Giant Magellan Telescope

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1 Giant Magellan Telescope Faint Object Adap6ve Op6cs Michael Hart Steward Observatory, The University of Arizona Challenges for the GMT Melbourne, June 16, 2010

2 Importance of AO The ELTs in general, including GMT, need AO to be worth building. Seeing limited light buckets can be built much more cheaply in other ways. Given that cost goes as ~D 2.5, GMT costs twice as much as seven 8.4 m telescopes. Enhancements in resolu'on and sensi'vity are crucial. You could make the same argument about 8 m class telescopes. (Jerry Nelson, 2000) Yes, and now there isn t a general purpose 8 m telescope in the world that doesn t have (at least plans for) AO. Keck II is scheduled for 44% AO in 2010A, 33% LGS, 11% NGS. Challenges for the GMT, Melbourne, June

3 Par[cular importance of AO to the GMT GMT is the smallest of the three planned ELTs. All will have AO correc[ng to the diffrac[on limit. GMT is at risk in the D 4 point source sensi[vity game. What roles can the GMT take that dis[nguish it scien[fically from other telescopes? What makes GMT worth building at all? Challenges for the GMT, Melbourne, June

4 Unique features of GMT to be exploited An adap[ve secondary mirror Cri[cal for wide field ground layer AO with FIVE TIMES the étendue of TMT in this mode. Low, low thermal background. No need to build a truck sized freezer for thermal cleanliness (NFIRAOS) before you get to the instrument. Large rigid op[cally smooth primary mirror segments Supports ground layer AO. Easier (not harder) to control PSF side lobes for very high contrast. Ah yes, the GAPS Phase errors across them MUST be corrected in real [me to get to the diffrac[on limit. Knowing the power law scaling of wavefront error with spa[al scale allows direct interpola[on across the gaps with reasonable accuracy, provided mechanical errors are well controlled. Challenges for the GMT, Melbourne, June

5 Present state of adap[ve secondaries Telescope Diameter (m) Actuators Status MMT Opera[onal (22% of scheduled observing [me since Jan 2010) LBT Running on sky LBT Complete; systems tes[ng underway Magellan Under construc[on VLT In design GMT 7 x x 672 (TBC) Planned Challenges for the GMT, Melbourne, June

6 LBT secondary #1 saw first light on May 25 Pyramid wavefront sensor with 30x30 subapertures 1 khz update rate 400 corrected modes Challenges for the GMT, Melbourne, June

7 The LBT s ASM number 1 ASM #1 installed (with its cover) on the SX side of LBT Challenges for the GMT, Melbourne, June

8 First light for the LBT adap[ve secondary #1 4 s exposure J and H band composite Challenges for the GMT, Melbourne, June

9 Seeing of 0.7 in H band LBT AO first light Achieved Strehl ra[os > 60% in H band (<200 nm rms wavefront error). These Strehl ra[os are among the best ever seen at a telescope of 8 10 m. Not bad for first light!! Challenges for the GMT, Melbourne, June

10 The LBT PSF in detail H band Linear intensity scale Log intensity scale m v = 5.8 SR = 68% Seeing = s exposure Challenges for the GMT, Melbourne, June

11 Triple star in H band Challenges for the GMT, Melbourne, June

12 M92 in H band ~15 HST WFC3 LBT with AO Challenges for the GMT, Melbourne, June

13 Applica[on of an adap[ve secondary mirror to ground layer AO Challenges for the GMT, Melbourne, June

2 khz Average power 30 W Launch telescope loca[on Behind secondary mirror Number of beacons 5,

14 The MMT s mul[ laser AO system Laser type 2 x doubled YAG (15 W each) Wavelength 532 nm Pulse rep rate 5.2 khz Average power 30 W Launch telescope loca[on Behind secondary mirror Number of beacons 5, arranged as a regular pentagon Enclosed field of view 2 arc minutes Beacon type Rayleigh scaqering Range gate km with dynamic refocusing Challenges for the GMT, Melbourne, June

