Version 10 (modified by kradhakrishnan, 4 years ago) (diff) |
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P2.6 Measurement of NCPA
- Phase : 2
- Status : Draft
- Category : Daytime testing (functionality and operability) (C3) + Daytime calibration (C4)
- Recurrence : after instrument installation at telescope platform
- Duration : 5 days
Description
- Measure the Non-Common Path Aberrations (NCPA).
Prerequisites
- Use of the Argos swing arm / RR mounted on the SX side. SHARK-NIR aligned to telescope.
- Phase-diversity algorithm is tested and working in simulation and using real-images from the SCICAM (at Padova).
Procedure
- Go to a specific elevation of the telescope.
- Close the AO loop to produce the best PSF at the pin of the pyramid of the SOUL WFS. KEep that shape steady on ASM.
- Now, optimize the PSF shape on the SCICAM using the trial & error algorithm. The ALPAO-DM on the SHARK-NIR Bench is used to apply different modes. [Currently, this is the baseline approach].
- For the same elevation, keeping the same ASM shape as before and the same source, perform the phase-diversity test (with flat ALPAO-DM) making use of the Wollaston prism and dual-band imager lens configuration. Apply the obtained NCPA on the ALPAO DM within SHARK. Take SCICAM images to see the improvement. [In case the NCPA produced by the baseline approach is not stable enough for a longer period and/or if more correction seems necessary for high contrast, we will be implementing this approach (for which we will be using the star itself as the source during nighttime)].
- Note that in the above two cases, the optical path contains the same optics (except for the Wollaston and DBI lens) including the dichroic and IN_TT of the deployable arm.
- Repeat these measurements for the decided discreet zenith angles (or elevation of the telescope), SHARK-NIR DROT angle (fixed), and star (source) brightness.
Success criteria
- NCPA estimated and applied on the ALPAO-DM.
- Satisfactory PSF quality with closed-loop.
- The total residual after NCPA correction should be <30nm.
Notes
- See activity 8.1 in AD4 for more details.
LBTO support
- Authorize SHARK-NIR on the SX side.
- Permission to use the Argos Swing Arm.
- When not using the Argos swing arm and for different elevation angle tests, RR will be required on the SX side.
- Support from LBT SW Team
Associated SHARK-NIR personnel
Date performed and by whom
Comments