NIO GSMT Overview

VLOT/GSMT WORKSHOP

Victoria, BC

17 JULY, 2001

S. Strom, L. Stepp

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.”

Goals of the NIO• Foster community interaction on GSMT

• Develop point design

• Conduct studies of key technical issues and relationship to science drivers

• Optimize community resources:– explore design options that yield cost savings, – emphasize studies that benefit multiple programs, – collaborate to ensure complementary efforts, – give preference to technologies that are extensible

to even more ambitious projects.

AURA New Initiatives Office

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Comparative performance of a 30m GSMT with a 6.5m NGST

1 101E-3

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10

Comparative performance of a 30m GSTM with a 6.5m NGST

S/N

Ga

in (

GS

MT

/ N

GS

T)

Wavelength (microns)

R=5 R=1,000 R=10,000

Assuming a detected S/N of 10 for NGST on a point source, with 4x1000s integration

GS

MT

a

dv

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GS

T a

dva

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R = 10,000 R = 1,000 R = 5

GSMT/NGST at High Spectral Resolution

1 10

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17.0

12.3

4.6

Molecular line spectroscopy S/N = 100

S/N

Gai

n (

GS

MT

/ N

GS

T)

Wavelength (microns)

R=10,000 R=30,000 R=100,000

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)– Define “Science Reference Mission”

KEY SCIENCE ENABLED BY GSMT

Origin of structure in the universe: from the big bang to planetary systems

Najita et al (2000,2001)

Tomography of the Universe• Goals:

Map out large scale structure for z > 3Link 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

Mass Tomography of the Universe

z~0.5

Existing Surveys + Sloan

z~3

Hints of Structure at z=3(small area)

100Mpc (5Ox5O), 27AB mag (L* z=9), dense samplingGSMT 1.5 yrGemini 50 yrNGST 140 yr

Tomography of Galaxies and Pre-Galactic Fragments

• Goals:Determine gas and stellar kinematicsQuantify SFR and chemical composition

• Measurements:Spectroscopy of H II complexes and underlying stars

• Key requirements:Deployable IFUs feeding R ~ 10000 spectrographWide FOV to efficiently sample multiple systems

• Time to complete study with GSMT: ~1 year• Issues

– Modeling surface brightness distribution– Understanding optimal IFU ‘pixel’ size

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, 3 limit at R=5,000

0.1”x0.1” IFU pixel(sub-kpc scale structures)

J H K 26.5 25.5 24.0

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; )

• Key requirements:On axis, high Strehl AO; low emissivity

• Time to complete study with GSMT:2 years

• IssuesUnderstand efficacy of molecular ‘tracers’Trades among emissivity; sites; telescope & AO design

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 emission Rotation separates disk radii in velocity High spectral resolution high spatial resolution

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).

S/N=100, R=100,000, >4m

Gemini out to 0.2kpc sample ~ 10s

GSMT 1.5kpc ~100s

NGST X

Stellar Populations• Goals:

Quantify IMF in different environmentsQuantify ages; [Fe/H]; for stars in nearby galaxiesDevelop 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

GSMT System Considerations

Science Mission- DRM’s

GSMTConcept

(Phase A)

Support &Fabrication

Issues

Active Optics (aO)

SiteCharacteristics

Enclosureprotection

Adaptive Optics

Instruments Full SystemAnalysis

NIO Approach

Parallel efforts

– Address challenges common to all ELTs

• Wind-loading

• Adaptive optics

• Site

– Explore point design

• Start from a strawman

• Understand key technical issues

Enemies Common to all ELTs

Wind…..

The Atmosphere……

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

0 50 100 150 200 250 300-2

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-1

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Time History: time (second)

pres

sure

(N

/m2)

AVERAGE Pressure (C00030oo)

10-3

10-2

10-1

100

101

100

101

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Frequency Response Function: frequency (Hz)

mag

nitu

de

AVERAGE Pressure (C00030oo)

SUM = -226

AnimationWind pressure: C00030oo

test_2, day_2, Azimuth angle=00, Zenith angle=30, wind_gate:open, open; wind speed=11 m/s

Wind Pressure Structure Function C00030oo

0 1000 2000 3000 4000 5000 6000 7000 80000

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sensor spacing, d (mm)

