9 March 2004 GIFTS Blackbody Subsystem Critical Design Review Blackbody Controller 9 March 2004 Scott Ellington

9 March 2004 Slide 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

9 March 2004 Slide 3 Subsystem Block Diagram

9 March 2004 Slide 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

9 March 2004 Slide 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)

9 March 2004 Slide 6 Blackbody Controller Operation

9 March 2004 Slide 7 Operational Commands Blackbody Modes -Constant Temperature -Constant Power Set Points Control Thermistor Select Temperature Measurement Range –Range Select –Autorange On/Off Reset Mode

9 March 2004 Slide 8 Electronics Error Budget Summary

9 March 2004 Slide 9 Power Budget Summary Worst-case for cold side of orbit

9 March 2004 Slide 10 Model Transient Response 0.14 W Blackbody Power Step Time (sec) Temperature Error

9 March 2004 Slide 11 Model Orbital Response Blackbody Power Temperature Error Time (Hours)

9 March 2004 Slide 12 Measurement Ranges and Self-Calibration Thermistor Voltage (V) ADC Output Self-Calibration Point

9 March 2004 Slide 13 Self-Calibration Example Self-Calibration Point CAL A CAL B NANA NBNB ADC Output Thermistor Voltage (V) VAVA VBVB

9 March 2004 Slide 14 Self-Calibration N A = Value at self-calibration point A N B = Value at self-calibration point B V A = Voltage at self-calibration point A (known) V B = Voltage at self-calibration point B (known) K 1 = Gain constant K 2 = Offset constant N = Value at measurement of unknown temperature V = Thermistor voltage at unknown temperature T = Blackbody Temperature Self-calibration corrects for drift of gain and offset in electronics Residual error depends mainly on stability of precision resistors

9 March 2004 Slide 15 Controller Parts Selection Summary

9 March 2004 Slide 16 Non-Standard Parts

9 March 2004 Slide 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 HS (Mpx) performance improves with additional shielding 110 mils (2.8mm) of additional aluminum shielding is provided for these parts

9 March 2004 Slide 18 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 Temperature results PWB Thermal Analysis Board layout Wedgelock

9 March 2004 Slide 19 Parts Derating Summary Note: Maximum PWB temperature 55°C

9 March 2004 Slide 20 Engineering Model Test Set-up

9 March 2004 Slide 21 Engineering Model Test Results Tested at +25° C only –Data Interface –Resistance Measurement –Temperature Control Preliminary results meet specifications

9 March 2004 Slide 22 Engineering Model 1 Photograph

9 March 2004 Slide 23 Flight Unit Acceptance Test Plan

9 March 2004 Slide 24 Electrical Test Outline

9 March 2004 Slide 25 Flight Test Set-up

9 March 2004 Slide 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.

9 March 2004 Slide 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