Proposal Call
The Green Bank Observatory (GBO) invites scientists to
participate in the 2025A Semester
Call for Proposals for the Green Bank Telescope (GBT).
The submission deadline for Semester 2025a proposals is
Wednesday, 31 July 2024, at 17:00 EDT (21:00 UTC).
The deadline is for the 25A semester observing period on the GBT:
1 February 2025 – 31 July 2025
The GBO would like to highlight the following:
- Low frequency (< 8 GHz) projects are encouraged
- Up to 200 hours per source or field is reasonable.
- Joint proposals with JWST, HST, Swift, Chandra, XMM-Newton, NICER, and Fermi.
- Expected hours available: ~1700-2500 hours.
- Shutdown May-September during next seven summers, 2025 through 2031, with no/little observing for infrastructure work
- Other shutdowns for infrastructure work may occur as necessary
- No more than 100 hours available for ν ≥ 50 GHz
- Monitoring observations will not be guaranteed cadence through shutdowns.
- 800 MHz is not expected to be available for monitoring observations in the 25B semester.
- Expect very little or no time to be available in the 0-9h LST range for observations using 8-18 GHz and 27.5-50 GHz
- We will not accept any proposals requesting UWBR in the 25A semester.
- S, Ku, Ka-bands, and 342 MHz receivers will not be available in the 25A semester.
- Multi-semester proposals will be considered.
- No large proposals will be accepted in the 25A semester.
- Undersubscribed LSTs
- Below 8 GHz in the 10-14h LST range
- 8-18 GHz and 27.5-50 GHz in the 9-13h LST range
A detailed timeline for the 25A Proposal Call is available here and summarized in the table below:
| Date | Action |
| 26 June 2024 | GBO/NRAO Call for Proposals |
| 31 July 2024 | GBO/NRAO Proposal Deadline @ 21:00 UTC |
| 29 August 2024 | Individual Science Reviews Completed |
| 13 September 2024 | Science Review Panel (SRP) Meetings Completed |
| 14-15 October 2024 | Telescope time allocation committee (TAC) meeting |
| 05 November 2024 | Disposition Letters Sent |
The GBO 2025A Call for Proposals is for observations with the GBT; the corresponding call for the VLBA/HSA/GMVA and VLA can be found at the NRAO Call for Proposals.
What’s New in 25A
NRAO and GBO Users’ Policies. The policies have been updated ahead of the 25A Call for Proposals.
The NRAO and GBO Users’ Policies have undergone several updates:
- REMINDER: The Dissertation Plan requirements (Section 7.2) were revised to specify that the plan must be written by the student. The Latex and Word templates are available online.
- The text in the Semester Observing Opportunities (Section 3.2.1) to clarify when proposals may be submitted in response to a Call for Proposals, the requirements for proposals are Triggered, and the requirements for those wishing to submit proposals requesting future capabilities.
- Clarifications regarding the criteria for Triggered Proposals were made in Sections 3.2.1 and 3.3.2.
See the NRAO and GBO Users’ Policies page.
PST Proposal Template
The NRAO now offers an optional Latex template for proposals. Proposers are strongly encouraged to use this template for all proposal types – Regular, Large and DDTs and to follow the appropriate guidelines for font size, page margins and references.
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 2025A 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 25A
The GBT is expected to be shut down from May-September over the next seven summer, 2025 through 2031. 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 1700-2500 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. The 800 MHz receiver is not expected to be available for monitoring observations in the 25B semester.
We expect very little or no time to be available in the 0-9h LST range for observations using receivers in the 8-18 GHz and 27.5-50 GHz range.
Receiver Availability
Ultra-wideband
We will not accept any new proposals requesting the UWBR for the 25A call.
S, Ku, Ka-bands, and the 342 MHz receivers not available
The S, Ku, Ka-band and 342 MHz receivers will not be available in the 25A semester. The Q and W-band receivers are expected to be available for the 25B semester.
Receivers available only during campaigns
The Prime Focus 800 MHz feed will only be available for campaigns during the 25A semester. The 800 MHz feed will be available monthly in the 25A semester. The 800 MHz feed is not expected to be available regularly in the 25B semester.
Receiver available during entire semester
It is expected that the L, C, X, KFPA, Q, W, Argus and Mustang2 receivers will be available during the entire 25A semester.