15 Closed loop GLAO opera[on at the MMT Closed loop ground layer mode is now opera[onal Correc[on signal is computed from the average of the five beacons Applied to the MMT s adap[ve secondary, the result is par[al seeing compensa[on over the 2 arcmin field spanned by the beacons Technical details: Correc[ons are applied at a rate of 400 Hz A basis set of 45 disc harmonic modes is used to build the wavefront correc[on A single natural star is needed for [p [lt correc[on, but can be as faint as V ~ 18 and > 1 arcmin off axis. Challenges for the GMT, Melbourne, June

16 K band GLAO imaging of M3 Central and edge sub-fields Uncorrected full field Uncorrected GLAO corrected Exposure [me = 60 s in each case (with and without correc[on) Hart et al., Nature, accepted Challenges for the GMT, Melbourne, June

17 GLAO performance on MMT K band Seeing = 0.61 in K band Mean corrected FWHM = 0.22 Corrected FWHM uniformity: rms Challenges for the GMT, Melbourne, June

18 GLAO performance on MMT FWHM averaged over the 2 field: J = 0.29 H = 0.29 K = 0.22 Challenges for the GMT, Melbourne, June

19 Take aways Adap[ve secondary technology has reached a level of maturity sufficient to be deployed in rou[ne daily opera[on at the world s largest telescope. Ground layer AO with an adap[ve secondary is now a demonstrated image sharpening technique with enormously broad applica[on. GMT, through ground-layer and thermal IR AO enabled by its adaptive secondary, will offer multiplexing and sensitivity superior to any other telescope, present or planned. Challenges for the GMT, Melbourne, June

20 GMT facility AO system design at present The GMT facility AO system is an integral component of the telescope. The design supports mul[ple modes of opera[ons: Natural Guide Star AO (NGSAO) Laser Tomography AO (LTAO) Ground Layer AO (GLAO) Extreme AO (ExAO) MCAO (MCAO) Challenges for the GMT, Melbourne, June

21 Key system components System is designed to maximize science return with minimal technical development: Adap[ve secondary mirrors are near replicas of LBT, VLT design Laser guide star system builds on Na laser development for current telescopes Laser projec[on system is similar to MMT design Expected AO performance is similar to LBT system Within the technical constraints above, the system is designed to achieve performance driven by the science requirements and the science instrument needs. Challenges for the GMT, Melbourne, June

22 AO wavefront error budget Wavefront error source RMS wavefront error (nm) NGS LTAO ExAO Primary mirror figure Secondary mirror figure Piston anisoplanatism (1 min calibration) Piston errors from primary edge sensors AO optical train (non-common path) Science instrument Fitting error Atmospheric temporal lag WFS measurement noise propagation Reconstruction error High order total Anisoplanatism error 1' 0 Residual windshake Total: On-axis Total: Off-axis 13 1 Challenges for the GMT, Melbourne, June

23 On axis performance AO system performance versus wavelength NGS performance versus guide star brightness Strehl Ratio S H = 56% S J = 36% S K = 72% S L = 90% S M = 94% K band Strehl Ratio 1 ms 2 ms 5 ms 10 ms Wavelength (µm) V magnitude (K5 star) Challenges for the GMT, Melbourne, June

24 AO system overview Laser Projector Adaptive Secondary Mirror (~4700 actuators) GLAO WFS Laser Housing AO relay and Narrow-field WFS GCAR, Pasadena CA, April 27 29, 2009 AO system 24

Anatomy of an Adap[ve Secondary Mirror Central flexure Permanent

7 mm thick cold plate shell reference body Projected actuator spacing

5 ms Edge sensors and hexapods provide inter segment control

25 Anatomy of an Adap[ve Secondary Mirror Central flexure Permanent magnets Zerodur shell, 1.7 mm thick cold plate shell reference body Projected actuator spacing is 23 cm Seqling [me is 0.5 ms Edge sensors and hexapods provide inter segment control Leverages development of ASM's for MMT/LBT/VLT electromagnets capacitive position sensors Challenges for the GMT, Melbourne, June segments on discrete hexapods 25

