Advanced Concepts Studies

The 100-m Thinned
Aperture Telescope (TAT)

Additional concept studies of a very large, up to 100 m aperture telescope, suggested by the Woods Hole Advisory Committee for Astronomy and Astrophysics, therefore bypassed the transportation question and relied on the as yet unverified solution of orbital assembly of mirrors, structure, light shield and telescope subsystems.

This 100 m Thinned Aperture Telescope (TAT) was to address the unresolved questions of the distance scale of the Universe. A major goal was to determine the population, brightnesses, abundance and distances of the constituents of the Virgo cluster.

The aplanatic two mirror telescope concept, which evolved from the recommendation of the Woods Hole Committee, is a 100 m diameter ring primary mirror telescope with a 45 degree incidence secondary mirror ring surrounding the central spacecraft module, Figure 6. The focal plane is contained in a telescoping instrument module forward of the entire telescope.

Examination of the optical design indicated that the cost in extravehicular activities in low earth orbit for construction of the telescope and the subsequent transportation of the telescope to a very high orbital altitude at which drag, gravity gradient and pointing constraints improve, would be prohibitive.