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Tip-tilt Systems

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Tip-tilt Systems

Original tip-tilt memo: Attach: INT-402-MIS-0034.pdf

Requirements document: Attach: INT-403-ENG-0003.pdf

  • Answer questions in requirements doc.
  • Insert values from new system error budget.

Specifications of tip-tilt secondary mirror: XXX

Open questions:

  • Detector choice: EMCCD or conventional CCD
  • If EMCCD, do we ever need to use photon-counting mode?
  • How to handle dispersion offset between TT band and science/FT bands, e.g.
    • Does subframe need to move on TT detector during an observation?
    • How do we determine the colour of the target?
    • Is dispersion significant when determining a pointing model?
  • What ratio sample rate/bandwidth is needed?
  • How do we measure the temporal seeing with the TT system?
  • How do we choose the bandwidth for a particular observation?
  • How to manage range of target magnitudes 0-16, e.g.
    • Do we need ND filters?
    • What detector parameters need to be varied
  • Do we always use the full aperture?
  • Centroiding algorithm
  • Can we achieve the required stability of reference direction?

Tasks:

  • Derived requirements
  • Critical software issues
    • At what level is the interface to RTC?
  • ROM cost

The expression for the control system error factor from the tip-tilt memo is

\gamma = \left[ \frac{2}{\Omega} \tan^{-1} \left(\frac{\Omega}{2}\right) \right]^{1/2} ,

where \Omega is the ratio of sampling frequency to 3dB bandwidth.


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Recent Changes (All) | Edit SideBar Page last modified on March 16, 2007, at 05:00 PM Edit Page | Page History
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