Proposal Process and Opportunities

Joint GBO and NRAO Telescope Time Allocation Process

Proposals to the Green Bank Observatory (GBO) and the National Radio Astronomy Observatory (NRAO) for the scientific use of its telescopes are evaluated on the basis of scientific merit and technical feasibility using a panel-based proposal review system.  This joint process is run by the NRAO in accordance with its policy of non-discrimination and inclusion.

The GBO 2024B Call for Proposals is for observations with the GBT; the corresponding call for the VLBA/HSA/GMVA and the VLA can be found at the NRAO Call for Proposals.

Low Frequency Science Opportunities

Low frequency (below 8 GHz) projects, especially those that may require significant amounts of observing time per source or field, are strongly encouraged.  Observations up to 200 hours per source or field at low frequencies is not unreasonable for the less subscribed LST ranges.  Please see the LST pressure plots in the Proposal Results for previous semesters located here.

Expected GBT time available in 24B

The GBT is expected to be shut down from May-September 2024 and May-September 2025.  During this shutdown repairs to the GBT infrastructure will be performed.  This includes azimuth wheel replacement, painting, and track, foundation and grout work.

Other shutdowns for infrastructure work may occur as necessary and with little warning.

It is expected that there will be about 2300-3100 hours of A and B ranked observing time that can be assigned to new projects.  It is also expected that no more than 100 hours of excellent weather high frequency time can be assigned to new projects.

We cannot guarantee that monitoring projects can be scheduled due to the planned infrastructure work.

Receiver Availability

Ultra-wideband shared risk

The new Ultra-wideband Receiver (UWBR) will undergo engineering changes and commissioning in early 2024.  Unfortunately, the UWBR will not be available for regular monitoring observations in the 24B semester.  We still anticipate that the UWBR could become available for some observations in the near future.  This would be for one (maybe two) short, weeklong campaigns occurring on irregular basis.

The UWB receiver is optimized for high-precision pulsar timing and wide-band observations of fast transients.  VEGAS will support coherent and incoherent dedispersion, and pulsar searching and timing modes over the full bandwidth of the receiver.  

For more information on the UWBR please visit here.

S, Q and W-bands not available

The S, Q, and W-band receivers will not be available in the 24B semester.  The Q and W-band receivers are expected to be available for the 25A semester.

Receivers available only during campaigns

The Prime Focus 342 and 800 MHz feeds, and the UWB receivers will only be available for campaigns during the 24B semester.  The 800 MHz feed will be available on a monthly basis.

Receiver available during entire semester

It is expected that the L, C, X, Ku, KFPA, Ka, Argus and Mustang2 receivers will be available during the entire 24B semester.

Continuing Opportunities

Joint Observing program

Access to the Joint Observing program will continue for the GBT, VLA, and VLBA for semester 24B.  This includes joint observations with JWST, NICER, the XMM-Newton Project, the Chandra X-ray Observatory, the Hubble Space Telescope (HST), the Swift Gamma-Ray Burst Mission, and the Fermi Gamma-ray Space Telescope.  For more details see the Joint Proposal page.

Director’s Discretionary Time Including Education and Public Outreach

Proposals for Director’s Discretionary Time (DDT) may be submitted at any time. They must be submitted through the PST. DDT proposals are intended to address targets of opportunity, high-risk/high-return exploratory time, or other science opportunities deemed sufficiently urgent to justify prompt action. 

DDT proposals may also be submitted for the purpose of education and public outreach—for example, to image an iconic source or to support an educational opportunity for students. Such proposals should clearly justify the requirements for the requested time allocation and observing mode on any given instrument, and should describe the anticipated impact of the observation.  

While there is not an a priori limit to time that can be requested via DDT, it is expected that no more than 5% of the available science time on each telescope will be allocated for this purpose.

