SST Subsystem Preliminary Design Review

1. SST SubsystemPreliminary Design Review Davin Larson, Thomas Moreau, Ron Canario, Robert Lee, Jim Lewis UCB

2. Overview • Solid State Telescope (SST) • Requirements and Specifications • Block Diagram • Mechanical Design • Detectors • Collimation • Magnets • Attenuator (aka shutter, door) • Detector placement / FOV issues • Mass estimates • Electrical Design • AFE – (Analog Front End) (aka: DFE) • ADC board (aka: DAP) • Power Estimates • Testing and Calibration • Schedule • Issues

3. Science Requirements • SST-1: The SST shall perform measurements of the tailward-moving current disruption boundary speed using the finite gyroradius technique (4.1.1.2, 4.1.1.5). • SST-2: The SST shall measure the time-of-arrival of superthermal ions and electrons of different energies emanating from the reconnection region to determine the Rx onset time (4.1.1.3, 4.1.1.5). • SST-3: The SST shall compute the partial energy moments due to the superthermal ions and electrons in the magnetotail plasma sheet (4.1.1.3, 4.1.1.6, 4.1.1.7, 4.1.1.9, 4.1.1.10). • SST-4: The SST shall obtain measurements of ion and electron distribution functions with one spin time resolution (<10sec required) (4.1.1.2, 4.1.1.3). • SST-5: The SST shall measure energetic electron fluxes as close to Earth as 6RE geocentric, at all local times. (Radiation belt science- tertiary objective – achieved by nominal design). • SST-6: The SST shall measure energetic ions in the solar wind, at the magnetopause and in the magnetosheath (Dayside science – secondary objective – achieved by nominal design).

4. Performance Requirements • SST-7: The SST shall measure energetic particles over an energy range of 30-300keV for ions and 30-100keV for electrons found in the magnetotail plasma sheet (SST-1, SST-2). • SST-8: The SST energy sampling resolution, dE/E, shall be better than 30% for ions and electrons (SST-1, SST-2). • SST-9: The SST shall be capable of measuring differential energy flux in the range from: 10^2 to 5x10^6 for ions; 10^3-10^7 for electrons (keV/cm2-s –st- keV) whilst providing adequate counts within a 10 second interval. (exact values TBD) (SST-1, SST-2) • SST-10: The SST shall measure over 90o in elevation with a minimum resolution of 45o (SST-1, SST-2, SST-3, SST-4). • SST-11: The SST shall have an azimuthal resolution of 45o (SST-1, SST-2, SST-3, SST-4). • SST-12: The SST shall supply the high energy partial moments at one spin time resolution (SST-3) • SST-13: SST calibration shall ensure <20% relative flux uncertainty over the ranges defined above (SST-1, SST-2).

5. Block Diagram IDPU Sensor Unit (2 DFEs) SST DAP Board (aka: ADC) ETC Board DCB Sensor Unit (2 DFEs)

6. Sensor Units • Each sensor unit is a: • Dual-double ended solid state telescope • Each double ended telescope (1/2 sensor) has: • Triplet stack of silicon solid state detectors • Foil (on one side) • Filters out ions <~350 keV • Leaves electron flux nearly unchanged • Magnet / Open side • Filters out electrons <300 keV • Leaves ion flux nearly unchanged • Mechanical Pinhole attenuator • Reduces count rate during periods of high flux • Reduces radiation damage (caused by low energy ions) during periods of high flux • Collimators • Preamplifier / shaping electronics

7. Sensor Unit Schematic Foil Detector Thick Detector Open Detector Lexan/Al Foil Collimator Attenuator Magnet

8. Sensor Units

9. Mechanical Design • Block Diagram Overview • Sensor Components • Detectors (& Associated Electronics) • Attenuator (aka shutter, door) • Detector Placement / FOV issues • Collimation • Magnet • Other Stuff • Cables • ADC Board • Mass Estimates

10. Detector Pixelation • Detectors similar to STEREO/STE • Produced at LBNL/Craig Tindall PI Active area 5 mm Guard ring 10 mm

11. Detector Stacking • Current Design +35 V ~200 A Dead Layer n Open p Thick{ Foil Pixelated side ~1200 A Dead Layer

12. Mechanical Presentation Robert K. Lee

13. SST Mechanical Design • Solid State Telescope (SST) • Mechanical Requirements • Mechanical Design • SST Sensor Unit • Attenuator Actuation • Attenuator Control • Electronics and Cabling • Sensor Orientation Relative to Spacecraft Bus • Thermal Summary • Mass Summary

