Transcript rymdens kretslopp

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Darwin/ Xtrasolar
AlbaNova
1 December 2005
p 1
Darwin
and
the Origins of
Extrasolar Species
Rene´ Liseau
Stockholm Observatory
Delegate to the Scientific Advisory Teams of
ESA : TE-SAT
NASA : TPFI-SWG
http://www.astro.su.se/groups/infrared/index.html
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Outline
Astronomical Jargon, Definitions & Acronyms
Extrasolar Planets (known)
Extrasolar Planets (expected)
Detection Techniques (known possibilities)
Detection Techniques (selected: ESA – Darwin, NASA – TPFI)
Optical Architecture (destructive interference, formation flying)
Mission Characteristics (payload, launcher, orbit selection)
The Future (future missions)
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Astronomical Jargon : shall attempt to avoid
Sorry, if too trivial...
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Definitions & Acronyms
1´´
1 AU
1. P arallaxsecond (pc)
a AU
d pc 
 arcsec
1 pc  3 1016 m  2  105 AU
( 3 lyr)
1 AU  1.51011 m
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Definitions & Acronyms
Seeing limited 1´´
8m diffraction limited
2. Diffraction - limitedfilled aperture(m)
 m
D m  250
 mas
AO  AdaptiveOptics
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Definitions & Acronyms
NASA  NationalAeronautics and Space Administration
T P F- I  T errest rial P lanetFinder - Interferom
eter
ESA
IRSI
 EuropeanSpace Agency
 InfraRedSpace Interferom
eter
Darwin  Detect ingand AnalysingRemot eWorl
ds
through Interferom
etric Nulling
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p 7
Goals of Darwin:
+
Find
other Earths
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Find
and
Darwin/ Xtrasolar
X-solar Life
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p 8
What is Known:
Discovery of Extra-solar Planets since 1995
M sin i
(M Jupiter )
update : 26 November 2005
Global statistics : 146 planetary systems 170 planets 18 multiple planet systems
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p 9
Earth
Uranus
Jupiter
Saturn
Sun
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Neptune
Exo-Planet Type
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p 10
mass = 0.003
mass = 1000 radius = 0.1
radius = 10 density = 5
density =
1
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mass = 1
radius = 1
density = 1
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p 11
Distribution of KNOWN Exoplanets
BIASED
by METHOD of
OBSERVATION
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p 12
Observation of STELLAR
REFLEX MOTION (Doppler)
P = 1 yr
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Earth:
30 km s-1
Sun: < 10 cm s-1
1 December 2005
p 13
Observation of STELLAR
REFLEX MOTION
P = 1 yr
Earth:
30 km s-1
Sun: 9 10-5 km s-1
12 yr Jupiter: O ( m s-1 )
5.2 AU Distance
Not Yet
Sensitivity
DV ~ 10 m s-1
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Besides Vrad , other known observational methods
planetary transits
micro-lensing
radius and density
of occulting planet
statistics of remote systems
distance of O (10 kpc)
direct imaging of structure in young disks
presence of planet(s)
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Besides Vrad , other known observational methods
pulsar timing
planet´s mass
first detection of Earth-mass planets...
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p 16
known observational methods useful for exo-Earths
?
radial velocities
stellar astrometry
N
Y
stellar activity of O (m s-1)
from space O (arcsec)
planetary transits
Y
from space ( DI/I < 10- 4 )
micro-lensing
Y
O (hour) , not repetitive
imaging of disk structure
N
O (MJup) , not unique
pulsar timing
Y
few systems, no Life
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known observational methods useful for exo-Earths
?
radial velocities
stellar astrometry
N
Y
stellar activity of O (m s-1)
from space O (arcsec)
planetary transits
Y
from space ( DI/I ~ 10-4 )
micro-lensing
Y
O ( hour) , not repetitive
imaging of disk structure
N
O (MJup) , not unique
pulsar timing
Y
few systems, no Life
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p 18
What is ?
How originated ?
Life
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p 19
Definition of Life... ?
(1). Organisms tend to be complex and highly organized. Chemicals found within their bodies
are synthesized through metabolic processes into structures that have defined purposes.
Cells and their various organelles are examples of such structures. Cells are also the basic
functioning unit of life. Cells are often organized into organs to create higher levels of
complexity and function.
(2). Living things have the ability to take energy from their environment and change it from
one form to another. This energy is usually used to facilitate their growth and reproduction.
We call the process that allows for this facilitation metabolism.
