esa’s darwin space interferometer huub röttgering sterrewacht leiden
TRANSCRIPT
ESA’s Darwin space interferometer
Huub RöttgeringSterrewacht Leiden
The InfraRed Space InterferometerDARWIN
• 2014• 6 1.5 m telescopes• Hexagonal configuration• Beam combiner• Passive cooling (40 K): 5-20 micron
Ringberg, 5-Sept-2003 Imaging with Darwin Page 3
Overview
Introduction– Timeline / status project– Relation with NASA’s Terrestrial Planet
Finder Imaging considerations Science
Ringberg, 5-Sept-2003 Imaging with Darwin Page 4
Finding and characterising exo-Earth’s– Nulling interferometry
Science
The Problem
Detecting light from planets beyond solar system is hard:– Planet emits few
photons/sec/m2 at 10 m– Parent star emits 106 more– Planet within 1 AU of star– Dust in target solar
system 300 brighter than planet
Finding a firefly next to a searchlight on a foggy night
Ringberg, 5-Sept-2003 Imaging with Darwin Page 6
Finding and characterising exo-Earth’s– Nulling interferometry– Atmosphere -> CO2
– Wet and pleasant H20– Life O3 (? / !)
High resolution and sensitive IR imaging– Cophasing using an off-axis reference star
Science
CO2
O3
H2O
(m)
6 8 10 12 14 16 18
Earth at 10pc
Ringberg, 5-Sept-2003 Imaging with Darwin Page 7
Darwin timeline 1993: Léger et al
– ``Darwin proposal’’ 2000 Presentation Alcatel system level study 2004 Results significant technology development
program (15 Meuro)– Optical components, coolers, thrusters, metrology,
control software, 2 breadboards … 2007 – SMART2 techno demonstration flight
– (mainly LISA technology) 2010 – SMART3 techno demonstration flight
– 2-3 space craft 2014 – launch
Ringberg, 5-Sept-2003 Imaging with Darwin Page 8
NASA’s TPF
Similar goals and timelines
1999:
IR interferometer with cooled 4x3.5 m mirrors and ~75-1000 m baseline
Vegetation edge
Blue sky
Earthspectrum
fromEarth-shine
2000
Variable-Pupil Coronagraph IR Nulling Interferometers
Large Aperture IR Coronagraph
SVS
coronagraphe
M2
M3
M1
Hyper-telescope
2001: 4 different studies
Variable-Pupil Coronagraph
IR Nulling Interferometers
•Coronagraph – Difficult•10-15 meter mirror with rms surface ~< 1 Å
–Deformable mirrors - control to <1 Å rms over wide range of scales
–Wavefront sensing - adequate for <1 Å control
•Interferometer - Complex–Cryogenic nulling - 10-5 or 10-6 depth across ~1 octave
–Wavefront & amplitude control - spatial filter in mid-IR (+ DM for low spatial freqs) + control of thermal & vibration effects + acc. amplitude measurement
–Beam transport issues (rejection of stray light at small angles)
2002: down selection for 2 concepts
Ringberg, 5-Sept-2003 Imaging with Darwin Page 12
Joined ESA/NASA mission MOU: aims for a joining in 2006 Plan
– Both sides continue technical studies– Regular scientific contact– Criteria to guide continuation after 2006
• #1: Sensitivity in finding and characterizing exoplanets• #2: Richness of astrophysical science opportunities• #3: Technology development needed• #4: Life-cycle costs• #5: Risk of cost, technology, schedule, on-orbit failures• #6: Reliability and robustness
Ringberg, 5-Sept-2003 Imaging with Darwin Page 13
Astrophysical imaging with Darwin
1. Imaging considerations2. Science
Röttgering et al. 2003, Heidelberg conference
Ringberg, 5-Sept-2003 Imaging with Darwin Page 14
Imaging performance at 10 micron
Sensitivity (Takajima and Matshura, 2001)• Limited by shot noise from the zodiacal background.• Similar to JWST
– Point source sensitivity• 1 hour, s/n=5: 2.5 microJy
– Image sensitivity • S_integrate/noise > 50 within FOV• > 2.5 microJy for a 100 hour
Resolution– Baselines up to 500 meter– 200 m baseline: 10 mas
• JWST 350 mas
Ringberg, 5-Sept-2003 Imaging with Darwin Page 15
Imaging considerations
PSF of an individual telescope: 1.4 arcsec– = maximum FOV for pupil combination
Mapsize (200 m baseline/telescope diameter) <~ 100 * 100 independent pixels
Complexity– per configuration maximum 6*5/2 = 15 uv points– number of uv-points >>~ number of image
parameters– for a complex map of 100 * 100 independent pixels:
• >>~ 666 configurations
Ringberg, 5-Sept-2003 Imaging with Darwin Page 16
Baseline dynamics
Fastest reconfiguration cycle takes about 16 hours
Snapshots will be taken “on the fly”
Basic reconfiguration approach
a single expansion up to baselines of 500 m and
contraction coupled to a 60o rotation
bang-bang thrust profile both radially and tangentially
<dB/dt> = 1.5 cm/s @ 1 mN
16
d’Arcio et al. 2001
Ringberg, 5-Sept-2003 Imaging with Darwin Page 17
UV coverageHexagonal array -> 9 independent visibilities per snapshot 600 snapshots, ~ 5400 uv points/reconfiguration cycle
-> Filling the UV plane is ’’easy’’ Ground based telescopes are ``fixed’’ (radio) Baseline/apertureis huge
17
d’Arcio et al. 2001
Ringberg, 5-Sept-2003 Imaging with Darwin Page 18
Issue: Cophasing How to phase-up the array not using the target?
