P2.6 NCPA measurements

• Phase : 2
• Status : Draft
• Category : Daytime testing (functionality and operability) (C3) + Daytime calibration (C4)
• Recurrence : once after instrument installation at telescope platform
• Duration : 8 days

Description

• Measure the Non-Common Path Aberrations (NCPA).

Prerequisites

• Use 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 for the on-axis light source 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), using 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 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) and SHARK-NIR DROT angle (fixed).

Templates

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.
• RR will be required on the SX side when not using the Argos swing arm and for different elevation angle tests.
• AO support.

Date performed and by whom