(3). Organisms tend to be homeostatic. In other words, they regulate their bodies and other
internal structures to certain normal parameters.
(4). Living creatures respond to stimuli. Cues in their environment cause them to react
through behavior, metabolism, and physiological change.
(5). Living things reproduce themselves by making copies of themselves. Reproduction can
either be sexual or asexual. Sexual reproduction involves the fusing of haploid genetic
material from two individuals. This process creates populations with much greater genetic
diversity.
(6). Organisms tend to grow and develop. Growth involves the conversion of consumed
materials into biomass, new individuals, and waste.
(7). Life adapts and evolves in step with external changes in the environment through
mutation and natural selection. This process acts over relatively long periods of time.
... etc ...
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p 20
Origin of Life ?
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p 21
What does Life DO ?
! Generates WASTE !
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p 22
Life transforms a planet - e.g. its Atmosphere
oxygen
methane
Time (Ga)
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p 23
Cyano Bacteria
produce sugar
`bluegreen algae´
and
OXYGEN
oxygenic photosynthesis:
2H2O + CO2 + hn  CH2O + O2 + H2O
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Chemical Disequilibrium Atmosphere :
simultaneously reducing .and. oxydizing
WATER .and.
CARBON DIOXIDE .and.
OXYGEN
2H2O + CO2 + hn  CH2O + O2 + H2O
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p 25
IMPLIES BIOACTIVITY
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p 26
IMPLIES BIOACTIVITY
Spectrum
in
Thermal Infrared
1. Earth is Hot
2. Atmospheric Lines
Opaque
Needs Space
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p 27
PROBLEM OF CONTRAST
1O10
Scattered Solar
Radiation
versus
107
log10
Planetary
Thermal Emission
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Visible
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InfraRed
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p 28
PROBLEM OF CONTRAST
1
10-11 to 10-7 of
central peak intensity
in the wings of the PSF
... and in real life
not inifinite signal-to-noise
PSF = Point Spread Function =
Fourier Transform of Modular Transfer Function (MTF)
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Solution:
Darwin the Mission
Nulling Interferometer
Destructive Interference
provides
Needed Contrast
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Long Baselines
provide
Needed Resolution
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Nulling Interferometer: Point Sources
simplest case:
2 element Bracewell
interferometer
to ``null´´ stellar radiation
[ e.g. at 10 pc distance and  = 10 m]
Sun 1.6
Jy*
Earth 0.23 Jy
=
(N = 3.6 mag )
(N = 20.7 mag)
star on optical axis
* 1 Jy = 10-26 W m-2 Hz-1
Rejection Rate:
=0
n > 105
n = 2 for Bracewell
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This is wonderful !
So - does everything come for free ?
We gain resolution but loose information and field
But for POINT SOURCES OK!
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p 32
D
Filled aperture D:
contains all spatial frequencies up to 1/D
=> Image of the source
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D
B
d/2
Interferometer B:
picks out 1 spatial frequency 1/B
in coherent field of view 1/d
Example:
 = 10 m, B = 200 m, d = 2 m
Resolution
= 10 milliarcsec
Field of view = 1 arcsec
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Equilateral triangle - Darwin architecture: 3.5 m
BCS in the centre of triangle
-120 deg between telescopes
-Variable distance TS to BCS
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p 35
Modulation properties
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p 36
Spectroscopy
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p 37
Beam Combination by Single Mode Waveguide
A
B
φA(t)
φB(t)
C
φC(t)
Focusing Optics
Single mode waveguide (SMW) used for
modal filtering to improve nulling ratio.
Phase relations in SMW of injected onaxis light such that resulting amplitude
is zero.
Internal modulation by alternating
phase shifts between
(-120º, 0º, +120º) and (+120º, 0º, -120º)
Stellar light can not
propagate in fibre
core and is rejected
into the cladding
Single Mode
Waveguide
Detector
Ref. O. Wallner et. al “Multi-axial single mode beam combiner”
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Beam Combination
Input wave
Applied chop
centre
A
A
0
reflected
90
Phase shift
90
180
Phase diff
180
A:
180
B:
C:
90
Phase shift
-120
A:
60
B:
C:
330
Input wave
SMW:
A:
B:
C:
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60
90
180
210
330
300
transm'd
0
0
0
270
0
120
30
120
30
0
270
240
120
150
AlbaNova
B
0
reflected
90
90
180
180
90
180
0
90
180
transm'd
0
0
0
0
270
0
0
270
C
0
reflected
90
90
180
180
transm'd
0
0
0
90
180
120
0
270
-120
210
300
240
150
result
red
channel
A:
0
30
B:
120
150
C:
270
240
1 December 2005
result
blue
channel
30
0
270
240
120
150
p 39
Signal-to-Noise (S/N)
Local zodi
Thermal BG
Exo zodi (10)
Detector
Total noise
Leakage
Transmitted
planet signal
Equivalent
signal of
absorption
lines
SNR integrated over
line width
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p 40
Science Requirements
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p 41
Science Requirements, cntd.
