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MROI.Tip-tiltSystems History

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March 16, 2007, at 05:00 PM by John Young -
Changed lines 10-26 from:
to:
  • 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:

Deleted lines 27-28:
  • Stability of reference direction
  • Sample rate/bandwidth
Added line 29:
  * At what level is the interface to RTC?
March 16, 2007, at 03:44 PM by John Young -
Changed lines 4-6 from:
to:
  • Answer questions in requirements doc.
  • Insert values from new system error budget.
Added line 14:
  • Critical software issues
March 16, 2007, at 03:38 PM by John Young -
Changed lines 1-16 from:

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

to:

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

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

Specifications of tip-tilt secondary mirror: XXX

Open questions:

  • Derived requirements
  • Stability of reference direction
  • Sample rate/bandwidth
  • 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.

March 16, 2007, at 03:00 PM by John Young -
Added line 1:

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

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