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Remote Eavesdropping

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* NOTE: Remote Eavesdropping is currently unavailable at Gemini North and South. *

For more details, please see here.

Eavesdropping enables you to watch the progress of your queue observing while it happens. If you sign up for eavesdropping, the observer may contact you when your program comes up in the queue and start a screen-sharing session so that you can see the data come in and help with the quality assessment. Note that observing is a high-pressure activity. Therefore, eavesdropping is at the observer's discretion - they may or may not call. This page lists the main features of eavesdropping, how to request it, and how to eavesdrop.

Eavesdropping is:

  1. Ability to see, and comment on, target acquisitions.
  2. Ability to assess data quality quickly enough to allow useful changes to be made while observing.
  3. Ability to understand what is happening while observing at any given time.
  4. Added value only. All observations must be executable without eavesdropping, no observation should rely on it.
  5. Initiated by the observatory.
  6. Ability to see data reduction products.
  7. Ability to request modifications to observation (change exposure time, re-arrange steps, change wavelength, add a filter, skip a previously included filter, etc.). Modifications must not significantly change the nightly queue plan in a way that the observer would not have done, and must not redefine the observation in a way which might duplicate some other observations in the database. (Guidelines will be needed for the observer in these cases.)
  8. Ability to interact with raw data for their project (and associated calibrations) stored at the observatory.

Eavesdropping is not:

  1. Ability to override queue decisions made by the observer and/or QC. All queue choices will be made in the same way as normal. This includes rapid Targets of Opportunity, which will continue to interrupt the current observation even if that observation is being eavesdropped upon. In marginal cases, e.g. very thin cirrus while observing a CC50 observation, and where there is no direct impact on higher-priority programs, the PI may be asked if they wish to continue. If they say yes, despite the weather conditions being outside their formal requirements, a “PASS” flag will be placed on the data in the Gemini Observatory Archive.
  2. Ability to directly execute (start, stop etc.) the sequence.
  3. Ability to directly control the instrument.
  4. Ability to see the summit OT (because of confidentiality of other programs).
  5. Ability for PI to communicate with QC (the observer will do this if needed).
  6. Allowed to result in additional staff hours at the observatory. In practice this means that eavesdropping cannot be used instead of observing during the classical observing runs.
  7. Allowed to result in reduced efficiency – emphasis remains on pre-preparation of observations. No preparation is done on the fly at night, and all time spent inspecting acquisition images etc. is charged to the PI’s programme.
  8. Allowed to produce additional work for QCs or observers.
  9. Applied to short observations (this is to avoid the overhead of contacting the PI, getting the eavesdropping session established etc. for an observation that may only take 15 minutes).


All Band 1 and 2 PIs are invited to eavesdrop if they wish, via the PI email announcing that they have been granted time. If a PI chooses to eavesdrop, they enter their range of dates for multiple contacts in a Google spreadsheet. Observers check this spreadsheet to see if a PI has an available contact for the current night. 

On a given night, should the program come to the top of the queue and be identified in the plan as an eavesdropping program for the night, the PI or designated contact receives a phone call stating that observations are about to begin. The observer will communicate the Zoom meeting ID number and password. The designated eavesdropper then connects to the control room and takes part in the observation, including watching and commenting on acquisitions, inspecting data frames and commenting on whether to continue or terminate an observation. If desired, the eavesdropper can access the data in near real time via the Gemini Observatory Archive (see section Accessing your Data). Note that observers have a discretion over eavesdropping and that data for an eavesdropping program may be taken without a phone call and eavesdropping. Such decision may be driven e.g. by variable weather, technical dificulties, cutting overheads etc.

To avoid confidentiality issues and debates between PIs during the night, only one program will be invited to eavesdrop at a time.

Brief records are kept in the night log of the key points of the dialogue between the observer and the PI.

Procedure to Request Eavesdropping

Initial contact

For non-Fast Turnaround proposals, PIs will be invited to participate in eavesdropping in the initial PI email announcing they have been allocated observing time. This email will also provide a link to the Google spreadsheet where you can request eavesdropping and specify availability. For Fast Turnaround proposals, PIs should send a request to their primary contact scientist to set up eavesdropping.

Providing eavesdroppers' contact information in the OT

If you wish to eavesdrop, you should provide contact details in the Observing Tool for up to three eavesdroppers:

  • name
  • email address
  • telephone number

Below is an example of an OT eavesdropping note:

Note that you can designate up to three sets of details. These may be used to give three different contact numbers for yourself, to be used at different times in the semester, three different Co-Is to cover different ranges of nights, or some combination of these. We use these contact information to establish the eavesdropping sessions. The three contacts are labelled "a", "b" and "c", respectively. Please refer to them as such in your communication in regards to eavesdropping.