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.  That the proposal is high risk/high reward should be designated both in the abstract and the science justification.
• Triggered Proposals: Observations for unknown sources that would be triggered by a celestial event (e.g., near Earth asteroid discovery, comet discovery, fast radio burst, etc.) can be submitted as a triggered proposal.  Any accepted triggered proposal will have proprietary rights to observations over any Director’s Discretionary Time (DDT) proposal.
• Filler Programs: Some programs are not time critical or do not 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.   The proposal should make clear in the abstract and early in the science justification that “filler” time is being requested.  Filler time requests will be ineligible for scheduling priority A or B.

GBT Proposal Guide

GBT Proposal Preparation

All proposals should state why the GBT is necessary for the requested observations in both the abstract and science justification.

Virtual Proposal Planning Office Hours will be held January 24, and 25.

Proposers are encouraged to look at past proposal call results, especially the LST pressure plots, which can be found in the TAC proposal result reports.  This information can be found here.

All proposers, including pulsar proposers, should use the GBT Sensitivity Calculator. 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 lessen the chances for error. 

If you are planning on making maps with the GBT, you should use the GBT Mapping Calculator tool.

TheGBT 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.

GBT Capabilities

The GBO encourages proposals that take advantage of the GBT’s unique capabilities across 0.29 to 116.2 GHz frequency range.  (Coverage is not available for 15.8-18.0 GHz, and 50.5-67.0 GHz).

Key science areas include, but are not limited to:

• low column density HI (N_HI ≈10¹⁷ cm^-2 galactic and extragalactic)
• star formation
• fast radio bursts
• galaxy and cluster evolution
• pulsars (searches and timing)
• cosmology
• radio recombination lines
• astrochemistry
• solar system science

Details of all GBT observing modes are inThe 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.

Large Proposals

The GBT only accepts large proposals once per year for the B semester proposal deadlines.  Large GBT proposals are not accepted at the A semester proposal deadlines.  This policy ensures equality for the reviews of all large proposals that can be scheduled across a full year.

Recall that all large proposals are restricted to using no more than 50% of the open skies time available under any weather category (poor, good, excellent) at any LST during any semester.

Regular and Large proposal size definitions for the GBO are as follows:

• 0-8 GHz (Any weather)
  • Regular:  < 400 hours and lasting ≤ 1 year
  • Large: ≥ 400 hours or lasting >1 year
• 8-18 and 27.5-50 GHz (Good weather)
  • Regular:  < 200 hours and lasting ≤ 1 year
  • Large: ≥ 200 hours or lasting >1 year
• 18-27.5 and > 50 GHz (Excellent weather)
  • Regular:  < 100 hours and lasting ≤ 1.5 year
  • Large:  ≥ 100 hours or lasting >1.5 year
• Fixed and Monitoring proposals
  • Regular:  < 200 hours and lasting ≤ 1 year
  • Large:  ≥ 200 hours or lasting >1 year

Proposers submitting Large Proposals should read the Large Proposal Policy to ensure that they address all of the mandatory requirements.

Currently Large proposals comprise 50% of the available time for excellent weather projects.  We do not anticipate accepting any Large proposals for excellent weather projects at the 24B proposal deadline.

High Frequency Observations

There are approximately 1000 hours of excellent weather (18-27.5 and > 50 GHz) available each semester for both open skies and sponsored time.    Prior commitments typically account for slightly more than half of this time which leaves only 420 hours available to be scheduled each semester.  Due to mechanical issues encountered in the 22B and 23A semester, we expect the amount of high frequency carry over time to be larger than normal for the 24B semester.  We anticipate that ≤ 100 hours of high frequency time will be available for new proposals in the 24B semester.

Starting with the 23B proposal, all A ranked excellent weather projects will be considered for scheduling for 3 semesters.

Instrumentation

The GBT receivers, backends, and observing modes that are available for Semester 2024B proposals are listed in Tables 1 and 2 below.

