Overview Instrument Role Science Niches Consortium science Kenneth Nordsieck University of Wisconsin Instrument Role Science Niches Consortium science Design Concept Performance Risks Oct 17, 2001 SALT PFIS PDR - Overview

Prime Focus Spectrograph Major instrument on the prime focus platform Straight-through focus position 8 arcmin diameter field of View Good response down to 320 nm Oct 17, 2001 SALT PFIS PDR - Overview

SALT PFIS PDR - Overview Instrument Role Provisional name: IMPALAS (Imaging Prime focus ArticuLAting Spectrograph) Common collimator with multi-object slitmasks (> 100 objects over 8 arcmin field) Visible beam 320 - 900 nm (first light) Simultaneous NIR beam 850 -1700 nm (growth path) Science niches: UV Spectroscopy (320 - 400 nm). Rare on large telescopes Dark sky; Good use of natural seeing large telescope Stellar, nebular lines; VUV features at low redshift Exploit SALT UV sensitivity and access to prime focus Oct 17, 2001 SALT PFIS PDR - Overview

SALT PFIS PDR - Overview Niches - cont Very high throughput, medium resolution spectroscopy Overcome sky background Galaxy stellar envelope kinematics Exploit VPH grating technology Fabry-Perot imaging spectroscopy Double etalon: unique on large telescope Efficient use of access to focal plane High Time resolution spectroscopy Rare on large telescopes Stellar astrophysics 0.1 sec – 100 sec Exploit CCD technology Spectropolarimetry. Rare on large telescopes. Photon starved technique Unique cross modes: medium resolution spectropolarimetry (Doppler tomography) Fabry-Perot imaging spectropolarimetry of scattered lines Oct 17, 2001 SALT PFIS PDR - Overview

Consortium Questionnaire Consortium roughly equally split between stellar and galactic/ cosmology programs Grating Spectroscopy (26 responses) Combination of wavelength and resolution Resolutions down to 500 Lower resolutions require good UV/ blue response Higher resolutions especially in red Slitmask configurations Long slit and slitmask programs evenly split Field of view Evenly split between narrower fields (< 4 arcmin) and largest possible fields (8 arcmin) Oct 17, 2001 SALT PFIS PDR - Overview

Consortium Questionnaire Time resolution (out of 26) > 10 Hz [ 3 ] (Requires high-speed readout) 1 - 10 Hz [ 6 ] (Requires high-speed readout) Several/ minute [ 13 ] one per night/none [ 18 ] Fabry-Perot Spectroscopy (17 responses) Combination of wavelength and resolution Few low resolution (single etalon) programs Wavelengths 400 – 900 nm Ha region important at higher resolutions Equal split absorption/ emission lines Equal split within and beyond F-P “bullseye” Oct 17, 2001 SALT PFIS PDR - Overview

Consortium Questionnaire Spectropolarimetry (10 Responses) Combination of wavelength and resolution UV/ blue response important at low resolution Ha programs at highest (reduced slit) resolution Linear spectropolarimetry - all Circular spectropolarimetry – 30% Most important: polarimetric precision, efficiency NIR Upgrade Path 38% would use it some; 54% would use it a lot 76% of NIR users would use simultaneous IR/ Visible Oct 17, 2001 SALT PFIS PDR - Overview

SALT PFIS PDR - Overview IMPALAS Layout Oct 17, 2001 SALT PFIS PDR - Overview

SALT PFIS PDR - Overview Structure Oct 17, 2001 SALT PFIS PDR - Overview

Grating Resolution-Wavelength 5 VPH gratings + 1 conventional R = 500 – 6500 (0.9” slit) 320 – 900 nm Oct 17, 2001 SALT PFIS PDR - Overview

SALT PFIS PDR - Overview Sensitivity VPH mode: low res = 780 l/mm; med res R = 4000 Competitive over entire wavelength range; superior in UV-blue Oct 17, 2001 SALT PFIS PDR - Overview

SALT PFIS PDR - Overview Risks In the Concept Proposal, these risks were identified (technical, cost, and schedule risk) Optics complexity (technical, cost, schedule) NaCl elements (technical) Structure – flexure, weight, articulation, mechanisms (technical, cost, schedule) All addressed in detail in the package Oct 17, 2001 SALT PFIS PDR - Overview