Technology Development for ELTs Doug Simons GSMT SWG April 28, 2003

2 Driving Science Themes The physics of young Jupiter's The Birth of Galaxies: The Archaeological Record Characterize Exo-Planets The Birth of Planetary Systems The Birth of Galaxies: Witnessing the Process Directly The Birth of Large-Scale Structure GSMT

3 Themes Drive Needed Performance The physics of young Jupiter's Near-diffraction limited performance over ~ 2 arc-minute fields High-dynamic-range imaging High sensitivity mid-IR spectroscopy Enhanced-seeing over ~ 5 arc-minute field Wide-field, seeing-limited multi-object spectroscopy GSMT

4 Achieving Needed Performance Requires Technology Development Mulriple ELT programs have identified key technology investments and studies required to achieve desired performance Four key areas require such investments: –Telescope systems –Facility AO systems –Site Evaluation –Science instruments For each of the above we summarize –The need for new or enhanced technology –Potential performance enhancements –Relationship to science enabled –Other investment returns: e.g. reliability; cost

5 Telescope Systems CELT Magellan 20

6 Key Technologies Adaptive secondaries High performance, durable coatings Alternate primary mirror materials

7 Adaptive Secondaries Requirement –~ 2m deformable mirror with ~2000 actuators + xx micron stroke Need –First element of AO systems –For Magellan 20: key to phasing optical elements –For CELT/GSMT: wind-buffeting compensation Potential performance enhancements –Efficient ground-layer compensation –Low emissivity, high throughput AO feed for mid-IR Potential science gain –Wide-field studies of high z galaxies –Imaging and spectroscopic studies of YSOs Potential cost/reliability gains –Possible simplification of controls systems

8 High Performance, Durable Coatings Requirement –High reflectivity from microns –Retain coating performance for ~10 years Need –Minimize time between coatings; mirror handling Potential performance enhancements –Higher throughput, lower emissivity Potential science gain –Reduced time to complete all programs Potential cost/reliability gains –Major savings in life-cycle costs

9 Alternate Mirror Technologies Requirement –Light weight, readily molded + polished segments of size 1-2m; e.g. SiC Need –Reduce complexity and cost for primary mirror system Potential performance enhancements –?? Higher bandwidth for active control system??? Potential science gain – none Potential cost/reliability gains –Major savings in life-cycle costs

10 Facility AO Systems

11 Systems & Key Technologies Multi-conjugate adaptive optics system –Systems design studies and performance simulations –Low cost, ultra-reliable Na lasers (20-50 W power) –Deformable mirrors –Fast readout, low-noise optical and infrared detectors Extreme AO system –Systems design studies and performance simulations –Deformable mirrors with up to actuators Ground-layer adaptive optics system –Systems design studies and performance simulations –Site studies to identify those best suited to GLAO –Pathfinder systems to verify proof of concepts

12 System Design Studies & Simulations Requirement –Simulation tools that enable evaluation of AO system performance –Evaluation of alternative approaches to wavefront sensing; reconstruction Need –Design optimized AO systems tailored to science requirements –Guide system-wide trade studies (e.g. controls; instrument design) Potential enhancements –Improved wavefront correction Potential science gains –Improved sensivity for all science programs Potential cost/reliability gains –Exploration of multiple design efforts prior to costly prototyping programs

13 Simulated MCAO Performannce

14 GLAO Simulation Natural (straight upper lines) and compensated (lower curves) FWHM averaged across field of view: Bands: V (solid), J (dot) K (dash) Pachon Cn 2 Profile

15 Deformable Mirrors Requirement –Wavefront correction elements with >1000 degrees of freedom; high stroke –Multiple technology paths need exploration (MEMS; thin face sheet DMs) Need –Enable high Strehl correction over desired FOV Potential enhancements –Significant improvement in delivered Strehl compared to current DMs –Extension of AO performance to shorter wavelength Potential science gains –Improved photometric accuracy; higher fidelity imaging of high contrast scenes Potential cost/reliability gains –Exploration of multiple design efforts prior to costly prototyping programs

16 Next Generation DMs MEMS ~ 1 cm Xinetics, ~12” clear aperture

17 Na Lasers Requirement –~50 W Na lasers –Low-cost, robust commercialized product (sollid-state; fiber options); multiple vendors Need –Provide all-sky coverage for SCAO systems –Provide multiple beacons to enable wavefront reconstruction for MCAO systems Potential enhancements –Strehl ~ 0.7 images at K-band over several arc-minute FOV Potential science gains –Enable accurate photometry in crowded fields –Extend AO performance to shorter wavelengths Potential cost/reliability gains –Increased reliability and reduced cost through investment in 2 or more product line

18 Prototype Fiber Laser

19 Wavefront Sensors Requirement –512x512 optical CCD with (?? 1 e readout noise); kHz readout rate –128x128 near-IR detector (??? Readout noise); kHz readout rate Need –Fast, well-sampled wavefront sensing –Fast tip-tilt correction in optically-obscured fields Potential enhancements –Improved delivered Strehl –Supports extension of AO performance to shorter wavelength Potential science gains – improved image quality for all programs Potential cost/reliability gains

20 Site Evaluation Remote sensing Wind CFD SimulationsWeather stationsTurbulence MASS

21 Key Requirement Uniform evaluation information + data for multiple sites –Cloud cover –Precipitable water vapor –Long-term weather patterns –Wind flow and turbulence modeling –in situ measurements of temperature; wind –Ground-layer and upper atmospheric turbulence measurements –Seismicity and geotechnical characteristics –Light pollution; demographic and ownership issues

22 Need for Investment Site choice is a key element in overall system performance –AO performance –Atmospheric transmission –Structure, enclosure and controls systems implications Delivered science is intimately linked with site characteristics At this stage a range of sites should be evaluated –Wide range of prime science cases among ELT groups –Final selection requires life-cycle cost vs science value trade Program must begin immediately –Site selection is on the critical path –A minimim 2-year base is desirable

23 Science Instruments

24 Technology Needs For Representative Instruments MCAO imager –Low cost HgCdTe/InSb detectors; 40 4Kx4K needed Deployable IFU spectrograph –Efficient image multiplexers lenslets; lenslets + fibers; slicers; micromirrors –Low cost HgCdTe/InSb detectors; Kx2K needed Mid-IR Echelle spectrograph –Large format doped Silicon arrays –Si immersion gratings –Reliable cryogenic mechanisms Wide-field optical spectrograph –Advanced gratings (e.g. VPH)

25 Design Concept Studies Additional investment in design concepts is critical –Engage university and private sector groups –Encourage innovative designs

Adaptive Secondary Durable Coatings Alternate Segment (SiC) AO system studies & simulations Deformable Mirrors Na Lasers Detectors for Wavefront Sensors Site Evaluation Large format near-IR detectors Large format mid-IR detectors ? Image multiplexers ? VPH; immersed Si gratings ? ? Instrument Concept studies CELT Mag 20LAT Investment needed by:

27 Conclusions Investment in key technologies critical to all ELT programs There is large overlap in technology developments needed by all ELT programs The GSMT SWG should strongly endorse the following recommendation from the decadal survey: “The committee recommends that technology development for GSMT begin immediately and that construction start within the decade.” Astronomy and Astrophysics Survey Committee