26 AO op[cal relay Purpose: Relay the focal plane to mul[ple instrument ports, providing cold baffling, atmospheric dispersion correc[on, and facility wavefront sensing. Designed by Phil Hinz (Steward Observatory) Wavelength range: 1 5 µm FOV: 2.5 arcminutes Instrument Ports: 1 direct Gregorian focus port 3 folded ports on the Instrument Plazorm. Internal mirror conjugated to 12 km al[tude for upgrade path to MCAO Challenges for the GMT, Melbourne, June

Op[cal layout of the relay Science focus (f/8) ADC Dichroic WFS window WFS port provides both NGS and LTAO WFS Light from telescope Entrance window M1 M3 WFS M2 is at an image of the

27 Op[cal layout of the relay Science focus (f/8) ADC Dichroic WFS window WFS port provides both NGS and LTAO WFS Light from telescope Entrance window M1 M3 WFS M2 is at an image of the secondary: - Provides cold baffle Direct Gregorian Port 0.7 m Fold mirror or dichroic Instrument Platform M1 is conjugate to 12 km: - MCAO upgrade path Challenges for the GMT, Melbourne, June

28 Layout on the instrument plazorm AO instrument 2 AO instrument 1 AO relay Phasing and guiding cameras Challenges for the GMT, Melbourne, June

29 Summary of Sensor Parameters Description Location N Wavelength Patrol Field Track 1 Rotate 2 Acq./Guide IP(SI) 3(1) Visible 15 Diam. Y Y Light Path Active Optics WFS IP 3 Visible 15 Diam. Y * Phasing Camera IP 1 Ks, Visible 15 Diam. Y N GLAO WFS IP nm 8 Diam. N N NGS WFS AOR 1 Visible 2.5 Diam. Y N LTAO WFS AOR nm 1.2 fixed N N Fast Tip-Tilt SI 1 IR 2.5 Diam. Y Truth WFS SI 1 IR 2.5 Diam. Y IP = Instrument Platform SI = Science Instrument AOR = AO Relay 1 = Sensor must track off-axis source trajectory from apparent sky rotation in image plane. 2 = Pupil mask must counter-rotate * = Pupil masking could be software-based Challenges for the GMT, Melbourne, June

30 Laser Guide Star Facility Provides a general purpose ar[ficial beacon for LTAO and GLAO Six beacon geometry uses GMT pupil to minimize fratricide Variable radius from 35 (LTAO) to 4' (GLAO) Fratricide from other beams when looking at the top beacon. The affected areas of the pupil are shown as lines with the offending beacon s color. Simulated Shack-Hartmann WFS affected by fratricide Challenges for the GMT, Melbourne, June

31 Instrument FOV Wavelengths AO Science TIGER (thermal IR imager) NIRMOS (near IR spectroscopy) GMTNIRS (high res. spectroscopy) GMTIFS (near IR integral field unit) AO instruments on the GMT How does the scien[fic reach of the first genera[on instrument suite take advantage of the GMT s natural AO capabili[es? μm NGS, LTAO Exoplanets, planetary discs, dusty AGN, extragalac[c star forma[on ~ μm GLAO Characteriza[on of first galaxies, early galaxy assembly Single object μm NGS, LTAO Exoplanet chemistry, GC kinema[cs (GR), protostars μm LTAO Galaxy dynamics, black hole masses Note also that near IR exoplanet imaging will be a par[cular strength of GMT (Olivier Guyon s talk), looking ahead to the second genera[on instrument suite. Challenges for the GMT, Melbourne, June

32 Summary GMT has the opportunity to stand out from the crowd with instruments that capitalise on its excellent AO thermal sensi[vity and large high resolu[on étendue offered by GLAO. A cri[cal design feature of the telescope in this regard is its adap[ve secondary mirror. LBT, with its first ASM, is now showing the best AO results from any 8 m class telescope. Because GMT has smaller aperture than E ELT and TMT, a strong emphasis should be maintained on exploi[ng its unique scien[fic phase space. Challenges for the GMT, Melbourne, June

Adaptive Optics for the Giant Magellan Telescope. Marcos van Dam Flat Wavefronts, Christchurch, New Zealand

Adaptive Optics for the Giant Magellan Telescope Marcos van Dam Flat Wavefronts, Christchurch, New Zealand How big is your telescope? 15-cm refractor at Townsend Observatory. Talk outline Introduction