Receiver	Frequency Range	Expected Availability
Prime Focus 1	290-395 MHz	Short campaigns with irregular intervals between
Prime Focus 1	680-920 MHz	Monthly 2-3 week campaigns.
Prime Focus 1	385-520 MHz and 510-690 MHz	High rank proposal demand only
Prime Focus 2	910-1230 MHz	High rank proposal demand only
Ultrawideband Receiver	700-4200 MHz	Short campaigns. Irregular intervals.  Shared-risk in 24B.
L-band	1.15-1.73 GHz	Entire semester
S-band	1.73-2.60 GHz	Not available
C-band (linear polarization only – see below)	3.8-7.8 GHz	Entire semester
X-band	7.8-11.6 GHz	Entire semester
Ku-band	12.0-15.4 GHz	Entire semester
K-band Focal Plane Array (7 pixels)	18.0-27.5 GHz	Entire semester
Ka-band	26.0-39.5 GHz	Entire semester
Q-band	39.2-50.5 GHz	Not available
W-band	67-93.3 GHz	Not available
ARGUS	75-116 GHz	Entire semester.  See The ARGUS Observer’s Web Page for further information
MUSTANG2 (shared-risk – see below)	90 GHz, Shared Risk	Entire semester.  Private instrument – proposals must include instrumentation team (see below).

Table 1

Backend	Observing Modes
Versatile Green Bank Astronomical Spectrometer (VEGAS)	Continuum (see below), spectral line, pulsar
Digital Continuum Receiver (DCR)	Continuum
Caltech Continuum Backend (CCB)	Continuum (Ka receiver only)
Mark6 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

Table 2

Permission required for instruments not listed as being available
Anyone requesting a receiver or instrument not listed as being available in the proposal call must have permission from the site director, interim site director, or the GBT schedulers before the proposal is submitted.

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

VLBI including the HSA and GMVA
Proposers should clearly justify the need for the GBT 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. 

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

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.

MUSTANG2
The GBO will accept proposals for shared risk observations using the MUSTANG2 instrument at the proposal deadline.  More information on Mustang2 can be found here.  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.  All MUSTANG2 proposals must have permission from the instrument development team – contact Emily Moravec, Simon Dicker or Brian Mason. 

Breakthrough Listen backend
The Breakthrough Listen project is making its backend available for shared-risk observations during the 2024B semester.  The instrument consists of a cluster of 64 Titan X and 1080 GPU-based servers capturing 8-bit baseband voltages over up to 12 GHz of instantaneous bandwidth.  Data rates are typically tens of TB/hr but a pipeline is available to generate spectra with adjustable frequency (> 3 Hz) 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 proposal preparation 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.

Continuum Observations
Proposers wishing to perform continuum observation should consult with a GBO scientist.  Some information on continuum observations 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.

Mapping
If you are considering mapping with the GBT such that there are major turns or moves (end of rows in raster map, petals in daisy maps, changes 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.

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. 

Scheduling Increments
Please note that the GBT is scheduled in 15 minute (0.25 hour) increments and that all proposals should request time appropriately. Time requests will be rounded down to the nearest 0.25 hour increment. 

RFI

The most recent RFI monitoring scans for the GBT can be found here.  These scans provide information on the frequencies that may encounter RFI.  Note that a Green Bank computing account is required to be able to view this information.  If you do not have a computing account, please contact the helpdesk to request the desired RFI plots.

Schools and Workshops

Observer Training Workshops
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 mapping, continuum, pulsar, etc.).

These workshops will be held several times a year and will complement traditional on-site training.  The next workshop will be held Feb 06-08, 2024.

More information can be found here.

Single Dish Training Workshop
The 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 next school is tentatively set to occur June 24-29, 2024.

Joint Proposals

Joint Proposals Between the GBT, VLBA and VLA

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.

Joint Proposals with External Facilities

Here we list opportunities for joint proposals with several external (non-AUI) facilities.  Agreements for Joint Observations with external facilities were made at different times across the boundaries when the NRAO was split into multiple observatories (NRAO, GBO, and LBO) in 2017, and when the LBO was reintegrated back into the NRAO in 2019.  Therefore, the agreements below will sometimes mention various combinations of the NRAO, GBO, and LBO.  Regardless, access to the Joint Observing program will continue for the VLA, VLBA, and GBT for semester 24B.

Joint Observations with JWST
By  agreement between the GBO and NASA, detailed in a Memorandum of Understanding, the GBO can award up to 50 hours of JWST observing time per year.  In return, JWST can award up to 5% of the GBT open skies observing time.  See the Joint Observations with JWST page for details.

