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THEMIS ELECTRIC FIELD INSTRUMENT (EFI) Dr. John Bonnell and the THEMIS EFI Team

THEMIS ELECTRIC FIELD INSTRUMENT (EFI) Dr. John Bonnell and the THEMIS EFI Team University of California-Berkeley University of Colorado-Boulder. Outline. Personnel and Organization Summary of EFI Status at MPDR Requirements, Specifications, and Design Compliance Design Overview

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THEMIS ELECTRIC FIELD INSTRUMENT (EFI) Dr. John Bonnell and the THEMIS EFI Team

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  1. THEMIS ELECTRIC FIELD INSTRUMENT (EFI) Dr. John Bonnell and the THEMIS EFI Team University of California-Berkeley University of Colorado-Boulder

  2. Outline • Personnel and Organization • Summary of EFI Status at MPDR • Requirements, Specifications, and Design Compliance • Design Overview • Top-Level Design • Designs of Individual Elements • Design Drivers and Compliance • DC Error Budget • AC Error Budget • Schedule • Design • Long-Lead Procurement • ETU • EPR Results

  3. Personnel and Organization • Organizational Chart (all UCB unless noted): • Prof. F. Mozer (EFI Co-I). • Drs. J. Bonnell, G. Delory, A. Hull (Project Scientists) • P. Turin (Lead ME) • Dr. D. Pankow (Advising ME) • B. Donakowski (EFI Lead ME, SPB) • R. Duck (AXB ME) • D. Schickele (Preamp, SPB ME) • C. Smith (THEMIS Thermal Eng) • S. Harris (BEB Lead EE) • H. Richard (BEB EE) • R. Abiad (BEB FPGA Eng) • G. Dalton (EFI GSE Mechanical and General Mechanical) • J. Lewis, F. Harvey (GSE) • Technical Staff (H. Bersch, Y. Irwin, H. Yuan, et al.) • R. Ergun (DFB Co-I; CU-Boulder) • J. Westfall, A. Nammari, K. Stevens (DFB Eng; CU-Boulder) • C. Cully (DFB GSR; CU-Boulder)

  4. EFI Status at MPDR • Design: • The current EFI design meets Mission and Instrument requirements (exception: SPB mass estimate). • The design will be ready for ETU fabrication on schedule. • The critical paths on the design (SPB boom length, AXB deploy and stability,Preamp electro-mechanical and thermal, DFB FPGA definition and requirements) have been identified, and design elements are mature (exception: radial boom length (see EPR-Radial Booms)). • Procurement: • All long-lead items have been identified: • EEE parts ordered; rad testing of required parts arranged. • SPB and AXB mechanical items (custom wire cable, stacers, actuators, motors) have been ordered, with exception of SPB motors (see Schedule and Procurement)). • Vendors for mechanical and electrical machining and fabrication identified at mission-wide level. • Personnel: • Team is essentially complete: • All design engineering positions filled. • Two remaining MT positions to be hired Nov-Dec ’03; on-board by ETU in Jan-Feb ’04.

  5. Mission Requirements

  6. Mission Requirements

  7. Mission Requirements

  8. Science Requirements

  9. Performance Requirements

  10. Performance Requirements

  11. EFI Board Requirements

  12. EFI Board Requirements

  13. EFI Boom Requirements

  14. EFI Block Diagram sheath sensor • A High-Input Impedance Low-Noise Voltmeter in Space preamp Floating ground generation BIAS USHER Bias channels GUARD VBraidCtrl VBraid BRAID Vref

  15. Top-Level Design (1) • Diagram of THEMIS EFI Elements

  16. Top-Level Design (2) • Description of THEMIS EFI Elements • Three-axis E-field measurement, drawing on 30 years of mechanical and electrical design heritage at UCBSSL. • Closest living relatives are Cluster, Polar and FAST, with parts heritage from CRRES (mechanical systems, BEB designs, preamp designs).

