Blue team
Mission proposal
Summer school Alpbach 2009
Mission Proposal
Extraordinary claims require extraordinary evidence
Outline
Scientific case
Mesurement requirements
Payload design
Spacecraft design
Mission Profile
Data analysis
Descoping options
Outreach
Conclusion and credits
Scientific objectives
Characterizing potentially habitable
planets and their evolution
by determining the atmospheric composition
and temperature
The Habitable Zone (after Kasting 1993)
Carbon-Silicate Cycle
www.shef.ac.uk
Observing potential biomarkers
integrated emission spectrum of Earth in the mid infra-red
Kaltenegger et al. 2009
Setting biomarkers in context
atmospheric species CST
will be able to detect
CO2 Origin?
H2O mid IR O2/O3 - photolysis of CO2
O3 loss of hydrogen to space
CH4 excess of O3
H UV
CO2+H2O+O3
CH4+O3
Evolution of atmospheres over time
3.9 Ga
2.3 Ga
0.3 Ga - now
Kaltenegger et al. 2009
Hydrogen-Rich Upper Atmospheres
by observation in the UV and mid IR range
• evaporating oceans
• CH4/NH3-rich reduced prebiotic atmospheres
(Super-Titan, ...)
• volcanic outgassing vs. escape rate (building blocks
of life)
• methane-rich atmospheres produced by
methanogenic bacteria
• timescales 10s to several 100s of Myrs
Evolution of atmospheres over time
evaporating
oceans volcanic
hydrogen
activity
methanogens
CH4 photolysis
Kasting 2004
Planet formation
Raymond 2007
Volcanic outgassing
building blocks of life
Methanogens
amino acids
Extended
hydrogen cloud
+
atmospheric possible
composition explanations
• strong H2O features evaporating ocean t
• methane + H2O methanogenic
• CH4 + low density bacteria t
• low levels of „Super-Titan“
methane volcanic outgassing
Changes with stellar type
Kaltenegger & Selsis 2009
Enlargement of hydrogen cloud
Extended hydrogen corona
of several planetary radii
Interaction with stellar
plasma flow (stellar wind,
CMEs), ENA production
Enlargement and
acceleration of corona
Observation of hydrogen cloud
Jupiter-type gas giant
planet HD 209458b
R=0.045 AU
D=47pc
Central star: G star
Holmström et al. 2008
Measurement Requirements
What? Temperature
Atmosphere: CO2, H2O, O3, (CH4)
Exosphere: H
How?
Transits
Coronography/interferometry was assessed infeasible
MIR (5-20 µm)
Only way to get temperature
Good molecular bands and contrast
UV (0.121 µm - Lyman alpha)
Exospheric mass loss (H)
Secondary eclipse
Nominal orbit
MIR radiation
Primary transit
Atmospheric MIR/UV absorption
Primary transit
Resolution required: λ/Δλ = 25 Kaltenegger et al 2009
Secondary eclipse method
Kaltenegger et al. 2009 MIR: Molecules + Temperature!
Diameter requirements
• Limiting case:
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...in terms of integration time needed
Limiting case:
Diameter = 7 m
We can definitely do M4-M9 stars!
These are suitable targets for UV study
(Fleming et al, 1995)
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1 Me 10 Me 10 Me
Ocean planet
MIR emission: higher SNR for Mass > 1 Me
MIR absorption: higher SNR for ocean planet
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Secondary eclipse method
High CH4 levels in early Earth could be detected!
Kaltenegger and Selsis, 2009
Availability of Earth-like transits
Best educated guess based on stellar statistics
90% of S/C mass space proven (TRL 8/9)
• Cost savings (AIT) if JWST is directly followed by CST
production (Cryosat-2 analogy)
• NRC reduction factor 0.5 due to heritage
• 50% of cost(JWST) are NRC
• COST(CST) = 75% COST(JWST) 3.75B$ 0.8€/$
3B€ (total cost)
Critical Points
Optical and thermo-mechanical design of UV
telescope system
Room for extension of sunshield
Launch mass (A5 EC-B to be operative)
Collaboration ESA/NASA neccessary
Master-Mission Schedule
Critical path is in red
Milestones in black
Risk assessment will be done during the phase A
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Science Impact Engineering Cost Reduction
Descope Impact
Options
UV photometry Less information on Detector Approx. €100k
instead of a atmospheric simplification and
spectrometer evolution size reduction
No UV system No possible - less development Significant cost
comparison of water effort -> higher TRL reduction (>20%)
data and its state of -300 kg less mass
evaporation - 150 W less power
required (11.3%
reduction)
- 52.4 bps less to
transmit
No extended mirror - less targets at 5 pc -No new technology 56% cost of JWST
(targets at 5 pc) - less M stars implemented (JWST (€2.25B)
similar case)
- 1100 kg less mass
on board
- Less power
required
- Lower amount of
data recollected
Conclusions
CST will observe the best targets for understanding :
What makes a planet habitable
Evolution of potential habitats
Influence of the host star
...and potentially detect signs of life on a world
other than our own!
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Credits
Tutors (Lisa Kaltenegger & Chris Carr)
Roving tutors (Helmut Lammer, Denis Moura, Peter
Habison, Annette Jäckel, Sven Wedemeyer-Böhm)
Nikola Radonjic, DAA Montenegro for the logo
Yann Lorber for the poster
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Glossary
Main Entry: characterize
Part of Speech: verb
Definition: typify, distinguish
Synonyms: belong to, brand, button
down, constitute,
define, delineate, describe, designate,
differentiate, discriminate, feature, identify, indicate,
individualize, individuate, inform, make
up, mark, outline, peculiarize, peg, personalize,
pigeonhole, portray, represent, signalize, singularize,
stamp, style, symbolize, tab, typecast
Apendices - Just in case we need this
Lammer et al. (2009)
Rough estimation
UV flux of G star
M star radius, smaller period, higher frequency of
transits
S / N = 1.5 (1 transit)
GALEX: 50 centimeter diameter primary mirror, S / N
= 10 (Welsh et al. 2006)
Our mirror: approx. 2 m diameter