Adaptive Optics System
Adaptive Optics (Unavailable): The original MMT f/15 adaptive secondary was built by the University of Arizona and Arcetri Observatory in Italy. The thin glass shell is 1.9-mm thick and 640-mm in diameter and is deformed by 336 voice coil actuators. It was used with instruments such as ARIES, PISCES, MIRAC and Clio.
The new upgraded and refurbished AO system – MAPS: the MMT AO exoPlanet characterization System – is being tested on the MMT currently and has had several runs in 2023. More details can be found in a recent SPIE paper and an updated status report.
For natural guide star observing, wavefronts were corrected at full speed for objects of V ~ 11-12 magnitude, depending on conditions. For target stars as faint as V ~ 13.5-14, fewer corrections could be applied, but improvements in image quality over the natural seeing were possible.
If the target star was fainter than V~14 there were three options.
- Leave the mirror flat and do no corrections.
- Use a very nearby (less than 20-30 arcseconds away) brighter star to correct on.
- Close the loop on a nearby bright star and “fix” the shape of the mirror, then return to the target star. Keep the mirror stationary for the duration of the science observations.
When the f/15 is mounted the wind constraints are tighter to protect the deformable secondary mirror. If pointing into the wind and the wind is sustained at 25 mph or gusting above 30 mph, then we must close. If pointing away from the wind and the wind is sustained at 30 mph or gusting above 35 mph, the front shutters must be closed. Additionally, if the wind is coming out of the North-East or East, then it arrives at the telescope over Mt. Wrightson and the ridge. This causes major turbulence above the telescope and will degrade the seeing and make it highly variable. In this case, there is nothing we can do to improve the conditions other than wait for the wind to change direction.
For additional information on the original MMT NGS-AO system performance see the MMT AO Performance: Analysis and Status technical memo.
For more information, please contact W. Goble.