  17. Radial Booms • Description of THEMIS EFI Elements • Radial booms: • 20.8 to 27.8 m long. • 8-cm dia., DAG-213 or Ti-N-coated spherical sensor. • 3-m fine wire to preamp enclosure. • USHER and GUARD bias surfaces integral to preamp enclosure. • BRAID bias surface of 3 to 6-m length prior to preamp (common between all 4 radial booms). • Sensor is grounded through 10 Mohm (TBR) resistance when stowed, providing ESD protection and allowing for internal DC and AC functional tests. • External test/safe plug (motor,door actuator,turns click, ACTEST) to allow for deploy testing/enabling and external signal injection.

  18. Axial Booms • Description of THEMIS EFI Elements • Axial booms: • 4-m stacer with ~1-m DAG-213-coated whip stacer sensor. • Preamp mounted in-line, between stacer and sensor. • USHER and GUARD bias surfaces integral to preamp enclosure. • No BRAID bias surface. • Sensor is grounded through TBD Mohm resistance when stowed, providing ESD protection and allowing for internal DC and AC functional tests. • External test/safe plug (deploy actuator, ACTEST) to allow for deploy testing/safing and external signal injection.

  19. Performance Specification • Performance Specification • EFI radial sensor baseline will be 41.6 m, tip-to-tip. • EFI axial sensor baseline will be ~10 m, tip-to-tip. • 16-bit resolution. • Spacecraft potential: +/- 60 V, 1.8 mV resolution, better than 46 uV/m resolution (allows ground reconstruction of E from spacecraft potential to better than 0.1 mV/m resolution). • DC-coupled E-field: +/- 300 mV/m, 9 uV/m resolution. • AC-coupled E-field: +/- 50 mV/m, 1.5 uV/m resolution. • AKR log(Power) channel: <= 70 uV/m amplitude, 100-500 kHz bandwidth.

  20. DFB Functional Block Diagram

  21. DFB Data Flow Block Diagram

  22. EFI Data Rates • Data Rates • Slow Survey • Spin-fit radial and axial E-fields; SC potential (via ptcls). • Filter Banks. • Fast Survey • 3 E-field at 32 samp/spin; 2-3 sphere potentials at 8 samp/spin. • Filter Banks and FFT spectra. • Particle Burst • 3 E-field at 128 samp/s; 2-3 sphere potentials at 32 samp/s. • Filter Banks and FFT spectra. • Wave Burst • 3 E-field at 1024 or 4096 samp/s; 2-3 sphere potentials at 256 or 1024 samp/s. • Filter Banks and FFT spectra. • Diagnostic Mode (TBR) • E-field and sphere potentials at >= 32 samp/s. • Bias control levels at >= 1 samp/s.

  23. Individual Design Elements • Radial Boom Unit (Spin-Plane Boom, or SPB) • Boom Motor Driver Board (BMD) • Axial Boom Unit (AXB) • AXB and SPB Thermal Modeling • Preamp (Mechanical and Electrical) • Boom Electronics Board (BEB) • Digital Fields Board (DFB; see Top-Level Design) • GSE (Mechanical and Electrical)

  24. SPB Design Overview Sphere and Preamp Main Wire Spool Meter Wheel Base (Magnesium) Release Doors (Spring Preloaded) Brushless Gearmotor With Bevel Gears 4 x Attach Legs with G10 Spacers for Thermal Isolation Exit Tube

  25. Customization of Design for THEMIS Use • Wire Length • Increased to 18 m; capability of 25 m. • Packaging for mounting to THEMIS Probe • Structure Attachment • Magnesium replaced 6061 Al for weight savings • Sphere Coating • Titanium Nitride may replace DAG 213 • DC Gearmotor • Same Motor Manufacturer (Globe Motors) • Similar Performance (300 ounce-inches Torque) • Brushless Unit Selected over Brushed • Brushless better design in vacuum • Better Thermal Characteristics • Less Stray Magnetic Field • Higher Performance in smaller package • New Electronics Drive Package Required (BMD) • Designed in-house • Prototype up-and-running 5 weeks without problems

