18A Semester

18A Proposal Call

The Green Bank Observatory (GBO) invites scientists to
participate in the GBO’s 2018A Semester
Call for Proposals for the Green Bank Telescope (GBT).

The submission deadline for Semester 2018A proposals is
Tuesday, 1 August 2017, at 17:00 EDT (21:00 UTC).

Proposals requesting the GBT as part of High Sensitivity Array (HSA), and Global 3mm VLBI Array (GMVA) should be submitted through the Long Baseline Observatory’s call (available here).

The GBO wishes to remind proposers of continuing opportunities for joint observations with the Chandra X-ray Observatory, the Hubble Space Telescope, the Swift Gamma-Ray Burst Mission and the Fermi Gamma-ray Space Telescope.

The GBO strongly encourages proposers to carefully read through the “News and Opportunities” section of the proposal below as there have been a number of changes made to instrument availability.

Proposal preparation and submission remain via the NRAO Proposal Submission Tool (PST) available at NRAO Interactive Services. Note that the PST use requires registration. Proposers who need assistance with proposal preparation or have questions regarding the Call or GBT capabilities should contact Observatory staff via the Helpdesk.

News and Opportunities

The 1 August 2017 deadline is for the 2018A Semester observing period on the GBT:
1 February 2018 – 31 August 2018

Details of all GBT observing modes are in The Proposer’s Guide for the Green Bank Telescope. Proposers should also consult the more general document The Performance of the GBT: A Guide for Planning Observations. Proposers should make sure that they are familiar with the latest versions of these documents before writing their proposal.

Observer Training

Due to reductions in the amount of NSF-supported “open skies” time on the GBT for use by the scientific community, it has become increasingly difficult to train new GBT observers in the way we have traditionally done in the past. As a result, we have introduced observer training schools. It is expected that new GBT observers will attend one of these schools to become qualified to observe on the GBT.  These provide an introduction to general radio astronomical techniques as well as onsite training for new GBT observers.

The next training school will be held September 18-22, 2017 in Green Bank.

We still support new observers who visit the Observatory, where their projects will receive an increased priority for scheduling and where local staff are on hand to assist in the observations.

While at some point observer training schools may be the primary means to certify new GBT observers, we remain committed to providing all the services necessary to ensure that the GBT remains accessible to the entire scientific community, and ask your patience in this time of transition.

Observing Team Members

We would like to remind all project teams of the Green Bank Observatory policy that all observers must be listed as a member of the project team in the GBT Dynamic Scheduling System.

Also, we would like to remind all observers that they should not log into any GBO computing system using another person’s account. Co-Is and students are required to have their own GBO login and account if they are to participate in observing and data reduction.

GBT Instruments

The GBT receivers, backends, and observing modes that are available in Semester 2017A are listed in Tables 1 and 2 below.

ReceiverFrequency RangeNote
Prime Focus 1290 – 395 MHz
680 – 920 MHz
L-band1.15 – 1.73 GHz
S-band1.73 – 2.60 GHz
C-band3.8 – 8.0 GHzlinear only, see below
X-band5 – 11.6 GHz
Ku-band12.9 – 15.4 GHz
K-band Focal Plane Array (KFPA)18 – 26.5 GHz7-pixel array
Ka-band26 – 39.5 GHz
Q-band38.2 – 49.8 GHz
W-band67 – 93.3 GHz
Argus80 – 115.3 GHzshared-risk, private PI instrument, 16-pixel array
MUSTANG-290 GHzshared-risk, private PI instrument
Table 1
BackendObserving ModeNote
VEGAScontinuum, spectral line, pulsarshared-risk
JPL Radar backendradarPrivate PI instrument, open for public use
Breakthrough Listen (BTL)Private PI instrument, shared risk
Table 2

Session lengths: Proposers should be aware that long scheduling blocks (more than 6 hours) will be very difficult to schedule as a result of the reduced open skies time from the divestment of the GBT by the NSF. Proposers must make clear in the technical justification section how their project can be scheduled in small observing blocks that would more easily fit into the GBT scheduling constraints. This is especially critical for proposals that require fixed or coordinated observing dates, e.g. VLBI observations, pulsar monitoring, radar, etc.

C-band: Proposals wishing to use the GBT C-band receiver should only use linear polarization outputs. The circular polarization of the receiver is currently not preforming correctly and we will not accept any proposals to use the circular polarization output of this receiver.

