Samuel C. Barden*(AAO), Arjun Dey (NOAO), Brian Boyle (ATNF), Karl Glazebrook (JHU)

1. KAOS: kilo-aperture optical spectrograph Samuel C. Barden*(AAO), Arjun Dey (NOAO), Brian Boyle (ATNF), Karl Glazebrook (JHU) *Email scb@aaoepp.aao.gov.au; phone +61 2 9372 4852; fax +61 2 9372 4880; web www.aao.gov.au KAOS (Kilo-Aperture Optical Spectrograph) is a facility capable of taking detailed spectroscopy of millions of objects in the Universe to answer fundamental questions relating to the equation of state of dark energy and to how the Milky Way galaxy formed.  KAOS can observe ~5000 targets in a 1.5° field at the prime focus of Gemini with a 4-element corrector, atmospheric dispersion compensator (ADC), and an Echidna-style fiber optic positioner.   The ADC doubles as a wobble plate to cancel out the wind buffeting. The fibers (reconfigurable in less than 10 minutes) feed to an array of 12 spectrographs located in the pier. The spectrographs are capable of providing spectral resolving powers of a few thousand up to about 30,000 or 40,000. The background image is from the NOAO Deep Wide-Field Survey (B.Jannuzi, A.Dey, NDWFS team/NOAO/AURA/NSF) • The figures above show clockwise from upper left: • The efficiency of 60-meter long optical fiber. • The raytrace schematic of the wide-field corrector. • A solid model of the top end corrector assembly. • A schematic showing how the fibers are arranged and positioned. • A solid model of the full set of ~5000 fiber spines. • A solid model of Gemini with KAOS showing the spectrographs located in the pier lab. • The circle and array of small circles give a full scale representation of the physical diameter of the focal surface and location of 4800 fibers. • Gemini is exploring the possibility of implementing a Wide-Field, Fiber-Fed, Optical, Multi-Object Spectrograph (WFMOS) as one of its next generation of instruments. A feasibility study is now ongoing with the AAO, CADC, JHU, NOAO, Durham, Oxford, and Portsmouth working together. It is hopeful that WFMOS might be on-line early in the next decade. The figures above show one possible spectrograph concept. Twelve spectrographs are implemented each viewing 400 fibers on 4k by 4k CCD’s. VPH gratings are used to get R=2000 to 20,000. R=30000 can be achieved through the use of R4 echelles. These figures show the overall system efficiency of photons detected to photons incident on the telescope excluding seeing losses (left) and the S/N detection threshold for 1 hour exposures at 500 nm in for three different resolution regimes. Acknowledgments: The KAOS concept and scientific application was developed by a large group of collaborators. Further information can be obtained from http://www.noao.edu/kaos. Members of the original KAOS team are: Sam Barden (NOAO), Chris Blake (UNSW), Joss-Bland Hawthorn (AAO), Brian Boyle (ATNF), Michael Brown (NOAO), Matthew Colless (AAO), Warrick Couch (UNSW), Len Cowie (IfA/UH), Arjun Dey (NOAO), Daniel Eisenstein (Univ. of Arizona), Ken Freeman (MSO/ANU), Karl Glazebrook (Johns Hopkins Univ.), Charles Harmer (NOAO), Buell Jannuzi (NOAO), Francis Keenan (Queens University, Belfast), Rolf Kudritzki (IfA/UH), Ming Liang (NOAO), Eric Linder (Lawrence Berkeley Laboratory), Anna Moore (formerly of the AAO), David Meyer (Northwestern Univ.), Jeremy Mould (NOAO), Joan Najita (NOAO), Robert Nichol (Carnegie Mellon Univ.), Knut Olsen (NOAO), John Peacock (ROE), James Robinson (NOAO), Rick Robles (NOAO), Hee-Jong Seo (Univ. of Arizona), Thaisa Storchi-Bergmann (UFRGS, Brasil), Steve Strom (NOAO), Nick Suntzeff (NOAO), Alex Szalay (Johns Hopkins Univ.), Rosie Wyse (Johns Hopkins Univ.).