  26. Theory of Operation • Integration and Launch • Stowed and Unpowered • Wire Wound about Spool, constrained by pinch wheels • Release Doors Closed • Sphere/Pre-Amp Constrained by Release Doors • Deployment • Release Doors Opened via SMA Pin-Puller • Spin of S/C puts outward force on Sphere and Preamp • Motor Acts as brake to prevent motion; coaxial wire in tension • Motor powers rotation of Meter Wheel • Sphere and Preamp is payed out • Release Doors Close Back Around Wire • As Centrifugal Force exceeds 2G at Sphere, Sphere Key Reel Spring force is overcome and Sphere moves away from Preamp • Monitoring • Limit Switch on Shaft counting Rotations • Tension Sensor to sense High Tensile Force • Science Ops • Deployed Booms Configuration Unchanged

  27. Theory of Operation Meter Wheel Preamp Pinch Rollers Motor Sphere Release Doors Motor Drive Electronics Main Wire Spool

  28. Materials and Construction • Standard UCB Construction • Most Components Machined Aluminum • 6061 T6 and 7075 T73 • Alodined and Anodized • Machined Plastics • PEEK • Machined Magnesium Alloy AZ31B • Chosen for Weight Relief in Structure • Not MSFC-SPEC-522 High Resistance to SCC • Table II ‘Moderate Resistance’ • Requires MUA for use • Thermal Treatments • Surfaces covered with VDA tape or blankets • No Heaters Required • Common manufacturing techniques used • No Unusually Tight Tolerances • No Difficult Fabrications

  29. SPB Boom Motor Driver (BMD) • BMD Requirements: • Brushless DC Motor driver • Sense rotor position with Hall Effect devices • Drive stator coils based on commutation logic • Supply voltage: 28 ± 6 Volts • Load current: ~300 mA • Higher radiation environment than IDPU (100-kRad) • Short term exposure (6 months)

  30. BMD Block Diagram Motor Driver Board Brushless Gearmotor

  31. Axial Boom (AXB) Overview • AXB are integral part of THEMIS probe • Primary probe structure provided by Swales Aerospace • AXB located along center axis of probe • AXB deployment through top and bottom decks of probe. Antennae Mount (TBD by Swales) AXB Assembly Composite Tube Upper AXB THEMIS Probe Upper Deck Mount Test & Safe Plug Lower Deck Mount Lower AXB AXB relative to THEMIS Probe AXB Housing Internal View

  32. Axial Boom General Assembly • Design Modifications • Stacer Length • Double Deploy Assist Device • SMA Frangibolt Actuation • Whip Sensor Whip Canister (Whip Sensor Inside) Preamp DDAD Doors Roller Nozzles Whip Doors Whip Posts Stacer Canister (Stacer inside) Double Deploy Assist Device (“DDAD”) Tube Mounting Brackets Frangibolt Actuator (inside) Cable Bobbin STACER INDIVIDUAL BOOM IN STOWED CONFIGURATION

  33. Integration & Loading Whip Sensor is loaded into whip canister Whip canister is locked to the preamp by the whip clamp Stacer is loaded into stacer canister, DDAD doors hold the DDAD, and whip doors hold the whip canister Removable stacer pin is inserted through stacer tip piece, which locks the stacer, DDAD, and Whip canister to the boom assembly Cable is spooled around the cable bobbin Stacer actuation bolt is threaded into Stacer tip piece and Frangibolt actuator is slid over bolt and screwed tight with nut. Stacer pin and whip clamp are removed Boom is loaded into housing Deployment SMA Frangibolt is actuated and actuation bolt is broken. Stacer tip piece is released DDAD extends and initiates stacer deployment DDAD separation opens whip doors, initiating whip sensor deployment Science Ops Deployed boom configuration unchanged AXB Theory of Operation

  34. Theory of Operation • Deployed Properties • Whip sensor deployed length: 40 inches • Stacer deployed length: 150 inches Roller Nozzle Whip Canister Whip Sensor 4” Whip Doors DDAD 4” DDAD Doors Stacer Canister Stacer Tip Piece Stacer Cable Bobbin with Cable Frangibolt Actuator Deployed Boom Stowed Boom Deployed DDAD 150” 40” Deployed Whip Sensor

  35. AXB Assembly & Materials • Standard Flight Materials • AL 6061 T6, SST 440, Eligiloy, PEEK, M55J Graphite Composite. • Standard Flight Coatings • DAG-213, DAG-154, Type 3 Hard Anodize. • Long Lead Items (see Schedule and Procurement) • Stacers, Multi-conductor wire, FrangiBolts.