C-band VLBI on the GBT: The GBO will only accept proposals for VLBI Stokes I continuum observations using the GBT C-band receiver (the observations will need to be done using full Stokes just to calibrate Stoke I). All other VLBI observations requesting the C-band receiver on the GBT will be disregarded. Please see the HSA section of  the Long Baseline Observatory call (available here) for proposals for more details.

VEGAS Continuum: All modes of VEGAS may now be used for continuum observations. The Proposal Submission Tool has not been updated to reflect this situation. Proposers should use the spectral line modes of VEGAS to choose the desired bandwidth and then note in the technical justification that the observations will be for continuum measurements.

VEGAS Pulsar: VEGAS pulsar modes will be released for observing.

Argus: Observers interested in shared-risk observations using the Argus instrument should see the Argus website for further information. All Argus proposals must have permission from the instrument development team.

VLBI: Time available for VLBI on the GBT will be extremely limited as a result of the reduced open skies time from the divestment of the GBT by the NSF. Proposers should only include the GBT in the proposal if it is essential for the science and if it is clearly justified in the text of the proposal. All Very Long Baseline Interferometry (VLBI) proposals requesting the GBT should include any needed setup and overhead time in the time request of their proposals. C-band VLBI observers should see the C-band VLBI note above.

MUSTANG 2: The GBO will accept proposals for shared risk observations using the MUSTANG-2 instrument at the proposal deadline. The GBO cannot guarantee that MUSTANG-2 will be cold at the start of scheduled observing due to low observing elevations or rotations of the turret from prior observations. Cool down time for MUSTANG-2 observations should be included in the overhead for MUSTANG-2 observations. All MUSTANG-2 proposals must have permission from the instrument development team.

Breakthrough Listen backend: The Breakthrough Listen project is making its backend available for up to 50 hours of shared-risk observations during the 2018A semester. The instrument consists of a cluster of 32 Titan X and 1080 GPU-based servers capturing 8-bit baseband voltages over up to 5 GHz of instantaneous bandwidth. Data rates are typically tens of TB/hr but a pipeline is available to generate spectra with adjustable frequency (> 3 GHz) and time (> 350 μs) resolutions, with possible science applications including fast radio transients, pulsar observations, stellar flares, SETI, etc. Before submitting a proposal, proposers must obtain permission from the Breakthrough Listen team at Berkeley SETI Research Center. The team will consult on poroposal preperation and data analysis. Any data acquired using the backend will be proprietary to the proposer per the standard GBO policies.
More information including a technical description of the backend and team contact details can be found here.

Mapping: If you are considering mapping with the GBT such that there are major turns or moves (end of rows in raster map, change in position for pointed maps, etc.) that occur with a cadence faster than every 30 seconds, you will need to consult with a GBT support scientist to ensure that the GBT can safely withstand the stresses induced by the mapping motions.


The GBT is scheduled by the Dynamic Scheduling System (DSS). The DSS system is fully described in the GBT Proposer’s Guide and the GBT Observer’s Guide.

GBT Proposal Preparation

Proposers should consult the The Performance of the GBT: A Guide for Planning Observations and the GBT Observer’s Guide. All proposers, including pulsar proposers, should use the GBT Sensitivity Calculator. Please see the Calculator’s User’s Guide for instructions. The Sensitivity Calculator results can be cut and pasted into the Technical Justification section of the proposal. This will streamline the creation of your Technical Justification and will increase your chances of getting a positive technical review. If you are planning on making maps with the GBT, you should use the GBT Mapping Calculator tool.

The GBT observing policies describe the telescope’s remote observing restrictions.

Proposers requesting GBT participation in High Sensitivity Array (HSA), Very Long Baseline Array (VLBA), or Global Millimeter Very Long Baseline Interferometry (GMVA) observations should consult the VLBAHSA, and GMVA Proposal Call.

GBT Shared Risk Observing

Observers requesting instruments that are shared-risk will be expected to travel to Green Bank for observations. The observers may be expected to help commission the instruments, to help debug observing and data reduction software, as well as helping to develop data reduction and calibration schemes.

Proposals to use Argus (80-115.3 GHz) will be accepted with the instrument development team’s permission. Proposals to use MUSTANG-2 will be accepted with the instrument development team’s permission. Proposals to use the Breakthrough Listen backend will be accepted with the instrument development team’s permission. The Green Bank Observatory will consider shared-risk proposals for observations during the 2018A semester with these instruments.

