Advancing GSMT Mission: NIO Overview and Objectives

1. NIO GSMT Overview S. Strom, L. Stepp 23 August, 2001

2. AURA NIO: Mission • In response to AASC call for a GSMT, AURA formed a New Initiatives Office (NIO) • collaborative effort between NOAO and Gemini to explore design concepts for a GSMT • NIO mission “ to ensure broad astronomy community access to a 30m telescope contemporary in time with ALMA and NGST, by playing a key role in scientific and technical studies leading to the creation of a GSMT.”

3. Goals of the NIO • Foster community interaction re GSMT • Develop point design • Conduct studies of key technical issues and relationship to science drivers • Optimize community resources: • emphasize studies that benefit multiple programs, • collaborate to ensure complementary efforts, • give preference to technical approaches that are extensible to even more ambitious projects. • Develop a partnership to build GSMT

4. AURA New Initiatives Office Contracted Studies Opto-mechanics Myung Cho Controls George Angeli Adaptive Optics Ellerbroek/Rigaut (Gemini)

5. Objectives: Next 2 years • Develop point design for GSMT & instruments • Develop key technical solutions • Adaptive optics • Active compensation of wind buffeting • Mirror segment fabrication • Investigate design-to-cost considerations • Involve the community in defining GSMT science and engineering requirements • Involve the community in defining instrumentation options; technology paths • Carry out conceptual design activities that support and complement other efforts • Develop a partnership to build GSMT

6. Resources: 2001-2002 • NIO activities: $3.6M • Support core NIO staff (‘skunk works team’) • Analyze point design • Develop instrument and subsystem concepts • Support Gemini and NOAO staff to • Explore science and instrument requirements • Develop systems engineering framework • Support community studies: • Enable community efforts: science; instruments • Enable key external engineering studies • Support alternative concept studies

7. Objectives: Next Decade • Complete GSMT preliminary design (2Q 2005) • Complete final design (Q4 2007) • Serve as locus for • community interaction with GSMT partnership • ongoing operations • defining; providing O/IR support capabilities • defining interactions with NGST

8. Resources: Next Decade • $15M in CY 2003-2006 from NOAO base • Enables start of Preliminary Design with partner • $25M in CY 2007-2011 from NOAO base • Create a ‘wedge’ of ~$10M/yr by 2010 • Enables NOAO funding of • Major subsystem • Instruments • Operations

9. Key Milestones • 2Q01: Establish initial science requirements • 3Q01: Complete initial instrument concepts • 3Q01: Complete initial point design analysis • 1Q02: Identify and fund alternate concept studies • 2Q02: Identify and fund key technology studies • 2Q02: Identify potential US and/or international partners • 1Q03: Complete concept trade studies • 2Q03: Develop MOUs with partner(s) • 2Q03: Establish final science requirements • 4Q03: Initiate Preliminary Design • 2Q05: Complete Preliminary Design • 4Q05: Complete next stage proposal

10. FIRST STEP: UNDERSTAND SCIENCE REQUIREMENTS

11. Developing Science Cases • Two community workshops (1998-1999) • Broad participation; wide-ranging input • Tucson task group meetings (SEP 2000) • Large-scale structure; galaxy assembly • Stellar populations • Star and planet formation • NIO working groups (MAR 01 – SEP 01) • Develop quantitative cases; simulations • NIO-funded community task groups (CY 2002) • NIO-funded community workshop (CY 2002) • Refine performance goals and requirements

12. Tomography of the Universe • Goals: Map out large scale structure for z > 3 Link emerging distribution of gas; galaxies to CMB • Measurements: Spectra for 106 galaxies (R ~ 2000) Spectra of 105 QSOs (R ~15000) • Key requirements: 20’ FOV; >1000 fibers • Time to complete study with GSMT: 3 years • Issues • Refine understanding of sample size requirements • Spectrograph design

13. Hints of Structure at z=3 (small area) Existing Surveys + Sloan z~3 z~0.5 Mass Tomography of the Universe 100Mpc (5Ox5O), 27AB mag (L* z=9), dense sampling GSMT 1.5 yr Gemini 50 yr NGST 140 yr

14. Tomography of Galaxies and Pre-Galactic Fragments • Goals: Determine gas and stellar kinematics Quantify SFR and chemical composition • Measurements: Spectroscopy of H II complexes and underlying stars • Key requirements: Deployable IFUs feeding R ~ 10000 spectrograph Wide FOV to efficiently sample multiple systems • Time to complete study with GSMT: ~1 year • Issues • Modeling surface brightness distribution • Understanding optimal IFU ‘pixel’ size

