MIT Lincoln Laboratory researchers have recently installed a 69-channel adaptive-optics system on the 60-inch telescope at the Mt. Wilson Observatory in southern California.
This adaptive-optics system, called ACE (for Atmospheric-Compensation Experiment), will dramatically enhance telescope performance by correcting for atmospheric turbulence-the phenomenon that makes stars twinkle and dance. Without turbulence correction the resolving power of a telescope (that is, the smallest angular separation at which two stellar objects can be distinguished) is only 0.5-1.0 arc sec, even at an excellent site such as Mt. Wilson. With the ACE system, however, the 60-inch telescope has the potential to achieve a resolution of 0.07 arc sec.
The increased resolution that adaptive-optics can provide to ground-based telescopes opens the door for many potential astronomical discoveries; for instance, it may be possible to observe planetary systems in the process of forming around stars.
Lincoln Laboratory originally developed the ACE system for DARPA (Defense Advanced Research Projects Agency) for use in compensating laser beams propagating through the atmosphere. In the early and mid 1980's Lincoln Laboratory researchers conducted a long series of laser experiments with the ACE system at an observatory on the top of Mt. Haleakala on the island of Maui, Hawaii.
These experiments were first sponsored by DARPA and then by SDIO (Strategic Defense Initiative Organization). In 1985 Lincoln Laboratory used the ACE system in a laser propagation experiment to the space shuttle Discovery-the first SDIO shuttle experiment. Later in 1985 Lincoln Laboratory used ACE in experiments to instrumented sounding rockets-the first demonstration of atmospheric compensation for a laser beam propagated from ground to space.
In the interest of transferring technology to the civilian sector, SDIO has funded Lincoln Laboratory to refurbish the ACE adaptive-optics system and to install it at Mt. Wilson. It is expected that further work with the ACE system will be funded by NSF (the National Science Foundation). With the ACE system installed, Lincoln Laboratory and Mt. Wilson scientists will collaborate in operating the system for astronomical observations.
The Mt. Wilson Observatory was established in the early 1900's under the directorship of George Hale. The 60-inch telescope, commissioned in 1908, occupies a prominent place in the history of astronomical telescopes. Designed by the noted telescope maker George Ritchey, it was the largest telescope in the world at the time and the first successful large, all-reflecting telescope. As such, it ushered astronomy into the twentieth century. Although over 80 years old and by today's standards no longer a "large" telescope, the Mt. Wilson 60-inch telescope remains a superb optical instrument.
With the installation of the 69-channel ACE system, the Mt. Wilson 60-inch telescope now has the largest adaptive-optics system operating at an astronomical site (surpassing the 19-channel system at the European Southern Observatory 3.6-meter telescope in Chile). Thus, this venerable telescope is helping to lead astronomy into the next century. In the twenty-first century adaptive-optics systems should become standard equipment for all ground-based telescopes, and the next generation of 8-10 meter telescopes equipped with adaptive-optics will provide unprecedented views of the cosmos.
A version of this article appeared in the May 27, 1992 issue of MIT Tech Talk (Volume 36, Number 32).