Status of mirror segment production for the Giant Magellan Telescope

Abstract

The Richard F. Caris Mirror Lab at the University of Arizona is responsible for production of the eight 8.4 m segments for the primary mirror of the Giant Magellan Telescope, including one spare off-axis segment. We report on the successful casting of Segment 4, the center segment. Prior to generating the optical surface of Segment 2, we carried out a major upgrade of our 8.4 m Large Optical Generator. The upgrade includes new hardware and software to improve accuracy, safety, reliability and ease of use. We are currently carrying out an upgrade of our 8.4 m polishing machine that includes improved orbital polishing capabilities. We added and modified several components of the optical tests during the manufacture of Segment 1, and we have continued to improve the systems in preparation for Segments 2-8. We completed two projects that were prior commitments before GMT Segment 2: casting and polishing the combined primary and tertiary mirrors for the LSST, and casting and generating a 6.5 m mirror for the Tokyo Atacama Observatory.

Lightweighting design optimisation for additively manufactured mirrors

“…A honeycomb is a construction that offers the largest volume (honey) for the minimum structure (beeswax) and it is created from two sets of hexagonal prisms ending in three rhomboidal faces placed back-to-back and offset to create a perfect tessellation, 20 as shown in Figure 15. A approximation to the honeycomb design has been an inspiration for several telescope mirror geometries 21,22 as well as mirror lightweighting structures; 23,24 however, applying the exact honeycomb cell geometry is challenging within traditional machining. The objective of this study is to apply the honeycomb construction that is seen in nature to create a lightweight sandwich mirror which exhibits two solid face plates and a rhombic dodecahedron interior.…”

Investigation of the polishing mechanism of magnetorheological elastic polishing composites

“…Ultra-precision polishing technology and processes have always been hotspots of research. In order to quickly produce high-quality surfaces, many ultra-precision polishing methods have emerged in recent years, such as stress disc polishing [1], airbag polishing [2], magnetorheological polishing [3], electrorheological polishing [4], shear thickening polishing [5], and chemical mechanical polishing [6], etc.…”

Manufacture of primary mirror segments for the Giant Magellan Telescope

“…We made a number of improvements in methods and equipment for fabrication and testing during and after the manufacture of Segment 1. [6] While some of the equipment upgrades delayed the start of work on the optical surface of Segment 2, so far they appear to be paying off in much more efficient figuring of Segment 2. We are confident that these improvements, and others that we are making based on the experience with Segment 2, will continue to accelerate production of the remaining segments.…”