1. The High Altitude Observatory (HAO) at the National Center for Atmospheric Research (NCAR) The National Center for Atmospheric Research is sponsored by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. COSMO Large Coronagraph Preliminary Design Review Mechanical Design Description Scott Sewell National Center for Atmospheric Research Boulder, Colorado November 16 & 17, 2015

2. COSMO PDR (November 16-17, 2015) Mechanical Design Description Mechanical Design Contributors HAO Instrumentation Group Phil Oakley Greg Card Pete Nelson (Sierra Scientific Solutions LLC) Haiying Zhang (Nanjing Institute of Astronomical Optics & Technology) Richard Blank(GL Scientific) Super-Tech Filters

3. COSMO PDR (November 16-17, 2015) Mechanical Design Description Mechanical Design Overview

4. COSMO PDR (November 16-17, 2015) Mechanical Design Description Mechanical Design Description Distributed Engineering and Fabrication Approach The COSMO Project Plan envisions a partnership between a Prime Contractor partner and a Central Engineering and Management Team within the High Altitude Observatory In 2014 a “Request for Information” process was conducted and which resulted in the identification of several potential partners for various observatory work packages as well as for overall construction project management o Site infrastructure, control building, dome enclosure design and construction efforts o Large coronagraph pier, equatorial mount and optical telescope assembly HAO will oversee top level requirements and interface definitions as well as lead the engineering effort for the filtergraph instrument

5. COSMO PDR (November 16-17, 2015) Mechanical Design Description Facilities and Infrastructure

6. COSMO PDR (November 16-17, 2015) Mechanical Design Description Building and Dome Overview Design heritage from Themis solar telescope (EIE Group-Italy) Improves air flow and seeing conditions around dome Minimizes aperture and dust entrainment within dome

7. COSMO PDR (November 16-17, 2015) Mechanical Design Description Lab Space and Pier Foundation Concept Pier is a hollow, steel reinforced concrete structure, mechanically isolated from the surrounding building Equipment is brought into the observatory through a 3m garage style door and raised to the observing floor via a hydraulic lift.

8. COSMO PDR (November 16-17, 2015) Mechanical Design Description Observatory HEPA System (Super-Tech Filter) Flanders 33,000 CFM HEPA filter systems (filter banks at bottom, below 14 HP motors). COSMO will require a pair of these systems to be able to prevent entrainment of dust carried by winds <10m/s. These systems are commonly employed for hospital surgical suite applications

9. COSMO PDR (November 16-17, 2015) Mechanical Design Description Large Coronagraph Overview

10. COSMO PDR (November 16-17, 2015) Mechanical Design Description Equatorial Yoke Mount (Zhang) Tip-Tilt plate to accommodate polar axis alignment due to fabrication errors Main RA bearings are large (140 kg) Timken bearings with heavy (2000 pound) custom pre-loads

11. COSMO PDR (November 16-17, 2015) Mechanical Design Description Tube vs. Truss FEA Preliminary work to evaluate collinearity of optical axis from objective lens through detector focal plane (very simple models were meshed for these results) Requirement for decenter is +/- 1.0 mm (COSMO-LC-TRD-48) Requirement for tilt errors is +/- 60 arc-seconds (COSMO-LC-TRD-48) Internal and external analyses suggest these are tight but not unachievable Hybrid Tube/Truss Decenter error of 0.3mm, tilt error of 18 arc-seconds Meets requirements (Zhang 2014.10.23) Serruier Truss Decenter error of 0.2mm, tilt error of 100 arc-seconds Almost Meets requirements, but study thinks the tilt error could be reduced to near zero with active alignment or counterweight system (Nelson 2014.10.24) Additional analysis will need to be performed to arrive at a final design approach but neither tube nor truss can be eliminated on performance alone

12. COSMO PDR (November 16-17, 2015) Mechanical Design Description Safety Shutter and Calibration Diffuser Assemblies (Nelson) Requirements Summary: To be able to protect equipment from intense irradiances in the event of an unplanned off- pointing situation Key Design Points: Normally closed, fail-safe spring loaded design Pneumatic or electric solenoid must be enabled to open Iris vanes close to ~95% for alignment purposes Flat fielding requires a relatively simple insertion mechanism for the diffusing material

13. COSMO PDR (November 16-17, 2015) Mechanical Design Description Occulter Station Overview Key Design Points: Water cooled occulting disk and post Occulter diameter must be computer controlled for different seasonal requirements Entire station must translate along optical axis for wavelength focusing Occulter disk must have radial and azimuthal control for selected off pointing studies Requirements Summary: Controls insertion and rotation of polarimetric calibration optics. Controls reflected and absorbed radiation loads. Mounted to a high capacity linear stage for focusing the coronagraph at different wavelengths.

14. COSMO PDR (November 16-17, 2015) Mechanical Design Description Variable Occulter (Nelson) Key Design Points: Water cooled system maintains highest temperatures to <65C with 20cc/s (pressure drop is 0.3 psi) 10 blade version is round to +/- 5 arc-seconds in image space Polished copper cone is 80% reflective Drive disk is rotated by a cable running up and down within the post Requirements Summary: Must accommodate approximately 2300W of solar irradiance delivered by the 1.5m objective lens. Must occult to 1.05R  with an accuracy of 2.5 arc seconds. Nominal diameter of 70mm must be continuously variable to accommodate seasonal changes and different wavelengths.

15. COSMO PDR (November 16-17, 2015) Mechanical Design Description Filtergraph Overview

16. COSMO PDR (November 16-17, 2015) Mechanical Design Description Pre-Filter Insertion Mechanism (Card) Design initially created for the Visible Spectro-Polarimeter

17. COSMO PDR (November 16-17, 2015) Mechanical Design Description Lens Cell Concept (Elements 4-6) (Oakley)

18. COSMO PDR (November 16-17, 2015) Mechanical Design Description Lens Cell Concept (Elements 7-11) (Oakley)

19. COSMO PDR (November 16-17, 2015) Mechanical Design Description Dual Lyot Filter – PBS Assembly Carrier

20. COSMO PDR (November 16-17, 2015) Mechanical Design Description HAO Lyot Filter Construction

21. COSMO PDR (November 16-17, 2015) Mechanical Design Description Hawaii 4RG Detectors (GL Scientific - Packaging, Markury Scientific – Readout and Interfacing) Stirling cooler cryostat design Mass is ~50 kg (plus additional off-filtergraph equipment) Focal plane is ~34mm from front window face (accommodates existing optical design) Considerable NRE will be required to produced these with requisite readout rates (additional ASICS must be placed outside the dewar but running warm is not expected to be an issue) 100 e- read noise can increase the speed of the readout <50 e- read noise requirements would required correlated digital sampling (CDS) (pixels are sampled before and after the integration) HOWEVER: Manufacturability issues exist (and cost is rising)

22. COSMO PDR (November 16-17, 2015) Mechanical Design Description Hawaii 2RG Detector Backup (GL Scientific - Packaging, Markury Scientific – Readout and Interfacing) Backup plan is butted 2k x 2k chips (2RG) 150 pixel gap between quadrants for Teledyne packaging 36 FPS with 1 ASIC per 2RG Pitch is 18 microns (rather than 15 microns for 4RG)

23. COSMO PDR (November 16-17, 2015) Mechanical Design Description Thanks! HAO Instrumentation Group Phil Oakley Greg Card Pete Nelson (Sierra Scientific Solutions LLC) Haiying Zhang (Nanjing Institute of Astronomical Optics & Technology) Richard Blank(GL Scientific) Super-Tech Filters