deutsches sofia institut universität stuttgart second gyro system for the sofia telescope j.f....

Deutsches SOFIA Institut

Universität Stuttgart

Second Gyro Systemfor the SOFIA Telescope

J.F. Wagner

Deutsches SOFIA Institut, Universität Stuttgart, Germany

Symposium Gyro Technology 2009 2

Deutsches SOFIA Institut

Universität Stuttgart

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

aircraft vibrations aero-acoustics

controller

commandedattitude

actualattitude

actuatorsstructure and mechanics

gyroscopes

perturbations

data fusion

tracker correction

Attitude Control: Inertial Stabilization

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Symposium Gyro Technology 2009 3

Deutsches SOFIA Institut

Universität Stuttgart

SOFIA’s Fiber Optic Gyroscopes

Optical sensor module

Opto-electronicmodule

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

Performance: Angular increment < 0.001 arcsecDynamic range > 10.3 °/sBandwidth > 1 kHzRandom walk 0.0003 °/√hIn-run bias stability 0.003 °/h

Symposium Gyro Technology 2009 4

Deutsches SOFIA Institut

Universität Stuttgart

SOFIA’s Fiber Optic Gyroscopes

Symposium Gyro Technology 2009 5

Deutsches SOFIA Institut

Universität Stuttgart

Constant Performance

• Two data sets available over a period of 9 years

• Data show very constant low noise behaviour

Calibration 1999/2003 Calibration 2008

Symposium Gyro Technology 2009 6

Deutsches SOFIA Institut

Universität Stuttgart

Spare partRepair

Second Gyro System

First possibility: Exchange of the gyro box

Gyro Box

2nd

Gyro Box

NasmythTube

ATCU TASCU

Failure

Gyro Box

Symposium Gyro Technology 2009 7

Deutsches SOFIA Institut

Universität Stuttgart

Failure

Second Gyro System

Second possibility: Parallel system (hot standby)

Gyro Box

2nd

GyroBox

NasmythTube

ATCU TASCU

2nd

ATCU

Gyro Box ATCU

Symposium Gyro Technology 2009 8

Deutsches SOFIA Institut

Universität Stuttgart

Second Gyro System

Comparison: Advantages (+) / Disadvantages (–) / Neutral (0)

Gyro Box Exchange Hot Standby

Accuracy + –

Cost – – –

Software modification 0 –

ATCU failure – – ++

“Save a mission” – ++

Flexibility of schedule – – +