Continuing Opportunities
Joint Observing program
Access to the Joint Observing program will continue for the GBT, VLA, and VLBA for semester 25A. 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 Guidance
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.
All proposals should state why the GBT is necessary for the requested observations in both the abstract and science justification.
Proposers who need assistance with their proposal should submit a helpdesk ticket via https://help.nrao.edu/. Proposers needing significant help should submit their requests to the helpdesk well before the deadline.
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 (NHI ≈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.
High Frequency Observations
We anticipate that ≤ 100 hours of high frequency time will be available for new proposals in the 25A semester.
Starting with the 23B proposal, all A ranked excellent weather projects will be considered for scheduling for 3 semesters.
The GBT receivers, backends, and observing modes that are available for Semester 2025A proposals are listed in Tables 1 and 2 below.
Instrumentation
The GBT receivers, backends, and observing modes that are available for Semester 2025A proposals are listed in Tables 1 and 2 below.
| Receiver | Frequency Range | Expected Availability |
| Prime Focus 1 | 290-395 MHz | Not available |
| Prime Focus 1 | 680-920 MHz | Monthly 2-week campaigns. |
| Prime Focus 1 | 385-520 MHz and 510-690 MHz | Not available |
| Prime Focus 2 | 910-1230 MHz | Not available |
| Ultrawideband Receiver | 700-4200 MHz | No new proposals. |
| 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 | Not available. |
| K-band Focal Plane Array (7 pixels) | 18.0-27.5 GHz | Entire semester |
| Ka-band | 26.0-39.5 GHz | Not available |
| Q-band | 39.2-50.5 GHz | Entire semester |
| W-band | 67-93.3 GHz | Entire semester |
| 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). |
| 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). Not available. |
| 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 |
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 prior 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 2025A 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.
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 workshops will be held October 8-10, 2024 (virtual only) and March 18-20, 2025 (in person only). More information can be found here
Single Dish Training School
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 date for the next school has not yet been determined.
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 25A.
Joint Observations with JWST
By agreement between the NRAO and the Space Telescope Science Institute (STScl), detailed in a Memorandum of Understanding, the NRAO can award up to 50 hours of JWST observing time per year. In return, STScI can award up to 5% of the NRAO scientific observing time on the VLA, VLBA, and GBT. Proposals for joint NRAO and JWST observations must be submitted to the observatory where more observing time is being requested. N.B., specific technical information must be supplied for the Partner Observatory. See the Joint Observations with JWST page for details.
Joint Observations with the Hubble Space Telescope (HST)
By agreement between the NRAO and the Space Telescope Science Institute, STScI can award up to 3% of the available time on NRAO’s North American facilities to highly ranked proposals that request time on both HST and NRAO telescopes. In return, STScI has offered 30 orbits of HST time for allocation by the NRAO TAC per year. 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. 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 has been established, detailed in a Memorandum of Understanding. By this agreement, the Swift Program permits NRAO to award up to 300 kiloseconds of Swift observing time per year. Similarly, NRAO permits the Swift Guest Investigator (GI) Program to award no more than 5% of the NRAO scientific observing time on the VLA, GBT and VLBA, or up to 200-300 hours per year on each telescope. See the Joint Observations with Swift page for details.
Joint Observations with Chandra X-ray Observatory
The community has the opportunity to propose for observing time on NRAO facilities through a joint program with the Chandra X-ray Observatory. Proposers to the NRAO have the opportunity to request time on Chandra, to be awarded on the recommendation of the NRAO Telescope Time Allocation Committee (TAC) and approved by the NRAO Director. Up to 120 ksec will be made available to NRAO proposers annually. The NRAO has allocated up to 3% of the open skies observing time on the VLA, the VLBA, and the GBT for Chandra joint proposals.
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 XMM-Newton
By agreement with the NRAO and GBO Observatories, detailed in a Memorandum of Understanding, the XMM-Newton Project may award up to 3% of NRAO/GBO open skies observing time. Similarly the NRAO/GBO 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 NICER
By agreement between the NRAO and NASA, detailed in a Memorandum of Understanding, the NRAO can award up to 250 ksec of NICER observing time per year. In return, NICER can award up to 5% of the NRAO scientific observing time on the VLA, VLBA, and GBT or up to 200-300 hours per year on each telescope. See the Joint Observations with NICER page for details.
