An adaptive steerable imaging array

We propose an optimised design for the redeployment of the Multiple Mirror Telescope (MMT) primary optics as an Adaptive Steerable Imaging Array (ASIA) providing direct focal plane image formation. The design incorporates concepts of active telescope alignment and adaptive optics proven in the existing MMT. Existing 25 m radio telescope mount technology could easily be adapted to provide support of the optics with tracking stability, against wind loading, sufficient to allow optical rigidity to be obtained using off-axis stellar references, a possibility only feasible with comounted MMT-like interferometer designs which mitigate the field-of-view limitations of long optical delay-lines. As a result of the Steward Observatory borosilicate honeycomb mirror development program a seventh mirror may also be available, giving the light gathering capability of a 4.8 m aperture but with the resolution of a 25 m aperture, for a facility dedicated to the advancement of interferometric imaging technology and high angular resolution astronomy. By utilising existing technology and providing weather proofing of the optics on its mount, an expensive telescope enclosure, as well as costly, complex laser metrology and optical delay lines, is avoided in a cost effective installation. ASIA fills an intermediate niche, between the optical very long baseline interferometers such as Keck + Keck2 and the ESO VLT (large apertures and baselines to 100 m) on the one hand and designs such as the Big Optical Array and Sidney University Stellar Interferometer (small apertures and baselines to 1 km) on the other hand, by providing the sensitivity of a 5 m aperture and 25 m resolution optimised for the large program of Infrared Astronomy to be done at that resolution. ASIA will provide 30 mas resolution imagery (λ/D) at its adaptive optics focus, without use of aperture synthesis techniques, at 3.5 μm. We propose using stellar references for active optics alignment, internal laser metrology, and inertial sensing to stabilize the optical point spread function in a optical design having only two reflections to a highly optimized infrared focus. We are also considering the design of an ASIA based upon even larger radio telescope mount technology (45 m to 100 m baselines) and utilizing adaptive Gregorian secondary optics, e.g. using Kaman's PAMELA technology for two-conjugate adaptive optics.