1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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