GIFTS Blackbody Subsystem Critical Design Review Blackbody Controller

1. GIFTSBlackbody SubsystemCritical Design ReviewBlackbody Controller 9 March 2004 Scott Ellington sellington@ssec.wisc.edu 608 263-6771

2. Blackbody Controller • Performance Requirements and Design Overview • Changes since PDR • Controller Operation • Electronics Error Budget • Power Budget • Supporting Analysis • Part Selection • Engineering Model Test Results • Controller Verification Plan • Calibration Overview

3. Subsystem Block Diagram

4. Key Electronics Requirements • Blackbody Temperature Measurement • Hot Blackbody Range 0 to +40˚C • Ambient Blackbody Range -40 to 0˚C • Long-term accuracy ±0.03˚C (Electronics only) • Measurement Update Rate 2.7 Hz • Blackbody Temperature Control • Constant Temperature and Constant Power Modes • HBB Control Temperature Range 0 to +40˚C • ABB Control Temperature Range -40 to 0˚C • Set Point Resolution ≤ 0.2˚C • Set Point Drift ≤ 0.005˚C, for a Controller board temperature change of 1°C • Electronics Power 1.2 W, maximum

5. Changes Since PDR • Control of both blackbodies • Maximum total power increases from 3.0 to 5.2 W • Redundant heater drivers deleted, dual heaters retained • Add low power “Reset” mode • Default operation for both blackbodies is constant temperature • Add autoranging of temperature measurement ranges • Change ±15V supplies to ±12V • Add primary overtemperature protection • Increase measurement update rate from 2.0 to 2.7 Hz • Command and data interface modified as necessary • Blackbody thermal environment is colder • Increase electronics power from 1.0 to 1.2 W • Change controller operating temperature range to -55 to +50°C. (Accuracy guaranteed -40 to +30°C only)

6. Blackbody Controller Operation

7. Operational Commands • Blackbody Modes • Constant Temperature • Constant Power • Set Points • Control Thermistor Select • Temperature Measurement Range • Range Select • Autorange On/Off • Reset Mode

8. Electronics Error Budget Summary

9. Power Budget Summary Worst-case for cold side of orbit

10. Model Transient Response 0.14 W Blackbody Power Step Temperature Error Time (sec)

11. Model Orbital Response Blackbody Power Time (Hours) Temperature Error Time (Hours)

12. Measurement Ranges and Self-Calibration Self-Calibration Point ADC Output Thermistor Voltage (V)

13. Self-Calibration Example Self-Calibration Point NB CAL B ADC Output NA CAL A VA VB Thermistor Voltage (V)

14. Self-Calibration Self-calibration corrects for drift of gain and offset in electronics Residual error depends mainly on stability of precision resistors NA = Value at self-calibration point A NB = Value at self-calibration point B VA = Voltage at self-calibration point A (known) VB = Voltage at self-calibration point B (known) K1 = Gain constant K2 = Offset constant N = Value at measurement of unknown temperature V = Thermistor voltage at unknown temperature T = Blackbody Temperature

15. Controller Parts Selection Summary

16. Non-Standard Parts

17. Radiation and Shielding Total mission radiation dose assumed to be 100K Rad, including X2 safety factor RH108A (Op Amp) requires additional shielding to 20K Rad 7872RPFS (ADC) and HS9-1840 (Mpx) performance improves with additional shielding 110 mils (2.8mm) of additional aluminum shielding is provided for these parts

18. PWB Thermal Analysis • Neglected radiation, assumed conduction only to edges at 50°C • Modeled board as single layer with equivalent lateral conductivity based on copper and polyimide layer thicknesses • Heat flux into board assumed uniform over each component’s area • Total power dissipation is 1.2W • Components shown total 0.81W, remaining 0.39W evenly distributed over remaining board surface • Heat to left edge is 0.43W, heat to right edge 0.77W • Maximum temperature is 54°C Wedgelock Wedgelock Board layout Temperature results

19. Parts Derating Summary Note: Maximum PWB temperature 55°C

20. Engineering Model Test Set-up

21. Engineering Model Test Results • Tested at +25° C only • Data Interface • Resistance Measurement • Temperature Control • Preliminary results meet specifications

22. Engineering Model 1 Photograph

23. Flight Unit Acceptance Test Plan

24. Electrical Test Outline

25. Flight Test Set-up

26. Testing Issues • SDL Bus Simulator built with commercial components may not allow testing of Blackbody Controller over entire temperature range. • SDL Bus Simulator required for all electrical tests • SDL Bus Simulator and Blackbody Controller must be installed on the common motherboard in close proximity • Temperature Tests of Blackbody Controller require SDL Bus Simulator to operate over the same temperature range • Motherboard does not allow direct measurement of Blackbody Controller power supply currents.

27. Calibration Overview • Direct Temperature Calibration Only • No Temperature to Resistance or Data to Resistance Calibration • Would require extremely precise resistance references • Intermediate calibration allows accumulation of errors • Interchangeability is not an issue • Acceptance Test Resistance Measurements • Verify measurement ranges • Linearity