17A TAC Report

by Dana Balser last modified Jan 31, 2017


A total of 207 proposals were submitted to NRAO's Karl G. Jansky Very Large Array (VLA) in semester 17A.  Proposals are reviewed on a competitive basis with a panel review system (see Proposal Review System).  Below are the statistics by proposal count and hours.  The oversubscription is the ratio of the number of submitted proposals to the number of approved proposals.  The pressure is the ratio of the requested time to the available time in hours.  Here we only include proposals submitted for the 17A semester that have been reviewed by the NRAO TAC.  We count HSA and GMVA proposal hours that request the VLA as a VLBI station.

Statistics by Proposal Count
Submitted 207
Approved   84
Filler   59
Rejected   64
Oversubscription 2.5
Statistics by Proposal Hours
ProposalsVLA (C)VLA (D)
Requested 2388.24 2441.98
Available 1685.50 1709.50
Approved 941.63 975.13
Filler 912.01 868.50
Rejected 534.60 598.35
Pressure 1.4 1.4

For the 17A semester, the NRAO had agreements with the Hubble Space Telescope (HST), the Swift Gamma-Ray Burst Mission, and the Chandra X-ray Observatory to submit joint proposals whereby the NRAO TAC could allocate time on these external facilities (see the 17A Call for Proposals).   The table below summarizes the results for 17A for the VLA.  The time available on the external facilities is per year.


Joint External Proposals

HST (Orbits)

Swift (ks)Chandra (ks)


30 300 120
Requested 8 115 144
Approved 8 27 0


Telescope Pressure Plots

Pressure plots show the total hours of allocated time as a function of LST.   Also shown are how the hours are divided with respect to weather conditions and observing priority.  Click on the plot to view the source file.  The VLA has two weather categories: high frequency (above 12 GHz, light shading) and low frequency (below 12 GHz, dark shading). The figures below shows the pressure for the D and C configurations.  The black lines indicate the total time available for science (solid), the time available for K-band and higher frequencies (dashed), and the time available for Q-band (dotted).  The letters A, B, C, and N correspond to the priorities assigned by the TAC where A and B are approved time, C is filler time, and N is rejected time.

Note that in D configuration in the LST range 17:00 to 21:00, there  is less time requested than is available.  This has led us to be more generous than usual in allocating filler time that covers this LST.

Contrary to previous practice, we have systematically taken account of frequency in assigning filler time.  Since, at most LSTs the good weather time  will be consumed by A and B priorities, we have usually not allocated high frequency filler.


VLA Pressure Plot 17A (D)


VLA Pressure Plot 17A (C)


Observation Preparation

 In semester 17A, D configuration daytime maintenance activities peak at about 00 hours LST, so observing pressure is highest there.  The corresponding time for the C configuration is about 08 hours LST. Proposals approved for priority A, B or C time become ineligible when the associated configuration ends, unless explicitly stated otherwise in the Comments from the TAC. Those allocated dynamic time should begin their scheduling block preparation about two weeks before the planned start of the configuration (see Configuration Plans).

Any approved time may be divided into multiple scheduling blocks as appropriate, considering the scheduling priority, observing frequency, LST range suitable for the target(s), and LST pressure. For advice, please consult the VLA Observing Guide.

Unless stated otherwise, any time allocated is only for the identified proposal, and no modification in the project should be made without obtaining permission from NRAO scheduling staff.  To seek permission, submit a ticket to the Proposal Review department of the NRAO Helpdesk.