Limited Time for “Fixed” and “Windowed” Observations

Due to varied pressures on the GBT’s schedule, the amount of time that can be accepted for fixed time observations (e.g. VLBI, pulsar transit observations, etc.) and windowed observations (e.g. monitoring observations) will be limited for the proposal call. Proposals needing fixed and windowed observations will likely have to be ranked at least in or near the top decile in order to be accepted.

Limited Instrument Availability

Due to existing obligations, the Prime Focus 800 MHz feed will only be available for approximately two weeks each month. The Prime Focus 342 MHz feed will only be available for approximately one week per month. The other Prime Focus feeds (450, 600 and Prime Focus 2) are unlikely to be considered for installation. Similarly, the Caltech Continuum Backend (CCB), Zpectrometer, Ku-wide and RRI receiver are also unlikely to be considered for installation. The PFS radar backend (PI: Margot) is available only with prior agreement by the PI.

Prime Focus 1450 and 600 feed: 385-690 MHz
Prime Focus 2910-1230 MHz
ZpectrometerPrivate PI instrument, shared risk
Ku-widenot for spectral line use
RRIPrivate instrument, shared risk
RPS RadarPrivate PI instrument

Other GBT Gregorian receivers (primarily, but not limited to, Ku, Ka, Q and W) may only be available during a few short, two or three week periods during the semester.

470-700 MHz RFI Digital TV transmissions above 470 MHz will make observing very difficult with the 450 and 600 MHz feeds of the PF1 receiver. Available RFI plots do not show the strength of these signals as they overpower the system: they are too low by a factor of 10 to 50. Observers should consult the GBT support scientists before submitting a proposal for these feeds.

RFI at 450 MHz and its harmonics: There is the potential for a major construction project near Green Bank in 2018-2019. For the safety of the workers, a portable radio system at 450 MHz is being proposed for use. Usage would be kept to a minimum. There is the potential for interference at 450 MHz and its harmonics during this time period.

Continuing Opportunities:

Joint Observations with Chandra X-ray Observatory

In previous semesters, the community has had the opportunity to propose for observing time on NRAO facilities through a joint program with the Chandra X-ray Observatory. The Green Bank Observatory will continue with this program and will allocate up to 3% of the open skies time to highly ranked proposals that request time on both HST and the GBT. Proposers to the GBO will have the opportunity to request time on Chandra, to be awarded on the recommendation of the GBO Telescope Allocation Committee (TAC) and approved by the GBO Director. Up to 120 ksec will be made available to GBO/LBO/NRAO proposers annually. See the Joint Observations with Chandra page for details.

Joint Observations with the Hubble Space Telescope (HST)

By agreement between the NRAO (and continued honoring by GBO) and the Space Telescope Science Institute, STScI will be able to award up to 3% of the available open skies time to highly ranked proposals that request time on both HST and the GBT. In return, STScI has offered 30 orbits of HST time for allocation by the GBO/LBO/NRAO TAC to proposals submitted for the GBO deadlines for Semester 2017B and Semester 2018A. See the Joint Observations with HST page for details.

Joint Observations with Swift Gamma-Ray Burst Mission

To foster correlative observations, a joint Swift/NRAO observing program was established, detailed in a Memorandum of Understanding. The GBO will continue to honor this agreement. By this agreement, the Swift Program permits GBO/LBO/NRAO to award up to 300 kiloseconds of Swift observing time per year. Similarly, GBO/LBO/NRAO permits the Swift Guest Investigator (GI) Program to award GBO observing time. See the Joint Observations with Swift page for details.

Joint Observations with Fermi Gamma-ray Space Telescope

We remind the community that it is possible to propose for observing time on the GBT through the Fermi Gamma-ray Space Telescope Joint Proposal Opportunity or the Cooperative Proposal Opportunity. See the Joint Observations with Fermi page for details.

Joint Proposals Between the GBT, LBO, and NRAO

Observing programs that require combinations of the GBT, VLBA, and/or the VLA should submit a proposal for each of the requested telescopes, with a clear justification for each, as has been the case to date. The proposals will be reviewed as before and considered jointly by the Time Allocation Committee. VLBI proposals which request the GBT or VLA (or the HSA, for example) as elements of the VLBI array do not need separate proposals – those telescopes can be selected as separate VLBI stations from a VLBA/HSA proposal.

