PAOLA

Performance of Adaptive Optics for Large Apertures, is a set of functions and procedures written in IDL (version 5.4 at least) for calculating the performances of an AO system installed at the focus of an astronomical telescope.

Unlike most of AO simulation packages, the code is not a Monte-Carlo one. It relies on an analytic expression of the power spectrum of the corrected phase, and its relation with the AO Optical Transfer Function (OTF). The advantage over Monte-Carlo codes is the huge decrease in computation time (few minutes instead of hours). The drawback is that it is difficult if impossible to simulate the ``second order'' behavior of a real AO system (misalignments, imperfect reconstruction matrix, imperfect mirror influence functions,...).

So, the assumption that makes the analytical approach possible is that the AO system is perfect, i.e. all the components are left with their own limitations, but without any manufacturing/assembling/software errors. As a consequence, PAOLA is not a tool for studying the fine details of an AO system design. Rather, it has been developed as a toll for assessing AO performance on a given site and telescope, mainly to do science cases (but not limited to).

4 modes are available: diffraction limited, seeing limited, classical AO correction, and Ground Layer AO. The WFS can be a SH or a pyramid sensor. The deformable mirror can be conjugated to any height in the atmosphere.

As a summary, PAOLA helps the user to answer the question : if a perfect AO system is installed on a certain telescope at a certain observation site, what performances can we get on the sky ? (Strehl, FWHM, limit magnitude, 50% energy radius ...)

The input parameters are:

• Telescope:
• Primary mirror diameter
• Central obscuration
• Wavelengths
• Number of segments (option)
• Segments gaps (option)
• Segment shape (hexagon, circle, square) (option)
• Segment piston RMS error (option)
• Segment tip-tilt RMS error (option)
• Segment decentering RMS error (option)
• Primary mirror radius of curvature (option)
• Number of spider's arms 2/3/4 or 6 (option)
• Width of the spider's arms (option)
• AO correction of the telescope static aberrations (AO feed-back) (option)

• Turbulent atmosphere:
• Seeing angle
• Cn² vertical distribution
• Turbulent layers thickness
• Wind velocity vertical profile
• Outer scale of turbulence

• Adaptive Optics parameters:
• Natural guide star off-axis angle and orientation
• Deformable mirror conjugation altitude
• Number of actuators across the DM diameter
• WFS integration time
• Servo-system time lag
• NGS magnitude (option)
• NGS temperature (option)
• WFS CCD read noise (option)
• GLAO WFS cone aperture (option)

The toolbox is given as a "tar.gz" archive file, and includes:

• a user manual
• a README file
• a development log file
• a set of functions/procedures.

Platform: IDL release 5.4 and after (no GUI)
Operating System: Any
Author: Laurent Jolissaint.

Available at: ftp://ftp.hia.nrc.ca/pub/staff/lj/softwares/paola