14. SST Mechanical Design • Mechanical Requirements • SWALES Mechanical Verification Specification 1c • Radiation shielding thickness driven by dose depth curve • Total subsystem mass < 1.2 kg • Two SST sensors • DAP electronics board with shielding • Harness • Nitrogen purge required • Attenuator actuation must complete motion < 1 minute • Attenuator used approximately 20 times per day

15. SST Mechanical Design • SST Sensor Unit • DFE Detector Board Subassembly • Magnet-Yoke Subassembly • Attenuator-Actuator Subassembly • Collimators • Support Structure • Bi-Directional FOV • Attenuator Actuation • Linear Actuators • Position Switches • Attenuator Control • Electronics and Cabling • DAP Board • Harness • Sensor Orientation Relative to Spacecraft Bus • Mass Estimate

16. SST Mechanical Design • DFE Detector Board Subassembly Detectors (4) Spring Clamp (2) BeCu Gasket (3) AMPTEK Shielding PEEK Spacer (3) Spring Plate (2) Kapton Flex-Circuit (4) • Detector Stack Composition (exploded view)

17. SST Mechanical Design • Typical Electrical Connection Between Detector and Flex-Circuit Wirebond (not shown to scale) Kapton Flex-Circuit Detector (pixelated side)

18. SST Mechanical Design • DFE Detector Board Subassembly Relative Positions • (2 per sensor) Detector Stack Subassembly Multi-Layer Circuit Board (62 mil thickness) AMPTEK Shielding

19. SST Mechanical Design • Magnet-Yoke Assembly Co-Fe Yoke (2) Sm-Co Magnet (4) Aluminum Magnet Cage

20. SST Mechanical Design • Attenuator Assembly Actuator Yoke (2) Attenuator (4) Cam (2) Sapphire Bearing (2)

21. SST Mechanical Design • Actuators and Position Switches Honeywell SPDT Hermetically Sealed Switch (2) NANOMUSCLE SMA Actuator (2)

22. SST Mechanical Design • Two Collimators Per Side Ion Side Electron Side

23. SST Mechanical Design • Four Collimators Per Sensor Ion Side Electron Side Electron Side Ion Side

24. SST Mechanical Design • Support Structure (back section) Housing (back section) Electrical Connector Bottom Closeout Panel

25. SST Mechanical Design • Support Structure (front section) Housing (front section)

26. SST Mechanical Design • Bi-Directional Fields-of-View

27. SST Mechanical Design • Attenuator Actuation – OPEN position Honeywell Switch (extended-position) Honeywell Switch (compressed-position) NANOMUSCLE Actuator (extended)

28. SST Mechanical Design • Attenuator Actuation – CLOSED position Honeywell Switch (compressed-position) Honeywell Switch (extended-position) NANOMUSCLE Actuator (retracted)

29. SST Mechanical Design • Attenuator Control – OPEN position SST Sensor PCB PCB +5V +5V Open Attenuator Close Attenuator R~5W NANOMUSCLE GND GND SPDT Switch Monitor Monitor

30. SST Mechanical Design • Attenuator Control – CLOSED position SST Sensor PCB PCB +5V +5V Open Attenuator Close Attenuator R~5W NANOMUSCLE GND GND SPDT Switch Monitor Monitor

31. SST Mechanical Design • Attenuator Control – Switch Activation Switch Roller during compressed-position Switch Toggle/Transition Cam Radius Switch Travel Length Switch Roller during extended-position Cam Rotation Angle Note: Sketch NOT drawn to scale

32. SST Mechanical Design • Linear Actuators • NANOMUSCLE Shaped Memory Alloy (SMA) • Single direction 125 gram pull-force • < 40 gram required force => F.S. > 3.0 • Operating temp range: -70°C to +75°C Extended Position Relative Size Retracted Position

33. SST Mechanical Design • Position Switches • Honeywell miniature hermetically sealed switches • Single-Pole-Double-Throw circuitry • Operating temperature range: -65°C to +121°C • Exceeds MIL-S-8805 shock and vibration requirements Roller Extended Position Compressed Position