Other Proposal Opportunities

The GBO would like to make users aware that there are additional proposal opportunities as follows:

High Risk Proposals: As a means of maximizing its scientific impact through cutting-edge observations, the Observatory encourages the submission of high-risk/high-reward proposals.

Filler Programs: Some programs are not time critical or require highly subscribed LST ranges. Such programs may be able to take advantage of “filler” time. There are opportunities for so-called “filler” programs on the GBT.

Further information about each of these programs can be found here.

18A Proposal Call Results

A total of 52 proposals requesting NSF funded “open skies” time were submitted to the Green Bank Observatory’s Robert C. Byrd Green Bank Telescope (GBT) for 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 Green Bank Observatory Telescope Allocation Committee (TAC).

A description of the 18A proposals accepted can be found in our NSF Open Skies Science Program section below.

Total Proposals52
Statistics by Proposal Count
Requested Time4843 h
Available Time1748 h
Approved981 h
Filler1099 h
Rejected2763 h
Statistics by Proposal Hours

GBT Pressure Plots

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 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 18A semester.

GBT Observation Preparation

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.

18A Science Program

A total of 52 proposals requesting NSF funded “open skies” time were submitted to the Green Bank Observatory’s Robert C. Byrd Green Bank Telescope (GBT) were received for the February 1, 2017 deadline for semester 17B.  The table below summarizes the approved observing programs for the GBT.  Listed are the PI name, proposal ID, proposal title, maximum hours approved and proposal type (Regular, Triggered, Large or External).  Proposals from previous semesters that were awarded time in the 17B semester are included.  The table also includes HSA and GMVA proposals that were awarded time on the GBT as a VLBI station as well as proposal accepted via external agreements with CHANDRA, Hubble Space Telescope, FERMI and Swift.

For each approved program, the Proposal Finder Tool will have access to its author, title, abstract and total approved hours.

A description of the Time Allocation Committee report for 18A can be found in the Proposal Call Results section above.

