Second Gyro System for the SOFIA Telescope

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Second Gyro Systemfor the SOFIA Telescope

• J.F. Wagner
• Deutsches SOFIA Institut, Universität Stuttgart,
  Germany

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Attitude Control Inertial Stabilization
aircraft vibrations aero-acoustics
perturbations
commandedattitude
controller
actuators
structure and mechanics


actualattitude
gyroscopes
data fusion
tracker correction

• Wide Field Imager (WFI)
• Fine Field Imager (FFI)
• Focal Plane Imager (FPI)

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SOFIAs Fiber Optic Gyroscopes

• Initial situation
• Telescope pointing budget allocatedfor gyro
  drift 0.04 arcsec
• Very low noise requirementdominated gyro design
• ? Optical fiber length 3.4 km? Mean coil
  diameter 150 mm? Closed loop operation

Optical sensor module
Opto-electronic module
Performance Angular increment lt 0.001
arcsec Dynamic range gt 10.3 /s Bandwidth gt 1
kHz Random walk 0.0003 /vh In-run bias
stability 0.003 /h
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SOFIAs Fiber Optic Gyroscopes
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Constant Performance

• Two data sets available over a period of 9 years
• Data show very constant low noise behaviour

Calibration 1999/2003
Calibration 2008
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Second Gyro SystemFirst possibility
Exchange of the gyro box
Gyro Box
ATCU
TASCU
Gyro Box
NasmythTube
Failure
Repair
Spare part
2ndGyro Box
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Second Gyro SystemSecond possibility
Parallel system (hot standby)
Gyro Box
ATCU
TASCU
Gyro Box
ATCU
NasmythTube
Failure
2ndATCU
2ndGyroBox
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Second Gyro SystemComparison Advantages ()
/ Disadvantages () / Neutral (0)
Gyro Box Exchange Hot Standby
Accuracy
Cost
Software modification 0
ATCU failure
Save a mission
Flexibility of schedule