15. Tomography of Individual Galaxies out to z ~3 • Determine the gas and stellar dynamics within • individual galaxies • Quantify variations in star formation rate • Tool: IFU spectra • [R ~ 5,000 – 10,000] GSMT 3 hour, 3s limit at R=5,000 0.1”x0.1” IFU pixel (sub-kpc scale structures) J H K 26.5 25.5 24.0

16. Origins of Planetary Systems • Goals: • Understand where and when planets form • Infer planetary architectures via observation of ‘gaps’ • Measurements: Spectra of 103 accreting PMS stars (R~105; l ~ 5m) • Key requirements: On axis, high Strehl AO; low emissivity • Time to complete study with GSMT: 2 years • Issues Understand efficacy of molecular ‘tracers’ Trades among emissivity; sites; telescope & AO design

17. Probing Planet Formation with High Resolution Infrared Spectroscopy • Planet formation studies in the infrared (5-30µm): • Probe forming planets in inner disk regions • Residual gas in cleared region low t emission • Rotation separates disk radii in velocity • High spectral resolution high spatial resolution S/N=100, R=100,000, >4m Gemini out to 0.2kpc sample ~ 10s GSMT 1.5kpc ~100s NGST X • 8-10m telescopes with high resolution (R~100,000) spectrographs can detect the formation of Jupiter-mass planets in disks around nearby stars (d~100pc).

18. Stellar Populations • Goals: Quantify IMF in different environments Quantify ages; [Fe/H]; for stars in nearby galaxies Develop understanding of galaxy assembly process • Measurements: Spectra of ~ 105 stars in rich, forming clusters (R ~ 1000) CMDs for selected areas in local group galaxies • Key requirements: MCAO delivering 2’ FOV; MCAO-fed NIR spectrograph • Time to complete study with GSMT: 3 years • Issues • MCAO performance in crowded fields

19. Derived Top Level Requirements

20. NIO Approach Parallel efforts • Address challenges common to all ELTs • Wind-loading • Adaptive optics • Site • Explore “point design” • Start from a strawman motivated by science • Understand key technical issues through analysis • NB: Point design is simply a starting point! • NIO will explore alternate approaches

21. Enemies Common to all ELTs • Wind….. • The Atmosphere……

22. Wind Loading • Primary challenge may be wind buffeting • More critical than for existing telescopes • Structural resonances closer to peak wind power • Wind may limit performance more than local seeing • Solutions include: • Site selection for low wind speed • Optimizing enclosure design • Dynamic compensation • Adaptive Optics • Active structural damping

23. Gemini South Wind Test Performed during integration of Gemini Telescope on Cerro Pachon • Enclosure has large vent gates – permits testing a range of enclosure conditions • Dummy mirror has properties equivalent to the real primary mirror, but can be instrumented • M1 is above the EL axis - open to the wind flow (similar to concepts for future larger telescopes)

25. Instrumentation 3-axis anemometers Pressure sensors, 32 places

26. Ultrasonic anemometer Ultrasonic anemometer Pressure sensors Sensor Locations

28. AnimationWind pressure: C00030ootest_2, day_2, Azimuth angle=00, Zenith angle=30, wind_gate:open, open; wind speed=11 m/s

29. Wind Pressure Structure FunctionC00030oo

30. Extrapolation to 30 Meters Pressure variation on 30-m mirror about twice 8-m Prms = 0.04d^0.5

31. Summary and Conclusions • Wind loading on M1 is strongly dependent on vent gate openings • Wind loading on M2 is not strongly dependent on vent gate openings • Control algorithm will maintain wind speed at M1 < 3 m/sec • With vent gates closed, M1 deformations remain within error budget even in high winds • Pressure variations on M1 are larger than average pressure • M1 wind deformations are dominated by astigmatism • M1 deformations are proportional to RMS pressure variations on surface • M1 deformations ~ proportional to (wind velocity at mirror)² • Pressure structure functions fit 0.5 power law • Structure functions allow extrapolation to larger telescopes – pressure range for 30m twice that of 8m

32. AO Technology Constraints:DMs and Computing power (50m telescope; on axis) r0(550 nm) = 10cm No. of Computer CCD pixel Actuator pitch S(550nm) S(1.65mm) actuators power rate/sensor (Gflops) (M pixel/s) 10cm 74% 97% 200,000 9 x 105 800 25cm 25% 86% 30,000 2 x 104 125 50cm 2% 61% 8,000 1,500 31SOR (achieved) 789 ~ 2 4 x 4.5 Early 21st Century technology will keep AO confined to l > 1.0 mm for telescopes with D ~ 30m – 50m