34. SST Mechanical Design • Sensor Orientation Relative to Spacecraft Bus • FOV is still being resolved

35. SST Mechanical Design • Thermal Summary - Heat Transfer • Power Dissipation • 6 Amptek 225s = 72 mW per sensor. • Steady state shadow temperature of -61 °C • Conduction • Corner panel reaches –60 °C in long eclipse • Isolated from corner panel with 1/8 inch G10 spacers. • Radiation • All surfaces covered with low ε VDA tape • Apertures and collimators dominate the heat leak

36. SST Mechanical Design • Thermal Summary - Temperature Limits • Steady state predictions from UCB based on corner panel temperatures from Swales • Cold prediction from 3 hour eclipse orbit • Hot prediction from hottest orbit and attitude • Average operating temperature around 25 °C • Better predictions await more complete instrument thermal models

37. SST Mechanical Design • Temperature Monitoring and Control • Modified Interface Monitoring • Probe Bus will monitor the SST temperature on one of the SSTs • Instrument Monitoring • IDPU will process thermistors near the detectors • Heaters • No operational heaters are required • Survival heaters will keep SST above Eclipse-Op limits • Two heater services provided by the probe bus • Primary service thermostat closes at –58 • Secondary service thermostat closes at -63

38. SST Mechanical Design • Nitrogen Purge Connection • Nitrogen line is connected to SST purge fitting during pre-flight operations to purge instrument interior • Gas supplied at 5 psig • Regulated and filtered to each detector stack at 1 liter/hour

39. SST Mechanical Design • Electronics and Cabling • DAP Board • Located within IDPU • Type 6U card • Radiation shielded with 5mm of aluminum • Will be discussed in further detail in IDPU section • Harness • Approximate length of 1.2m • Composition: • 10 coaxial cables (36 AWG) • 4 twisted wire pairs (26 AWG) • 4 single wires (36 AWG)

40. SST Mechanical Design • Mass Summary

41. SST Mechanical Design • Questions/Comments?

42. Design Details • Design Details • Thomas Moreau

43. Sensor Considerations • Detector system • Measure electrons and protons > 20 keV • Geometrical analysis • Collimator aperture • Solid state detector size • Thin foil • Stop protons < 350keV • Magnet system • Deflect electrons < 200 keV • Not to disturb particle trajectories out of the magnet gap • Low stray magnetic field at the position of the magnetometers • Attenuator System • Reduce count rate during high flux • Reduce radiation damage (especially to open side)

44. F T O Detector System • Detectors stacked in “Triplet” sequence: • Foil (F) | Thick (T) | Open (O) • Area used 1.0  0.5 cm2 • Front detectors F and O are 300 m thick while T is 600 m (with two detectors back to back) • Detectors associated with a system of coincidence/anticoincidence logic

45. Opto-Mechanical System Most of stray light from an out-of-field source are eliminated by a proper design Critical one-bounce scatter 28 Section view of the wide aperture Section view of the narrow aperture 48 28

46. Collimator System • 3D numerical model (GEANT3) of the collimator with detectors/foil • Collimator baffle offers 48  28 rectangular full field-of-view • Tungsten knife-edges intercept out-of-beam low-energy particles and reduce scattered light • Aluminum housing shielding (0.5 mm) stops normally incident protons < 8 MeV and electrons < 400 keV • Al:Si/Lexan/Al:Si three layer foil (1449Å/3.877m/1353Å) absorbs protons < 350 keV while permitting electrons ~20 keV to penetrate • Geometric factor ~ 0.11 cm2sr

47. Telescope Response • Monte-Carlo simulation • 3D ray tracings • Angular response 37  22 FWHM • Efficiency plots for electron and proton

48. Magnet System • Magnetic circuit design • 4 permanent magnets + 2 yokes • Two oppositely oriented dipoles • Stray fields < 10 nT at 1m distance Magnet gap Permanent magnet [Samarium-Cobalt 18 MGOe] Magnetic flux density Yoke [Vacoflux 50 Iron-Cobalt alloy]

49. Magnet System • Particle tracing simulations

50. Electrical Design • Block Diagram • DFE–Analog Front End (aka: AFE) • Functions: Preamp/Shaping • Schematics • Parts • Layout • Testing • DAP board (aka: ADC) • Functions: Baseline restoration, Peak detect, ADC, Logic • Schematics • Parts • Layout (currently incomplete) • Testing • Actel Specs • Power Estimates