Joint Observations with NICER
By agreement between the GBO and NASA, detailed in a Memorandum of Understanding, the GBO can award up to 250 ksec of NICER observing time per year.  In return, NICER can award up to 5% of the GBT open skies observing time. See the Joint Observations with NICER page for details.

Joint Observations with XMM-Newton
By agreement with the Green Bank Observatory, detailed in a Memorandum of Understanding, the XMM-Newton Project may award up to 3% of GBT open skies observing time. Similarly, the GBT Time Allocation Committee may award up to 150 ks of XMM-Newton time per year. See the Joint Observations with XMM-Newton page for details.

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 Chandra 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/NRAO proposers annually. 

Due to Chandra’s increasingly challenging thermal constraints, the amount of Chandra exposure time available for High Ecliptic Latitude (HEL) targets with |bGal| > 55deg is extremely limited.  If you request joint time on Chandra, please avoid long exposures on such targets if at all possible.  You must note explicitly the requested amount of Chandra HEL time in the body of your science justification.

N.B., Chandra ToO proposals are not supported under the Chandra-NRAO joint program.  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 per year of HST time for allocation by the GBO/NRAO TAC.   See the Joint Observations with HST page for details.

N.B., HST “Snapshot” observations are not supported under the HST-NRAO Joint program since there is no guarantee that Snapshot targets will be completed.

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/NRAO to award up to 300 kiloseconds of Swift observing time per year.   Similarly, GBO/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.

GBO and NRAO Users’ Policy

Th new users’ policy manual is available here

Tips for Proposers

Scientific Justification

The NRAO proposal evaluation and time allocation process is panel based. That is, members of the scientific community are responsible for reviewing proposals based on their scientific merit through the Science Review Panels. As a means of broadening the scientific perspective of its reviewers, and of increasing the participation of the wider astronomy and astrophysics community in the science program of NRAO facilities, SRP membership is deliberately selected to include some colleagues that are not necessarily experts in radio observational techniques. This being the case, we encourage proposers to consider the following when preparing their proposals:

• Avoid the use of radio astronomy jargon.
• Do not assume the reader is familiar with a particular observing technique – explain it briefly.
• Do not assume the reader is familiar with an earlier rationale for a developing line of research – provide adequate historical context and connect the dots as necessary.
• Describe previous observations and publications relevant to the proposed observations.
• If a particular point source or brightness temperature sensitivity is required, justify it.

Source Lists

The Observatory requires proposers to specify their source lists in full. This enables the Observatory to identify potential conflicts between observing programs and to better understand scheduling pressure on the instruments it operates. It may be the case that the final target list has not been selected at the time a proposal is submitted. In such cases, all potential targets and fields should be listed. The only exceptions to this requirement are for Triggered proposals to observe targets that are unknown a priori. Proposal source lists are not made public by the Observatory.

Dissertation Plans

The Plan of Dissertation is important in the proposal review process and should be well written; it is not a placeholder and should not be a replica of the proposal.  The plan must be compliant with specific requirements, which includes following a Plan of Dissertation Research template.  See Section 7.2 of the NRAO Users’ Policy guide for details.

Useful Resources & Tools

Note: you must be a registered NRAO user to access some of these resources. Please go to NRAO Interactive Services. If you are already a registered user, you are encouraged to update your profile.

Proposal Submission Tool
The Proposal Submission Tool and associated documentation is accessed through NRAO Interactive Services.

Proposal Finder Tool
The Proposal Finder Tool (PFT) may be used to search cover sheets of proposals approved for time on NRAO telescopes. The PFT returns the proposal’s authors, title, abstract, and, if available, approved hours.

Green Bank Telescope (GBT)

• GBT Performance
• GBT Proposer’s Guide
• GBT Observer’s Guide
• GBT Sensitivity Calculator
• GBT Mapping Planner

NRAO Helpdesk
For help on any aspect of proposing or observing not found in our documentation, please file a ticket with the NRAO helpdesk.

Proposal Results

Will be published when available