IRIS OIWFS Concept Study D. Loop1, M. Fletcher1, V. Reshetov1, R IRIS OIWFS Concept Study D. Loop1, M. Fletcher1, V. Reshetov1, R. Wooff1, J. Dunn1, G. Herriot1 A. Moore2, R. Dekany2, A. Delacroix2, R. Smith2, D. Hale2, J. Larkin3, L. Simard4, D. Crampton4, B. Ellerbroek4, C. Boyer4, L. Wang4 1NRC-Herzberg Institute of Astrophysics 2California Institute of Technology 3University of California Los Angeles 4TMT Observatory Corporation AO4ELT 2009 Conference June 25, 2009 TMT.IAO.PRE.09.036.DRF01

Outline We report on the concept study of the On-Instrument low order natural guide star WaveFront Sensors (OIWFS) for the TMT IRIS science instrument, a collaborative effort by NRC-HIA, Caltech, UCLA, TMT AO team, and TMT Instrument team. This includes work on sky coverage modeling, patrol geometry, detector alternatives, acquisition, guiding, and dithering scenarios, probe optics & mechanics, control architecture, and interfaces with NFIRAOS, IRIS, and TMT observatory. TMT.IAO.PRE.09.036.DRF01

IRIS on TMT NFIRAOS  IRIS TMT.IAO.PRE.09.036.DRF01

Key OIWFS Requirements Instrument rotator & services wrap - alignment between NFIRAOS delivered beam and IRIS science instrument Critical to IRIS image quality 2 tip/tilt and 1 tip/tilt/focus wavefront sensors Fast guiding, focus and tilt anisoplanatism 2 mas positioning accuracy > 4.4 µm at focal plane OIWFS are the positional reference for astrometric performance High sky coverage - < 2 mas tip/tilt jitter at galactic pole Near infrared, 1.0 to 1.7 µm, sensing on ‘sharpened’ guide stars High acquisition probability = low acquisition time TMT.IAO.PRE.09.036.DRF01

Work Breakdown Structure MGT OIWFS Management D Loop, HIA, A Moore, CIT SYS OIWFS Systems Engineering R Dekany, CIT, D Loop, HIA ENC OIWFS Enclosure V Reshetov, HIA ENC.ROT Instrument Rotator, Cable Wrap ARM OIWFS Probe Arms D Loop, HIA ARM.MEC Probe Arm Mechanics ARM.OPT Probe Arm Optics M Fletcher, HIA CC OIWFS Component Controller B Wooff, J Dunn, HIA CAM OIWFS Cameras R Smith, CIT CAM.DET Camera Detectors CAM.MEC Camera Mechanics A Delacroix, CIT CAM.AC Detector Controllers D Hale, CIT INT OIWFS Integration & Test Equip. TMT.IAO.PRE.09.036.DRF01

Sky Coverage (Lianqi Wang, Brent Ellerbroek, 2008) 1 TTF + 2TT probes TMT.IAO.PRE.09.036.DRF01

Object Selection Mechanism Object Select Mechanisms considered Robot placed pickoff & pathlength mirrors (EAGLE concept) Tip/tilt mirror tiling of focal plane (Caltech TIPI concept) Theta-Phi, 2 rotation stages (Flamingos-2 OIWFS, etc) Theta-R, 1 rotation + 1 linear stages (IRMOS, KMOS, etc) Requirements for positioning accuracy, dithering, non- sidereal tracking Theta-R concept chosen for initial sky coverage analysis TT and TTF function change – versus - 2 probe planes TMT.IAO.PRE.09.036.DRF01

Patrol Geometry (Lianqi Wang, Brent Ellerbroek, 2008) 3 identical ‘theta-R’ probes at 120 degree spacing Each probe capable of TT or TTF (key for sky coverage) Only need to reach 50% across 2’ field TMT.IAO.PRE.09.036.DRF01

Theta-R Patrol Geometry The Information Herein is Subject to the Restrictions Contained on the Cover Page of this Document TMT.IAO.PRE.09.036.DRF01

Theta-R Probe Optics TTF TT Converter lens and fold mirror Field stop Collimator ‘Trombone’ mirrors Fold mirrors ADC Lenslet array Imager Detector Dewar ‘face’ TTF TT Converter lens brings NFIRAOS exit pupil closer so that collimator can form image further downstream in a more convenient location Detector TMT.IAO.PRE.09.036.DRF01

Theta-R Probe Mechanics TMT.IAO.PRE.09.036.DRF01

Macro Mechanics TMT.IAO.PRE.09.036.DRF01 The Information Herein is Subject to the Restrictions Contained on the Cover Page of this Document TMT.IAO.PRE.09.036.DRF01

Exploded View TMT.IAO.PRE.09.036.DRF01 The Information Herein is Subject to the Restrictions Contained on the Cover Page of this Document TMT.IAO.PRE.09.036.DRF01

OIWFS Probe Platform TMT.IAO.PRE.09.036.DRF01 OIWFS platform assembly (with pickoff arms integrated) G10 or titanium flexures Thermal insulation (bottom part) Dewar interface frame (aluminum) The Information Herein is Subject to the Restrictions Contained on the Cover Page of this Document TMT.IAO.PRE.09.036.DRF01

OIWFS Cameras TT pixel scale = lH/2D = 5.67 mas/pixel TTF pixel scale = lH/D = 11.34 mas/pixel Same detectors can be used for TT and TTF functions Analysis of tip/tilt jitter & image wander during acquisition shows worst case of ~250 mas at 4 sigma and 5.67 mas/pixel > minimum of ~180x180 pixels Acquisition probability > larger probe FoV > more pixels Hawaii HxRG 1024x1024 HgCdTe detector w/new MBE material testing underway – read noise, dynamics Speedster 128x128 HgCdTe detector testing soon HgCdTe e-APDs and InGaAs emerging technologies TMT.IAO.PRE.09.036.DRF01

Acquisition Probability (Corinne Boyer, Luc Simard, 2008) 1024x1024 pixels 5.8’ probe FoV 1’ Telescope pointing σθ (worse at 1st light) provide on-chip small dithering capability (2-3’) TMT.IAO.PRE.09.036.DRF01

Sky Coverage Update (Lianqi Wang, Brent Ellerbroek, Jean-Pierre Veran, 2009) NGS mode errors combined with LGS mode errors of 178 nm RMS Overall on-axis budget of 187 nm RMS met at 45% sky coverage Shortfall (in quadrature) of ~28 nm RMS at 50% System optimization still underway Detector performance “Fitting field” for LGS modes Optimal choice of NGS modes and reconstructor TMT.IAO.PRE.09.036.DRF01

Control Architecture NFIRAOS RTC Engineering GUI Time Service Position Logging & Status Service AO Sequencer TCS Command Service IRIS IS Shared Memory Environ- mental Service House- keeping Service Motion Control Service Engineering Data System TMT.IAO.PRE.09.036.DRF01

Acknowledgements The authors gratefully acknowledge the support of the TMT partner institutions They are the Association of Canadian Universities for Research in Astronomy (ACURA) the California Institute of Technology and the University of California This work was supported as well by the Gordon and Betty Moore Foundation the Canada Foundation for Innovation the Ontario Ministry of Research and Innovation the National Research Council of Canada the Natural Sciences and Engineering Research Council of Canada the British Columbia Knowledge Development Fund the Association of Universities for Research in Astronomy (AURA) and the U.S. National Science Foundation. TMT.IAO.PRE.09.036.DRF01