Blue team Mission proposal Summer school Alpbach 2009 by shelseaZvansky

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									        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:




                                                    26
...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)
                                                     27




    1 Me                  10 Me          10 Me
                                      Ocean planet

  MIR emission: higher SNR for Mass > 1 Me
  MIR absorption: higher SNR for ocean planet
                                                     28
 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




< 10 pc: expect 21 planets around M-stars
< 20 pc: expect 170 planets around GKM-stars

<5 pc: 50 stars targeted intensely by search programs!
                                                             30
Putting planet Earth into context
                        Study potential
                       exoplanet habitats

    Atmospheric                             Exospheric water
    composition                                   loss
                                        Water loss signatures
Biomarkers in mid-IR
                                                in UV


                   Transits and eclipses


                   Dedicated and updated
                    JWST-type telescope
Assessment of future observatories
• Ground-based: UV and mid-IR
  not accessible




                   • JWST: mid-IR-capabilities, but
                     exceedingly long observation
                     time necessary
Science payload: Infrared

Main Infrared Telescope
(MIT):
  Expanded JWST main
  mirror
  Korsch design with fine
  steering mirror
  39m2 collecting area
  Effective focal length 130m
  → f/# = 20 – 16




Science payload: Infrared
Mid-Infrared Spectrograph (MIS):
  Range 5-20μm divided into bands (5-8, 8-13, 13-20 μm)
  Slit sizes: 3.43“, 5.58“, 8.58“
  Low-resolution ZnS prisms for R=25 (minimum)
  MIRI SiAs 5122 px detector, 30 μm pixels, 105 e- well
  depth, cooled to 7K
  Increase of dynamic range: defocus of spectra in cross-
  dispersion over 10 pixels
  Target acquisition mode (imaging)
  Refocusing mechanism
Science payload: Infrared
 Fine Tracking Imager (FTI)
   Long-pass filter 5 μm cut-on wavelength
   Fine pointing during observation
   MIRI detector 1k x 1k, 30 μm pixels
   Imaging camera during main mirror alignment and
   phasing
   Refocus mechanism




Science payload: UV
 UV Spectrometer (UVS)
   Deployable telescope underneath
   s/c bus: effective diameter 1.9m
   4nm bandpass around Lyman
   alpha
   Window size 0.22“
   Grating with spectral resolution
   R=7500
   UV MAMA detector 1024x512
   pixels
                   Earth trailing                                         L2
No orbit maintenance required                     Regular maintenance required
Benign thermal and radiation environment          Optimal thermal and radiation environment
High sky accessibility                            Highest sky accessibility
No perigee passes or eclipses                     No perigee passes or eclipses
Good ground-station visibility (8h for low-to-mid Good ground-station visibility (8h for low-to-mid
latitude station                                  latitude station

Close to Earth after launch                       Far from Earth

Lower mass can be injected                        Higher mass can be injected
Large increasing communication distance           Almost constant communication distance
Significant drift-away (0.1 AU/year in Spitzer No significant drift
case)

Interesting in short missions                     Interesting in long missions
Sun and Earth directions evolving with time Sun and Earth behind the S/C always (line of
(line of sight can be interfered)           sight is not interfered)

Bad conditions for cooling the telescope          Good conditions for cooling the telescope




Sky coverage


                                                                    ~30 %


                                                                                      ~70 %
                                                                          Top view
     Launcher

                         ARIANE ECB

        Performance escape    ~7,5 t
        to L2
        Fairing height        17 m

        Fairing diameter      5,4 m




     From launch to L2

1. Launch: Ariane 5 ECB rocket from Guiana Space Centre
   (Kourou, French Guyana)
2. Escape orbit:
       Upper stage of Ariane 5    L2 trajectory
       No engine for major orbital manoeuvres (only minor
       corrections)
3. 90 days after launch: insertion in Halo orbit around L2
 Delta V and fuel budget
Manoeuvre               ∆ v [m/s]
Halo orbit insertion    25
Orbit correction        75
Pointing                14
TOTAL                   114




     •315 kg fuel Hydrazine
     •12 x 10N thrusters
     •ISP= 230 s
 AOCS: actuators
  3 axis stabilized Spacecraft:

  6 sets of Reaction Wheels W45
  assemblies (RWA) for momentum
  change
   12 x 10 N hydrazine thrusters for
  desaturation and HALO orbit
  insertion
   The RWA are controlled by a
  Wheel Drive Electronics Box
  (WDEB)




AOCS: sensors

Inertial sensors:
  4 fiber optic gyroscopes Astrix 200




Reference sensors:
  3 Star tracker SED 26
Thermal Control System
                             Sunshield shields MIR
                             instruments from Earth, Sun and
                             Moon radiation
                             Radiative cooling down to 30 K
                             Mechanical Cryocooler System to
                             cool to 7K
                             MLI rear shielding of UV mirror
                             Shielding of the UV mirror from
                             the reflected sunlight




Power System
   System                       Power [W]
   AOCS                         86
   Power Control and            70
   Distribution
   Thermal Control              250
   TM/TC                        335
   Data Handling                39
   Payload                      426
   TOTAL                        1327
   Power generation: Solar array
             Efficiency of solar cells: 25%
             Solar array surface: S=11.23 m2
   Power storage: Li-Ion batteries
    Ground segment
      ESTRACK: ESA’s Deep Space Network:
          New Norcia (close to Perth, Australia)
          Cebreros (close to Avila, Spain)
          Working in X-band and S-band frequencies.

                                                  Characteristic               Values
                                                  Antenna dish diameter         35 m
                                                            TRANSMIT FREQUENCY
                                                  S-band [MHz]               2025-2120
                                                  X-band [MHz]               7145-7235
                                                             RECEIVE FREQUENCY
                                                  X-band [MHz]               8400-8500
                                                           TELEMETRY (DOWNLINK)
                                                  Max data rate [Mbps]        up to 105
                                                          TELECOMMAND (UP-LINK)
                                                  Normal data rate [Kbps]        2




    Link budget: Telemetry

      Point-to-Point communications architecture
      Gimbaled dished antenna

                 SATELLITE (Tx)
      Frequency [GHz]           8,45 (X-Band)
      Data rate (Mbps)              3,17
         C/No [dB]                    73                      GROUND (Rx)
        EIRP* [dBW]                 36,47           Frequency [GHz]       8,45 (X-Band)
    Antenna gain [dB]              7,86               (G/T) (dB/K)              50
   Antenna diameter [m]            0,72           Antenna diameter [m]          35
       Beam width                  3,43º
*TWT TH 4300 C/R transmitter from Thales Alenia
Space
   Link budget: Telecommand
               GROUND* (Tx)
     Frequency [GHz]      2,1 (S-Band)
        Data rate               2 Kbps
 Transmitted power [kW]          2 - 20

*New Norcia antenna is the only one
transmitting in S-Band




   Mass budget

                                      JWST            CST
  Area IR mirror                      25 m²    +55%   39 m²
  Area sunshield                      220 m²   +10%   242 m²
  Mass IR mirror                      2t              3.2 t
  (1/3 of S/C)
  Mass UV mirror                                      0.2 t
  Mass sunshield                      1t       +10%   1.1 t
  Mass instruments                    0.6 t           0.3 t
  Mass Service Module                 2.5 t    +5%    2.6 t

  Mass Total                          6.2 t           7.4 t
Volume Budget
                                        Fairing storage:
Mirror storage CST vs JWST:




        V(CST) <=V( JWST)




Technology Readiness Level
       Component                  TRL
       Service Module             8
       - AOCS                     8/9
       - Structure                8/9
       - TCS                      8/9
       - EPS                      8/9
       - TM/TC                    8/9
       - Sunshield                8/9
       MIT                        5
       - Primary Mirror           5
         - Segments               8/9
         - Deployment mechanism   6/7
             - Hinges             5/6
             - Release Latches    5/6
       MIS + FTI                  2
       UVS                        2
  Cost budget
• Cost (JWST=5B$)
   • Less complex IR instrument
   • UV focal plane less expensive than IR focal plane
   • Increase of IR mirror and sunshield covered TRL
   • > 90% of S/C mass space proven (TRL 8/9)
   • Cost savings (AIT) if JWST is directly followed by CST
     production (Cryosat-2 analogy)
       • NRC reduction factor 0.5 due to heritage
       • 50% of cost(JWST) are NRC
• COST(CST) = 75% COST(JWST)          3.75B$ 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
                                                                                     57




                     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!



                                                         60
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

								
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