Progress on the 30 m Giant Segmented Mirror
- Slides: 40
Progress on the 30 m Giant Segmented Mirror Telescope AURA New Initiatives Office Leiden, 17 May 2001 Matt Mountain Jim Oschmann Knut Olsen 1
GSMT • Partnership between Gemini, NOAO and our communities • Science Enabled • Implementation Concepts • Resources • Interfaces • Issues 2
Science & Instrument workshops l l l Madison MAXAT science - 1998 Woods Hole MAXAT technology -1999 Tucson MAXAT instruments -2000 Tucson GSMT science – 2000 Subsystem working group meetings 19992000 l l Systems, optics, structures… OPTICON, Edinburgh, Leiden 3
GSMT System Considerations - Astronomers View Science Mission - DRM’s Instruments Adaptive Optics Active Optics (a. O) Full System Analysis Site Characteristics Enclosure protection Support & Fabrication Issues GSMT Concept (Phase A) 4
Derived Top Level Requirements 5
30 m Giant Segmented Mirror Telescope concept GEMINI 30 m F/1 primary, 2 m adaptive secondary 6
The Enemies…. . • Wind…. . • The Atmosphere…… 7
Enabling techniques • Active and Adaptive Optics • Active Optics already integrated into Keck, VLT and Gemini • Adaptive Optics “added” to Keck, Gemini (and soon) VLT Ø Active and Adaptive Optics will have to be integrated into GSMT Telescope and Instrument concepts from the start 8
GSMT Control Concept Deformable M 2 : First stage MCAO, wide field seeing improvement and M 1 shape control Active M 1 (0. 1 ~ 1 Hz) 619 segments on 91 rafts LGSs provide full sky coverage Ø M 2: rather slow, large stroke DM to compensate ground layer and telescope figure, Øor to use as single DM at >3 m. (~8000 actuators) Ø Dedicated, small field (1 -2’) MCAO system (~4 -6 DMs). 10 -20’ field at 0. 2 -0. 3” seeing 1 -2’ field fed to the MCAO module Focal plane 9
AO Technology constraints (50 m telescope) Actuator pitch r 0(550 nm) = 10 cm S(550 nm) S(1. 65 mm) No. of actuators Computer power (Gflops) CCD pixel rate/sensor (M pixel/s) 10 cm 74% 97% 200, 000 9 x 105 800 25 cm 25% 86% 30, 000 2 x 10 4 125 50 cm 2% SOR (achieved) 61% 8, 000 789 1, 500 ~2 31 4 x 4. 5 Early 21 st Century technology will keep AO confined to > 1. 0 m for telescopes with D ~ 30 m – 50 m 10
MCAO on a 30 m: summary • MCAO on 30 m telescopes should be used > 1. 25 m • Field of View should be < 3. 0 arcminutes, ( m) 1. 25 1. 65 2. 20 Delivered Strehl 0. 2 ~ 0. 4 ~ 0. 6 ~ 0. 8 Rigaut & Ellerbroek (2000) 9 Sodium laser constellation 4 tip/tilt stars (1 x 17, 3 x 20 Rmag) PSF variations < 1% across FOV • Assumes the telescope residual errors ~ 100 nm rms • Assumes instrument residual errors ~ 70 nm rms – Equivalent Strehl from focal plane to detector/slit/IFU > 0. 8 @ 1 micron – Instruments must have: • very high optical quality • very low internal flexure 11
AO an integral part of the GSMT Concept • Low order correction for wind buffeting and “seeing improvement” – 3 Natural Guide stars give full sky coverage • Narrow Field AO requires at least one LGS for <5 m – Science requires low emissivity implementation • MCAO requires multiple NGS and multiple DM’s 12
Comparative performance of a 30 m GSMT with a 6. 5 m NGST advantage R = 10, 000 R = 1, 000 R= 5 GSMT advantage Assuming a detected S/N of 10 for NGST on a point source, with 4 x 1000 s integration 13
Comparative performance of a 30 m GSMT with a 6. 5 m NGST 100 m advantage NGST advantage R = 10, 000 R =R 1, 000 =5 R= 5 OWL Assuming a detected S/N of 10 for NGST on a point source, with 4 x 1000 s integration e = 15% 14
GSMT Implementation concept - wide field (1 of 2) Barden et al (2001) 15
Optical “seeing improvement” using low order AO correction Image profiles are Lorenzian 16 consecutive nights of adaptive optics the CFHT 16
GSMT Implementation concept - wide field (2 of 2) 1 m 20 arc minute MOS on a 30 m GSMT • 800 0. 75” fibers • R=1, 000 350 nm – 650 nm • R=5, 000 470 nm – 530 nm • Detects 13% - 23% photons hitting 30 m primary Barden et al (2001) 17
GSMT Implementation concept - MCAO/AO foci and instruments Oschmann et al (2001) MCAO optics moves with telescope elevation axis Narrow field AO or narrow field seeing limited port MCAO Imager at vertical Nasmyth 4 m 18
Spot diagrams for MCAO + Imager Diffraction limited performance for 1. 2 m – 2. 2 m can be achieved 19
MCAO Optimized Spectrometer • Baseline design stems from current GIRMOS d-IFU tech study occurring at ATC and AAO – ~2 arcmin deployment field – 1 - 2. 5 µm coverage using 6 detectors • IFUs – 12 IFUs total ~1. 5”x 1. 5” field – ~0. 05” spatial sampling R ~ 6000 (spectroscopic OH suppression) 20
GSMT Implementation concept - MCAO/AO foci and instruments Oschmann et al (2001) MCAO optics moves with telescope elevation axis Narrow field AO or narrow field seeing limited port MCAO Imager at vertical Nasmyth 4 m 21
GSMT Implementation concept - MCAO/AO foci and instruments Oschmann et al (2001) MCAO optics moves with telescope elevation axis Narrow field AO or narrow field seeing limited port MCAO Imager at vertical Nasmyth 4 m 22
