Oct 30, 2003PFIS - Student Wkshop1 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? –Big telescope  Big instrument optics –Making good use of your observing time New Ones –The SALT prime focus –New optics: holography

Oct 30, 2003PFIS - Student Wkshop2 Making a Powerful Astronomical Instrument Efficiency –Minimize loss in optics –Extract maximum data Spectroscopy: composition, motion Polarimetry: structure, magnetic field –Observe many objects simultaneously Resolution –Spread out colors more Spectrograph Spectro- polarimeter Imager Imaging High-Speed

Oct 30, 2003PFIS - Student Wkshop3 Perseus Cluster of Galaxies Perseus A in Hydrogen Light Imaging Spectroscopy Filters Fabry-Perot etalons (selects wavelength) Many wavelengths

Oct 30, 2003PFIS - Student Wkshop4 Hubble Deep Field (South) Up to 100 Spectra Slitmasks (selects objects) Filters VPH Grating (Splits colors) Multi-Object Grating Spectroscopy

Oct 30, 2003PFIS - Student Wkshop5 Optics Design Challenges 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 Sodium Chloride (salt) Fused Quartz Fused Silica Calcium Fluoride 300 nm UVBlueGreenYellowRedInfrared Wavelength PFIS range Collimator Camera Telescope Focus Grating CCD detector

Oct 30, 2003PFIS - Student Wkshop6 Collimator Fused Quartz CaF 2 Fused Quartz CaF 2 Fused Silica (NaCl)

Oct 30, 2003PFIS - Student Wkshop7 Camera CaF 2 Fused SilicaCaF 2 Fused Silica NaCl (Fused Silica)

Oct 30, 2003PFIS - Student Wkshop8 Multi-object Spectroscopy with custom masks Laser-cut slit masks Unique mask cut for each individual observation Slit mask magazine will hold 30 multi-object slit masks Reload once/ week Giant Elliptical Galaxy NGC1399 at focus of telescope: Mask with slits cut in it to let through selected nebulae in galaxy

Oct 30, 2003PFIS - Student Wkshop9 New Challenges: on SALT Prime Focus Tracker Prime Focus Spectrograph Motion of tracker and illumination of primary mirror as an object sets The instrument must be:

Oct 30, 2003PFIS - Student Wkshop10 Small and Lightweight DEIMOS on Keck 3x4m, 9000 kg PFIS on SALT 1.5x2m, 500 kg Open space frame welded from hollow square tubes of invar (low- expansion stainless steel)

Oct 30, 2003PFIS - Student Wkshop11 Stiff CAD 3D model of PFIS structure FEA ("Finite Element Analysis") showing how it bends under gravity Plus model of how tracker moves and PFIS optics shows how image moves during exposure

Oct 30, 2003PFIS - Student Wkshop12 Remote control Filter Jukebox Grating Jukebox Shutter Slitmask Jukebox Waveplate Rotator Etalon Insertors Camera Articulation

Oct 30, 2003PFIS - Student Wkshop13 Compact New technology: Grating "grooves" formed by hologram Interference pattern from two laser beams on gelatin film Efficient, large, inexpensive custom gratings

Oct 30, 2003PFIS - Student Wkshop14 Astronomical Instrumentation is a exciting business. A big demand for: Astronomers Physicists Optical Engineers Mechanical Engineers Software Engineers