P2.6 Measurement of NCPA

• Phase : 2
• Status : Draft
• Category : Daytime calibration (C3)
• Recurrence : after instrument installation at telescope platform
• Duration : 10 days

Description

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

Prerequisites

• Use of Argos swing arm / RR mounted on the SX side. SHARK-NIR aligned to telescope.

Procedure

• Go to a specific elevation of the telescope.
• In closed-loop, the Arcetri team optimizes the PSF shape on the SCICAM using the trial & error algorithm (used by the LBTO team during LUCI calibrations) changing M2 reference shape applying modes coefficients. [Currently, this is the baseline approach].
• For the same elevation, keeping the M2 flat, using the same source, perform the phase-diversity test script which will make use of the Wollaston prism and dual-band imagers 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)].
• Make the ALPAO DM flat and using the internal calibration sources, run the phase-diversity script. Apply the obtained NCPA on the ALAPAO DM. Take SCICAM images. Note that this NCPA correction does not account for any aberrations caused by the Dichoics and internal TT mirror within the deployable arm. [This NCPA will only be used if the previous two options are not possible or good enough for a given case/target.]
• Repeat these measurements for 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 ASM (need to define a quantitative value?)
• Satisfactory PSF quality with closed-loop and get a new and improved daytime telescope model for SHARK-NIR?

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 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