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ure,

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/m2)

Average Structural Function for C00030oo

Prms = 0.076124 d ** 0.4389

How to scale to 30 meters:

D(d) = 0.076 d 0.43

0 1000 2000 3000 4000 5000 6000 7000 80000

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1.5

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sensor spacing, d (mm)

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/m2)

Average Structural Function for C00030oo

Prms = 0.076124 d ** 0.4389

30M

RMS pressure differences

Spatial scale

The Gemini South wind test results

are available on the NIO Web site at:

www.aura-nio.noao.edu

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(1.65m) 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 31 SOR (achieved) 789 ~ 2 4 x 4.5

Early 21st Century technology will keep AO confined to > 1.0mfor telescopes with D ~ 30m – 50m

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:(m) 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

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

Site Evaluation

NIO gathering uniform data for sites in:– Northern Chile – Mexico and Southwest US– Hawaii

Point Design: Philosophy

Select plausible design that addresses 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!

Point Design: Motivations

Provide a practical basis for wide-field, native seeing-limited instruments– science drivers strong

Explore a radio telescope approach– possible structural advantages

• elevation bearing size comparable to primary– possible advantages in accommodating large

instruments

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

Derived Top Level Requirements

Narrow field AO 1 2 3 MCAO 1 2 3 Low order AO 1 2 3 Seeing limited (PF) 1 2 3Field of View 10 arcsec + - + 2 arcmin + + 2 arcmin + 20 arcminPrinciple wavelegths 1.0 - 2.5 microns 1.0 - 2.5 microns 1.0 - 20 microns 0.4 - 2.5 micronsPSF

Resolution Diffraction limited + + Diffraction limited + 0.1-0.2 arcsec + 0.4-0.7 arcsec +Stability 1% + 5% - - 2% 2%

Strehl 80% 50% <10% 0%Photom. accuracy(derived) 1% 5% - - 2% 1%

Astrometric accuracy 10 -̂4 arcsec + + 10 -̂3 arcsec - 10 -̂2 arcsec 0.05 arcsecStability timescale 3,600 s 3,600s 3,600s 10,000 sEmissivity <20% - <20% 10% 15%Maintenance/Ops <15% <15% <15% <15%Reliability 90% 90% 90% 90%Science Efficiency 90% 90% 90% 90%

1 Galaxy Evolution and LS Structure2 Stellar Populations3 Star and Planet Formation

Key:+ meets needs- does not meet needs

irrelevant or not critical

How to r ead this table:

Four telescope “Operating regimes” are defined and the specs for thetelesc ope (not the instrument) in each regime are cited. There are columns atthe right of each regime labeled 1,2,3 for the th ree science programsdiscussed in the NO AO panel W orkshop. In these columns the spe cs areassessed in term s of the adequacy for each sc ience program .

Matt:I think this mode is important, its our only "thermal IR" mode, and we may find some spectroscopy modes are so photon starved they

30m Giant Segmented Mirror Telescope Point Design Concept

Typical 'raft', 7 mirrors per raft

Special raft - 6 places, 4 mirrors per raft

1.152 m mirror across flats

Circle, 30m dia.30m F/1 primary, 2m adaptive secondary

GEMINI

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

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

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

0.001 0.01 0.1 1 10100

Ze

rnik

e m

od

e s

Bandwidth [Hz]

~100

~50

~20

~10

2

Controls Approach:Offloading Decentralized Controllers

aO (M1)

AO (M2)

Main Axes

LGS MCAO

Secondary rigid body

temporal avg

spatial & temporal avg

spatial & temporal avg

spatial & temporal avg

spatial avg

spatial avg

GSMT Control ConceptLGSs provide full sky coverage

Deformable M2 : First stage MCAO, wide field seeing improvement and M1 shape control

10-20’ field at 0.2-0.3” seeing

1-2’ field fed to the MCAO module

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).

Focal plane

Active M1 (0.1 ~ 1Hz)619 segments on 91 rafts

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

Enclosures

Design options under study

Response to Wind

Current concept will now go through “second iteration” of design in response to wind analysis

Fig. 4-7 – Central Raft Displacement Power Spectral DensityVent Gates Open, Wind Screen Open, Pointing into Wind, Zenith Angle = 30 deg.

