Download - Science Goals and AO for the TMT
TMT.PSC.PRE.09.031.REL01 1
Jerry NelsonUniversity of California at Santa Cruz
Adaptive Optics for Extremely Large TelescopesParis, 2009June23
Science Goals and AO for the TMT
TMT.PSC.PRE.09.031.REL01 2
Outline
Project IntroductionTelescope overviewScience-based metricsTMT key featuresMajor science goalsScience Instruments
TMT.PSC.PRE.09.031.REL01 3
Project Introduction
Time line– 2004 project start, design development– 2009 preconstruction phase– 2011 start construction– 2018 complete, first light, start AO science
Partnership– UC– Caltech– Canada– Japan– NSF?– Others?
TMT.PSC.PRE.09.031.REL01 4
Telescope Overview
Tensional members
M2 hexagonal ring
M2 support tripod
M2 support columns
Elevation journal
M1 cell Azimuth truss
Azimuth cradle
M2 structural hexapod
LGSF beam transfer
LGSF launch telescope
Nasmyth platform
Laser room
TMT.PSC.PRE.09.031.REL01 5
TMT Optical Design:Ritchey Chrétien
M1 Parameters – ø30m, f/1, Hyperboloid
k = -1.000953– Paraxial RoC = 60.0m– Sag = 1.8m– Asphericity = 29.3mm (entire M1)
M2 Parameters– ø3.1m, ~f/1, Convex hyperboloid,
k = -1.31823– Paraxial RoC = -6.228m– Sag = ~650mm– Aspheric departure: 850 m
M3 Parameters– Flat – Elliptical, 2.5 X 3.5m
TMT.PSC.PRE.09.031.REL01 6
Segment Size
TMT.PSC.PRE.09.031.REL01 77
Primary Mirror Control System (M1CS)
The M1CS, with the Alignment and Phasing System, turn the 492 individual segments into the equivalent of a monolithic 30 meter diameter mirror.TMT control strategy is an evolutionary improvement on the successful strategy used at the two Keck Telescopes.
SSA prototype with dummy segment
TMT.PSC.PRE.09.031.REL01 8
M1CS off: 223 nm RMS
M1CS on: 14 nm RMS
M1 surface error from wind disturbance
M1CS OverviewM1CS maintains the overall shape of the primary mirror
– Attenuates gravity, temperature, wind, and vibration disturbancesThe primary mirror is aligned and phased using the Alignment and Phasing System (APS) every 4 weeks or after a segment exchange.
– Look up tables are used in between calibration runsM1CS controls the global shape of the M1 using segment-mounted edge sensors and actuatorsReal time “On-instrument Wavefront Sensors” (OIWFS) measurements or AO system offloads will augment the static look up tables built using APS data
TMT.PSC.PRE.09.031.REL01 9
Science-based Metrics
We use the time needed to make an observation as our metric– Generally assume that we are observing point sources– Generally assume the sources are background limited (most
photons come from background, rather than source)– In detail this is based on King’s paper that shows
For these assumptions we get
This is true for seeing-limited or diffraction-limited observations
€
point source sensitivity (PSS) ~ 1/equivalent noise area ~ PSF2∫ (θ)dθ
€
PSS ~ 1t
~ area * throughput(background/solid angle) * (image solid angle)
TMT.PSC.PRE.09.031.REL01 10
Science Merit Function
For seeing-limited observations – PSS ~ D2/image diameter2
For diffraction-limited observations– image solid angle varies as 1/area, so we get the well known
PSS~D4 rule– For finite Strehl, the signal strength is reduced by S, but the
background is not reduced, so one gets PSS~S2 where
€
Strehl = S = e−σ 2
and σ is the wavefront error in radians
TMT.PSC.PRE.09.031.REL01 11
Reflectivity, emissivity, throughput
Clearly we want the highest possible reflectivity of our optics– Obvious, since PSS ~ throughput– In the visible r ~ 0.9, so for 3 mirrors, net throughput ~ 0.73– But, as important, thermal emission from the warm optics can
increase the IR background, particularly in K band– When the IR sky is dark (between OH lines) the telescope
emission can be the dominant background source– Background ~ (# warm mirrors)*(1-reflectivity)
So it can be VERY important to minimize the number of warm mirrors between the target and the IR instrument
