optical fabrication

Engineers inspect beryllium primary mirror of the Infrared Telescope Technology Testbed (ITTT), fabricated by Hughes Danbury Optical Systems (HDOS; Danbury, CT) as part of a Jet Propulsion Laboratory (JPL; Pasadena, CA) technology development and demonstration program for NASA`s Space Infrared Telescope Facility (SIRTF). To minimize weight while maximizing performance, the 85-cm-diameter primary mirror tapers rapidly from a thickness of 50 mm in its central region to 6 mm at the outer edge. The

optical fabrication

Beryllium makes ultrathin precision mirror strong

Kristin Lewotsky

Engineers inspect beryllium primary mirror of the Infrared Telescope Technology Testbed (ITTT), fabricated by Hughes Danbury Optical Systems (HDOS; Danbury, CT) as part of a Jet Propulsion Laboratory (JPL; Pasadena, CA) technology development and demonstration program for NASA`s Space Infrared Telescope Facility (SIRTF). To minimize weight while maximizing performance, the 85-cm-diameter primary mirror tapers rapidly from a thickness of 50 mm in its central region to 6 mm at the outer edge. The bare mirror weighs 15 kg, while the integrated primary mirror assembly weighs 21 kg; the stiffness-to-weight ratio of beryllium allows engineers to fabricate a mirror weighing only half as much as a glass version with comparable self-weight deflection.

The mirror assembly is shown mounted on an aluminum plate for its initial cryogenic testing at 5 K in the SIRTF. The ITTT telescope is a Richey-Chrètien configuration designed for diffraction-limited performance at 6.5 µm. Hughes engineers have completed the secondary mirror assembly, which will be integrated with the primary mirror after JPL finishes the final cryogenic testing; a single-component beryllium metering tower that will support the secondary mirror assembly is still under fabrication at HDOS.

More in Optics