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Further Progress on the SALT 11- meter telescope and the Prime Focus Imaging Spectrograph

Further Progress on the SALT 11- meter telescope and the Prime Focus Imaging Spectrograph. Eric B. Burgh SALT/PFIS Instrument Scientist. The Southern African Large Telescope. SALT is based on the Hobby-Eberly Telescope (HET). 11 m segmented spherical primary Fixed altitude design

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Further Progress on the SALT 11- meter telescope and the Prime Focus Imaging Spectrograph

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  1. Further Progress on the SALT 11- meter telescope and the Prime Focus Imaging Spectrograph Eric B. Burgh SALT/PFIS Instrument Scientist

  2. The Southern African Large Telescope SALT is based on the Hobby-Eberly Telescope (HET) • 11 m segmented spherical primary • Fixed altitude design • Prime focus instrument package

  3. 11-meter diameter primary mirror constructed from 91 individual 1-meter hexagonal, spherical mirrors 11.1 meters (36.4 feet) 9.8 meters (32.2 feet)

  4. Shack-Hartmann wavefront sensor • Course alignment with 91 element lenslet array • Fine alignment with 7 x 91 lenslet array • capture range ± 3 arcsec • can measure low-order Zernike terms for individual segments • - diagnose mount errors

  5. PFIS Rotation Stage and Cable Wrap SAC

  6. The Prime Focus Imaging Spectrograph • First generation, all purpose spectrograph for SALT • Optical Imaging 320 – 900 nm. • All-refractive collimator and camera utilizing crystals for UV throughput • Upgrade capability for infrared camera

  7. Optics: • Fused Silica, CaF2 and NaCl

  8. Optomechanics • All optics currently being mounted by The Pilot Group

  9. The Prime Focus Imaging Spectrograph Grating Server Collimator Optics Camera Tube Detector Dewar Slit Mask Server Waveplate Mechanism Filter Server Articulation Rail Open Truss Structure Fabry Perot Etalons

  10. Open Truss structure • Welded Hollow Invar Box Beam (Rutgers Machine Shop) • Mass = 112 kg

  11. PFIS Mechanisms

  12. The Prime Focus Imaging SpectrographNiche Science • Ultraviolet Spectroscopy • to the atmospheric limit (~320 nm) • Spectropolarimetry • Fabry-Perot Spectroscopy • High-time-resolution spectroscopy • 0.1 – 100 sec • Volume Phase Holographic (VPH) Gratings • High throughput, low scatter • Tunable efficiency } Rare on large telescopes

  13. Laser-cut slit masks Unique mask cut for each individual observation Slit Server will hold 30 multi-object slit masks Studies of multiple objects in field of view Best utilizes CCD real estate E.g. Chemical abundances and kinematics of Planetary Nebulae in NGC 1399 The Prime Focus Imaging SpectrographMulti-object Spectroscopy

  14. The Prime Focus Imaging SpectrographTechnical Challenges } • Prime Focus: • Weight/space constraints • Accessibility • Wavelength coverage: • Crystals (CaF2 and NaCl) • Anti-reflection coatings (0.5% reflections) • High UV Quantum Efficiency CCDs (Marconi) • VPH gratings: • Articulating Camera • Multiple configurations: • Complex mechanisms/interfaces Similar to spaceflight instrumentation

  15. The Prime Focus Imaging SpectrographCurrent Status • All optics fabricated, coated, and being mounted now – delivery in two weeks. • Most mechanisms built and tested: • Slitmask, Waveplate, Grating, Filter, Articulation, Etalon, Focus, Beamsplitter • Structure fabricated and heat treated, still needs machining and painting – delivery in a few weeks. • Detector CCDs mosaiced and on-sky tests now – delivery in mid-May.

  16. The Prime Focus Imaging Spectrograph Upcoming Schedule: • Assembly and alignment to begin upon arrival of structure and optics – lasts 3 months. • Testing and calibration – lasts 3 months. • Shipping to South Africa in November 2004 • Installation and commissioning – lasts 6 months

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