17A TAC Report

by Dana Balser last modified Nov 10, 2016


A total of 37 proposals were submitted to LBO's Very Long Baseline Array (VLBA)/High Sensitivity Array (HSA) 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 LBO TAC.


Statistics by Proposal Count
Submitted 37
Approved  20
Filler   7
Rejected   10
Oversubscription 1.9
Statistics by Proposal Hours
Requested 1653.0
Available 1284.5
Approved 633.0
Filler 471.0
Rejected 549.0
Pressure 1.3

 For the 17A semester, the LBO 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 LBO TAC could allocate time on these external facilities (see the 17A Call for Proposals).   The table below summarizes the results for 17A for the VLBA.  The time available on the external facilities is per year.


Joint External Proposals

HST (Orbits)

Swift (ks)Chandra (ks)


30 300 120
Requested 2 27 0
Approved 0 27 0


Telescope Pressure Plots

Pressure plots show the total hours of allocated time as a function of GST.   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 VLBA has two weather categories: high frequency (above 12 GHz, light shading) and low frequency (below 12 GHz, dark shading).  The two black lines are 50% (solid) and 70% (dashed) of the time available, respectively. 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.  Pre-committed (carryover) time is time allocated by a TAC from a previous semester that is being executed in the 17A semester.


VLBA Pressure Plot 17A


Observation Preparation

In semester 17A, Galactic parallax projects require much of the VLBA time in inner Galaxy GSTs (~2100 - 0400 GST) in the parallax "season", which is approximately ±3 weeks centered on the equinox.  Twenty-four hour blocks are especially very difficult to schedule during that time.   If at all possible, dynamic blocks should avoid those GSTs during that time of the year.

Unless otherwise stated in the TAC comments, proposals approved for priority A time will be eligible for scheduling in semesters 17A and 17B, and proposals approved for priority B or C time will be eligible for scheduling only during semester 17A.

IMPORTANT:  Those allocated dynamic time should begin their .key file preparation about two weeks before 2017 February 1,  the start of semester 2017A. 

Any approved time tabulated above may be divided into multiple scheduling  blocks as appropriate, considering the scheduling priority, observing frequency, GST range suitable for the target(s), and GST pressure. For advice on preparing your scheduling blocks, please consult the VLBA Observing Guide or use the helpdesk.