High resolution, high Signal/Noise observations Detecting the molecular gas from gaps swept out by a Jupiter mass protoplanet, 1 AU from a 1 MO young star in Orion (500 pc) (Carr & Najita 1998) GSMT observation ~ 40 mins (30 mas beam) 23
GSMT will need an Adaptive Secondary 30 cm actuator pitch Good conditions (0. 5" seeing): lambda diameter["] %energy 1. 25000 0. 0226732 0. 338447 1. 60000 0. 0290217 0. 473207 2. 25000 0. 0408118 0. 613434 3. 8 0. 71 5. 00000 0. 0906928 0. 758112 10. 0000 0. 181386 0. 789314 20. 0000 0. 362771 0. 797315 8, 960 actuators, 30 cm spacing on Primary 3, 225 actuators, 50 cm spacing 50 cm actuator pitch Good conditions (0. 5" seeing): lambda diameter["] %energy 1. 25000 0. 0226732 0. 251838 1. 60000 0. 0290217 0. 395080 2. 25000 0. 0408118 0. 559923 3. 8 0. 66 5. 00000 0. 0906928 0. 744220 10. 0000 0. 181386 0. 785671 20. 0000 0. 362771 0. 796393 24
Sky coverage and Strehl for narrow field, thermal infrared observations using an adaptive secondary (wind buffeting on M 1) (Rigaut, 2001) Ø for < 10 m single laser beacon required 25
End-to-End Approach • Science Requirements (including instruments) • Error Budget • Enclosure concept – Interaction with site, telescope and budget • Telescope structure – Interaction with wind, optics and instruments • Optics – Interaction with telescope, a. O/AO systems and instruments • AO/MCAO – Interaction with telescope, optics, and instruments • Instruments – Interaction with AO and Observing Model • Observing Model 26
Wind Loading • Driving characteristic may be wind – Lower wind sites with good seeing – How to protect telescope • • Enclosure needs May be more limiting than local seeing to performance Cost drivers Advance methods for correcting More critical than for existing telescopes 27
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Average pressure PSD DATA - effect of enclosure shutters 29
average pressure PSD by EL Ø Note: No elevation dependence on average pressure on primary 30
How to scale to 30 meters: Average pressure SF (C 00030 oo) RMS pressure differences D(d) = 0. 096 d 0. 41 30 M Spatial scale 31
An enclosure is essential: scaled up and taller variation of JCMT Enclosure 32
30 m Giant Segmented Mirror Telescope concept Horizon Pointing - Mode 1 = 2. 16 Hz 33
Response to Wind Current concept will now go through “second iteration” of design In response to wind analysis 34
Point Design Initial Analysis • Finite element model of structure – Gravity sag and initial modal analysis • Wind PSD’s calculated from Gemini tests – To be applied to current model • Structure function approach to scaling Gemini data on wind buffeting to 30 meter – Preparing to apply wind buffeting to point design • Aid in systems flow down of requirements • Early trades possible soon 35
Objectives: Next 2 years • Develop point design for GSMT & instruments – Carried out within NIO • Attack key technical problems – Adaptive optics – Wind loading – Mirror segment fabrication • Continue community involvement in defining: – Science & technical requirements – Instrumentation options; technology paths • Support design studies that complement other projects (CELT, FELT, OWL, etc. ) 36
Resources: Next 2 years • • Combined Gemini partnership + NOAO resources: $2. 1 M Core NIO effort focused on studies to: • Additional US National efforts: $2. 0 M external studies: – Analyze point design – Attack key technical issues – Develop instrument and subsystem concepts – Explore science and instrument requirements – Enable community efforts: science; instruments + Study contracts + Broad community workshops – Enable key external engineering studies; alternate concepts + End-to-end system model + detailed error budget + Alternate system design concept studies + Alternate AO system design and modeling studies + Develop site testing equipment; apply in Chile 37
AURA New Initiatives Office Adaptive Optics Francois Rigaut (Gemini) 38
GSMT STEERING COMMITTEE Present Members Cf. A John Casani Alan Dressler Richard Ellis Bob Fugate Jay Gallager Bob Gehrz Riccardo Giovanelli Bob Kirshner Rolf Kudritzki Simon Lilly Joe Miller Jerry Nelson Larry Ramsey Chuck Steidel Jet Propulsion Laboratory Carnegie Observatory Cal. Tech Starfire Optical Range University of Wisconsin University of Minnesota Cornell University Harvard-Smithsonian, University of Hawaii HIA University of California Penn State University Cal. Tech 39
Interfaces • Community task groups; workshops • NSF, other Gemini Agencies (PPARC, NRC, ARC. . ) • Potential partners: CELT; ESO; others • Other next generation telescope projects • Private sector/government lab consultants • NIO steering committee • US System steering group – GSMT is the apex of US system – System must support GSMT • OPTICON 40
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