Wide Field Optical Spectrograph - WFOS Architecture ...
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Context: WFOS is a first light instrument. The 2016/2017 OMDR phase concluded that the previous concept had insurmountable technical challenges. During the OMDR and WFOS Conceptual Design 1 phases, fiber and reconfigurable (Xchange) spectrograph architectures were developed (2017/2018). Top: Illustrations of the sampling of the TMT focal plane for the Xchange (far left) and fiber fed forms of the WFOS instrument when sky nodding. 7’ diameter field is for 4 modular spectrographs with 22” pitch, 100% overlap fiber positioners. Left: Xchange-WFOS instrument design concept (upper) and optical layout (lower) showing articulated camera positions for high spectral resolution modes. Right: Modular Fiber-WFOS instrument design concept showing the full potential 9 spectrographs and 700 fiber collectors over 10’ field (baseline is 4 spectrographs). Background subtraction with Fibers Analysis shows that for observations lasting many hours, requiring sky subtraction precision of 0.1%, negligible fiber systematics are expected when sky- nodding. https://www.ucolick.org/home/facilities/instruments/wfos.html Principal investigator: Kevin Bundy Project manager: Maureen Savage (UC Observatories) Project scientist: Chuck Steidel (Caltech) Cross partnership development team Downselection process and timeline: - Technical review 4/5 April, 2018 – Concluded all architectures are technically feasible - Re-assessment of top level WFOS science requirements by SAC, using community input – 26 July, 2018 - Downselect to single architecture – Early October 2018 8.3’ 3’ 1” 60 targets 155 sky-target pairs – 4 spectrographs Key Science areas driving the designs: - IGM/CGM tomography and characterization - Stellar populations throughout the local group - High redshift galaxy evolution - Transient science Xchange-WFOS Fiber-WFOS Spectral resolution Baseline 1500 – 5000, grating dependent Fixed 3500 to 5000. Binning for lower resolution Limiting magnitude ~24.1 g(AB) in 1hr S/N=5 ~24.0 g(AB) (Compare to 22.1 for GMOS) Wavelength coverage 0.31-1.0μm continuous at R=1500. 40nm in the blue, 140nm in the red at R=4500 0.31-1.0μm continuous at R=5000 Xchange-WFOS Fiber-WFOS - baseline 4 spectrographs Focal plane for 9 spectrographs Wide Field Optical Spectrograph - WFOS Architecture Downselect Slit based monolithic - versus - fiber-fed modular
Transcript of Wide Field Optical Spectrograph - WFOS Architecture ...
Context:WFOSisafirstlightinstrument.The2016/2017OMDRphaseconcludedthatthepreviousconcepthadinsurmountabletechnicalchallenges.DuringtheOMDRandWFOSConceptualDesign1phases,fiberandreconfigurable(Xchange)spectrographarchitecturesweredeveloped(2017/2018).Top:IllustrationsofthesamplingoftheTMTfocalplanefortheXchange(farleft)andfiberfedformsoftheWFOSinstrumentwhenskynodding.7’diameterfieldisfor4modularspectrographswith22”pitch,100%overlapfiberpositioners.Left:Xchange-WFOSinstrumentdesignconcept(upper)andopticallayout(lower)showingarticulatedcamerapositionsforhighspectralresolutionmodes.Right:ModularFiber-WFOSinstrumentdesignconceptshowingthefullpotential9spectrographsand700fibercollectorsover10’field(baselineis4spectrographs).BackgroundsubtractionwithFibersAnalysisshowsthatforobservationslastingmanyhours,requiringskysubtractionprecisionof0.1%,negligiblefibersystematicsareexpectedwhensky-nodding.
https://www.ucolick.org/home/facilities/instruments/wfos.html
Principalinvestigator:KevinBundy Projectmanager:MaureenSavage(UCObservatories)Projectscientist:ChuckSteidel(Caltech) Crosspartnershipdevelopmentteam
Downselectionprocessandtimeline:-Technicalreview4/5April,2018–Concludedallarchitecturesaretechnicallyfeasible-Re-assessmentoftoplevelWFOSsciencerequirementsbySAC,usingcommunityinput–26July,2018-Downselecttosinglearchitecture–EarlyOctober2018
8.3’
3’
1”
60targets 155sky-targetpairs–4spectrographs
KeyScienceareasdrivingthedesigns:
- IGM/CGMtomographyandcharacterization- Stellarpopulationsthroughoutthelocalgroup- Highredshiftgalaxyevolution- Transientscience
Xchange-WFOS Fiber-WFOS
Spectralresolution Baseline1500–5000,gratingdependent Fixed3500to5000.Binningforlowerresolution
Limitingmagnitude ~24.1g(AB)in1hrS/N=5 ~24.0g(AB)(Compareto22.1forGMOS)
Wavelengthcoverage
0.31-1.0μmcontinuousatR=1500.40nmintheblue,140nmintheredatR=4500
0.31-1.0μmcontinuousatR=5000
Xchange-WFOS Fiber-WFOS-baseline4spectrographs
Focalplanefor9spectrographs
WideFieldOpticalSpectrograph-WFOSArchitectureDownselect
Slitbasedmonolithic-versus-fiber-fedmodular