TMT.PSC.PRE.09.031.REL01 12
Blackbody Flux vs wavelength (various T's)
1.E+06
1.E+07
1.E+08
1.E+09
1.5 1.7 1.9 2.1 2.3 2.5
Wavelength (µm)
Photons/s/arcsec2/µm/TMT
5°C0°C-5°C-10°C-15°C-20°C-25°C
TMT.PSC.PRE.09.031.REL01 13
Thermal backgrounds
Previous graph shows the blackbody fluxCooling the optic by ~ 30° reduces the flux in this wavelength region by a factor of ~ 15Below ~ 2µm the flux is lower than natural backgroundsThese fluxes are multiplied by the mirror emissivities and the number of mirrors
Observatory created backgrounds– Three ambient temperature telescope mirrors (M1, M2, M3)– NFIRAOS science path
1 ambient window5 cold mirrors1 cold beam splitter1 cold window
TMT.PSC.PRE.09.031.REL01 14
K band thermal background
In the near IR, only K band will see significant thermal flux from telescopeTelescope– 3 mirrors at 1.5% emissivity each– Segment gaps 0.5%– Net background ~ 0.05*ambient blackbody flux
NFIRAOS– Net throughput 85%, so emissivity ~ 0.15– Cooling 30° reduces flux by a factor of ~ 15, so – Net added background ~ 0.01*ambient blackbody flux
TMT.PSC.PRE.09.031.REL01 15
Field of View
For many science programs larger field of view is useful– Multiple targets– Complex targets (galaxies, etc)– Astrometry where reference objects are needed
Seeing-limited unvignetted 15 arcmin FoVAtmospheric angular anisoplanatism limits the correctable field of view for AO– One must measure the atmosphere over a sufficient volume to
know what the angle dependent correction needs to be– With lasers, one must do tomography to get this information– One must have multiple deformable mirrors to make the added
correction
TMT.PSC.PRE.09.031.REL01 16
Impact of multiple deformable mirrors
More DM’s allow greater 3-d fidelity of atmospheric correction, improving correction over larger field of view
Strehl Ratio
Off axis angle (arcsec)
Wavelength 0” 6” 12” 18”
J 1 DM 0.56 0.42 0.21 0.07J 2 DM 0.60 0.60 0.58 0.51
H 1 DM 0.72 0.61 0.40 0.21H 2 DM 0.75 0.75 0.73 0.70K 1 DM 0.83 0.75 0.60 0.41K 2 DM 0.85 0.85 0.84 0.81
TMT.PSC.PRE.09.031.REL01 17
TMT design path
30m diameter telescopeHigh reflectivity opticsOnly 3 reflections to science instruments or NFIRAOSNFIRAOS cooled by 30° to reduce thermal emissionNFIRAOS is initial AO system and can feed 3 instFor AO, two DM’s for increased field of viewFor AO, large sky coverage enabled by using 3 partially corrected natural stars (focus, tip, tilt) with 6 LGS15 arcmin unvignetted field of view for seeing-limitedAll instruments always available in < 10 minutes
TMT.PSC.PRE.09.031.REL01 18
Nasmyth Configuration: First Decade Instrument Suite
TMT GCAR, April 2009 18
/IRMS
TMT.PSC.PRE.09.031.REL01 1919
NFIRAOS MCAO has better performance than current systems
Strehl Ratio Band SRD (120 nm) Baseline (177
nm) Baseline + TT
R 0.313 0.080 0.052 I 0.411 0.145 0.105 Z 0.566 0.290 0.236 J 0.674 0.424 0.366 H 0.801 0.617 0.569 K 0.889 0.774 0.742
Dual conjugate AO system– Order 61x61 DM and TTS at h=0 km– Order 75x75 DM at h=12 km
– Better Strehl than current AO systems (e.g., Keck ~280-300nm WFE)
Completely integrated system Fast (<5 min) switch between targets
>50% sky coverage at galactic poles (w/<2mas TT error)
IRIS
IRMS (NIRES)
(WIRC)
NFIRAOS
TMT.PSC.PRE.09.031.REL01 2020
• Nature and composition of the Universe• Formation of the first stars and galaxies• Evolution of galaxies and the intergalactic medium• Relationship between black holes and their galaxies• Formation of stars and planets• Nature of extra-solar planets• Presence of life elsewhere in the Universe
TMT: Key Science
TMT.PSC.PRE.09.031.REL01 2121
Science Drivers for large O/IR Telescopes:3 Basic Types
Science that you know you want to do now, but have discovered to be out of reach through experience on 8-10m telescopes.
