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Old Challenges What kind of scientific observations? Big telescope  Big instrument optics

The Prime Focus Imaging Spectrograph – Old Challenges and New Ones K. Nordsieck, Principal Investigator Jeff Percival, Eric Burgh, Michael Smith Univ of Wisconsin Ted Williams, Chuck Joseph Rutgers University Darragh O'Donoghue + SAAO. Old Challenges What kind of scientific observations?

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Old Challenges What kind of scientific observations? Big telescope  Big instrument optics

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  1. The Prime Focus Imaging Spectrograph – Old Challenges and New OnesK. Nordsieck, Principal InvestigatorJeff Percival, Eric Burgh, Michael SmithUniv of WisconsinTed Williams, Chuck JosephRutgers UniversityDarragh O'Donoghue + SAAO • Old Challenges • What kind of scientific observations? • Big telescope  Big instrument optics • Making good use of your observing time • New Ones • The SALT prime focus • New optics: holography PFIS - Student Wkshop

  2. Efficiency Minimize loss in optics Extract maximum data Spectroscopy: composition, motion Polarimetry: structure, magnetic field Observe many objects simultaneously Resolution Spread out colors more High-Speed Imager High-Speed Imaging Spectrograph Imaging Spectro- polarimeter Making a Powerful Astronomical Instrument PFIS - Student Wkshop

  3. Fabry-Perot etalons (selects wavelength) Many wavelengths Perseus A in Hydrogen Light Perseus Cluster of Galaxies Imaging Spectroscopy Filters PFIS - Student Wkshop

  4. Filters VPH Grating (Splits colors) Up to 100 Spectra Hubble Deep Field (South) Multi-Object Grating Spectroscopy Slitmasks (selects objects) PFIS - Student Wkshop

  5. 300 nm 400 500 600 700 800 900 UV Blue Green Yellow Red Infrared Wavelength PFIS range Fused Silica Fused Silica Fused Silica Fused Silica Fused Silica Calcium Fluoride Calcium Fluoride Calcium Fluoride Sodium Chloride (salt) Calcium Fluoride Fused Silica Calcium Fluoride Sodium Chloride (salt) Calcium Fluoride Fused Quartz Fused Quartz Calcium Fluoride Fused Quartz Optics Design Challenges CCD detector Camera Grating • For highest efficiency: use lenses instead of mirrors • Need many lenses to correct color aberration  CAD • Wavelength range: require crystals to work into UV • Lenses need to be very large (up to 25 cm) • Assembled into large holders with coupling fluid Collimator Telescope Focus PFIS - Student Wkshop

  6. Collimator Fused Quartz Fused Quartz Fused Quartz CaF2 CaF2 CaF2 (NaCl) PFIS - Student Wkshop Fused Silica CaF2

  7. CaF2 Camera CaF2 Fused Silica CaF2 (Fused Silica) Fused Silica (Fused Silica) NaCl (Fused Silica) PFIS - Student Wkshop

  8. Laser-cut slit masks Unique mask cut for each individual observation Slit mask magazine will hold 30 multi-object slit masks Reload once/ week Mask with slits cut in it to let through selected nebulae in galaxy Multi-object Spectroscopy with custom masks at focus of telescope: Giant Elliptical Galaxy NGC1399 PFIS - Student Wkshop

  9. New Challenges: on SALT Prime Focus Spectrograph Prime Focus Tracker Motion of tracker and illumination of primary mirror as an object sets The instrument must be: PFIS - Student Wkshop

  10. Open space frame welded from hollow square tubes of invar (low- expansion stainless steel) Small and Lightweight DEIMOS on Keck 3x4m, 9000 kg PFIS on SALT 1.5x2m, 500 kg PFIS - Student Wkshop

  11. CAD 3D model of PFIS structure Plus model of how tracker moves and PFIS optics shows how image moves during exposure FEA ("Finite Element Analysis") showing how it bends under gravity Stiff PFIS - Student Wkshop

  12. Grating Jukebox Etalon Insertors Slitmask Jukebox Filter Jukebox Waveplate Rotator Shutter Camera Articulation Remote control PFIS - Student Wkshop

  13. Compact New technology: • Grating "grooves" formed by hologram • Interference pattern from two laser beams on gelatin film • Efficient, large, inexpensive custom gratings PFIS - Student Wkshop

  14. Astronomical Instrumentation is a exciting business. A big demand for: Astronomers Physicists Optical Engineers Mechanical Engineers Software Engineers ........... PFIS - Student Wkshop

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