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For Band 3 Programs

With Gemini's queue observing process, you need to consider much more than your science justification when preparing your proposal. While you hope to end up in Band 1 or 2, there is a chance that you will end up in Band 3. It is important to understand that Band 3 overfills the queue once losses due to weather are taken into account. Consequently only some Band 3 programs will get data, and completion rates can vary a lot from semester to semester. The Band 3 tab in the Phase I Tool allows you to modify your program to increase the chances of having it executed if it ends up in Band 3, while still achieving a good fraction of the original science goals.

You should use the Band 3 tab to decline a Band 3 allocation if your program is time-critical, if it requires the LGS system, or if the optimising strategies suggested below will prevent you from achieving your science. Your Band 3 requirements can be the same as your default requirements if your program is already easily schedulable and observable, as outlined below. Most likely, however, you will need to make some alterations to your observing constraints, target sample or instrument configuration, to optimise your Band 3 chances. If you choose this approach you will need to explain how you will achieve reasonable scientific goals to your TAC in the text box provided in the Band 3 tab.

We list some strategies here for both the Phase I and Phase II stage of the Gemini process. You can still optimize your chances after your award of Band 3 time, as we describe below.

Phase I 

  • Relaxing your program's observing constraints.   Band 3 programs will stand a much better chance of being executed if the program utilizes poorer than median conditions.   Relaxing your image quality, cloud cover, sky background or water vapor requirements can greatly increase the chances of your program getting data.  Remember, there aren't many Image Quality 20%-ile nights (corresponding to 0.45arcsec seeing in V), and when they do occur there are usually Band 1 and Band 2 programs in the queue with higher priority than Band 3 programs.   If your program is doable in the commonly occurring conditions, there are many more of those nights available.  In the mid-infrared, near-diffraction-limited mid-infrared observations can often be obtained even when the optical seeing is not great. Also, you may be able to relax photometric constraints by using one image obtained in photometric conditions to calibrate other images of the same field taken under non-photometric conditions.  As a rough rule of thumb for Band 3 programs:

    Image Quality=85, Cloud Cover=70 has a good chance of getting data (more than 70% of executed Band 3 observations are taken in IQ=85 or worse) 

    Image Quality=70, Cloud Cover=70 has some chance

    Image Quality=70 or better, Cloud Cover=50 or better has little chance of getting data.

    More detailed information can be found on the Gemini Science Operations Statistics web page, and the Observing Constraints web page.

    • Target Selection.   Telescope time oversubscription varies with RA. At Gemini North, the RA range 11 - 15 hours is typically heavily oversubscribed, for example. Having targets well distributed across the semester's allowed RA range can significantly increase the chances of being awarded time, and the chance of a Band 3 observation being scheduled to fill a gap in the nightly queue plan. 

    • Instrument Configurations.   For some instruments, the instrument configuration on any given night is determined by higher-ranked programs. If your Band 3 GMOS program is the only one using a particular grating, for example, then it might not be possible to include it in the queue plan.   At both Gemini North and South, the B600 and R400 are the most popular gratings and are typically installed in GMOS for the entire semester. The third available slot in the instrument will be occupied by one of these three gratings: B1200, R150, R831, driven by the nightly queue plan.

    Phase II

    • Get your Phase II ready early.   The sooner your program can be scheduled in the queue, the greater your chances of getting data.  As we near the end of each semester there are sometimes gaps in the nightly queue plan that can be filled with targets from programs in the following semester (e.g., starting a 2021A program at the end of 2020B).  So if you have targets that can take advantage of this then get your Phase II in before the deadline! 

    • Be flexible with your targets.   If your program aims to study a class of objects (e.g., elliptical galaxies) rather than a specific object (e.g., M87) then don't hesitate to submit a change request to refresh your target list if some of your original targets set during the semester.  Alternatively, you might consider submitting a larger list of targets than you've been awarded time for and indicate a priority for each target (high, medium, low). This will allow us to continue to execute your program even if some of your targets set during the semester. Also, try to avoid imposing additional scheduling restrictions, such as airmass, time, etc., or be as flexible as possible about such constraints.

    • Prioritize your observations.   If you've got a large program in Band 3, let us know what portion of your program is most important to you. Don't hesitate to add notes to your program.  If it's not possible to get all your program's data, we can at least try to get the data that would be most valuable for you.

    • Consult with your NGO or Contact Scientist. General questions about preparing your Phase II should be submitted to the Gemini HelpDesk; most queries will usually be answered quickly by your NGO and the remaining forwarded to your Contact Scientist.

    Best of luck with your Band 3 program!

Advice | Gemini Observatory


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