– These tend to be what is written in “design reference mission” or “science case” documents
Solving problems we do not even know about yet – Thinking about “capability space”, or “discovery space”, rather than specific
science cases– Some intuition is necessary- where will the surprises be, what will we need to
follow them up?Supporting roles and “complementarity” with other facilities on ground, in space.
– Harder to make such roles sound exciting/compelling… BUT next-generation O/IR telescopes will play key role in supporting ALMA, JWST, CCAT, LSST, IXO (CON-X), ZEUS, etc.
– While many other facilities may not publicly admit that they “need” large O/IR telescopes on the ground (for the same reason), in fact, history suggests that they will.
TMT.PSC.PRE.09.031.REL01 22
TMT Detailed Science Case
22
•~100 page summary of TMT science case (David Silva, editor), completed and posted publicly in October 2007. (http://tmt.org)•Developed with AURA/NOAO as full partner (US community interests accounted for). •Includes science cases developed by instrument feasibility study teams•From fundamental physics and cosmology, to galaxy and structure formation, to extra-solar planets, to solar system studies.
TMT.PSC.PRE.09.031.REL01 2323
Key TMT features for Science
30m, f/1 primary, RC telescope, ~20’ field– 30-m is a judgment about the proper balance between science benefit, cost,
technological readiness, and scheduleFilled aperture, 492 1.44m segments– produces a more concentrated point spread function (PSF), improving signal-
to-noise ratios and easing data analysis Integrated AO systems, including Laser Guide Star (LGS) facility– MCAO, MOAO, GLAO, MIRAO, ExAO – Sensitivity: D4 advantage for background-limited point sources with AO
Wavelength range: 0.31 - 28 microns (entire UV-mid-IR)Spatial resolution: 0.007” at 1 micron, 0.014” at 2 micronsInstruments on large Nasmyth platforms, addressed by articulated tertiary– Rapid switching between targets with different instruments (< 10 min)– (Rapid target acquisition: time between targets < 5 min)
TMT.PSC.PRE.09.031.REL01 2424
SAC Instrument Prioritization
Desire to fund first-light instrument suite out of cost-capped construction budgetDiscovery space: largest gains in broadest range of science in the near-IR (0.8-2.5 microns)@diffraction limit
– IRIS: IFU+diffraction limited imager– IRMS: multiplexed faint object spectroscopy in the near-IR -- leverages investment
in facility MCAO system. Ability to perform guaranteed high-priority science we can think of now
– WFOS– PFI very focused, but very powerful (GPI as a pathfinder...)– HROS workhorse capability, strong science case
Raw gains in sensitivity (D4) over existing or planned facilities, well defined science
– MIRES (mid-IR echelle)– NIRES (near-IR echelle)– WIRC (wider field diff. limited imager)
TMT.PSC.PRE.09.031.REL01 2525
Instrument Spectral Resolution Science Case
Near-IR DL Spectrometer & Imager(IRIS)
~4000
Assembly of galaxies at large redshift Black holes/AGN/Galactic Center Resolved stellar populations in crowded fields Astrometry
Wide-field Optical Spectrometer
(WFOS)1000-5000
IGM structure and composition 2<z<6 High-quality spectra of z>1.5 galaxies suitable for measuring stellar
pops, chemistry, energeticsNear-field cosmology
Multi-slit near-DL near-IR Spectrometer
(IRMS)2000 - 5000 Near-IR spectroscopic diagnostics of the faintest objects
JWST follow-up
Mid-IR Echelle Spectrometer & Imager
(MIRES)5000 - 100000
Physical structure and kinematics of protostellar envelopes Physical diagnostics of circumstellar/protoplanetary disks: where and
when planets form during the accretion phase
ExAO I(PFI)
50 - 300 Direct detection and spectroscopic characterization of extra-solar planets
High Resolution Optical Spectrograph
(HROS)30000 - 50000
Stellar abundance studies throughout the Local Group ISM abundances/kinematics, IGM characterization to z~6 Extra-solar planets!
