French expertise in SiC for large telescopes

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French expertise in SiC for large telescopes
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SiC technology

• Technology promoted and developped by French
  industry for more than 10 years for space
  applications.
• Technology renowned in the whole world.
• All developments in europe including a large
  telescope are currently manufactured with SiC
  technology.
• Herschel telescope, diameter 3.5 m, mass 300 kg
• Aladin lidar (wind), diameter 1.5 m, mass 72 kg
• Primary GAIA mirror, off axis aspherical, 1.45 x
  0.55 m, 36 kg

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Key advantages of SiC technology

• Very high weight reduction thanks to an
  exceptional stiffness of the material (5 times
  higher than aluminium or Zerodur)
• Optical material, very good specularity of SiC
  CVD (Chemical Vapor Deposition)
• Homogeneous material with a cristalline
  structure, low CTE (Coefficient of Thermal
  Expansion) and high thermal conductivity, usable
  on a large thermal range (0K 1800K)
• High mechanical stiffness permitting to
  manufacture the structure in SiC
• The material is insensitive to radiation and
  humidity
• Existing industrial facilities and mature
  technology to manufacture large parts. Assembling
  technology controled
• ? high eigen frequencies possible, robust thermal
  control, stability, robustness of manufacturing
  and modelisation, all SiC telescope performance
  preserved at cryogenic temperatures

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Achievements examples, all SiC design
ROCSAT2 Telescope, launched in 2004 600 mm
diameter Telescope mass 70 kg
Osiris telescope (Rosetta mission launched in
2004) 150 mm diameter Operational temperature
-100/70C
Herschel telescope (ESA program) 3.5 m diameter,
80 µm to 670 µm, no CVD) Cryogenic temperature
(80 K) Primary mirror mass 210 kg (22 kg/m²)
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Achievements examples
AEOLUS/ALADIN (ESA program, Wind Lidar 360
nm) Telescope delivery 2005, launch 2008 1.5 m
diameter, no CVD Primary mirror mass 50 kg (28
kg/m²)
GAIA (ESA program) M1 mirror delivery 2005 1.45 x
0.55 mirror off axis CVD Primary mirror mass 36 kg
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Proposal for a SNAP PASO Study
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Plannification of PASO Studies

• PASO Studies are decided on an annual basis
• A preselection of studies have been proposed,
  including SNAP Study
• Resources for preselected studies are being
  evaluated (human CNES resources and/or cost)
• A final choice will be done before end of year
  considering availability of CNES technical
  services and financial allocations

Next slides describe a proposition for this SNAP
study
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Purpose of the SNAP PASO Study

• Assess a possible french participation to SNAP
  mission
• Spectrometer supply
• Optical Telescope Assembly (OTA) supply
• Other supply
• ROM cost
• Better understand Weak Lensing (WL) problematic
  through an iteration between scientific
  requirements and induced outcomes on second level
  requirements and telescope design
• Work has still to be done to clearly establish
  relations between Weak Lensing requirements and
  design features at all levels (mission, system,
  spacecraft, instrument, optics, etc ), as it is
  not straighforward
• To make a good proposal means to clearly
  understand the requirements.

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Expectations

• A possible proposal for a french participation to
  SNAP mission
• Technical outline
• Technical solution
• ROM cost
• A french expertise on Weak Lensing problematic
• An enhance french scientific contribution to SNAP
  team
• A PASO report including
• Proposal for enhanced Weak Lensing requirements
• A scenario for a telescope design consistent with
  Weal Lensing and Supernovae requirements
• PSF models to allow iterations between
  technicians and scientists
• A detailed cost estimate for the telescope
  supply.
• An expertise for the spectrometer development in
  LAM

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Study schedule

• Phase 0.1 Requirements and design options,
  required interface SNAP data
• Study kick off (French scientific group,
  CNES/partners)
• Progress meetings
• Phase 0.1 Key Point (French scientific group,
  CNES/partners, SNAP team invited)
• Phase 0.2 Telescope design options studies, PSF
  modelisation, ROM cost
• Progress meetings
• Phase 0.2 and final Key Point (French scientific
  group, CNES/partners, SNAP team invited)

