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Stephen Kent, 07/23/2012 09:40 AM


PSF-G1

Telescope alignment errors / aberrations inferred from field dependence of moments of PSF on science array agree with those inferred from donut data, to within ??? waves of wavefront error.

Prerequisites

Static LUT for alignment has been installed and is being applied. F/A donuts are being analyzed, but alignment tweaks need not yet be implemented. Results of F/A analysis are stored in database or equivalent. Focus loop is implemented and working. (One MIGHT be able to do this test with open-loop focus adjustments, but not sure.)

Procedure

This test can be performed using science data alone. Science data must be taken in good seeing (FWHM < 1.2" ???). One computes moments of stars on all science CCDs and uses the
patterns to derive a misalignment (including defocus). The numbers are compared with those derived from F/A donuts.

Verdict

The numbers agree at the same level that BCAM and donut data should agree (translation within 200 microns; tilts and defocus to some equivalent values).

Consequences

This test is intended to determine what is possible using the pattern of PSF shapes. It is possible that one cannot derive a non-degenerate solution.