SOFIA Telescope Manufacturing Lessons Learned - · PDF fileSOFIA Telescope...
Transcript of SOFIA Telescope Manufacturing Lessons Learned - · PDF fileSOFIA Telescope...
04.04.2007 Hans J. Kärcher1
SOFIA Telescope Manufacturing-
Lessons Learned
Hans J. Kaercher, Senior Telescope EngineerMT Mechatronics GmbH, Mainz, Germany
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Experience with Telescopes at Exposed SitesRadio Telescopes
30m IRAM Spain
9m O‘HigginsAntarctica
50m LMT Mexico
15m IRAM France
APEX, ALMA
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Experience with Telescopes at Exposed SitesOptical Telescopes
2.7m Airborne Telescope SOFIA
1.5m Solar TelescopeGREGOR
1m Solar Balloon Telescope Sunrise
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SOFIA Main Telescope Components
Primary Mirror
Secondary Mirror
TertiaryMirror
ScienceInstrument
MeteringStructure
Counter Weights
SuspensionAssembly
Imagers
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• Access to the Science Instrument during flight
• Research flight hours per year 960 hours
• Time per flight at 12.5 km altitude > 6 hours
• Unvignetted elevation range 20 - 60 degrees
• Effective telescope aperture 2.5 m
• Telescope optical image quality 1.5 arcsec
• Telescope pointing stability rms 0.2 (0.8) arcsec
SOFIA Main System Requirements
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SOFIA Telescope Optics will be in Cold Environment (- 50° C, 0.2 bar)
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SOFIA Telescope Science Instrument FlangeAccessible during Operations from the Cabin Side
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Thermal Barrier
Pressure Barrier
+ 20° C - 50° C0,8 bar 0,2 bar
Cabin
Cavity
Steady State Type Environmental Influences on the Telescope
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Metering Structure
Mirror Cell
Nasmyth Tube
Bearing Sphere
SOFIA Structural SystemCarbon Fiber Composites
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SOFIA Primary Mirror System
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Suspension Assembly
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Secondary Mirror Assembly Attitude Controlwith fiber-optical gyros
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M2 Mirror
SiC/C 35cm Ø
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M2 Focus-Center MechanismHexapod Qualified for – 50°C Operational Environment
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Environmental Influences on the Telescope
Science Instrument
Shear Layer at Cavity Opening
Standing Waves Excited by the Shear Layer
Wind in Cavity Induced by the Shear Layer
Aircraft Vibrations
Cabin
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End-to-end Simulation Model
1image m
unbalance
torque driv e
raytrace
position contro lle r
mirror 2image motion
e stimator for M 2
image motione stimator for
position controlle r
gyro
fe e d forward filte r M 2
be aring
acce le rome te rs
Vibration IsolationAsse mbly (VIA)
Te le scope Asse mbly (TA)Structure
2aircraft acce le ration
1ae rodynamic disturbance
es t im atedim age m otion
pos it ioncom m ands angular displacem ent of M2
56 f orces
u,v ,w accelerat ion
torque (as f orces to rotor segm ents )
torque to telescope
torque to c radle
all VIA f orces
torque com m ands
v eloc ity and displacem ent
all VIA displacem entsand v eloc it ies
c radlerotat ional displacem ent
and v eloc ity
telescoperotat ional displacem ent
and v eloc ity
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Servo Domain Aero-acoustic Domain
Image Quality
„Low“ structural damping (0,5 – 1 %)
„High“ structural damping (1 – 2 %)
RMD for 32,2 Hz mode (5 %)
32,2 Hz mode
22,4 Hz dumbbell
Influence of SMMvia FBC
~ 75 Hz rocking mode
End-to-end Simulation Results
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Summary of SOFIA Experience
• System Level– Thermal System Design– Pointing System Design
• Subsystem Level– Optics, Structure– Suspension Assembly– Secondary Mirror Mechanism– Servo Control System
• Material Selection etc.– Structures in Carbonfiber Composites– Dedicated Metals for Mechanisms– Same for Motors, Drives etc.
• QA, RAMS– Quality Control absolute essential– Reliability, Maintainability same– Methods qualified in Aircraft and
Space Business are adequate– Management has to accept
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Recommendations for Arena
< 2m
- Material Choice- Low Temperature qualified
Mechanical Component- Low Temperature qualified
Motors, Encoders- Thermal Concept for Optics,
Controllers- QA, RAMS
CFRP Tube elements with
integrally manufactured stringers
Tube Elements
Primary Mirror Cell Outer Ring
Spokes
Inner Ring
GluedCleat
GluedCleat
Spiders / Headring
A-AA
AB
B
B-B
A-AA
AB
B
B-B
Sunrise CarbonfiberTechnology
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Thermal Concept for Sunrise
PrimaryMirrorCooling
IR Radiation and Reflection from „Warm“ Earth
IR Radiationto Cold Sky
IR Radiationto Warm Earth
Cold Sky < 100 K ??
Surrounding Air Temperature ∼ 200 K / 290 K ?
Antarctic Ice ∼ 250 K
Insolatio
n
∼6000 K
Balloon-Gondola-
TelescopeTemperature
∼ 200 K∼ 0° - 70° el
HeatRejectionCooler
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Recommendations for Arena
> 2m
Combination of O’Higgins Pedestal with SOFIA Mirror
Compare with exposed design
(e.g. Gregor)
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Conclusions from Engineers Point of View
• Challenging!• Interesting!
• Nice, Funny!
Let’s do it!