SOAR Adaptive Module (SAM)
The SOAR Adaptive Module (SAM) will provide improved angular resolution
in a relatively wide field at optical and infrared wavelengths by compensating
selectively low-altitude turbulence.
The PSF metrics (FWHM, ellipticity, energy concentration and
Strehl) depend on the wavelength, observing conditions and instrument
parameters. The performance prediction for a representative set of
conditions and wavelengths is given in
this document [PDF]
The picture on the right shows the SAM field. The nominal science
field is 3'x3' square. Two tip-tilt natural guide stars (R>18mag) will be found
on opposite sides of the science field, up to 2/5' distance from the
center. The laser beam footprint (at nominal range of 10km) is shown
by a blue circle at the center. PSFs are computed on at 5 locations in
the field (empty circles) and compared to the un-corrected
seeing-limited PSF, plotted at 2.5' distance.
The plots show various PSF metrics (FWHM, ellipticity, encircled
enerdy in 0.3" diameter and gain of the central PSF intensity over
seeing in magnitudes) for the wavelength of 0.7 micron. Full, dashed
and dot-dashed lines correspond to the good (best 25%), typical
(median) and 75% observing conditions. Object at zenith distance 45
degrees. The last points show metrics of the un-corrected PSF.