## MROI.Tip-tiltSystems History

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?

Deleted lines 27-28:
• Stability of reference direction
• Sample rate/bandwidth
  * 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.
• 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 -