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Instrumentation

Instrumentation. K. Constantikes. New PTCS Instruments. Structural Temperature. ~ 30 locations, 0.2C interchangeable accuracy, 0.01C resolution, 1Hz. COTS solution. Estimate gradients in alidade, horizontal and vertical FA, primary.

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Instrumentation

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  1. Instrumentation K. Constantikes

  2. New PTCS Instruments

  3. Structural Temperature • ~ 30 locations, 0.2C interchangeable accuracy, 0.01C resolution, 1Hz. COTS solution. • Estimate gradients in alidade, horizontal and vertical FA, primary. • RSI predicted 19” pointing error for 5C (uniform) gradient w/ 270 solar azimuth. • Uses: • Temp dependent optical alignment model (focus tracking) • Temp dependent primary model • Temp dependent pointing model • Implementation order • Vertical FA • Alidade • Encoder • Primary • Horizontal FA

  4. Temperature Sensor Locations

  5. Pointing Accuracy, 5° C Gradient, 95° El

  6. Pointing Accuracy, 5° C Gradient, 5° El

  7. Tipping Structure Contributions, 5C in X direction

  8. Tipping Structure Contributions, 5C in Y direction

  9. Tipping Structure Contributions, 5C in Z direction

  10. Quadrant Detector • Measures FA tip displacement in plane ~ normal to principle ray of GBT • 10 Hz, ~12mm resolution. FS Nonlinearity < 5mm. Noise strongly dependent on atmosphere, ~<300mm. • Tested summer ’02. Upgrades in temp stability, control, monitoring, and calibration in progress • Uses: • Short-term SR control signals (may use accelerometers and dynamical model) • Assist in FA LRF position estimation

  11. Quadrant Detector

  12. QD Performance Prediction

  13. Accelerometers • 10 Hz 3-axis seismic MEMS accelerometers, ~2mG/root-Hz • Locations: FA tip, left and right El bearings • Uses: • Rate assist QD • Structural vibration mode shape and frequency • Inclinometers

  14. Vertical Air Temperature • ~ 13 locations on alidade and vertical FA, 0.2°C accuracy, 0.01°C resolution, 1 Hz. • DNg/DT ~ -.9 ppm/ °C : Need path average < 0.4ppm • Expect to use same COTS solution as structural temp

  15. FA Tip Barometer • LRF DNg/DP ~ 0.3ppm/mbar: Need path average Hg < 0.4 ppm. • Path barometric pressure thought to be more predictable than temperature. • Use ADC and control in QD laser assembly

  16. Hot-Wire Anemometers • Possible locations on FA tip, primary rim, alidade. • 0.1m/s accuracy, 0.05 resolution, 10 Hz rate, 0-25 m/s • Uses: • Correlation and correction of wind loading pointing effects

  17. Existing PTCS Instruments • Az/El encoders • SR link encoders • Active surface panel encoders • Holography • Weather stations (3) • 2-axis FA tip accelerometer • LVDT primary temperature sensors

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