  36. SPB and AXB Thermal (1) • Heat Transfer • 80 mW dissipated at preamp irrelevant to bus temperatures. • Essentially inert hunks of metal after deployment • Long eclipse temperatures: • Top deck, -93 C. • Bottom deck, -36 C. • Preamp, -170 C. • AXB and SPB are heat leaks for bottom deck, and are isolated with 1/8-th inch G10 spacers. • All surfaces covered with low e VDA tape or blankets. • External snout of SPB dominates its heat leak; black-body open end of AXB tube dominates its heat leak. • Monitoring and Control • Probe bus monitors near one SPB; no monitoring on AXB. • No thermistors in preamp. • No operational heaters required. • No survival heaters needed after deploy. • Unlikely to need deploy heaters.

  37. SPB and AXB Thermal (2) • Steady state prediction based on deck temperature from Swales • Cold prediction from cold orbit, not long eclipse. • Hot prediction from hottest orbit and attitude. • Will not deploy in extreme hot or cold cases. • Better predictions await more complete instrument thermal models.

  38. Preamp and Sensor Geometry • Evolution of CLUSTER-II sphere/”puck” design • Simple design, flight-proven components 3m Preamp Housing, d ~2.3 cm 3m thin wire, d ~10 mil sphere, d ~8 cm 1 m Preamp Housing, d ~2.3 cm

  39. Preamp Requirements • DC - 500 kHz • DC: Coupling impedances up to 10,000 M. • AC: Minimize capacitive voltage division (low input capacitance) • Radial Ccoupling ~13 pF, Axial Ccoupling ~6.5 pF • Wide temperature range (+100-370º K) • Survive high radiation exposure (~750 kRad/year behind 1 mm of Al)

  40. Preamplifier Mechanical Design • Goal: Minimize preamp-sphere interference (shadowing, photoelectrons, potential geometry…)

  41. Sphere Preamplifier Sensor Electronics Design ±40 V

  42. Preamplifier IC • Op-Amp: OP-15AJ • MIL-STD 883, CRRES Heritage • Rin ~1012 ohms, Cin ~3 pF • Low Power Dissipation (<80 mW) • Internally compensated, unity-gain stable • Capability to drive capacitive loads (>4000 pF) • 40 kRADs with little performance degradation (satisfied behind ~7 mm Al over two years)

  43. BEB Requirements • Functional Requirements • Spin Plane Booms, for each provide: • Floating Ground Driver • “Bias”, “Stub”, “Usher” programmable potentials • “Braid” programmable, switchable potential • AC test signal source • Axial Booms, for each provide: • Floating Ground Driver • “Bias”, “Stub”, “Usher” programmable potentials • AC test signal source

  44. BEB Requirements (con’t)

  45. BEB Analog Electronics

  46. BEB Block Diagram

  47. BEB Braid Bias

  48. Mechanical GSE Requirements • Functional Requirements • Provide for simulation of actuators and motors during functional tests, FSW testing, etc. • Connect through test/enable plugs on SPBs and AXB pair.

  49. Electrical GSE • Block Diagram of EFI/BEB GSE

  50. Electrical GSE Requirements (1) • Power/Thermal/Mechanical • Provide regulated voltages. • Facilitate current measurements. • 6U VME support (w/out Wedgelocks) for BEB. • Portable and rugged for transport. • Open rack for access while under test. • Connectors acceptable for Flight interconnection • Electrical Interface • Backplane interface per IDPU backplane specification. • 1 MUX’d analog housekeeping output (ANA HSK). • GSE interface circuitry must be flight-grade.

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