Joint Observations with Fermi Gamma-ray Space Telescope
It is possible to propose for observing time on NRAO facilities through the Fermi Gamma-ray Space Telescope Joint Proposal Opportunity or the Cooperative Proposal Opportunity. A maximum of 5% of the NRAO open skies observing time is made available on the VLA, the VLBA and the GBT, or up to 200-325 hours per year on each telescope. 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.
25a Proposal Call Results
A total of 99 proposals requesting NSF funded “open skies” time were submitted to the Green Bank Observatory’s Robert C. Byrd Green Bank Telescope (GBT) for semester 25A. 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 25A semester that have been reviewed by the Green Bank Observatory Telescope Allocation Committee (TAC).
Statistics by Proposal Count
| Total Proposals | 52 |
| Approved | 27 |
| Filler | 6 |
| Rejected | 19 |
| Hold | 0 |
| Withdrawn | 0 |
| Oversubscription | 1.9 |
Table 1
Statistics by Proposal Hours
| Requested Time | 2340.01 hours |
| Available Time | 1544.25 hours |
| Approved | 1276.25 hours1 |
| Filler | 272.5 hours |
| Rejected | 791.26 hours |
| Pressure | 1.52 |
Table 2
1Includes hours accepted for future semesters.
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 between 8-21 GHz and 23-50 GHz), and excellent (observation in the 21-23 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 black 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 25A 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.
25a 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) for the July 31, 2024 semester 25A deadline . The table below summarizes the approved observing programs. 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 25A 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, HST, JWST, FERMI, NICER, SWIFT, and XMM-Newton.
For each approved program, the Proposal Finder Tool will have access to its author, title, abstract and total approved hours.
| PI | ID | Title | Hours | Type |
|---|---|---|---|---|
| Alexander, Kate | GBT23A-273 | Monitoring the Exceptional Jetted Tidal Disruption Event AT2022cmc | 17.5 | Regular |
| Balser, Dana | GBT24B-101 | Ionization State of the Warm Ionized Medium in the Inner Galaxy | 27 | Regular |
| Barcos-Munoz, Loreto | GMVA24B-356 | Arp 220: AGN or not AGN?, that is the question… | 16 | Regular |
| Bhakta, Deven | GBT24B-430 | The Search for New Cluster Pulsars | 25 | Regular |
| Blackmon, Victoria | GBT24B-374 | Continued observations of an eccentric, relativistic binary pulsar | 36.75 | Regular |
| Bolatto, Alberto | GBT21B-024 | GBT EDGE: A Representative Survey of the z=0 Universe with Full IFU Spectroscopy | 300 | Large |
| Busch, Michael | GBT24B-320 | A Follow-up GBT Survey for OH in the Milky Way’s Nuclear Wind | 121 | Regular |
| Busch, Michael | GBT25A-129 | A Survey for OH in the Northern Molecular Ring of M31 | 176 | Regular |
| Butterfield, Natalie | GBT23B-202 | BARFLYS: Investigating the Star Forming Potential of the Galactic Bar Dust Lanes | 227.5 | Large |
| Cannon, John | GBT24B-157 | Newly Discovered Local Volume Dwarf Galaxies | 43 | Regular |
| Chen, Che-Yu | GBT20A-322 | Characterizing the Internal Velocity Fields of Star-forming Cores with GBT-Argus | 228.5 | Large |
| Cromartie, Thankful | GBT24B-427 | The North American Nanohertz Observatory for Gravitational Waves | 1723.5 | Large |
| Dai, Shi | GBT25A-073 | Verifying the binary hypothesis of a repeating fast radio burst | 24 | Regular |
| Das, Jyotirmoy | GBT25A-349 | Deep Search and Follow-Up of Newly Discovered MSPs in Four Globular Clusters | 24 | Regular |
