1. September 24, 2005 Magellan F/15 Chopping Secondary 1 Magellan F/15 Chopping Secondary Magellan SAC Meeting Laird Close (Principle Investigator) Victor Gasho (Program Manager) September 24, 2005

2. September 24, 2005 Magellan F/15 Chopping Secondary 2 Project Overview Develop Magellan f/15 Chopping Tip-Tilt secondary –Si clad SiC Mirror Lightweight (~8 kg) using egg-crate rib structure and thin face-sheet Very Stiff (~900Hz) Low CTE (2ppm/C) High thermal conductivity (better than aluminum) – Physik Instrumente HVPZT Tip/Tilt/Chop Stage Capable of 2 Axis chopping Reactionless (98% Goal) High speed (~1 kHz)

3. September 24, 2005 Magellan F/15 Chopping Secondary 3 Brief Project History 1)From the beginning it was recognized that Magellan needed a low emissivity secondary mirror. Factor of ~3 gain in exposure time possible for Mid-IR science at Cass. 2)A conceptual design was made ~1995, and contract placed with Lockheed to produce a tip-tilt chopping SiC secondary for ~900k$. 3)Polished Reaction Bonded SiC was found rougher than ~100A rms --project canceled. 4)In 2002 a 1.3 M$ NSF MRI award (PI Close) was made to provide Magellan with an adaptive secondary with tip-tilt capabilities to be provided in the funded phase 1. Full AO was to be provided at a later date from another unidentified grant. 5) Applications for enough money to finish & commission the AO secondary were turned down by AODP (twice) and TSIP (once). No further funds identified at this point. 6) NSF has denied year 3’s funding due to risk, cost, & management. NSF expects SAC decision on a successful approach by end of Sept. NSF approved CDR required in fall. 7) On the Sept 9, 2005 the SAC unanimously directed Close & Gasho to pursue a lightweight f/15 tip-tilt chopping secondary and not continue with the adaptive secondary. 8) Here is an overview of how we can accomplish the original goals of a low emissivity tip-tilt chopping secondary for MIRAC4 and deliver the funded MRI science (and optical speckle).

4. September 24, 2005 Magellan F/15 Chopping Secondary 4 Preliminary Specs of Mirror MaterialSi Clad Silicon Carbide Diameter641.47 mm Mirror Mass~8.0 kg Mirror Surface Error40 nm rms Mirror Surface Roughness20 Å rms Support Mass~160 kg Mirror Moment of Inertia @ CG~0.30 kg/m 2 System Resonance Frequency>300 Hz Chopping Movement+/- 45” sky @ 0.5 Hz +/- 16” sky @ 2Hz +/- 3.5” sky @ 10Hz Tip/Tilt Movement +/- 0.5” sky @ 100Hz Angular Resolution0.010” sky Chopping MechanismHVPZT Reactionless CoatingGemini Silver?

5. September 24, 2005 Magellan F/15 Chopping Secondary 5 MIRAC 4 and f/15 Secondary Mounted

6. September 24, 2005 Magellan F/15 Chopping Secondary 6 F/15 Secondary Swing Arm Swing Arm Allows for fast deployment. Borrowed from previous Magellan f/15 design. When in retracted position will intrude in aperature and block 0.15% light. Trade off of optical performance vs operational needs.

7. September 24, 2005 Magellan F/15 Chopping Secondary 7 F/15 Secondary Assembly

8. September 24, 2005 Magellan F/15 Chopping Secondary 8 F/15 Secondary SiC Mirror

9. September 24, 2005 Magellan F/15 Chopping Secondary 9 PI Stage Chopping Simulation

10. September 24, 2005 Magellan F/15 Chopping Secondary 10 Examples of Chopping Secondaries IRTF (Infrared Telescope Facility) Mirror diameter: 244 mm (SiC) Tip/Tilt range: ±250 µrad (PI PZT) 10 Hz chopping Resonant frequency: 490 Hz SOFIA Mirror diameter: 350 mm (SiC) Tip/Tilt range: ±10 mrad (CSEM Voice Coil) 20 Hz chopping Resonant frequency: 422 Hz UKIRT (United Kingdom Infra-Red Telescope) Mirror diameter: 314 mm (Zerodur) Tip/Tilt range: ±500 µrad (PI PZT) Resonant frequency: 280 Hz 6 Hz chopping

11. September 24, 2005 Magellan F/15 Chopping Secondary 11 Example of Large Si Clad SiC Mirror

12. September 24, 2005 Magellan F/15 Chopping Secondary 12 MIRAC and Tip Tilt Camera

13. September 24, 2005 Magellan F/15 Chopping Secondary 13 Camera and Optics ~100” MIRAC FOV (~60mm Optics) 25 mm travel x-y stage (0.3  m accuracy)

14. September 24, 2005 Magellan F/15 Chopping Secondary 14 Tip/Tilt Camera Andor iXon DV-860 Camera

15. September 24, 2005 Magellan F/15 Chopping Secondary 15 Schedule

16. September 24, 2005 Magellan F/15 Chopping Secondary 16 Questions?