2018B Call for Proposals

The Green Bank Observatory invites scientists to participate in the 2018B Semester Call for Proposals for the Green Bank Telescope (GBT).  The entire proposal call can be found on this page. The submission deadline for Semester 2018B proposals is Thursday, 1 February 2018, at 17:00 EST (22:00 UTC).

The Green Bank Observatory encourages proposals that take advantage of the GBT’s unique capabilities. Key science areas include, but are not limited to: astrochemistry, cosmology, fast radio bursts, galaxy and cluster evolution, HI (galactic and extragalactic), pulsars (searches and timing), radio recombination lines, solar system science, and star formation.

All proposals should state why the GBT is necessary for the requested observations in both the abstract and science justification.Triggered proposals can be submitted for studies of transient objects such as fast radio bursts, near Earth asteroids, comets, and other transients.

We strongly encourage proposers to carefully read through the “News and Opportunities” section of the proposal as there have been a number of changes made to instrument availability. New instruments include ARGUS, Mustang2, wide bandwidth C-band receiver, VEGAS spectral line and pulsar modes

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).

We wish 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.

Proposal preparation and submission remain via the NRAO Proposal Submission Tool (PST) available at NRAO Interactive Services. Note that use of the PST 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

Proposal Deadline

The 1 February 2018 deadline (22:00 UTC) is for the 2018B Semester observing period on the GBT: 1 August 2018 – 31 January 2019.

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.

Instrumentation News

The GBT receivers, backends, and observing modes that are available in Semester 2018A are listed in Tables 1 and 2 below.

[table caption=”Table 1″ width=”80%” colwidth=”150|150″ colalign=”left|left”]
Receiver;Frequency Range
Prime Focus 1;290-395 MHz and 680-920 MHz
L-band;1.15-1.73 GHz
S-band;1.73-2.60 GHz
C-band (linear only – see below);3.8-8.0 GHz
X-band;8.0-11.6 GHz
Ku-band;12.0-15.4 GHz
K-band Focal Plane Array (7 pixels);18.0-26.5 GHz
Ka-band;26.0-39.5 GHz
Q-band;38.2-49.8 GHz
W-band;67-93.3 GHz
ARGUS (shared-risk – see below);80-115.3 GHz, Private PI Instrument, Shared Risk
Mustang2 (shared-risk – see below);90 GHz, Private PI Instrument, Shared Risk

[table caption=”Table 2″ width=”80%” colwidth=”20|100|50″ colalign=”left|left”]
Backend;Observing Modes
Versatile Green Bank Astronomical Spectrometer (VEGAS);Continuum (see below), spectral line, pulsar
Digital Continuum Receiver (DCR);Continuum
Mark V Very Long Baseline Array Disk Recorder;Very Long Baseline Interferometry
JPL Radar backend;Private PI Instrument – Open for Public Use
Breakthrough Listen;Private PI Instrument, Shared risk

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 using the GBT C-band receiver for VLBI Stokes I continuum observations (the observations will need to be done using full Stokes just to calibrate Stoke I). Please see the HSA section of the Long Baseline Observatory call (available here) for proposals for more details


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.

Pulsar: VEGAS pulsar modes will be released for observing. NOTE: If VEGAS Pulsar Modes are not release by the start of the 18A semester then all projects will be reverted back to using GUPPI where possible.

ARGUS: Observers interested in shared-risk observations using the ARGUS instrument should see http://www.gb.nrao.edu/argus/ 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 open skies time has been greatly reduced as part of the divestment of the GBT by the NSF. Proposers should only include the GBT in the proposal if it is essential for the science. This should be 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 MUSTANG2 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 MUSTANG2 observations should be included in the overhead for MUSTANG2 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.

Observing and Scheduling Constraints

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.

Session lengths:  Proposers should be aware that long scheduling blocks (more than 6 hours) may be very difficult to schedule as a result of the reduced open skies time following 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.

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.

Limited Time for “Fixed” and “Windowed” Observations:

Due to varied pressures on the GBT’s schedule resulting from the reduced open skies time as a result of the divestment of the GBT by the NSF, 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) is limited.  Proposals needing fixed and windowed observations will likely have to be ranked at least in or near the top 10% of all AUI telescope proposals in order to be accepted.

Limited Instrument Availability:

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

[table caption=”Table 3″ width=”80%” colwidth=”20|100|50″ colalign=”left|left”]
Prime Focus 1;450 and 600 feed: 385-690 MHz
Prime Focus 2;910-1230 MHz
Zpectrometer;26.0-29.5 GHZ, Private PI Instrument, Shared Risk
Ku-wide;12-18 GHz, not for spectral line use
RRI;Private Instrument, Shared risk
PFS Radar; Private PI Instrument

The availability of GBT Gregorian receivers will be based on demand from the accepted proposals.  Some receivers may be available only for a few short, two or three week periods during the semester.

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 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 VLBA, HSA, and GMVA Proposal Call.


RFI Monitoring Scans: The most recent RFI monitoring scans for the GBT can be found here. These scans provide information on the frequencies that may encounter RFI.

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 the RFI overpowers the system: the plot intensities are estimated to be too low by a factor of up to 10 to 50. Observers should consult the GBT support scientists before submitting a proposal for these feeds. Also, “TV Whitespace” usuage of these frequencies is expected to begin in 2018.

Potential for RFI: It is likely that there will be 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, but there will be the potential for interference at 450 MHz and its harmonics during this time period. There remains the potential for RFI at other frequencies from other equipment used in this project.

Schools and Workshops

Observer Training

The Green Bank Telescope (GBT) Remote Observer Training Workshop will provide the essential skills and knowledge needed to use the GBT and maximize its scientific output. It is intended for experienced astronomers who need to learn the specifics of observing with the GBT. After completing the workshop, an attendee will be certified to use the GBT as a remote observer. The workshop will focus on hands-on training in the observing techniques most relevant to participants (e.g. high frequency map, continuum, pulsar, etc.).
These workshops will be held three times a year and will complement traditional on-site training. The 2018 workshops will be held January 15-18, May 24-25 and September 17-18.

Single Dish Training Workshop

The Green Bank Telescope (GBT) Single Dish Training School will provide graduate students, post-docs, and experts in other fields of astronomy with both knowledge and practical experience of the techniques and applications of single-dish radio astronomy using the GBT as the primary example. The school will be based around an intensive series of lectures from experts, as well as hands-on radio-astronomy projects and tutorials. Topics to be covered include radio telescope fundamentals, key single-dish science areas, observing and calibration techniques, the impact of weather, the GBT observing procedures and software, and data reduction.
The school will be held once per year. An intensive GBT remote observer training workshop will be held immediately following the school for those who wish to obtain remote observing certification.

The 2018 workshop will be held May 19-23.

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 that are not time critical or require highly subscribed LST ranges can request designation as a “filler program.” Such programs may be able to take advantage of gaps in the GBT schedule, but there no guarantee that any GBT time will be allocated. Proposals requesting a designation as filler should do so in the proposal abstract and in the science justification. All filler programs will be given a ranking of C

Triggered Proposals: Observations for unknown sources that would be triggered by a celestial event (e.g. near Earth asteroid, comet, fast radio burst, etc.) can be submitted as a triggered proposal. Any accepted triggered proposal will have proprietary rights to observations over any DDT proposal.

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