– Essential to• integrate longer than the coherence time of the interferometer
(~10 sec)• Measure complex visibilities (Amplitude and phase) needed for
imaging– Off-axis bright stars (there are enough!)
• Similar to PRIMA instrument for the VLTI (Quirrenbach, this meeting)
• Multiplexing in wavelengths has the advantage that science and reference beams travel along common path (Alcatel)
– Implementation1. Modification to the nulling beamcombiner (Alcatel)2. Separate imaging beamcombiner
How to get a large Field of View?– Mosaicing
• Expensive in time– homothetic mapping
• Relative complex• Pupil matching in
magnification and orientation before image plane combining
• Implementation
– Pupil matching/zooming optics at central beamcombiner
– Pupil matching/zooming at telescopes
(see d’Arcio and le Poole, 2003)
positioning stages
4kx4k detector
imaging telescope
Zoom optics(5-50x)
Light f rom telescope
Afocal zoomoptics (5-50x)
Lo
(fi xed)
Light f rom telescope
conventionalpupil mapping
variable magnification
positioning stages
4kx4k detector
imaging telescope
Zoom optics(5-50x)
Light f rom telescope
Afocal zoomoptics (5-50x)
Lo
(fi xed)
Light f rom telescope
conventionalpupil mapping
variable magnification
Physical processes observable at 6-20 micron– Molecules: Rotational and
vibrational lines • Temperatures, densities,
kinematics, Chemistry
– Ions: Forbidden fine-structure lines• Temperatures, densities,
kinematics, abundance's
– Dust: PAH features, continuum shape• Composition, temperature
– Late type stars: continuum (high z)• Spatial scales
ISO observationsStarburst galaxy
Circinus
Ringberg, 5-Sept-2003 Imaging with Darwin Page 21
Appropriate sensitivity and angular resolution ?
Star and planet formationAGN
Distant galaxies
Star and Planet formation
Sketch of scenario maybe in place (Shu et al. 87)
Vast range of conditions and relevant timescales– densities 10^4 - 10^13
/cm^3– temperatures 10 - 10,000 K – month - 10^6 years
Issues– density, temperature and
dynamical structure of disks?
– At what stage and when do planets form?
Compendium of Monnier and Millan-Gabet of K-band sizes of YSOs
Disk models of D’Alessio, Merin
An unphysical, unrealistic extrapolation-> fainter YSO are small (10-100 mas ?)
Log
Rad
ius[
mas
]
4
2
0-2 -1 0
Log flux @ 14 micron [Jy]
ISOCAM survey of your starclusters at 6.6 and 14.3 micron (Eiroa et al)
Darwin
MIDI
Ringberg, 5-Sept-2003 Imaging with Darwin Page 25
Active galactic Nuclei Zoo: Seyfert, Starburst
quasars ... – unification: orientation,
time-evolution, mass, spin
1000 times more AGN at z=2 than z=0
Every galaxy has a central massive Blackhole (?)
Issues:– Physics? When and how
do BH form?– Relation to Galaxy
formation?
Ringberg, 5-Sept-2003 Imaging with Darwin Page 26
AGN may contain dusty tori– can obscure the central QSO– feeds the massive Black Hole
Radiative transfer model of a dusty torus – size scales with QSO
luminosity– SED from = 1 - 300 m– morphologies at = 10 m
Models of Tori of Granato et al.
Adapted to NGC 1068, Heijligers etal.
Darwin observations of Tori D = 300 times the sublimation radius
NGC1068:
– Bight, low luminosity nearby AGN
• ~10 Jy: prime target for MIDI/VLTI in 2003
• 1.7 1031 erg/s/Hz at = 10 m
– (prime target for MIDI/VLTI in 2003)
Weak AGN observable up to z = 1 - 2
Stronger AGN up to z = 10NGC1068
0.01 0.1 1 10 redshift
1’’
0.1’’
0.01’’
50 Jy
5 JyL (
10
m [
1030
erg
/s/H
z]
Distant Galaxies When and how do galaxies form?
– Star formation history, galaxies shapes– Relation to black hole formation
8-10 meter telescopes: a few thousand with 3<z<6 and still counting– Hardly morphological information
Darwin: morphologies of the older stellar component– observe 2 micron rest == 10 micron for z=4
Semi-analytical models of galaxy formation as guidance – input: evolution of cold-dark matter halos, prescriptions for cooling, star
formation and feedback, dust…– output: large samples of mock galaxies and their properties (SF, mass,
type)
FIRES survey IsaacVLT
: 2.5^2 arcmin 96 h in J, H, K
HDFS limit in K = 24.4
mag Image HST
I+H+K Franx, Labbe,
Forster,schreiber, Rix, Rudnick, Röttgering, etal.
Ringberg, 5-Sept-2003 Imaging with Darwin Page 30
SED fittingwith galaxy templates
•Photometric redshift•Estimate 10 micron flux density
Rudnick, Labbe et al.
Ringberg, 5-Sept-2003 Imaging with Darwin Page 31
JWST resolutionAt 10 micron(0.35 arcsec)
Ringberg, 5-Sept-2003 Imaging with Darwin Page 32
100 hour, S_int/noise=50
F (
10
m )
J
y
(photometric) redshift
100 hourPointsource S/N=5
Ringberg, 5-Sept-2003 Imaging with Darwin Page 33
Conclusion
Darwin will be a powerful instrument for – Finding and characterizing exo-Earth– Astrophysical studies
Sensitivity is similar to JWST– Cophasing is an important issue
Size scales, AGN, YSOs, distant galaxies are appropriate– Case for larger fields
2025Terrestrial planet imager?20 8-m telescopes