TAC Report for Semester 2015A
The ProcessThe Observatory has completed the Semester 2015A proposal evaluation and time allocation process for the Karl G. Jansky Very Large Array (VLA), the Very Long Baseline Array (VLBA)/High Sensitivity Array (HSA), and the Robert C. Byrd Green Bank Telescope (GBT). A total of 375 new proposals were received for the 1 August 2014 submission deadline. In aggregate the proposals covered the broad spectrum of modern research in astronomy and astrophysics. A total of 1432 unique authors submitted proposals to the Observatory. The proposals were reviewed for scientific merit by eight Science Review Panels (SRPs). The proposals were also reviewed for technical feasibility by NRAO staff. Reviews were completed in September and then cross-reconciled by the Time Allocation Committee (TAC) during a telecon on 9 October 2014 and a face-to-face meeting on 21-22 October 2014 at NRAO in Green Bank, WV. The TAC consists of the chairs of the SRPs and was charged with recommending a science program for Semester 2015A to the NRAO Director. The recommended program was reviewed and approved on 5 November 2014. A disposition letter was sent to the principal investigator and co-investigators of each proposal on 13 November 2014. A TAC report (this document) containing information for proposers and observers, including statistics and telescope pressure plots, was released the same day. The approved science program will be posted soon. For each approved proposal in the science program, the Proposal Finder Tool will have access to its authors, title, abstract, and approved hours. The Observatory welcomes community feedback on its process for proposal evaluation and time allocation. Please provide such feedback via the Proposal Review department of the Observatory's Helpdesk.
Science ScoresLinear-rank science scores are assigned by the SRPs. The Observatory uses a scale from 0 to 10 to score proposals. A science score of 0 corresponds to a high-ranked proposal. A science score of 10 corrresponds to a low-ranked proposal. The quartile boundaries for the science scores are 2.5, 5.0 and 7.5.
Scheduling PrioritiesThe Observatory's telescopes are predominantly dynamically scheduled. Taking into account the time available as a function of LST, the TAC assigns a scheduling priority to each session in each proposal. The assigned scheduling priority depends on the linear-rank score of the proposal, the LSTs involved in the session (daytime is harder to accommodate than nighttime), the total time requested in the session, and the competition from better-ranked proposals requesting time at similar LSTs. For further VLA details, see http://www.aoc.nrao.edu/~schedsoc/VLAprioritizerMemo.pdf For the VLA and VLBA, possible scheduling priorities are: A = the observations will almost certainly be scheduled
B = the observations will be scheduled on a best effort basis
C = the observations will be scheduled as filler
N*= the observations will not be scheduled because they were explicitly rejected by the TAC
N = the observations will not be scheduled because they could not fit in the time available
H = not assigned because the proposal is being held for for consideration at a future TAC meeting For the GBT, the scheduling priorities reflect a combination of the time available and the quartile of the SRP science score. The scheduling priority along with the LST pressure plots should be used to determine the likelihood that your project will be scheduled. For the GBT, possible scheduling priorities are: A = the observations will almost certainly be scheduled B = the observations will be scheduled on a best effort basis or were ranked in the 2nd quartile
C = the observations will be scheduled as filler or were ranked in the 3rd quartile
N*= the observations will not be scheduled because they were explicitly rejected by the TAC N = the observations will not be scheduled because they could not fit in the time available H = not assigned because the proposal is being held for for consideration at a future TAC meeting
StatisticsThe tables below provide statistics by proposal counts and by proposal hours. Entries are binned according to time approved at scheduling priorities A or B, time approved at scheduling priority C only, and no time approved. To effectively schedule each NRAO telescope, it is necessary to approve more time than is actually available.
We are also pleased to report the statistics stemming from the new joint opportunities that NRAO has with the HST and Swift missions:
Pressure PlotsThe GBT plots below show the total hours of allocated time for each individual LST hour. The horizontal black line represents the total number of hours available in Semester 2015A for each LST hour. Carryover includes all active projects allocated time that will continue into Semester 2015A and all maintenance time needed for Semester 2015A. The available time and maintenance times are assigned fractionally to each weather category based on historical weather averages for Green Bank (50% poor, 25% good, 25% excellent). The observation frequency of carried over active projects is used to assign the weather category for this part of the carryover. The GBT has three weather categories: poor, good and excellent. These categories reflect the type of weather needed to successfully carry out a typical observation for a given receiver band. Any observation below 8 GHz is assigned to the poor weather category. Observations between 8-18 GHz and 26-50 GHz are assigned to the good weather category. Observations between 18-26 GHz and above 65 GHz are assigned to the excellent weather category.
For the VLBA, the plot below shows the pressure on dynamic time for each hour of GST, given the time committed before the 1 August 2014 deadline and the time approved for scheduling priorities A, B, C and N for Semester 2015A. The dashed (70%, assumed for the tabulated hours) and solid (50%) lines refer to percentages of the total calendar time in the semester, after only removing time for weekly and monthly maintenance. In Semester 2015A, 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 equinoxes. 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.
For the VLA, the pressure on dynamic time as a function of LST is shown in the pressure plots below for the B, BnA and A configurations planned for Semester 2015A. The plots encode pressure by scheduling priority, as well as by frequencies above 10 GHz (light shading) and below 10 GHz (dark shading). The time available per LST hour is shown by the solid black line for all frequencies, by the long-dashed black line for K-band conditions, and by the short-dashed black line for Q-band conditions. Engineering and enhancement activities cause the thick black line to be less than the total number of LST days in the configuration. Such activities dominately occur during daytime, causing the black lines to dip for daytime LSTs. In Semester 2015A, the competition for time was especially fierce in the B configuration at 0600-1400 LST because of an on-going large proposal VLA/13B-266. Further information on that proposal is available
Observation PreparationFor the GBT, procedures for observation preparation are described within the Green Bank Science Web Site. For the VLBA, proposals approved for priority A time will be eligible for scheduling during up to two semesters and proposals approved for priority B or C time will be eligible for scheduling during only one semester, unless explicitly stated otherwise in the Comments from the TAC. Those allocated dynamic time should complete their key file preparation well before 1 February 2015, the start of semester 2015A. Procedures for key file preparation are described at VLBA. For the VLA, 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. Configuration plans are available here. 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 Guide to Observing with the VLA. Procedures for observation preparation are described at VLA. 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. Page maintained by schedsoc
Modified on Thursday, 11-Dec-2014 16:31:09 MST