| Das, Nabanita | GBT25A-334 | Tully-Fisher Distance to MCG-06-30-15 | 99 | Regular |
| Di Gennaro, Gabriella | GBT24B-194 | SZ observations of MaDCoWS clusters with diffuse radio emission at z=0.8-1.34 | 45 | Regular |
| Di Teodoro, Enrico | GBT23A-131 | Measuring 12CO(1-0) emission in the Milky Way’s Nuclear Wind | 6.5 | Regular |
| Dicker, Simon | GBT24A-291 | Quantifying biases in selection functions of Sunyaev-Zel’dovich Effect surveys. | 16 | Regular |
| Fallon, Paul | GBT25A-001 | Full Stokes polarization of rare 4.660 GHz OH masers in W51 and IRAS 18460-0151 | 4.5 | Regular |
| Fiore, William | GBT24B-393 | Search for Radio Pulsations from the Candidate Black Widow ZTF J1406+1222 | 2.75 | Regular |
| Gallimore, Jack | VLBA25A-217 | Monitoring Anomalous Megamaser Proper Motions in NGC 1068 | 8 | Regular |
| Gorai, Prasanta | GBT22A-398 | Exploring Carbon Chain Chemistry of Massive Protostars | 22 | Regular |
| Gupta, Harshal | GBT21B-316 | Molecular Exploration of the Diffuse Interstellar mediUM (MEDIUM) | 285.75 | Large |
| Gusinskaia, Nina | GBT24B-435 | Continued Timing of a Millisecond Pulsar in a Stellar Triple System | 31 | Regular |
| Horton, April | GBT25A-413 | The Origin Story of a Young Halo Star Cluster: Mapping its Birthplace | 20 | Regular |
| Hunter, Laura | GBT25A-155 | Distances to Low-Surface Brightness Satellite Galaxies | 129.75 | Regular |
| Janssen, Michael | GMVA24B-054 | Precision astrometry of Sgr A* with 3mm VLBI observations of SiO stellar masers | 8 | Regular |
| Kam, Minchul | GMVA24B-376 | Pinpointing the jet launching mechanism in 3C 84 with GMVA+ALMA+GLT | 20 | Regular |
| Kanekar, Nissim | GBT24B-340 | The Atomic Gas Content of Green Pea Galaxies | 92.5 | Regular |
| Karunakaran, Ananthan | GBT24B-330 | Understanding the Baryon Cycle of Ultra-Diffuse Galaxies | 63 | Regular |
| Karunakaran, Ananthan | GBT25A-028 | HI Observations of Dwarf Galaxies at the edge of the Local Group and Beyond | 68 | Regular |
| Klingler, Noel | GBT25A-273 | GBT Observations of a Candidate Transitional Millisecond Pulsar | 2 | Triggered |
| Kumar, Pravir | GBT24B-066 | Probing the dynamic environment of FRB20180301A | 30 | Regular |
| Kuo, Cheng-Yu | GBT25A-023 | The GBT survey for 22 GHz H2O Gigamasers from High-z Compton-thick Quasars | 68 | Regular |
| Lah, Philip | GBT25A-102 | Further HI Observations of Giant Low Surface Brightness Galaxies | 18 | Regular |
| Li, Jiaxuan | GBT25A-148 | A Census of Neutral Gas Content in Nearby Isolated Quiescent Dwarf Galaxies | 10.5 | Regular |
| Li, Megan | GBT25A-305 | A search for technosignatures around sun-like stars | 2 | Regular |
| Liu, Mengting | GBT25A-123 | Exploring Magnetic Field in Molecular Clouds with Pulsars | 34 | Regular |
| Liu, Yuxiang | GBT25A-339 | Dense gas in the Cold GMCs Discovered in M31 Inter-arm Regions | 7.5 | Regular |
| Lorimer, Duncan | GBT24B-298 | GREENBURST Single Pulse Census of Nearby Galaxies | 32.5 | Regular |
| Lu, Rusen | GMVA24B-165 | Probing the dynamic jet-disk connection in M87 | 19 | Regular |
| Luo, Gan | GBT25A-106 | Mapping HI Narrow Self-absorption toward dense cores | 2 | Regular |
| Margot, Jean-Luc | GBT25A-083 | Moment of Inertia and Size of the Core of Venus | 3.75 | Regular |
| McGuire, Brett | GBT23A-047 | Closing the Loop: PAHs Toward Cyg OB2-12 | 6 | Regular |
| McKee, James | GBT24A-255 | Broadband observations of giant pulses from PSR J0218+4232 | 8 | Regular |
| McLaughlin, Maura | GBT25A-369 | No Pulsar Left Behind: Confirmation of Student-Discovered Pulsar Candidates | 20 | Regular |
