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
Halfjaarcijfers 2010 Amsterdam, 25 augustus 2010 Raad van Bestuur Vincent de Bok Huub van der Vrande
Halfjaarcijfers 2012 Amsterdam, 29 augustus 2012 Raad van Bestuur Vincent de Bok Huub van der Vrande