled as described in Item 1 above, except that if two or more EVN institutes are requested, then it is a global proposal and must be submitted to both the VLBA and the EVN. A VLBA program involving affiliates other than the VLA might be run outside of a regular VLBI Network session, depending on which affilliates are involved. In particular, about 20 days of time per year, outside of regular VLBI Network sessions, has been reserved for joint VLBI programs involving the VLBA and Effelsberg; submit proposals for such joint time both to the NRAO and to the EVN scheduler.

Once the appropriate VLBI array is selected, run the NRAO SCHED program (Walker 2006) to determine the Greenwich Sidereal Time range during which the VLBI target sources are up at the selected antennas. This program can also be used to evaluate the $u$-$v$ plane coverage and synthesized beams provided by the selected antennas (see Section 10).

Requirements for source position accuracy at correlation time are discussed by Ulvestad (2004). An accurate source position service is available through NRAO, but requests to it should be made no later than proposal time for positions needed at correlation time (Walker 1999a).

Proposals requesting more than 200 hours of total time on the VLBA, the HSA, or various combinations of NRAO telescopes in VLBI and non-VLBI modes, are covered under the NRAO Large Proposal Policy described at
http://www.nrao.edu/administration/directors_office/largeprop.shtml .