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UH/IfA commitments to ATST and its science

This article discusses the SOLARC off-axis reflecting coronagraph, the world's largest, and its operational capabilities as a test-bed for the Advanced Technology Solar Telescope (ATST). It explores the design concept, alignment issues, and post-focus instrumentation, including an imager and spectrograph. The article also highlights the contributions of the University of Hawaii's Institute for Astronomy (UH/IfA) to the ATST project.

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UH/IfA commitments to ATST and its science

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  1. UH/IfA commitments to ATST and its science Principle NSF/ATST grant participants: J.R. Kuhn, R. Coulter, H. Lin, D. Mickey • Some of the most exciting science in the next decade will come from coronal ATST observations • SOLARC: The worlds largest off-axis reflecting coronagraph is on Haleakala (built as partnership with AFOSR, NASA) • Lessons learned for ATST

  2. Images aren’t enough (from Chen et al., Low, Gibson)

  3. Our “dark energy problem”

  4. Why an IR (reflecting) off-axis coronagraph? • Zeeman magnetic sensitivity • Lower scattered sky background • Lower scattered instrument optics background • Lowered scattered dust background

  5. Scattering sources • Atmosphere • “seeing” • aerosols • atomic molecular scattering • Telescope • diffraction • mirror roughness • mirror dust

  6. Atmospheric backgrounds

  7. Optical backgrounds Mirror roughness Diffraction 4.0m 0.5m

  8. SOLARC • Reflecting - broadband, IR • Off-axis - unobscured, low scattering, relatively fast optical configuration

  9. SOLAR-C Gregorian focus 8m f.l. M2 M1: 0.5m F/3.7 F/20, efl 8m, prim-sec 1.7m 0.5m, 1.5m fl primary 55mm, secondary l/10 p-v figure diff. Limited @ 1micron over 15’fov 10.4 deg tilt angle

  10. Measured secondary PSF Over 5 orders of magnitude no mirror or other spurious scatter terms detected l = 656 nm Short exposure images nearly diffraction limited

  11. Prime focus occulter issues Secondary Prime focus, occulter Final image Lyot stop Primary (M2 illumination from limb)

  12. SOLARC photosphere observations achieve high resolution

  13. Summary • The SOLARC off-axis coronagraph on Haleakala is operational as test-bed • Optical fabrication and alignment issues are quite comparable to a conventional telescope • Post-focus instrumentation includes • 1-5 micron imager • Near and mid-IR spectrograph

  14. UH/IfA ATST Contributions • SOLARC design concept and testbed • Sky brightness monitor design and fabrication • Haleakala site survey activities • Infrared spectrograph design concepts (coronal and disk) • Contributions toward global ATST EA/EIS studies

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