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Magellan F/15 Chopping Secondary Magellan SAC Meeting Laird Close (Principle Investigator)

Magellan F/15 Chopping Secondary Magellan SAC Meeting Laird Close (Principle Investigator) Victor Gasho (Program Manager) September 24, 2005. Project Overview. Develop Magellan f/15 Chopping Tip-Tilt secondary Si clad SiC Mirror

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Magellan F/15 Chopping Secondary Magellan SAC Meeting Laird Close (Principle Investigator)

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

  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. Brief Project History 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). • 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. • A conceptual design was made ~1995, and contract placed with Lockheed to produce a tip-tilt chopping SiC secondary for ~900k$. • Polished Reaction Bonded SiC was found rougher than ~100A rms --project canceled. • In 2002 a 1.3 M$ 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.

  4. Preliminary Specs of Mirror

  5. MIRAC 4 and f/15 Secondary Mounted

  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. F/15 Secondary Assembly

  8. F/15 Secondary SiC Mirror

  9. PI Stage Chopping Simulation

  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. Example of Large Si Clad SiC Mirror

  12. MIRAC and Tip Tilt Camera

  13. Camera and Optics 25 mm travel x-y stage (0.3 mm accuracy) ~100” MIRAC FOV (~60mm Optics)

  14. Tip/Tilt Camera • Andor iXon DV-860 Camera

  15. Schedule

  16. Questions?

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