0.001

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Frequency (Hz)

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Goal: 8000 actuators30cm spacing on M1

Options: low- to high-order • Compensate for wind-driven M1 distortions• Deliver high Strehl, mid-IR images with low emissivity• Deliver high-Strehl, near-IR images

Adaptive M2 Intrinsic to Point Design

Key Point-Design Features

2m diameter adaptive secondary mirror– Advantages:

• Correction of low-order M1 modes• Enhanced native seeing• Good performance in mid-IR• First stage in high-order AO system

– Disadvantages:• Increased difficulty (i.e., cost)

Sky Coverage vs Wavelength; Strehl for an Adaptive M2 (single laser guide star; Rigaut, 2001)

GSMT Implementation Concept- MCAO/AO foci and instruments

MCAO opticsmoves with telescope

Narrow field AO ornarrow field seeing limited port

MCAO Imagerat vertical Nasmyth

elevation axis

4m

Oschmann et al (2001)

MCAO Near-IR Imager (1:1 Unfolded)

40 mm Pupil

~2 arc minute field

Instruments• Telescope, AO and instruments must be

developed as an integrated system

• NIO team developing design concepts– Prime focus wide-field MOS

– MCAO-fed near-IR MOS

– MCAO-fed near-IR imager

– AO-fed mid-IR HRS

– Wide-field deployable IFU spectrograph

• Build on extant concepts where possible

• Define major design challenges

• Identify needed technologies

Optical “seeing improvement” using low order AO correction

16 consecutive nights of adaptive optics the CFHT

Image profilesare Lorenzian

Multi-Object Multi-Fiber Optical Spectrograph (MOMFOS)

•20 arc-minute field

• 60-meter fiber cable• 800 0.7” fibers

• 4 spectrographs, 200 fibers each• VPH gratings• Articulated collimator for different resolution regimes

Resolution Example ranges with single grating• R= 1,000 350nm – 650nm• R= 5,000 470nm – 530nm• R= 20,000 491nm – 508nm

• Detects 13% - 23% of photons hitting the 30m primary

Prime Focus MOMFOS

Barden et al (2001)

Key Point-Design Features

MOMFOS located at prime focus– Advantages

• Fast focal ratio leads to reasonably-sized instrument• Adaptive prime focus corrector allows enhanced seeing

performance

– Disadvantages• Issues of interchange with M2

MOMFOS with Prime Focus Corrector

Conceptual design fits in a 3m dia by 5m long cylinder

R=20000mode

R=5000mode

R=1000mode

MOMFOS Spectrograph

500mm pupil; all spherical optics

Spot Diagrams for Spectrograph

R=1000 case with 540 l/mm grating.

R=5000 case with 2250 l/mm grating.

350 nm 440 nm 500 nm 560 nm 650 nm

470 nm 485 nm 500 nm 515 nm 530 nm

On-axis

On-axis

Circle is 85 microns equal tosize of imaged fiber.

Barden et al (2001)

Key NIO Activities in 2001

• Core NIO team in place and working• Science case studies underway• Point design structural concept developed by SGH• Wind loading test data analyzed • AO system concept being developed• Instrument concepts

• MCAO imager• MCAO NIR MOS• IFU spectrograph• Wide-field prime-focus MOS• High resolution mid-IR spectrograph

• Chilean site characteristics assembled• Initial analysis of point design underway

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 formal partnership to build GSMT

Objectives: Next Decade • Complete GSMT preliminary design (2Q 2005)• Complete final design (Q4 2007)• Serve as locus for

– community interaction with GSMT consortium– ongoing operations– defining; providing support capabilities– defining interactions with NGST

Key Milestones2Q01: Establish initial science requirements

• 3Q01: Complete initial instrument concepts

• 3Q01: Complete initial point design analysis

• 2Q02: Identify key technology studies

• 1Q03: Fund technology studies

• 1Q03: Complete concept trade studies

• 2Q03: Develop MOUs with partner(s)

• 2Q03: Initiate Preliminary Design

• 4Q03: Complete SRM; establish science requirements

• 2Q05: Complete Preliminary Design

• 4Q05: Complete next stage proposal

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

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