Proposing

  • GBT Observer Alert

    Change in balance command

    We have released a change in the behavior of the Balance() command on the GBT.

    Read More …

Current Call for Proposals

  • Special Call for GBT 25B-26A Filler Time Proposals

    The Green Bank Observatory (GBO) invites the scientific community to submit Special Call proposals for filler-time observations on the Green Bank Telescope (GBT) during the 25B and 26A semesters. Approved projects will be conducted through July 31, 2026.

    Submission Deadline:
    Friday, November 28, 2025, at 22:00 UTC (17:00 Eastern Time)

    Read more

Additional Information

Proposer’s Guide (PDF)

Proposal Formatting Guidelines

Proposal Evaluation and Time Allocation Process

Useful Resources

Proposal Submission Tool

Proposal Finder Tool

NRAO science justification LaTeX template

Sensitivity Calculator

Mapping Planner

Information for Accepted Proposals

The linear-rank score from the SRP is on a scale from 0 (a high-ranked proposal) to 10 (a low-ranked proposal).

Scheduling priorities in the dynamic queue are assigned by the TAC. There are five levels:

  • A
  • B
  • C (filler)
  • D (filler) and
  • N (rejected).

A star indicates that the priority was set explicitly by the TAC and not due to ranking or LST availability. Priorities are based on the proposal’s linear rank score and the LST availability. Proposals with linear ranked scores in the top half (0-5) are allowed a maximum priority of A, third quartile rankings (5-7.5) are allowed a maximum priority of B, and all other quartile rankings (7.5-10) are allowed a maximum priority of C. If time is not available at a given LST in the appropriate weather category then the priority of the session is reduced. The weather categories are

  • poor (frequencies below 8 GHz),
  • good (8-21 GHz, 23-50 GHz) and
  • excellent (21-23 GHz and frequencies above 50 GHz).

Priority A will have the highest scheduling priority. Poor and Good weather priority A projects can be considered for scheduling for up to two semesters (up to one year). Excellent weather priority A projects will be considered for up to three semesters (two night time semesters). We expect that these observations could receive most, if not all, of their granted observing time if they are always available to be scheduled.

Priority B will have the next highest scheduling priority. They will be considered for scheduling for only one semester. We expect that these observations can receive a portion of their granted observing time. We recommend that the project team consider visiting Green Bank to help increase their chances of completing their project.

Priority C will be considered as filler time. They will be considered for scheduling for only one semester. We recommend that the project team consider visiting Green Bank to help increase their chances of receiving observing time on the GBT.

Priority D will have the lowest scheduling priority. They will be considered for scheduling for only one semester. We recommend that the project team consider visiting Green Bank to help increase their chances of receiving observing time on the GBT.

Priority N will not be scheduled due to the lack of available observing time.

Please work with your project friend to prepare for your observing scripts. Once you have developed observing scripts, you must then select active observers and enable sessions in the GBT Dynamic Scheduling System (DSS) before the project can be scheduled. You should check that all DSS parameters have correct values before enabling a session.

To avoid scheduling when an observer is not available see here.

All observers must be part of the project team and listed in DSS. To add a project team member please contact your project friend for instructions.

For further information on the DSS see here.

Contact your project friend if you need observer training and you are not able to attend the Observer Training Workshop.

Contact your project friend or Jill Malusky (ude.o1763688181arn@y1763688181ksula1763688181mj1763688181) if you will have – or wish to have – a press release.

During the summers of 2024-2031 the GBT will be shutdown during most of the summer months – beginning of May through the end of September.

Painting will be performed in the summer. There will be no observing between May and September.

Work on the GBT’s infrastructure may also require the telescope to be shutdown unexpectedly for extended periods of time. These shutdowns may impact the scheduling of your accepted observations. Observations that do not occur due to changes in the infrastructure work will not be guaranteed that their observations will be rescheduled.

Previous Calls for Proposals

In the posts below you will find information on previous proposal calls (in reverse-chronological order) including for each semester the proposal call results and a list of the science program.

View all past proposal calls