Alberdi, AntonioVLBA18A-075Probing the polarized innermost structure of the relativistic jet of 4C+01.289Regular
Anderson, LorenGBT17B-173The GBT Diffuse Ionized Gas Survey (GDIGS)368Large
Andersson, B-GGBT17B-051Small Scale Selective Photo-Dissociation of CO isotopes in IC63 and IC5920.5Regular
Beasley, AnthonyGBT17B-131GBT Observations of 36 GHz Methanol Masers Towards the Galactic Center24Regular
Blumer, HarshaGBT17B-292Follow-up observations of pulsars discovered by the Pulsar Search Collaboratory34Regular
Bordoloi, RongmonGBT17B-015GBT high-sensitivity mapping of an HI cloud in the Fermi Bubble wind78Regular
Brodwin, MarkGBT18A-272MUSTANG-2 Observations of MaDCoWS, the Most Massive Galaxy Clusters at z > 195Regular
Cameron, AndrewGBT18A-261Continued timing observations of a new eccentric, relativistic binary pulsar117Regular
Courtois, HeleneGBT18A-021Cosmic flows in the Local Universe518Large
Cromartie, ThankfulGBT17B-306Measuring the Mass of Two Outstanding MSPs via Shapiro Delay24Regular
DeCesar, MeganGBT18A-193A Continued Search for Pulsed Emission from MSP Candidates in Globular Clusters25Regular
Demorest, PauGBT15B-160The North American Nanohertz Observatory for Gravitational Waves183Large
Deneva, JuliaGBT18A-306Searching for MSPs and Young Pulsars in Steep-spectrum Galactic Center Sources28.5Regular
Di Francesco, JamesGBT16B-278KEYSTONE: KFPA Examinations of Young Stellar (O-star) Natal Environments82Large
Ford, AlysonGBT17B-369A Survey of Extended HI Disks Around Nearby Galaxies39.75Regular
Fox, AndrewGBT18A-221Properties of the Galactic Nuclear Wind at Low Latitudes19Regular
Galaz, GasparGBT18A-291Detecting molecular gas in the giant low surface brightness galaxy Malin 130Regular
Ghirlanda, GiancarloG17C001Do binary neutron star mergers always produce a jet?17Regular
Ginsburg, AdamGBT18A-014MUSTANG Galactic Plane survey pilot: Protoclusters & Massive Stars31Regular
Gomez, Jose L.G17A004Probing the Innermost Regions of AGN Jets and their Magnetic Fields50Regular
Gomez, Jose L.GMVA17B-203Understanding jet formation and testing the binary SMBH model in OJ28714Regular
Jackson, JamesGBT16A-353The Radio Ammonia Mid-Plane Survey69Large
Johnson, MichaelGMVA17B-260Imaging the Global Accretion and Outflow of Sgr A*: 3mm VLBI with GMVA+ALMA12Regular
Karunakaran, AnanthanGBT18A-301Searching for HI in Low Surface Brightness satellites in the Local Volume15Regular
Kepley, AmandaGBT17B-151Extragalactic GBT+ARGUS Gas Density Survey491.25Large
Kovalev, YuriGBT17B-210Evolution of High Brightness Temperature AGN Cores with RadioAstron81Regular
Lin, Yen-TingGBT17B-101A MUSTANG-2 Survey of Massive Clusters from Subaru Hyper Suprime-Cam Survey36Regular
Linden, SeanGBT18A-366Building integrated SEDs with the GBT for LIRGs in GOALS9Regular
Lobanov, AndreiGMVA17B-324Magnetic field in the vicinity of central black holes in 3C273 and 3C27912Regular
Lockman, FelixGBT18A-246Project AMIGA: The Circumgalactic Medium of M31 — The Neutral Component II176Regular
Lorimer, DuncanGBT17B-221A FLAG Survey for Millisecond Pulsars and Fast Radio Bursts10Regular
Lu, RusenGMVA17B-304Lifting the Curtain in M87: From Accretion to Jet Formation14Regular
Maccarone, ThomasVLBA17B-152A trigonometric parallax for a globular cluster7.5Regular
Mason, BrianGBT18A-336Detailed Sunyaev-Zel'dovich Effect Imaging of z > 1 Galaxy Clusters47.25Regular
McGuire, BrettGBT18A-333An Extremely Deep GBT Survey of TMC-1422.5Large
McGuire, BrettGBT17B-004PRIMOS-2: Line Surveys of Molecule-Rich Sources57.25Regular
McKean, JohnVLBA18A-270Quantifying dark matter substructure in gravitational lens galaxies18Regular
Minter, AnthonyGBT18A-314Does The Smith Cloud Have A Debris Stream?90Regular
Monson, NathanielGBT18A-400Uniform Silicon Isotope Ratios Across the Milky Way Galaxy15Regular
Mroczkowski, TonyGBT18A-175A GBT+MUSTANG-2 Measurement the SZ Power Spectrum (continued)58.5Regular
Oslowski, StefanGBT18A-268Follow-up of FRBs discovered by ASKAP162Regular
Ransom, ScottGBT17B-255Continued Timing of a Millisecond Pulsar in a Stellar Triple System65Regular
Ransom, ScottGBT17B-256Long Term Timing of 58 Recycled Pulsars in Bulge Globular Clusters75Regular
Requena-Torres, Miguel AngelGBT18A-363Increasing molecular complexity in the Galactic Center Molecular Clouds12Regular
Romero, CharlesGBT18A-353MUSTANG-2 Explores the Final Frontier Fields!30Regular
Salas, PedroGBT17B-157Mapping the cold neutral medium in the G35–1 region14.5Regular
Simard, DanaVLBA17B-064Scintillation of FRB121102 and the associated persistent radio source46Regular
Spekkens, KristineGBT18A-239The HI Content of Field Ultra Diffuse Galaxy Candidates135Regular
Stinebring, DanielGBT18A-349Pulsar Scintillation Arcs – An L-band Follow-up to Previous GBT Detections16.25Regular
Storm, ShayeGBT17B-196Characterizing the Internal Velocity Fields of Cores with GBT-ARGUS21Regular
Stovall, KevinGBT17B-325Continuing the GBT All-Sky 350-MHz Pulsar Survey1400Large
Swiggum, JosephGBT18A-43615 New Nulling Pulsars from the GBNCC Survey31.5Regular
Swiggum, JosephGBT17B-28518 GBNCC Discoveries: Probing the Recycled Pulsar Population43Regular
Swihart, SamuelGBT17B-172Sleuthing the Pulsar in a New Long-Period Gamma-ray Loud Binary7Regular
Vedantham, HarishGMVA17B-299Search for an intermediate-mass gravitational lens towards PKS1413+13516Regular
Watson, DarachGBT18A-230Detecting CO in a normal galaxy at z=7.13268Regular
White, JacobGBT18A-329Measuring the Emission from Sirius A's Stellar Atmosphere4Regular

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