Primary Mirror (Reflector) T.A. Sebring ITT Industries Rochester, NY Xinetics Inc., Devens, MA Composite Mirror Applications Tucson, AZ 13,14 July 2005 Feasibilty/Concept Study Mid Term Status Review

Issues In PM Design Configuration Trades Segment Issues Active vs Passive Segment Alignment Panel/Truss vs Panel/Raft/Truss Configurations Segment Issues Segmentation Geometry Segment Support Strategies Segment Manufacturing Approach Actuation and Sensing Panel Position Sensors Calibration Alignment Sensors M1/M2 Alignment Sensing M1 Is Budgeted to Achieve __ µ RMS Surface Figure With Respect to the Nominal Design Shape…This is ~2.5x Better Than ALMA

Active vs Passive Segment Alignment Best Operating Submm Primary Mirrors Currently: CSO 10m ~10-14 µ RMS Active Using Thermal Actuators SMA 10m ~14 µ RMS Passive, CFRP Truss and Panels APEX 10m~15µ RMS Passive, CFRP Truss & Al Panels CCAT is 25m Diameter and System Specified at 9.3 µ RMS Conversations with Vertex RSI Indicate They Do Not Believe that ALMA Technology (passive overconstrained panels on dimensionally stable truss) Can be Extrapolated Consensus Among Study Participants that CCAT Needs to Have Actively Controlled Panels to Meet Specifications Decision Has Been Made to Utilize Steel PM Truss (<< Cost than CFRP) and to Actively Control Panel Rigid Body Position

Panel/Truss vs Panel/Raft/Truss Configurations Error Budget Analysis Show that Either Approach Could be Made to Work To Be Continued Part Count: Higher for Rafted Panels Rafts, Adjusters for Panels, More Panels, Same Actuators for RAFT Rigid Body Positioning Weight: Higher for Rafted Design Sebring Calculates ~3x Higher for Rafted Design…Drives Truss and Mount Design Cost: Depends on Cost of Large Segments…If Panels <$6-7 million, then Panel/Truss is Probably Cheaper Adjustment: Raft Design Requires CMM of High Precision (~1 micron) to Adjust Panels on Raft…Not Required for Panel/Truss Design

PM Study Point Design Steel Bolted Truss Cost Effective to Manufacture via Existing Industrial Capabilities Easily Test Assembled, Packaged, Shipped, Assembled On Site Provides 3 Mount Points per Segment on Front Surface Back Surface of Truss Engineered to Mate with Telescope Mount Truss Dimensionality Controlled by Manufacture…Not Assembly

PM Study Point Design Segmentation Facilitates Replication 6 Annular Rings Segments Max 2m x 2m Wide Latitude in Design Facilitates Replication Only 6 Different Types Size Compatible With Several Manufacturing Techniques Geometry Needs Study Edge Sensors Work Better With Some Configurations 3 Point Support of Segments May Drive Shape

PM Study Point Design Mounting on 3 Kinematic Points Actuation Segments Must Maintain Shape Over Gravity Range Bipod Flexure Mounting Eliminates Segment Deformation by Truss Actuation Segments Adjust in Tip/Tilt/Piston Three Actuators per Segment Actuators Mount to Front Surface Nodes of Truss

Discussion of Approach Very Simple: Low Part Count & Complexity Low Mass: Enables Lighter Truss and Mount, Smaller Mount Drives, Better Structural Performance and Scanning Rates/Accelerations Not Overconstrained: Panel Figure is Self Determined No Adjustment Required (or Possible) Changes in Truss Dimensions (Gravity or Thermal) Do Not Affect Panel Figure 3 Point Support is Sparse, Panels Must be Very Stiff to Minimize Gravity Driven Sag Initial Analysis Indicates Major Content of Deformation is Power and Can Presumably be Remediated by Focus Shift Panels This Stiff and Light May be Expensive

Actuators Requirements Document Written & Distributed Length: < 50 cm Diameter: <25 mm <10 kg/actuator Range: >20mm Coarse >10mm Fine Support Panel Lateral Loads Internal Position Sensors System to Include all Electronics, Wiring, Software Vendors Interested: Polytec PI, Auburn, MA Danaher Motion, Salem, NH Working on Initial Concept Designs and Cost Estimates Manufacturers Judge Actuators Well Within SOTA Need to Fund Engineering Concept Design in Next Phase

Panels Focus on Replication Technology Manufacture of Precision Mandrels One Time Only Six Mandrels Required for Current Segmentation Scheme Specular Finish for Panels Desired Enables IR Guiding Enables IR Sparse Aperture Interferometry Science Provides Lower Surface Emissivity and Better Thermal Performance Panel Precision of ~5 µ RMS as a Goal Includes All Contributions: Mandrels, Replication, Thermal, Gravity, Ageing, Wind Concepts Utilizing ALMA Panel Technology Held as Backup Position

Three Panel Studies In Work Composite Mirror Applications, Tucson, AZ GrEp/Al/GrEp Sandwich Successfully Used by MAN for SMT, Achieving 14 µ RMS Low CTE, High Specific Stiffness Xinetics Inc., Devens, MA Nanolaminate Front Shell (LLNL Technology) Laminated to SiC Lightweighted Support Structure Proprietary Casting/Sintering Process ITT Industries, Rochester, NY (Former Kodak GSD) Borosilicate Glass Forming Precision Slumping of Glass Over Mandrels Proprietary Process for Forming Lightweight Core Between Face and Back Sheets

Segment Coating Required for Glass and GrEp Panels Panel Requirements Call for Manufacturers to Specify Compatible Coating/Stripping Process 2m Capacity DC Magnetron Coating Facility Not Particularly Expensive VISTA Chamber Large Area Coating Single Pass Low Pumping Volume Short Throw High Energetics Dense Deposition Durable Coatings