Specifying contact availability

For non-Fast Turnaround proposals, you will receive a link to a Google spreadsheet in the initial email. For Fast Turnaround proposals, you will be provided with a link to the sheet after you request eavesdropping from your primary contact scientist and the sheet has been edited by the contact scientist to include your program. This sheet is where you tell us who is available and when. The data entry sheet looks like this:

Google Spreadsheet

All you need to do is locate the "Availability" tab (bottom of the browser window) for the telescope you wish to eavesdrop at, and enter "a", "b" or "c" into each date on which your contacts are available (only one contact per night). Please be sure to consider the target observability and enter contacts, if possible, at the earliest possible date - your program may well be observed as soon as the targets become available.

Procedure to Eavesdrop

A designated eavesdropper for a given program is contacted at night to take part in target acquisition and data assessment in real time. This section gives information you will need to know in order to participate in an eavesdropping session.


Queue observing of high-priority science is intensive and can be intrinsically stressful for observers. Please be aware of the following points, which seek to ensure that observers can do their job efficiently:

  • All eavesdropping sessions are done at the discretion of the observer. As noted above, eavesdropping is defined as added value only, and not necessary for the successful completion of the observation.
  • Network connection problems in the course of a session may or may not be fixed. The observers often have their hands full. If you get disconnected, try to call back but don't assume that the observer has time to investigate what happened. They will, by definition, carry on with your observation.
  • The observer may be a staff scientist or a member of the Science Operations Specialists group. They are trained in the use of the instrument but you should not assume that they are familiar with your science.
  • Please don't ask the observer for advice on observing technique or data reduction. Such enquiries, along with questions about Phase I and II preparation, should be directed first to your NGO.
  • The observer and telescope operator work with observing systems and telescope systems as-is. They are not responsible for the properties or efficiency of these systems. If you, as eavesdropper, wish to critique any aspect of these systems, please do so to the Head of Science Operations during daytime hours. Any attempt to engage the night crew in such discussion will normally result in a swiftly terminated session.
  • The observer is empowered to ensure that an eavesdropping session does not interfere with the nightly queue plan. If, for example, the queue plan states that your observation must stop at some defined time in order to get onto a high-priority observation in the queue, they will stop it at that time.
  • If you are not content with any of the above as it pans out in any given eavesdropping session, you should contact the relevant Head of Science Operations. Do not debate with the observer.

Initiating an Eavesdropping Session

  1. Observer calls the designated eavesdropper 15-30min before starting the observation, and provides the Zoom meeting ID number and password. (Sorry if we wake you up!)
  2. Eavesdropper joins the observing Zoom channel either via the Zoom application or browser.
  3. Observer starts sharing one of their screens to show the incoming data and target acquisition.
  4. Eavesdropper can optionally log into the Gemini Observatory Archive to be able to access their data in near real time if they wish (see section Accessing your Data).


Two people are typically present in the control room: one runs the telescope, the other runs the science program. Eavesdropping adds you. The observing process is described below.

  1. Observer loads your program in the OT and selects the observation.
  2. Observer sends the observation to the SeqExec which then runs it.
  3. Telescope operator slews to the target, while instrument is automatically configuring (can be a few minutes depending on distance to target).
  4. Telescope operator acquires guide star and sets guiding going (up to six minutes total for steps 1-4 combined).
  5. Observer, telescope operator and eavesdropper acquire the target, which involves taking an image, using "gacq", and iterative pointing offsetting. Acquisition overheads are instrument specific, see the instrument overhead webpages for details.
  6. Observer starts running the SeqExec and thus exposing.
  7. First frame comes in and is displayed in the screen sharing session. Eavesdropper and observer inspect the frame and confirm continuation.
  8. Eavesdropper has a choice to either watch the incoming frames in the screen sharing session, or download them from the Gemini Observatory Archive within a minute after each readout.

Accessing your Data

The Gemini Observatory Archive is designed to make data available for download within a minute or so after readout, and is the recommended way to download data during eavesdropping sessions. Data access via the Archive during eavesdropping is the same as the regular post observing data access.

Your science data will be proprietary. In order to access proprietary data for your program, you will need to have created an account on the archive and be logged in, and you will also need to have registered your program ID with your archive account. Details of this process are provided here. You are encouraged to do this ahead of time, both so that you don't need to do it in real-time when we've just woken you up and as we're observing your project, and also so you get to see the system ahead of time.

Once logged in, we recommend you put both your program ID and the current UT date in the search form to see your data from tonight. Clicking the "Search" button will update the results. Click the [D] next to a file to download that one file. The [P] gives a jpeg preview of the file if available - the preview for each file may take an extra minute or two to become available, so very recent data may not have a [P] link.