The Next-Generation Adaptive Optics System

at Keck Observatory

Introduction & Overview

Michael Liu & Claire Maxon behalf of the NGAO study group.

NGAO Study Contributors

• Solar System: Franck Marchis (UC Berkeley)– Maté Adamkovics (UC Berkeley), Antonin Bouchez (Caltech), Josh

Emery (NASA-Ames), Keith Noll (STScI),

• Galactic Astronomy: Michael Liu (Hawaii)– Andrea Ghez (UCLA), Tom Greene (NASA-Ames), Lynne

Hillenbrand (Caltech), Jessica Lu (UCLA) Bruce Macintosh (LLNL), Stan Metchev (UCLA), Nevin Weinberg (Caltech)

• Extragalactic Astronomy: Claire Max (UC Santa Cruz)– Mark Ammons (UCSC), Aaron Barth (UC Irvine), Rich Dekany

(Caltech), Don Gavel (UCSC), David Koo (UCSC), Patrick Jonsson (UCSC), David Law (Caltech), James Larkin (UCLA), Laura Melling (UCSB), Greg Novak (UCSC), Tommaso Treu (UCSB), Chuck Steidel (Caltech)

• Technical and Science Instruments: Peter Wizinowich (WMKO)– Sean Adkins, Brian Bauman, Jim Bell, Antonin Bouchez, Rich

Dekany, Ralf Flicker, Don Gavel, Olivier Lai, David Le Mignant, Bruce Macintosh, Keith Matthews, Chris Neyman, Viswas Velur

Agenda for today’s presentations1. NGAO science case: led by AOWG

• Introduction & Executive Summary (30 min)• Extragalactic Science (20 min)• Galactic Science: Star & Planet Formation (20 min)• Solar System Science (15 min)• Galactic Science: Galactic Center (10 min)• Summary

2. NGAO technical case: led by WMKO• Introduction & Point Design (15 min)• Performance Budgets (30 min)• Point Design Feasibility and Subsystems (25 min)• Science Instruments (10 min)• Management & Budget plan (20 min)• Summary

Recall the Keck Strategic Plan: Twenty-year strategic goals for astronomy

• Leadership in high angular resolution astronomy

• Leadership in state of the art instrumentation

• Highly efficient observing

• Complementarity with ELTs

• NGAO addresses all of these!

Keck Next-Generation Adaptive Optics (NGAO) will provide a powerful new suite of capabilities1. Near diffraction-limited in the near-IR (K-Strehl

>80%)• A PSF with unprecedented precision, stability and

contrast.

2. Vastly increased sky coverage and multiplexing• Enables a much broader range of science programs.

3. AO correction at red optical wavelengths (0.6-1.0 m)• Highest angular resolution of any filled-aperture

telescope.

Keck AO has been a tremendous success thus far

NGSAO

LGSAO

Titan

AU Mic debris disk

Kuiper Belt objects

Titan Galactic Center

Merging galaxies Substellar binaries

Refereed science papers from LGS AO: Keck has already had a big impact in first 1.5 yrs

Keck Keck LGSLGS2005-2005-20062006

Competitive landscape: Other 8-10 meter telescopes are aggressively pursuing new AO systems.• Other observatories are focusing on high-

contrast imaging or ground-layer AO1. High-contrast (Extreme AO): powerful, but highly

specialized– Gemini (GPI, NICI), VLT (SPHERE), Subaru (HiCIAO)

2. Ground-layer AO (“Seeing Improvement”)– VLT (to feed MUSE and HAWK-I)– Gemini study

• Only Gemini is pursuing well-corrected wider-field AO

– Multi-Conjugate AO (~2’ FOV, K-Strehl~0.4)

• Current Keck AO system is ~10 years old.

Keck AO Strategic Plan

• AO strategic plan established by Keck AO Working Group in Nov 2002, reaffirmed in Sep 2004:

“AOWG vision is that high Strehl, single-object, AO will be the most important competitive point for Keck AO in the next decade.”

• Late 2005: New AOWG tasked by Observatory and SSC to develop science case for next-generation Keck AO.

Overview of this year’s NGAO study • Solicit broad participation from science & technical

expertise in Keck community

• General approach:– Analyze a limited set of key science cases, spanning the

range of community interests.– Develop science requirements for AO and science

instruments– Generate simulations of NGAO performance– Iterate on science requirements.– Develop point design.