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p 42
Assumptions
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p 43
Main Observational Requirements
•
•
•
•
•
Nulling of “on axis” star by
Baseline accuracy
Optical Path Difference (OPD)
Telescope pointing
Amplitude matching
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105
1 cm
20 nm
24 mas
10- 2
1 December 2005
p 44
Control Modes
Flyers randomly
distributed in a
sphere (15 km)
Baseline Control Mode
Baseline accuracy = 1 cm
Array attitude: 0.1 deg.
Pointing: 1 arcsec
Fringe Acquisition Mode
Optical Links acquisition
Fringes Acquired
Freeze of baselines
External OPD rate damping
Normal Operation Mode
OPD control to 20 nm
New target / baseline
re-arrangement
Pointing control 24 mas
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p 45
Baseline Control Mode
•
•
•
•
mN-FEEP
Inertial attitude using star-trackers [ ~1” ]
RF range measurement [ 1 cm ]
RF goniometry
– omni-directional [10 deg ]
– narrow angle scanning antennae [ 0.06 deg ]
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Propulsion
•
•
•
•
Fine control:
N - thrust
Coarse control:
mN - thrust
FEEP - Field Emission Electric Propulsion
Cold gas
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p 47
Micro propulsion
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p 48
Preliminary Mission Analysis
Mission analysis initiated with ESOC.
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p 49
IRSI - Darwin Nuller at L2
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p 50
•
Completed system studies
• Alcatel (1997 → mid 00)
– Seven spacecraft in formation
– Launched to L2 by Ariane5
– Mission feasible !
• ESA internal studies
– “Theta-2” stellar rejection suffices
• Reducing number of collectors
– Dual launch feasible
• Two Soyuz could be used
– Multi Axial Beam Combination
• New conceptual payload design
• Wavefront filtering and
Beam combination by Single Mode Fibre
– Minimum number of collectors (3)
• 3 collectors
• 1 beam combiner
– Analysis of variability noise
– Spectral range
• Various technology developments
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•
Current System Assessment Study
– Parallel study Alcatel and Astrium
– Phase 1
(Sep. 05 → Spring 06)
• Review
– Requirements
– Payload
– Mission
• Trade-off
– Phase 2
(Spring 06 → Oct. 06)
• Preliminary design
– Payload
– Spacecraft
• Redundancy philosophy
• Mission analysis
– Phase 3 (Oct. 06 → Spring 07)
• Design consolidation
– Payload
– Spacecraft
• Imaging mode implementation
• Ground segment
• Development plan and costing
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Launch Vehicle
Dual Soyuz
- Cost of a Soyuz / Fregat launch vehicle assumed to be 40 Meuro
- Cost of A5 launch vehicle assumed to be 150 Meuro
- The cost of Soyuz from Kourou is expected to increase
- Extra cost (= fuel and complexity) for rendez-formation not
accounted for.
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• The challenges
– Technological
(but no show stoppers!)
• Nanometer and milli-arcsecond beam control
– Optical path length control < 1 nm
– Beam intensity matching < 1%
• Formation flying
– 4 (or more) spacecraft in close formation
– Correction of relative displacement and attitude
• Cryogenic payload
– Passive cooling to 40K of optical elements
– Detector operating at 6-8K
– Funding
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(major obstacle!)
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1 December 2005
p 54
Testing Formation Flying
Swedish precursor mission PRISMA
Possible Future Big Darwin
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p 55
The Future: Planet Imager
20 x 20 pxl image of Earth at 10 pc
0.02 arcsec pxls
6250 km baselines
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1 December 2005
p 56
Possible Architecture: Planet Imager
Densified pupil supertelescope
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p 57
and fly it in space
or pack down the VLA
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p 58
Thanks !
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``cold´´ gas micro propulsion
Courtesy Lasse Stenmark, Ångström Lab, Uppsala
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