18A TAC Report

by Dana Balser last modified Nov 13, 2017 by Mark Claussen


A total of 48 proposals were submitted to LBO's Very Long Baseline Array (VLBA)/High Sensitivity Array (HSA) in semester 18A.  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 18A semester that have been reviewed by the LBO TAC.

Statistics by Proposal Count
Submitted  48
Approved  21
Filler  14
Rejected   13
Oversubscription 2.3
Statistics by Proposal Hours
Requested 1407.0
Available 1123.8
Approved   788.2
Filler   353.5
Rejected   265.3
Pressure      1.3

For the 18A 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 18A Call for Proposals).  The table below summarizes the results for 18A for the VLBA.  The time available on the external facilities is per year and includes the GBT and VLA.


Joint External Proposals

HST (Orbits)

Swift (ks)Chandra (ks)


30 300 120
Requested   8 147     0
Approved   8   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 observing priority. Click on the plot to enlarge. The upper black line with squares is 60% of the wall-clock time available (after removing time for maintenance) and the lower black line is half that (i.e. 30% of wall-clock time).  The colors correspond to pre-committed time (green), priority A (dark blue), priority B (light blue), priority C (yellow), and priority N (red). 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 18A semester.


VLBA Pressure Plot 18A


Observation Preparation

Unless otherwise stated in the TAC comments, proposals approved for priority A time will be eligible for scheduling in semesters 18A and 18B, and proposals approved for priority B or C time will be eligible for scheduling only during semester 18A.

IMPORTANT:  Those allocated dynamic time should begin their .key file preparation about two weeks before 2018 February 1,  the start of semester 2018A.  Those with fixed-date allocations (e.g. HSA proposals) will be informed of the date/time of observation about one month prior and their schedules will be due two weeks prior to observation.

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.