• 2006 Mar: Science workshop at CfAO/UCSC

• 2006 Apr: Technical retreat in Indian Wells, CA

• 2006 May: Work meeting at SPIE meeting in Orlando, FL

Science requirements for NGAO

• High-level summary of required AO capabilities

Optical Near-IR Thermal-NIRnarrow field,

modest Strehlnarrow field, high Strehl

narrow field, v.high Strehl

Solar System Key Yes Yes Maybe -

Galactic Yes Key Maybe Key -

Extragalactic Key Key - Yes Key

High Contrast

Wide-Field, Multi-Object

NGAO will allow us to tackle many high impact science areas1. Near diffraction-limited in the near-IR (Strehl >80%)

• Direct detection of planets around low-mass and young stars• Astrometric tests of general relativity in the Galactic Center• Detailed structure/kinematics of high redshift galaxies

2. Vastly increased sky coverage and multiplexing• Multi-object IFU surveys of GOODS-N, COSMOS, etc.• Resolving the earliest stages of star + planet formation

3. AO correction at red optical wavelengths (0.6-1.0 m)• Scattered-light studies of debris disks and their planets• Masses and composition of asteroids and Kuiper Belt objects• Kinematic mass determinations for super massive black holes

NGAO Architecture

• Tomography to measure wavefronts and overcome cone effect

• IR tip-tilt stars, partially AO-corrected, for broad sky coverage

• Closed-loop AO for narrow fields

• Open-loop AO for deployable IFUs

What is Tomography ?

90 k

m

Key performance metrics: Strehl vs. observing wavelength

Key performance metrics:Sky coverage and Strehl vastly better with NGAO • For narrow-field science, Keck NGAO produces high

Strehl ratios over most of the sky in the near-IR.

K-band Strehl

Sky coverage

all-sky averageall-sky averagerr00 = 18 cm, z=30° = 18 cm, z=30°

NGAO has dramatically better sensitivity: Example of near-IR IFU spectroscopy

• Plot shows S/N ratio for redshifted H, OSIRIS-like IFU: for 0.6 < z < 2.3, NGAO shows factor of 3 to 6 improvement in signal to noise ratio.

• Factor of 9 to 36 shorter integration times (!)

• If IFU has 6 deployable units, multiply by another 6x

NGAO + d-IFU has 50-200x higher

throughput than LGS AO today!

NGAO + d-IFU has 50-200x higher

throughput than LGS AO today!

NGAO has dramatically better sensitivity: Point source sensitivity (1 hour, 5)

Filter Current LGS AO

330 nm WF error

Proposed NGAO

140 nm WF error

Magnitude improvement

V 27.6 28.7 1.1

R 27.1 29.0 1.9

I 26.5 29.0 2.5

J 24.4 27.0 2.6

H 24.4 25.8 1.4

K’ 24.4 25.2 0.8

L’ 19.2 19.5 0.3

Ms 16.4 16.6 0.2

NGAO: Science Instrument Priorities

1. Near-IR imager

2. Visible imager

3. Near-IR IFU (OSIRIS?)

4. Visible single-field IFU

5. Thermal near-IR imager

1. Deployable near-IR multi-object IFU (N~6)

Single-object Multi-object

NGAO risk reduction: Key technical elements are already being tested in the lab and on the sky• Lasers

– Situation much improved in last few years

• Tomography– Gemini-South, solar, VLT/MAD, Palomar

NGS

• Visible-wavelength AO– Air Force (demonstrated), Mt. Wilson

(demonstrated), Palomar, Lick

• MEMS deformable mirrors– Nact=1024 working in UCSC lab, funded by

consortium up through Nact=4096

• Open-loop AO– Testing now at Lab for Adaptive Optics– On-sky demonstration coming to Lick

Important linkages between Keck NGAO and TMT • NFIRAOS: high-order correction, narrow-field MCAO

– Lessons Learned about: IR tip-tilt sensors,sky coverage issues, multiple laser guide stars, optical design of relay

• IRMOS: multi-object AO system with deployable IFUs– We envision the Keck NGAO deployable-IFU system to be

analogous to TMT IRMOS, but much less complex– Half a dozen IFUs instead of 16-20– More forgiving optical design

– We are benefiting from two excellent TMT feasibility studies for IRMOS

• TMT invested ~$2 M in feasibility studies for NFIRAOS and IRMOS

• In the opposite direction, Keck NGAO experience will help TMT– Continuing R&D, validation tests– Earlier implementation on telescope

Uniqueness space for Keck NGAO

• Enables a wide variety of new science within the interests of the Keck Community

• Enables a wide variety of new science within the interests of the Keck Community

• High Strehl in near-IR

• “Precision AO” - both high Strehl and more stable PSF

• AO at optical wavelengths Takes full advantage of the unsurpassed aperture size of our 10-m telescope (and opens a new long-term opportunity for WMKO).

• Deployable AO-corrected IFU instrument

• Takes advantage of world-class AO expertise in the Keck Community