The daily AO (adaptive optics) check is a pipeline supported technical
calibration. About once a day the CheckAOCorrection template is executed for 5
different AO configurations:
dichroic = VIS, WFS type = VIS, WFS mode = 1-3, camera = S27
dichroic = VIS, WFS type = VIS, WFS mode = 5-1, camera = S27
dichroic = N20C80, WFS type = IR, WFS mode = 3-2, camera = S27
dichroic = N20C80, WFS type = IR, WFS mode = 6-1, camera = S27
dichroic = N20C80, WFS type = IR, WFS mode = 9-1, camera = S27
The set of frames contain a dark exposure and a exposure, that shows an image
of the internal PSF fiber source. According to the NACO operations manual the
shape of the PSF fiber image can be either
diffuse, meaning at least one of the optical components of the AO system
is not aligned,
a circular image, meaning the optical path is well aligned, but AO loop is
not closed
a nearly diffraction limited Airy pattern, meaning the AO loop
is closed. In this latter case the pipeline retrieves the Strehl ratio
as a the key performance of the NACO adaptive optics system. In this
situation, the AO system has to corrected well a more static wave front
distortion induced by the reflections inside the optical system. While
in the case of observing stars through the earth atmosphere (see
here), the NACO AO system has to correct
a dynamically modulated wave front with a high frequency (~30Hz).
CHECK AO frame This is an example of the
master calibration CHECK AO frame. It is a pipeline product of the
"naco_img_strehl" recipe. The point like source is an image of the
instrument internal NIR PSF
Zoomed, the AO loop is closed and diffraction rings are resolved.
Example: the AO loop is not well closed
Example: the AO loop is not well closed
Example: the AO loop is not well closed
Example of a badly aligned calibration fiber optics
An ideal optical system projects a point source into a circular image with
a central core surrounded by Newton rings, the Airy pattern. The ratio
between the peak and the integrated counts of the Airy function is the
Strehl value for this optical system. The observed Strehl value, which
is usually smaller, divided by the theoretical Strehl value is the Strehl
ratio and serves as a measure of the optical performance (image quality)
in the environment of disturbing diffraction sources like optical surfaces, wind, medium turbulence.
The NACO internal fiber image (no atmospheric seeing) is statically disturbed by the
reflections within the optical system. The Strehl ratio of the fiber image
measures the quality of the AO system in the absence of atmospheric
turbulence.
mirror sites:
PL (internal link)
HQ
[?]
Strehl ratio of the fiber image