| Michail, Joseph | VLBA25A-312 | Continued Radio Monitoring of Sgr A* with the 2025 EHT Multiwavelength Campaign | 14 | Regular |
| Morgan, Lawrence | GBT25A-335 | Methanol Maser COMBS: Completing the Original Multi-Beam Survey | 330 | Regular |
| Ocker, Stella | GBT24B-290 | An Ultra-Wideband Study of Repeating Fast Radio Bursts | 27.5 | Triggered |
| Parent, Emilie | GBT25A-195 | Pinpointing the onset of radio pulsations in a new transitional pulsar candidate | 6 | Triggered |
| Park, Jongho | GMVA25A-145 | Peering into M87’s black hole in multiple colors with GMVA+APEX+LBA | 16.5 | Regular |
| Patil, Swarali Shivraj | GBT25A-378 | Measuring Scintillation-Arc Variations in NANOGrav Binary Pulsars | 72 | Regular |
| Pearlman, Aaron | GBT24B-310 | Exploring the Origins of Nearby Repeating FRBs via Multiwavelength Observations | 20 | Triggered |
| Pineda, Jaime | GBT23A-199 | Ions vs Neutrals in a Dense Core – copy | 18 | Regular |
| Polisensky, Emil | GBT24B-365 | Searching for Pulsations from VLITE Neutron Star Candidates | 24 | Regular |
| Ransom, Scott | GBT24B-410 | Long Term Timing of 76 Recycled Pulsars in Bulge Globular Clusters | 210 | Large |
| Remijan, Anthony | GBT25A-215 | Characterizing select molecules and a dedicated search for C2H- in TMC-1 | 10 | Regular |
| Remijan, Anthony | GBT25A-218 | A Deep Targeted Line Survey of TMC-1 at X-band – Continuing Our Pilot Study | 166.5 | Regular |
| Roberts, Hayley | GBT25A-376 | A GBT Survey of OHMs in Northern GOALS LIRGs | 82.25 | Regular |
| Romero, Charles | GBT23A-086 | SZ Constraints of Shocks in CIZA J2242.8+5301 | 40 | Regular |
| Sarazin, Craig | GBT23A-028 | Bridges of Intergalactic Gas Connecting ACT Cluster Pairs | 35 | Regular |
| Schmiedeke, Anika | GBT23A-360 | Exploring the kinematics in a filamentary infrared dark cloud | 40 | Regular |
| Scibelli, Samantha | GBT24B-077 | A Quest for More GLUCOSE: the GBT L1544 Unbiased Complex Organics SurvEy | 556 | Large |
| Sherman, Myles | GBT25A-328 | Searching for Radio Emission from the Four `Low B-Field' Magnetars | 14.25 | Regular |
| Shirley, Yancy | GBT23A-161 | PROBING DUST OPACITY VARIATIONS: MUSTANG-2 IMAGING OF THE PRESTELLAR CORE L183 | 12 | Regular |
| Singal, Jack | GBT19A-083 | How Bright is the Radio Sky? A 310 MHz Absolute Map | 30 | Regular |
| Spekkens, Kristine | GBT22B-139 | Atomic Gas in the Host Galaxies of Gravitational Wave Events – LVK O4 | 40 | Triggered |
| Squillace, Reynier | GBT23A-263 | A Survey of 15-Nitrogen Fractionation in Prestellar Cores | 36 | Regular |
| Stark, David | GBT24B-263 | HI-MaNGA: HI Followup for MaNGA Galaxies | 379.5 | Large |
| Stephens, Ian | GBT25A-124 | Mapping Ammonia in Bones: Understanding our Magnetized Spiral Potential | 90 | Regular |
| Tang, Ningyu | GBT25A-259 | HI and OH survey toward Taurus B7 region | 22.25 | Regular |
| Tremblay, Chenoa | GBT24B-234 | Magnetic Properties in Star Formation through observations of CH and OH | 10 | Regular |
| Urquhart, James | GBT23A-350 | Search of Hypercompact HII Regions Towards Methanol Masers | 56.25 | Regular |
| Uttarkar, Pavan | GBT25A-240 | Solving an enigmatic long-period pulsar through timing and spectropolarimetry | 12 | Regular |
| Uttarkar, Pavan | GBT25A-240 | Solving an enigmatic long-period pulsar through timing and spectropolarimetry | 12 | Regular |
| van Marrewijk, Joshiwa | GBT24A-249 | Resolving SZ-selected clusters in the epoch of most rapid cluster growth | 42 | Regular |
| Yang, Zonglin | GBT24B-003 | Looking for the companion of PSR J1922+1512g | 2.5 | Regular |