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DARA

DARA. The new Three-Cavity Digitally- Controlled Radiometer for Space Application. Features. 3 independently controllable cavities Offers several open/close measurement sequences Independent PID controllers for closed and open shutter state

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DARA

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  1. DARA The new Three-Cavity Digitally- Controlled Radiometer for Space Application dlab GmbH CH-8400 Winterthur

  2. Features • 3 independently controllable cavities • Offers several open/close measurement sequences • Independent PID controllers for closed and open shutter state • ~20 bit data acquisition for each I, U and PWM channel • Measurement period down to a few seconds • Uncorrelated sinus carrier for thermal error signal • Convex cavities with minimal dynamic“Non-Equivalence” • Very fast shutter speed (one step) • Two data analysis methods were available • Tail Integration Method (TIM) • Phase Sensitive Analysis (PSA) dlab GmbH CH-8400 Winterthur

  3. Overview dlab GmbH CH-8400 Winterthur

  4. 3 Cavity Design dlab GmbH CH-8400 Winterthur

  5. Thermal Simulation dlab GmbH CH-8400 Winterthur

  6. Instrument Geometry A) Precision Aperture B) Cavity, Aeroglaze Z302 Coating C) Heat Sink D) Thermal Resistor E) Thermometer F) Electrical Heater G) Radiation Shield H) Shutter I) View Limiting Aperture dlab GmbH CH-8400 Winterthur

  7. Design Goals • Reduce dynamic & static „Non-Equivalence“ • Reduce the number of Bonds • New Aperture Geometry • Reduce Stray Light • Remove uncertainties due to “Aperture Warming” dlab GmbH CH-8400 Winterthur

  8. Sinus Carrier for Thermal Balancing • Decoupling from PWM by using an uncorrelated sine carrier • Means fSin is not an overtone of fPWM • fPWM = 20 Hz, fSin = 1010 Hz dlab GmbH CH-8400 Winterthur

  9. PID Controller Switching • How can the settling time be reduced when changing the shutter state? • Two PID controllers per channel • Significantly less settling time is needed • Measurement period can be reduced dlab GmbH CH-8400 Winterthur

  10. Power Measurement and Sampling • PWM frequency:20 Hz • Duty cycle resolution 19.9 bit • The heater current can be set by a DAC • The effective heater current is measured by a 20 bit ADC • Heater voltage is sampled when PWM is high and measured by a 20 bit ADC dlab GmbH CH-8400 Winterthur

  11. TIM Measure • Tail Integration Method or Traditional Irradiation Measure • The tail data are integrated • The sun power is calculated as the difference of 2 measurements made with closed shutter and 1 with open shutter • One measure per open/close turn dlab GmbH CH-8400 Winterthur

  12. PSA Measure • Phase Sensitive Analysis Measure • Heater PWM signal is weighted by a synchronous sine signal • All data are taken into account for the analysis • Two measures per open/close turn dlab GmbH CH-8400 Winterthur

  13. Data Management • RS422 communication • Robust communication protocol • EGSE software for data visualization and data storage dlab GmbH CH-8400 Winterthur

  14. First Measurements Not characterized yet! dlab GmbH CH-8400 Winterthur

  15. First Measurements PWM Signal Ratio Cavity A/Cavity C dlab GmbH CH-8400 Winterthur

  16. IPC Results dlab GmbH CH-8400 Winterthur

  17. Outlook • Characterization (Ground & Space) • Visit Calibration Facilities • Verify WRR Scale • SuMo Instrument on PROBA III (2015?) dlab GmbH CH-8400 Winterthur

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