Ground-layer and high-order adaptive optics with adaptive secondary mirrors

Michael Hart (U. Arizona)

The adaptive optics group at Arizona has been pushing novel AO
technologies for two decades now.  The first closed-loop demonstration
of a sodium laser guide star was made in the mid 90s at the old MMT,
when it still was a Multiple Mirror Telescope, which also saw the
first use of a focal-plane wavefront sensor to co-phase a segmented
aperture telescope in real time.  In more recent work, the new 6.5 m
MMT now hosts the first adaptive secondary mirror.  The very clean
thermal signature of an AO system that does not require warm reimaging
optics makes the MMT the most sensitive ground-based telescope in the
world for high-resolution point source imaging in the thermal IR.  In
addition, the large physical size of the ASM preserves a high etendue,
which has been exploited in the first demonstration of laser-guided
ground-layer AO.  That system is now being transitioned to science
operations.  Building on our experience with the MMT's adaptive
secondary, two more have been built for the Large Binocular Telescope
with upgraded design and improved performance.  The first of those has
been put into service at the LBT.  In this talk, I will very briefly
review some of the historical highlights before describing results
from the ground-layer AO work at the MMT, and the first light AO work
at the LBT.  I will end with a few remarks about the bigger picture of
where all this is headed in the context of science from the
forthcoming Extremely Large Telescopes.