16B TAC Report

by Dana Balser last modified Jan 31, 2017

Summary

A total of 326 proposals were submitted to NRAO's North American facilities for semester 16B.  These includes the Robert C. Byrd Green Bank Telescope (GBT), the Very Long Baseline Array (VLBA)/High Sensitivity Array (HSA), and the Karl G. Jansky Very Large Array (VLA).  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 16B semester that have been reviewed by the NRAO TAC.  For the VLA and GBT we count HSA and GMVA proposal hours that request them as a VLBI station.  For the VLBA we include the 25 GMVA proposals.

 

Statistics by Proposal Count
ProposalsGBTVLBAVLANRAO
Submitted 58 61 207 326
Approved 22 28   75 125
Filler   8   8   63   79
Rejected 28 25   69 122
Oversubscription 2.6 2.2 2.8 2.6

 

Statistics by Proposal Hours
ProposalsGBTVLBAVLANRAO
Requested 5080.0 2732.3 4473.5 12285.8
Available 2252.0 1550.3 2048.5  5850.8
Approved 2365.5 1942.5 1404.1  5712.1
Filler   326.8   284.5 1407.1  2018.4
Rejected 2387.0   505.3 1662.3  4554.6
Pressure 2.3 1.8 2.2 2.1

 

For the 16B 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 16B Call for Proposals).   The table below summarizes the results for 16B.

 

Joint External Proposals

HST (Orbits)

Swift (ks)Chandra (ks)
Available 30 300 120
Requested 24 21.5 277.6
Approved 14 0 0

 

Telescope Pressure Plots

Pressure plots show the total hours of allocated time as a function of LST (or GST for the VLBA) for each telescope.   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.

 

GBT

Observations in high frequency bands require better weather conditions than observations in lower frequency bands. The GBT uses three weather categories: poor (for observations below 8 GHz), good (observations between 8-18 GHz and 26.5-50 GHz), and excellent (observation in the 18-26.5 GHz band and above 50 GHz).  The first three figures below show the pressure plots for each these weather categories.  The last figure includes all weather categories.  The grey horizontal line shows the total available hours.  The letters A, B, and C correspond to the priorities assigned by the TAC where A and B are approved time and C is filler time.  Carryover is time allocated by a TAC from a previous semester that is being executed in the 16B semester.

 

 GBT Pressure Plot 16B (poor)

GBT Pressure Plot 16B (good)

GBT Pressure Plot 16B (Excellent)

GBT Pressure Plot 16B (total)

 


VLBA

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 16A semester.

 

 VLBA Pressure Plot 16B

 


VLA

The VLA has two weather categories: high frequency (above 12 GHz, light shading) and low frequency (below 12 GHz, dark shading). The figure below shows the pressure for the A configuration.  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.

 

 VLA Pressure Plot 16B (A)

 

 

Observation Preparation

 

GBT

Please use the GBT Dynamic Scheduling System (DSS) to enable observing sessions, select observers for your project, and enter your blackout dates. The DSS Home Page has additional information about the DSS.  See GBT Observing for information about how to prepare for your observations.

Please note that the DSS uses the average Right Ascension (RA) and Declination (Dec) of all sources within a session.  The average RA and Dec will be used to determine when the session can be scheduled.  You will need to carefully check the RA and Dec, along with the minimum and maximum session lengths, to make sure that these values are satisfactory and will allow all your sources to be observed before enabling the session.

 

VLBA

In semester 16B, 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 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 16B and 17A, and proposals approved for priority B or C time will be eligible for scheduling only during semester 16B.

IMPORTANT: Those allocated dynamic time should begin their .key file preparation about two weeks before 2016 August 1, the start of semester 16B.

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.

 

VLA

In semester 16B daytime maintenance activities peak at about 17 hours LST for A configuration, so observing pressure is highest there.  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.