MCAO imager(WIRC)
5 - 100 Precision astrometry Stellar populations to 10Mpc
Near-IR, DL Echelle(NIRES)
5000 - 30000 Precision radial velocities of M-stars and detection of low-mass planets IGM characterizations for z>5.5
TMT First Decade Instrument/Capability Suite
TMT.PSC.PRE.09.031.REL01 2626
Instrument Spectral Resolution Science Case
Near-IR DL Spectrometer & Imager
(IRIS)~4000
Assembly of galaxies at large redshift Black holes/AGN/Galactic Center Resolved stellar populations in crowded fields Astrometry
Wide-field Optical Spectrometer
(WFOS)1000-5000
IGM structure and composition 2<z<6 High-quality spectra of z>1.5 galaxies suitable for measuring
stellar pops, chemistry, energeticsNear-field cosmology
Multi-slit near-DL near-IR Spectrometer
(IRMS)2000 - 5000 Near-IR spectroscopic diagnostics of the faintest objects
JWST followup
Mid-IR Echelle Spectrometer & Imager
(MIRES)
5000 - 100000
Physical structure and kinematics of protostellar envelopes Physical diagnostics of circumstellar/protoplanetary disks: where
and when planets form during the accretion phase
ExAO I(PFI)
50 - 300 Direct detection and spectroscopic characterization of extra-solar planets
High Resolution Optical Spectrograph
(HROS)
30000 - 50000
Stellar abundance studies throughout the Local Group ISM abundances/kinematics, IGM characterization to z~6 Extra-solar planets!
MCAO imager(WIRC)
5 - 100 Galactic center astrometry Stellar populations to 10Mpc
Near-IR, DL Echelle(NIRES)
5000 - 30000 Precision radial velocities of M-stars and detection of low-mass
planets IGM characterizations for z>5.5
TMT Early Light Instrument Suite
TMT.PSC.PRE.09.031.REL01 27
TMT Science and “Flow-down”Requirements for early light capabilities have been fine- tuned as a balance between unfettered science-driven desires and technical/fiscal realities (SAC/Project interactions have been crucial). We are proposing to build the most powerful suite of capabilities we can, through close interaction between science and engineering. Currently-envisioned capabilities address a huge range of questions we can formulate now (and complement other powerful facilities)The same capabilities will make new discoveries and will be the primary diagnostic tool for making sense of the discoveries made elsewhere.
