GBT Time Allocation

The Green Bank Telescope has time available for all qualified astronomers worldwide through a peer-reviewed process.

We handle the GBT proposal submission, evaluation, and approval process jointly with the National Radio Astronomy Observatory (NRAO). The policies are outlined in the NRAO and GBO Users’ Policy https://science.nrao.edu/observing/policies/docs/manuals/users-policy.


Once a project is accepted for observations, the principal investigator has the responsibility for proper supervision of all aspects of the observing program. The Observatory staff endeavors to provide access to accurate calibration values, tables, and recommended observing and data analysis techniques. Confirmation and proper application of data calibration techniques and overall confirmation of data quality is the sole responsibility of the observers.

Please budget time for consultations with the staff and for calibration, pointing,, and data quality checks during the observing run to ensure that the data will meet your scientific goals.

All observers should coordinate with observatory staff to prepare for observations well in advance of the first opportunity for them to be scheduled.

Remote Observing

Certified members of the project may observe remotely.

To be certified for remote observing, observers must generally attend one of the GBO’s official observer training workshops typically held every spring and fall.

Observers can also be trained one-on-one either remotely or by visiting the observatory for a period long enough to ensure that there will be weather conditions suitable for scheduling the project (typically two to three weeks, depending on the nature of the project).


Instrumentation and Software

Visitors who require special hardware or software configurations for their projects must make their requests at the time the proposal is submitted. Requests for non-standard facilities or capabilities will be considered in light of feasibility, priorities, Time Allocation Committee (TAC) grade, project schedules, etc. Observers will be notified of the outcome when the results from the TAC are distributed. Last minute requests for non-standard capabilities cannot be granted, in general.


Each observer is scheduled on the GBT with the understanding that they are to pursue only the program, instrument(s), and source(s) described in their observing requests. As we have many observers from various institutions working on related programs, we require that any observer wishing to change their program in any way from that which was accepted by the TAC, do so only with the consent of the Director and Telescope Scheduler.

Observer Comments

A form to submit the Observer Comments is available online (DSS account required). Please note: These remarks are usually distributed to a number of staff and managers, and are usually not kept confidential. Confidential remarks should be made to the Scheduler or Director.

Observer Assistance

Each observing program will be assigned a “friend” from among the scientific staff. You will be notified of who your friend is prior to your observing run by the Head of GBT Science Operations. The friend will serve as your contact person both before, during, and after your run for all scientific and technical issues. Additionally the GBT has an on-duty support scientist available 24 hours a day. Through arrangement with your project friend, the on-duty support scientist can generally be available at the start of your run to assist in initial setup, and can be available as required during the course of the run. The friend (or in their absence the Head of GBT Science Operations) will coordinate assistance from others on the technical or scientific staff whose assistance or expertise may be needed.

Triggered Observations

Triggered proposals are for pre-planned observations of transients whose event times are unknown a priori.  Well defined triggering criteria are required. 

Triggered proposal for open skies observations must be submitted at the normal February 1 or August 1 proposal deadlines.  

Similar to fixed and windowed observations, triggered proposals should be ranked in the top quartile to be accepted with an A ranking.  Triggered proposals ranked below the top quartile would only be accepted as a result highly unusual circumstances and would receive a B or C ranking.

Once a trigger is activated, the following guidelines will be followed:

  1. A triggered observation will not be allowed to automatically override a sponsored time observation.  If the trigger has an A ranking and time permits, the GBT scheduler will attempt to negotiate with any sponsor to determine if the sponsored observation can be rescheduled in a reasonable and timely fashion to allow the triggered observation to occur.
  2. A triggered observation will not be allowed to override a fixed time observation (such as a VLBI observation or a pulsar Shapiro delay observation, etc.). 
  3. A triggered observation will only be allowed to occur under high frequency observing conditions if the trigger has an A ranking.  B or C ranked triggered observations will be limited to low frequency weather condition observing.
  4. Triggered observations can not automatically override a windowed observation’s default time.  For an A ranked triggered observation the GBT scheduler will work with the windowed observation’s proposal team to secure a new default observing time when possible. 
  5. A triggered observation will not be allowed to automattically override a maintenance period, a maintenance chance, shutdown periods, or any other time when telescope motion is not permitted (Thanksgiving and Christmas shutdowns, high winds, snow, etc.).  If the triggered observation has an A ranking, the GBT scheduler will work with the GBT Head Enigeer to determine if the observation can occur without interference to necessary maintenance activities if the observation can be scheduled on a maintenance day or a maintenace day chance.

Extra-Large Proposal Observing Blackout Policy

Extra-Large proposals are defined as any proposal requesting more than 1000 hours of observing time and typically running over multiple semesters.

Extra-Large proposals require a significant scheduling commitment for the Green Bank Observatory (GBO).  These proposals can strongly influence the ability to schedule other projects on the GBT.  In order to maintain a fair and balanced environment for all projects that are dynamically scheduled on the GBT, Extra-Large proposals must be able to observe any time they can be scheduled.  This means that while individual observers can take advantage of the blackout dates, Extra-Large proposals will not be allowed to blackout any time when observations can be scheduled.

The GBO is willing to work with projects to develop alternatives that may include operator run observing or service observing if the observing process is straightforward.

Baseband Recording Policy

Baseband recording using the VEGAS Pulsar Modes is an undocumented, unreleased mode that is not publicly available. In order to request use of this mode, a request to the GBT schedulers (ude.oarn.bg@ssd-ksedpleh) must be submitted and approved before the proposal is submitted.

Baseband recording uses very large volumes of disk space. This currently prohibits GBO from being able to archive this data. We are unable to keep the data on disk for no more than one week. Depending on the available disk space and the requirements of ??normal?? observations, baseband data may be deleted on a shorter timescale than one week. Also, there may be limitations on how close in time observations requesting baseband recording can be performed due to disk space availability.

The proposals requesting this mode must include a comprehensive plan that details how much disk space will be used, how the proposers plan on reducing the data or moving the raw data to personal storage within the one-week period, and what GBO computing resources, including human resources, will be needed during this process.

Baseband recording and storage of baseband data will not be allowed to interfere with “normal” observations on the GBT.

Data Access


The Observatory will archive and save all data from the GBT, with the possible exception of very large data volumes or data from user-supplied backends. These archives will be stored in a safe location and will be available for backup copies should they be needed at some point.

Data Proprietary Period

Principle Investigators have proprietary rights to the data for 12 months following the observation. After this proprietary period, the data will be available from the Observatory Archive for reduction by others upon their request. Those wishing to use data from the archive are encouraged to contact the original observers to ensure that any special issues concerning the data are understood. While this contact is encouraged, it is not required, and observers should be aware that the data will be in the public domain and subject to open use after 12 months.



Whenever research using one of the instruments or data from one of the instruments at the Green Bank Observatory is published, we request that the author include a footnote in the paper:

The Green Bank Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

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