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Altair Phase II (OT) Checklist

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Altair is an Adaptive Optics instrument with no science detector. Here we cover only the checklist important for Altair use, not the specific science instruments which collect the data. Please ensure that you also follow the checklist for your current instrument.

  • Guide Stars
    • Make sure you have the guide star configured properly for the guiding mode that has been selected. The OT is designed to trigger warnings if you violate these rules as well as if you violate magnitude limits or distance limits. Please heed any warnings triggered by the OT and consult your contact scientist if you do not understand why the warnings were triggered. 
    • Natural Guide Star (with and without Field Lens) requires an AOWFS target defined in the Target component. This star will be used for the correction. Brightness, distance limits and guidelines for extended objects are described at http://www.gemini.edu/sciops/instruments/altair/use-ngs#guidestars.
    • Laser Guide Star in all modes implies that high order correction (everything except tip/tilt and focus) will be done with the Laser projected on-axis towards the pointing center of the telescope. The tip/tilt/focus guide star is described in the Guide Star Type. 
    • AOWFS will use Altair’s onboard STRAP/SFO for tip/tilt/focus. Verify brightness and distance limits as well as guidelines for extended sources conform to http://www.gemini.edu/sciops/instruments/altair/use-lgs. Consider whether to operate with the SFO open-loop as described here: http://www.gemini.edu/sciops/instruments/altair/use-lgs#NoSFO
    • PWFS1 will use the peripheral wavefront sensor for tip/tilt/focus and is Altair’s “super-seeing” mode. Verify magnitude / distance limits are followed; these are the same as for seeing-limited PWFS1 at http://www.gemini.edu/ sciops/observing-gemini/phase-ii-and-s/w-tools/observing-tool/ot/phase-iichecklist/sciops/telescopes-and-sites/guiding-and-wavefront-sensors/peripheral-wfs
    • OIWFS will use a star on the instrument’s OIWFS so you should verify the star follows the limitations on the individual instrument pages. If an instrument does not list an AO-specific limiting magnitude, then you should follow the guidelines for seeing limited. This mode is not currently commissioned for any instrument but it is foreseen as a future upgrade. 
    • Non-sidereal objects may be used as a guide star, a science target or both. If you use a non-sidereal object, verify it conforms to the instructions for non-sidereal objects. Check with your contact scientist regarding this as there are some subtleties for some modes of use (Laser clearance for instance or observing near very bright objects such as major planets). 
    • The very faintest guide stars (near the LGS AOWFS limit) often have unreliable magnitudes. Sometimes this is because of catalog errors and sometimes it is because of mis-identification (a faint star is actually a galaxy). Verify suitability of your guide star. If you are unsure whether your guide star is suitable, discuss with your contact scientist whether there are alternatives, such as overfilling your program with additional targets should one of your targets prove difficult / impossible for guiding.
  • Instrument Configuration / OT Setup 
    • The Atmospheric Dispersion Corrector is currently not enabled so the status of this check box has no effect. • The Dichroic Beamsplitter should be 850 nm - 2.5 microns until we commission the 850 nm - 5 micron dichroic which will replace it. The future 589 nm dichroic will only be used with GMOS + Altair in LGS mode. 
    • Cass Rotator should be Following if you want to specify a position angle for your target on the sky. If you specify Fixed, the operator will by default put the Cass Rotator at 0 degrees to minimize the effect of primary mirror vibrations on the science beam but the field will slowly rotate, so ensure your exposures are short enough for your science case. You may specify other cass rotator states as well via a note in the program after checking with your contact scientist (fixed at a nonstandard angle, or following but with a sky position angle chosen upon slew to minimize vibrations). 
    • ND filter should be used for stars too bright for NGS or LGS. The OT should issue a warning if you need this feature. Limits are described in the pages referenced above in the Guide Star checks. The ND filter only affects the Altair path, not the science path so calibrations should remain the same. 
    • If in NGS mode, decide if you do not need the field lens. LGS mode requires the field lens and most NGS modes will benefit from the field lens, as described on this page: http://www.gemini.edu/sciops/instruments/altair/field-lens-option . 
    • Include a finder chart. This is particularly important for very faint LGS AOWFS observations where the observer must identify the correct guide star. 
  • Standards and Calibrations 
    • GCAL calibrations cannot be done through Altair. Verify that this is suitable for your science goals or discuss the implications of this with your contact scientist. 
    • For all standards, verify using the ITC that the standard star will not saturate your science detector when using AO even in good conditions (IQ=20/70 and CC=50). This is particularly important for near-IR imaging standards and spectroscopic telluric stars in low resolution modes. If you cannot find a suitable standard, consult your contact scientist about wether you should operate open-loop, but still have Altair in the science beam. 
    • Consider whether you want a point-spread-function standard. This will be most effective if you can recreate the guide star details used for your science target: guide star magnitude, separation, guide star to target position angle, and a similar location on the sky. These are not part of the baseline calibrations so will be charged to your program. 
    • Verify that other modes are the same for the standard and science (for instance the use of the dichroic and field lens). 
    • Check that standards for LGS science are done in NGS mode. The science paths are identical and overheads are reduced so NGS calibrations for LGS are encouraged. 
  • Imaging
    • Verify that your science target will not saturate. If your target is close to a very bright guide star (for example, NGS exoplanet imaging), include a note to the observer indicating the valid area of saturation. 
    • If delivered image quality needs to be constrained, include a note to the observer indicating the constraints. This is not needed if the standard observing condition constraints are sufficient for your program. 
    • If the observer needs to make nighttime decisions concerning the exposure time and coadds depending on conditions, include information regarding this. 
  • Spectroscopy 
    • Verify LGS super-seeing mode is not being used for longslit spectroscopy. This is not a commissioned mode due to flexure issues. It is allowed for IFU spectroscopy provided your source is not a blind offset target. The flexure issues may be improved in the future if there is user demand. 
    • Ensure that your science target or nearby bright guide stars will not saturate. 
    • If the observer needs to make nighttime decisions concerning the exposure time and coadds depending on conditions, include information regarding this.

 


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