== 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.
* AO support.


**Associated SHARK-NIR personnel**


**Date performed and by whom**

**Comments**