X-ray Wide Field Imager

1. X-ray Wide Field Imager Thermal Systems Kimberly Brown 16 – 20 April, 2012

2. Thermal System Overview • S/C bus is thermally isolated from each FMA, both conductive and radiatively • Insulated MLI on exterior s/c bus, metering structure, top deck • 15 layer make-up • Silver conductive composite coating ITO/SiOx/Al203/Ag • Low absorptance (0.08 at BOL) and high emittance 0.6 • Radiator Panel for Bus (located on anti-sun side) • Coating NS43G yellow paint • High emittance 0.9 • Radiators sized for DEA’s, tracked in S/C MEL • Bus Heat Pipes (CCHPs) • Transfer heat from boxes to 2 radiator panels • Heat pipes embedded in 2 radiator panels to spread heat • Heater Control for Propulsion, Gimbals, Battery, Star Trackers • Mechanical thermostats (operational and survival) • Primary and redundant heater circuits • Two thermostats in series per circuit • Kapton film heaters attached to components

3. Spacecraft Temperature Limits • Propulsion System • +10°C to 40˚C • S/C Components Electronics • -10°C to +40°C operational and -20°C to +50°C survival • Avionics, comm system • Solar Array Temperature - Operational -100°C to +106°C (10°C above predict) • CommSystem: • HGA, two axis Gimbal motors 0°C to 40°C • Antenna Dish -40°C to 65°C • Xband: Operational +10°C to 40°C • Li Ion Battery Temperatures - Operational 0°C to +30°C

4. X-Ray WFI Configuration MLI, Sunshield for WFI MLI, conical FMAs Backside of Solar Arrays Coated white paint MLI, Sunshield for FMAs

5. S/C Bus Thermal Control Subsystem Functional Block Diagram 3 Thrusters RW RW RW RW RWE RWE RWE RWE Battery (Li-Ion) Radiators Reject Waste Heat to Space PSE Comm System Avionics Gyro Propellant Tanks, Lines and Fill-and-Drain Valves FMA (qty 3) Radiators MLI Thermostatically controlled heaters

6. Instrument components included in S/C MEL • MLI for each Metering Structure (3) • Each FMA isothermalized from spacecraft – heat pipes and MLI internal • Radiators for WFI DEAs (3) • Sunshield for each Camera Assembly • Radiator for DPA and RIU in Spacecraft Bus • MLI on Top Deck of Bus • Sunshield for FMA MLI

7. S/C Bus Thermal Control For FMA MLI on interior to radiatively isolate from FMA CCHPs isothermalizes mounting interfaces for each FMA (redundancy not shown)

8. Summary of X-Ray WFI Radiator Sizes s/c radiator based on 478 Power Watt load – includes DPA and RIU Updated in study this week Customer provided

9. Heater Circuits Summary

10. Spacecraft Total Heater Power * Operational heater circuits

11. Propulsion Subsystem Schematic • MLI over tanks • Heater control by mechanical thermostats for all propulsion components N2 N2H4 N2 N2H4 N2 N2H4 P P P Diaphragm Tanks F 22 N Thrusters FD Valves Pressure Transducer Filter Latch Valve F P

12. Propulsion System Thermal Design • Tank (3) • Conductively isolated tanks from Bus structure with isolation like aluminum support struts • Radiatively isolated by blanketing the tanks (6 layer) inside the S/C bus with a low emittance coating • Bottom deck covered with MLI blanket (15 layer) • Heaters for tanks thermostatically controlled, prime and redundantheaters with mechanical thermostats • Fuel Line Design • Fuel Lines assumed to be internal from tank to thrusters • All lines wrapped with heater elements spirally wrapped • Heaters are thermostatically controlled • All lines spirally wrapped with 5 mil aluminum tape with 50 % overwrap • Lines to be low ε taped then wrapped with MLI sleeve blanketing (15 layer) external • Zonal heaters • Thrusters (12) 5lbf (22N) • Heaters thermostatically controlled • Prime heater per thruster with two mechanical thermostats per circuit • Thruster has MLI boot blanket cap with over-temperature outer layer for soak back • Current Heater Power Estimate for Propulsion 67 Watts

13. Propulsion System Heater Power Top view of Tanks

14. Verification of Thermal System • Perform Thermal Vacuum Thermal Balance Testing Per GEVS at System level. • Perform 4 Hot/Cold Thermal Vacuum Cycles • Perform Thermal Balance Tests Subjecting X-Ray WFI to Worst Hot and Cold Case Conditions. • Verify Thermal Models, Perform Model Correlation to Test Data. • Verify Proper Operation and Design of Heater Circuits • Verify Proper Thermistor Calibration, Operation and Placement • Verify each FMA Interface to S/C Interface • CCHP for Spacecraft Bus • Conduct detail TB tests for Spacecraft Bus during Observatory level testing. • Component Level Testing Shall be Performed by the Vendor Prior to Shipment to S/C Vendor: • Heaters, Thermostats, Thermistors • Electronic boxes test 8 hot/cold TV cycling • S/A deployment.

15. Instrument TB/TV test • Instruments test 8 hot/cold TV cycles. • Each Instrument conduct TV qualification and TB testing during instrument level testing of 3 FMA, 3 Camera Assemblies and 3 DEAs. • Instrument thermal performance fully tested at Instrument level test.

16. Issues / Potential Risks / Future work Issues – None Risks: • Risk minimized due to no cryocoolers • Instrument radiators are all passive designs (no CCHPs required), simplifies testing Future work: • Study top deck layout to ensure electronics boxes and CCDs are properly shielded from sun for any pointing orientation. • STOP analysis to determine gradients of the metering structure and the effects of any structural distortion • Layout of CCHPs to test in TV

17. Acronym List MLI: Multi-layer insulation CCHP: Constance conductance heat pipe FMA: Flight mirror assembly TCS: Thermal control system BOL: Beginning of Life HGA: High Gain Antenna MEB: Main Electronics Box DEA: Detector Electronics Assembly DPA: Digital Processor Assembly RIU: Remote Interface Unit

18. Backup Material