33. AO Technology Constraints:Guide stars and optical quality MCAO system analysis by Rigaut & Ellerbroek (2000): • 30 m telescope • 2 arcmin field • 9 Sodium laser constellation 10 watts each • 4 tip/tilt stars (1 x 17, 3 x 20 Rmag) • Telescope residual errors ~ 100 nm rms • Instrument residual errors ~ 70 nm rms System performance: l(mm) Delivered Strehl 1.25 0.2 ~ 0.4 1.65 0.4 ~ 0.6 2.20 0.6 ~ 0.8 PSF variations < 1% across FOV

34. Site Evaluation • ELT site evaluation more demanding • Evaluation criteria include • surface and high altitude winds • turbulence profiles • transmission • available clear nights (long-term averages) • cirrus cover (artificial guide star performance) • light pollution • accessibility • available local infrastructure • land ownership issues

35. Site Evaluation • NIO gathering uniform data for sites in: • Northern Chile • Mexico and Southwest US • Hawaii • Effort led by NIO staff • Parallel effort in Mexico, aligned with NIO-developed criteria

36. POINT DESIGN APPROACH

37. GSMT System Considerations Science Mission Adaptive Optics Active Optics (aO) Support & Fabrication Issues Full System Analysis Instruments GSMT Concept (Phase A) Site Characteristics Enclosure protection

38. Point Design: Philosophy • Select plausible design • must address key science requirements • Identify key technical challenges • Focus analysis on key challenges • Evaluate strengths and weaknesses • guide initial cost-performance evaluation • inform concept design trades • Point design is only a strawman!

39. Point Design: Motivations • Enable high-Strehl performance over several arc-minute fields • Stellar populations; galactic kinematics; chemistry • Provide a practical basis for wide-field, native seeing-limited instruments • Origin of large-scale structure • Enable high sensitivity mid-IR spectroscopy • Detection of forming planetary systems

40. Choices for NIO Point Design • Explore prime focus option • attractive enabler for wide-field science • cost-saving in instrument design • Assume adaptive M2 • compensate for wind-buffeting • reduce thermal background • deliver enhanced-seeing images • Explore a radio telescope approach • possible structural advantages • possible advantages in accommodating large instruments

41. Point Design: End-to End Approach • Science Requirements (including instruments) • Error Budget • Control systems • Enclosure concept • Interaction with site, telescope and budget • Telescope structure • Interaction with wind, optics and instruments • Optics • Interaction with telescope, aO/AO systems and instruments • AO/MCAO • Interaction with telescope, optics, and instruments • Instruments • Interaction with AO and Observing Model

42. 30m Giant Segmented Mirror TelescopePoint Design Concept GEMINI 30m F/1 primary, 2m adaptive secondary

43. Key Point-Design Features • Paraboloidal primary • Advantage: Good image quality over 20 arcmin field with only 2 reflections • Seeing-limited observations in visible • Mid-IR • Disadvantage: Higher segment fabrication cost

44. Key Point-Design Features • F/1 primary mirror • Advantages: • Reduces size of enclosure • Reduces flexure of optical support structure • Reduces counterweights required • Disadvantages: • Increased sensitivity to misalignment • Increased asphericity of segments

45. Key Point-Design Features • Radio telescope structure • Advantages: • Cass focus can be located just behind M1 • Allows small secondary mirror – can be adaptive • Allows MCAO system ahead of Nasmyth focus • Disadvantage: • Requires counterweight • Sweeps out larger volume in enclosure

46. GSMT Control Concept Deformable M2 : First stage MCAO, wide field seeing improvement and M1 shape control LGSs provide full sky coverage • M2: rather slow, large stroke DM to compensate ground layer and telescope figure, • or to use as single DM at >3 m. (~8000 actuators) • Dedicated, small field (1-2’) MCAO system (~4-6DMs). Active M1 (0.1 ~ 1Hz) 619 segments on 91 rafts 1-2’ field fed to the MCAO module 10-20’ field at 0.2-0.3” seeing Focal plane

47. Enabling Techniques Active and Adaptive Optics • Active Optics already integrated into Keck, VLT, Gemini, Subaru, Magellan, … • Adaptive Optics “added” to CFHT, Keck, Gemini, VLT, … Active and Adaptive Optics will have to be integrated into GSMT Telescope and Instrument concepts from the start

48. 30m GSMTInitial Point-Design Structural Model Horizon Pointing - Mode 1 = 2.16 Hz

49. Response to Wind Need to quantify wind effects, and develop control system responses to correct pointing, focus, and optical aberrations

50. Modeling of Active Corrections We are considering two approaches: • Partition mode shapes + line-of sight equations • Ray-tracing mode shapes