Feasibilty/Concept Study Mid Term Status Review M2 & M3 T.A. Sebring 13,14 July 2005 Feasibilty/Concept Study Mid Term Status Review

M2 and M3 Are Too Large To Make Monolithic Make in Segments Dimensions Approximate PM Segments Can Use Same Panel & Process Bond Together? SiC Brazed by Boostec (FR) for Herschel Telescope @~3.5m Epoxy Bonding for CFRP Expensive…Risky? Metrology? Mount as Segments? Require Stable Back Structure Increased Mass & Complexity Active or Passive? 1.6m 2.26m 3.2m 1.3m 1.9m 2.6m

Feasibilty/Concept Study Mid Term Status Review M2 is 3.2 meters in diameter Formed from 4 panels @ 10kg/m2 Panels Maintain Figure over Full Gravity Range Mounted on 3 Points Manufacturing Process Identical to Primary Mirror Panels 13,14 July 2005 Feasibilty/Concept Study Mid Term Status Review

Notional Panel Mounting Locations Anticipate Bipod Flexures at Each Point Panels Will Have Mounting Features

First Layer of Support Truss CFRP with Bonded Invar or CFRP Joints

Upper Support Truss Interface to M2 Positioning Hexapod Superimposed on First Truss Layer

Notional Illustration of Truss Top View

Side View Shows Truss Top Layer, Bottom Layer, Notional Struts Red Boxes are Voicecoil Actuators with Internal Position Sensors

Mirror Mounts to Nutator Assembly M2 Support Nutator Assembly Mirror Mounts to Nutator Assembly Rigid Body Positioning of M2/Nutator Assembly Via Hexapod Entire Assembly Weighs ~ 270 kg 80 kg Mirror, 40 kg Truss, 100 kg Nutator, 50 kg Hexapod

M2/M3 Mechanisms M2 Nutator M2 Hexapod S. Radford Designed Nutator for ALMA Probably Scaleable to Some Performance Level Increases Mass at M2 M2 Hexapod ALMA Hexapod Custom Designed/Built by Polytec PI Polytec PI Will Provide Concept Design and Cost for CCAT

M3 Fabrication May Be Possible to Manufacture as Monolith Plano Figure Implies That Any Flat > 2.6 m in Diameter Could Serve as Mandrel GrEp Mirror Formed on Mandrel Seems Acceptable Flexure Mounting to Rotation Turret Had Considered Fast Tip/Tilt Mount for M3 If Mount Has Unacceptable Residual Jitter Use High Bandwidth Guider for Input Large Aperture Should Average Atmospheric Effects in IR Inertial Sensors Possible but Expensive to Sufficient Resolution Resolution: Don’t Do It Unless Necessary

M3 Rotator & Tip/Tilt? SOAR M3 Turret Tip/Tilt 0.18 arc sec repeatability DC Torque Motor Large Instrument Bearings Inductosyn Encoder Should Be Scaleable Requires Attention to Detail Tip/Tilt Not Currently Part of Baseline Will Be Expensive and Difficult Need to Characterize Requirements Complex and Challenging System

Remaining Work for This Phase Find Possible Vendors Develop Baseline Cost Estimate Assess Maturity of Constituent Technologies Investigate Approach to Calibration Alignment of M2/M3 Segments CMM Setup Use of Telescope Calibration WFS Identify Critical Risk Elements and Associated Approaches to Mitigation