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Visitor Facilities and Policies

Welcome to Green Bank! We look forward to working with you .Please review the following information to ensure that your visit is both easy and rewarding.


Eclipse Event at Green Bank Observatory

Ecplise with corona
Image similar to what West Virginians will see if they observe the eclipse this August.

Image above is similar to what West Virginians will see if they observe the eclipse this August! (Image source:

Have you heard?! This summer, you have the chance to experience a spectacular stellar event! On August 21, the star that brings us spring flowers, warm days by the pool, and the northern lights, a.k.a. our Sun, will be eclipsed by the Moon. Want to see it? You’re invited!


Dynamic Scheduling System


The GBT spans a larger range of frequencies than other comparable centimeter/millimeter single-dish telescopes, and is located in a continental, mid-latitude region where weather is dominated by water vapor and small-scale effects. As a result, the observing efficiency of the GBT is enhanced significantly by the GBT’s Dynamic Scheduling System (DSS), which allows observers to optimally match their desired weather conditions to their observations, resulting in considerably increased observing efficiency.

Unlike “standard” telescope dynamic scheduling systems, the GBT DSS is not queue based.  That is, the GBT DSS schedules observers, not scripts. This fact is key to the overall underpinnings of the DSS which creates notifies observers 24-48 hours in advance of their observations.

At the start of a semester, at any any time during the semester, observers are required to indicate when they will not be available to observe on the GBT. Using this information, combined with the availability of the required hardware, the scientific priority of the projects, the predicted weather, and a number of other factors, the DSS will build a schedule every 24 hours for the period 24-48 hours from that time.  Once the schedule is built, the relevant observers will be notified that their observations have been placed on the schedule.  If the weather deteriorates after the schedule is built, the project observers can choose to give up their time to a backup project, or to observe in spite of the weather.

One of the components of the GBT DSS, which will both improve the ease of use of the GBT and make the DSS plans feasible, is the implementation of an observer’s availability calendar for each project. With this calendar each observer can note the times he or she cannot be available for observing, blocking anything from an hour to months. The exciting part of this system is that any observer can update it at any time as that information will be immediately and automatically fed into the scheduling software. As a result, it is extremely easy for observers to make sure that GBT observing does not conflict with any other commitment.

There are, of course, many other details to the GBT DSS, such as the ability to schedule monitoring and fixed time observations, a ranking scheme for scheduling the projects, etc. All these details are publicly available through the DSS Memo series (NRAO Wiki site). An overview of the DSS process is given in the figure below.

DSS proecess
Click on the image for a larger version

Benefits of the DSS

In addition to improving the observing efficiencies for high-frequency observers, the DSS will allow for more flexible use of the GBT. This will benefit both high and low-frequency observers in many ways, including:

  • Pre-scheduled and elective projects (such as VLBI) have can have significantly more chances of successful observations
  • Observations affected by transient RFI can be halted and seamlessly rescheduled;
  • System faults (both in hardware and software) will be easier to work around and fixes will be easier to schedule, making the running of the GBT smoother and more efficient;
  • Any “make-up time” needed for a project will be easily rescheduled, allowing the observations to be completed within the requested trimester;
  • Rapid Response Proposals will be scheduled without disrupting another observer’s scheduled time;
  • Observers will be able to state when they wish to travel to Green Bank for observations, rather than being told by the telescope scheduler when to arrive;
  • Observers will be able to change their availability for observing even as the trimester progresses rather than only a few months before a trimester begins
  • Observers will be able to block out many small amounts of available time (e.g. when teaching classes) rather than needing to adjust their personal schedule to a pre-set telescope schedule;
  • Observers will have the ability to observe a small part of their allotted time and then request a few days (or more) to analyze the data before using more telescope time;
  • Complicated monitoring programs will be easily handled by the DSS;
  • The GBT scheduling process will be transparent, allowing users to discern the likelihood of attaining telescope time as the trimester progresses.

More Information

Observing Policies

Home » Science » GBT Observers » Observing with the GBT » Observing Policies


The Green Bank Telescope is operated as a national visitor facility for qualified professional astronomers, including both expert and novice radio observers. General information on observing at the GBT and visiting Green Bank are described in the visitor information.