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Phase 0.1

• Tasks
• Analyse current SN and WL requirements
• Analyse SNAP current design
• Analyse current telescope requirements
• Confirm or complete WL requirements (with
  scientists)
• Update telescope requirements if necessary
• Define or complete SNAP/OTA interface (ICD)
• Define relations between WL requirements and
  design options
• Propose telescope design options
• Elaborate scenarios for WL requirements versus
  design options
• Define the outline of a PSF modelisation
• List effects to be taken into account
• Define PSF modelisation depth
• Define the SNAP/OTA interface data needed for the
  PSF modelisation
• Define the PSF calibration process outline

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Phase 0.1

• Outputs
• Options for the telescope design
• PSF modelisation method
• Calibration process outline
• Exchange data format between scientists and
  technical team (for PSF for instance)
• Preliminary SNAP/OTA Interface (ICD)
• Needed data from SNAP US team (SNAP/OTA interface
  data), specificaly for PSF modelisation
• General mission data (scanning laws, orbit
  simplified model )
• Spacecraft simplified general thermal model
• Focal plane detailed thermal/thermoelastic model
• Detectors characteristics (charge diffusion, .)
• Attitude control characteristics and features
  (jitter amplitudes, frequencies and orientation,
  )
• Etc
• Phase 0.1 Key Point presentation

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Phase 0.2

• Tasks
• Study telescope design options
• Elaborate a PSF modelisation including OTA
  effects and external effects
• Analyse the sensitivity of Weak Lensing
  performances to telescope design features and PSF
  shape (iterative process between engineers and
  scientists)
• Define the PSF calibration process
• Confirm WL requirements at all levels
• Make recommandations on the design (confirmations
  or alternatives)
• At system level (scanning, WL/SN observation
  sequences, etc .)
• At spacecraft level (thermal, attitude control,
  instrument,)
• At instrument level (Focal Plane/Optics
  interface, )
• At telescope and spectrometer level (proposed
  design options)
• Define needed Research and Technology
  anticipating program
• Estimate the cost for a french participation to
  SNAP

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Phase 0.2

• Outputs
• PSF models
• A Weak Lensing sensitivity analysis (from french
  scientific group)
• A PASO report including
• A proposal for a telescope and spectrometer
  design for SNAP, with the justification of chosen
  technical options
• The definition of a calibration process and the
  associated requirements
• Telescope and spectrometer performances budgets
• Risk analysis
• Costs
• TRL level for telescope and spectrometer items
  and needed Research and Technology actions
• A phase 0.2 Key Point presentation

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Organisation

• Proposal for a french participation to SNAP

CNES Program and strategy department (study
client)

• Final PASO report

• SNAP study request

CNES team (Statement of work study follow
up Interface)

• Study Proposal
• Needed SNAP/OTA inteface data
• Progress meetings
• Final technical report

• SNAP/OTA interface data supply

• Statement of work/Follow up
• Key point organisation
• SNAP/OTA interface data supply

• SNAP/OTA interface data

SNAP team
Technical team

• Scientific requirements
• Calibration process design (WL)

• Final PASO report

• Scientific requirements
• Calibration process design (WL)
• WL sensitivity analysis

• Scientific requirements

French scientific group

• PSF models
• Telescope design definition
• Spectrometer expertise

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Tentative Schedule
2007
2006
Présentation
Instruction/Statement of work
KO Ph0.1
Ph01 KP
CENA
Phase 0.1
Ph02 KP
Phase 0.2
PASO Report
CENA Commission dEngagement des Nouvelles
Affaires KO Kick-Off KP Key Point
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About this proposal

• Activities, organisation, schedule in these
  slides are only suggestions for a statement of
  work preparation
• They are subject to changes due to
• SNAP team comments
• LAM and French scientific group comments
• PASO activities and funding
• Availability of CNES technical teams