27
TMT.PSC.PRE.09.031.REL01 28
IRIS Conceptual Design Team
James Larkin (UCLA), PI, Lenslet IFSAnna Moore (Caltech), co-I, Slicer IFSRyuji Suzuki, Masahiro Konishi, Tomonori Usuda (NAOJ), ImagerBetsy Barton (UC Irvine), Project ScientistScience Team
– Mate Adamkovics(UCB), Aaron Barth(UCI), Josh Bloom(UCB), Pat Cote(HIA), Tim Davidge(HIA), Andrea Ghez(UCLA), Miwa Goto(MPIA), James Graham(UCB), Shri Kulkarni(Caltech), David Law(UCLA), Jessica Lu(UCLA),Hajime Sugai(Kyoto U), Jonathan Tan(UF), Shelley Wright(UCI)
OIWFS (On Instrument Wavefront Sensor) Team (HIA + Caltech)– Led by David Loop, Anna Moore
NSCU (NFIRAOS Science Calibration Unit) Team (U of Toronto)– Led by Dae-Sik Moon
TMT.PSC.PRE.09.031.REL01 29
Motivation for IRIS
Should be the most sensitive astronomical IR spectrograph ever builtUnprecedented ability to investigate objects on small scales. 0.01” @ 5 AU = 36 km (Jovian’s and moons)
5 pc = 0.05 AU (Nearby stars – companions)100 pc = 1 AU (Nearest star forming regions)1 kpc = 10 AU (Typical Galactic Objects)8.5 kpc = 85 AU (Galactic Center or Bulge)1 Mpc = 0.05 pc (Nearest galaxies)20 Mpc = 1 pc (Virgo Cluster)z=0.5 = 0.07 kpc (galaxies at solar formation epoch)z=1.0 = 0.09 kpc (disk evolution, drop in SFR)z=2.5 = 0.09 kpc (QSO epoch, H in K band)z=5.0 = 0.07 kpc (protogalaxies, QSOs, reionization)
Titan with an overlayed 0.05’’ grid (~300 km) (Macintosh et al.)
High redshift galaxy. Pixels are 0.04” scale (0.35 kpc).Barczys et al.)
M31 Bulge with 0.1” grid (Graham et al.)
Keck AO images
TMT.PSC.PRE.09.031.REL01 30
WFOS/MOBIE Team
Rebecca Bernstein (UCSC), PIBruce Bigelow (UCSC), PMChuck Steidel (Caltech), PSScience Team: Bob Abraham(U Toronto), Jarle Brinchmann(Leiden), Judy Cohen(Caltech), Sandy Faber(UCSC), Raja Guhathakurta(UCSC), Jason Kalirai(UCSC), Gerry Lupino(UH), Jason Prochaska(UCSC), Connie Rockosi(UCSC), Alice Shapley(UCLA)Some “flagship” science cases, “work horse capability”
– High quality spectra of faint galaxies/AGN/stars– IGM tomography
Great “follow-up” and “discovery” potential - full wavelength coverage with spectral resolutions up to R = 8000
– JWST, ALMA, etc., follow-upSensitivity >14 x current 8m telescopes
TMT.PSC.PRE.09.031.REL01 31
IR Multi-Slit Spectrometer(IRMS)
IRMOS (deployable MOAO IFUs) deemed too risky/expensive for first light=> IRMS: clone of Keck MOSFIRE, first step towards IRMOS
– Multi-slit NIR imaging spectro: – 46 slits,W: 160+ mas, L: 2.5”– Deployed behind NFIRAOS
2’ field60mas pixelsEE good (80% in K over 30”)
– Spectral resolution up to 5000– Full Y, J, H, K spectra (one at a time)
Images entire 2’ field
Slit width
Whole 120” field
TMT.PSC.PRE.09.031.REL01 32
IRMS Spectra
Configurable Slit Unit originally developed for JWST (slits formed by opposing bars)Full Y, J, H, K spectra with R ~ 5000 with 160mas (2 pix) slits in central ~1/3 of field
TMT.PSC.PRE.09.031.REL01 33
Summary
TMT will be a 30-m telescope with AO capabilities from the start – ~ 190 nm rms wavefront error over 10 arcsec– First light 2018
Very large and exciting science case8 instruments planned for the first decade3 instruments planned for first light– IRIS (an AO NIR integral field spectrograph and imager)– IRMS (an AO NIR multi object spectrometer (46 slits)– WFOS (a seeing-limited multiobject spectrometer with R<8000,
and ~ 50 arcmin2coverage)Many papers will elaborate on TMT AO in this conference