In addition to web documentation for self help (see the GBT Proposer’s Guide and the GBT Observer’s Guide), GBT Operations has a limited number of staff support astronomers who will aid observers in the setup and execution of their observations. In order to make most efficient use of the telescope and to conserve the time of our staff, we describe here the present practices and policies for GBT observing. Any changes and enhancements to policies, procedures, and observing facilities will be publicized through the Newsletter, our web pages, and through contact with the support staff.

General Information

OBSERVER RESPONSIBILITIES: As a general rule, the principal investigator has the responsibility for proper supervision of all aspects of the observing program. This means, for example, that each principal investigator is responsible for enabling all observing sessions, ensuring observers are available for observations, and obtaining all calibrations and other receiver/telescope parameters necessary for the reduction of his or her data. For this reason, we require that an observer be on site to conduct observations or a qualified remote observer be available.  In the case of student observers, the student’s adviser must accompany the student for at least the first observing run on the GBT.

REMOTE OBSERVING: The GBT supports remote observing provided the remote observer has been qualified for remote observing by the Head of GBT Science Operations. Most but not all of the required tools, procedures, and infrastructure are in place. Only those observers who have used the GBT before and have demonstrated that they are fully able to set up and observe on the GBT without staff assistance may observe remotely. Experience has shown that if an observer requires significant assistance, the process of providing this remotely is awkward to all involved, is an inefficient use of telescope time, and is overly time-consuming and taxing for our staff. Observers who are less experienced with the GBT are required to observe on site.

Observers who are sufficiently experienced and wish to observe remotely must contact the GBT Head of Science Operations (Toney Minter) at least two weeks in advance to request approval. The decision will be based on demonstrated experience of the observer and suitability of the program for remote execution. If permission for remote observing has been granted to a particular observer, it is required that he or she carry out the observations. The approved remote observer specifically must not pass off the responsibilities to an unapproved collaborator or student.

For approved remote observers, guidelines and suggestions for remote observing are posted online.

OBSERVER ASSISTANCE: Each observing program will be assigned a staff support astronomer (“friend”) to assist in the preparations for the observing run. You will be notified of who your support friend is when your project is approved for scheduling. The friend will serve as your contact person both before and after your run for all scientific and technical issues. Because of the support rotation scheme in use, a different scientist may be assisting you during your observations. This support scientist is generally available at the start of your run to assist in initial setup. This person or another scientist will be available as required during the course of the run, according to duty rotations. The friend or on-duty support scientist (or in his/her absence, the Telescope Operator) will coordinate contacting the technical or scientific staff whose assistance or expertise may be needed.

STUDENT OBSERVING: Many proposals have students who are either the P.I. or a CoI where the observations are conducted by students. To minimize the load of the GBT support staff, the first time that a student observes using the GBT, he/she must be accompanied by their supervisor (or an experienced GBT astronomer) and must carry out their first observations on site in Green Bank.

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

PROPRIETY: Observers are scheduled on the telescope with the understanding that they will pursue only the program described in their observing request. Since we have many observers from various institutions working on related programs, we require that any observers wishing to change their program (e.g., source list, observing frequencies, etc.), or to exchange time with other observers, do so only with the consent of the Site Director and Head of Telescope Operations.


Regardless of whether observations are conducted on site or remotely, the observing will be most efficient if the observer and the support scientist work together to prepare for the run well in advance of the observations. Please make the following arrangements:

  • Contact your assigned staff astronomer before the start of the semester in which you may be scheduled. The program can be discussed, computer accounts and disk directories set up, and initial observing scripts created and reviewed. Having these scripts in place prior to the run will save much time in starting up the observing run.
  • If you plan on coming on site, arrive on site at least one business day in advance of your observations. This will allow observing plans to be reviewed and all last-minute preparations made. The staff astronomers can also give demos of the control and data reduction software which will save much time at the telescope.
  • Enable your project sessions as soon as you are prepared to observe to ensure the maximum possible opportunities are given to your project.

Telescope Scheduling

The GBT presently operates from ~300 MHz to ~100 GHz. Observations at frequencies above ~10 GHz are affected by atmospheric water vapor, and are best done in clear, cool, and dry weather conditions. Since Green Bank weather is highly variable, a dynamic scheduling system has been instituted.  This system is fully described on the GBT scheduling page.

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.

News and Events

News Related to Science

For stories about Green Bank “In The News” press, please visit our main News link.

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