1. THEMIS Instrument CDR 1 UCB, April 19-20, 2004 THEMIS Electric Field Instrument (EFI) Instrument CDR The THEMIS EFI Team

2. THEMIS Instrument CDR 2 UCB, April 19-20, 2004 Outline Personnel and Organization Summary of EFI Status at MPDR Requirements, Specifications, and Design Compliance Design Overview Top-Level Design Design Drivers and Compliance DC Error Budget AC Error Budget

3. THEMIS Instrument CDR 3 UCB, April 19-20, 2004 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, Facilities) R. Duck (AXB ME) D. Schickele (Preamp, Sensor Cables, Facilities ME) G. Dalton (SPB, EFI GSE Mechanical) S. Harris (BEB Lead EE) H. Richard (BEB EE) J. Lewis, F. Harvey (GSE) Technical Staff (H. Bersch, Y. Irwin, H. Yuan, Wm. Greer (UCLA), et al.) R. Ergun (DFB Co-I; CU-Boulder) J. Westfall, A. Nammari, K. Stevens (DFB SysE, EE; CU-Boulder) C. Cully (DFB GSR; CU-Boulder)

4. THEMIS Instrument CDR 4 UCB, April 19-20, 2004 EFI Status at I-CDR Requirements and Design: –The current EFI design meets Mission and Instrument requirements. –The design is complete. –One new requirement (CG positioning) has been imposed post-PDR. Procurement: –All long-lead items have been procured in sufficient quantities to allow for ETU and initial FLT production: –EEE parts ordered; rad testing of required parts arranged. –SPB and AXB mechanical items (custom wire cable, stacers, actuators, motors) are in-house, or on order with expected delivery on schedule for FLT build up. –Vendors for mechanical and electrical fab identified through ETU production Dec ’03 through Mar ’04. Personnel: –Team is complete: –All design engineering positions filled. –One FT MTech position filled Mar ’04; two PT Mtech positions filled internally by personnel transitioning over from STEREO. Assembly and Test: –ETUs of all major elements have been assembled and partially or largely tested. –Testing will be completed by M-CDR (June 15-16 ’04).

5. THEMIS Instrument CDR 5 UCB, April 19-20, 2004 RFA and Design Trade Closure RFAs from I-PDR and M-PDR all closed out: –ESC Spec is on Rev. D1; includes detailed specs on the requirement and methods to achieve it; ESC roster developed in Feb ’04, allowing close collaboration between Swales and UCB on problem areas and mitigation techniques. –EMI Spec completed Mar ’04. –Detailed Instrument I&T plan under development as part of ETU Testing; synthesized from Polar, Cluster, etc. Open Design Trades from PDR closed out: –Boom lengths set at 50/40/7.67 meters tip-to-tip based on CBE of Probe mass properties and std. GSFC and UCB dynamic stability requirements and boom mode resonance keep-outs. –Ti-N chosen over DAG-213 for SPB sensor coating. –Heritage brushed motor chosen for SPB deploy. –Braid biasing selected, and Distal Braid length set at 3 m. –DAC implementation on BEB chosen (ADC5544), and bias offset range of +/- 40 V maintained. –EFI filters on DFB chosen to be Bessel-type. –Others to be covered in individual presentations.

6. THEMIS Instrument CDR 6 UCB, April 19-20, 2004 REQUIREMENTEFI DESIGN IN-1. The Instrument Payload shall be designed for at least a two-year lifetime. Compliance. Lifetime has been considered in all aspects of EFI and DFB design (parts, performance degradation, etc.). IN-2. The Instrument Payload shall be designed for a total dose environment of 33 krad/year (66 krad for 2 year mission, 5mm of Al, RDM 2) Compliance. Common Parts Buy for Instrument Payload. All parts screened for total dose. Radiation testing planned if TID is unknown. IN-3. The Instrument Payload shall be Single Event Effect (SEE) tolerant and immune to destructive latch-up. Compliance. Common Parts Buy for Instrument Payload. All parts screened for total dose. Radiation testing planned if LET is unknown. DFB design includes latchup mitigation circuits on ADCs, inclusion contingent upon results of LTC1604 radiation testing. Mission Requirements

7. THEMIS Instrument CDR 7 UCB, April 19-20, 2004 REQUIREMENTEFI DESIGN IN-7. No component of the Instrument Payload shall exceed the allocated mass budget in THM-SYS-008 THEMIS System Mass Budget.xls Compliance. SPB: 1.88 kg Allocated; 1.61 kg CBE (CAD model). AXB: 2.30 kg Allocated; 1.97 kg CBE (CAD model). BEB: 0.396 kg Allocated; 0.426 kg CBE (ETU) DFB: 0.396 kg Allocated; 0.360 kg CBE (BB) Harness: 0.58 kg (modeling) (Harness, BEB and DFB tracked with IDPU) IN-9. No component of the Instrument Payload shall exceed the power allocated in THM-SYS-009 THEMIS System Power Budget.xls Compliance. Preamps: 0.09 W Allocated; 0.08 W CBE (ETU). note: Preamp power included in BEB allocation. BEB: 1.76 W Allocated; 1.1 W CBE (ETU). DFB: 1.00 W Allocated; 1.1 W CBE (BB+modeling). IN-13. The Instrument Payload shall survive the temperature ranges provided in the ICDs Compliance. SPB/AXB ICDs signed off. Verification by Environmental Test planned. IN-14. The Instrument Payload shall perform as designed within the temperature ranges provided in the ICDs Compliance. SPB/AXB ICDs signed off. Verification by Environmental Test planned. Special thermal shock testing of preamp ETU planned. Mission Requirements

8. THEMIS Instrument CDR 8 UCB, April 19-20, 2004 REQUIREMENTEFI DESIGN IN-16 The Instrument Payload shall comply with the Magnetics Cleanliness standard described in the THEMIS Magnetics Control Plan Compliance. THM-SYS-002 Magnetics Control Plan. Budget for EFI Magnets (Boom Motors) is <0.75nT @ 2 meters. IN-17 The Instrument Payload shall comply with the THEMIS Electrostatic Cleanliness Plan Compliance. Design, fabrication, and testing in accordance with THM-SYS-003 Electrostatic Cleanliness Plan. IN-18 The Instrument Payload shall comply with the THEMIS Contamination Control Plan Compliance. Design and fabrication in accordance with THM-SYS-004 Contamination Control Plan. IN-19. All Instruments shall comply with all electrical specifications Compliance. Design in accordance with THM-IDPU- 001 Backplane Specification (BEB, DFB). IN-20. The Instrument Payload shall be compatible per IDPU-Instrument ICDs Compliance. THM-SYS-103 DFB-to-IDPU ICD signed off. THM-SYS-104 BEB-to-IDPU ICD signed off. Verification Matrices to be completed. IN-21. The Instrument Payload shall be compatible per the IDPU-Probe Bus ICD. Compliance. Both THM-SYS-108 Probe-to-EFI Radial Booms ICD. THM-SYS-109 Probe-to-EFI Axial Booms ICD are signed off. Verification Matrices to be completed. IN-23 The Instrument Payload shall verify performance requirements are met per the THEMIS Verification Plan and Environmental Test Spec. Compliance. THM-SYS-005 Verification Plan and Environmental Test Specification preliminary draft. Verification matrix to be completed. IN-24 The Instrument Payload shall survive and function prior, during and after exposure to the environments described in the THEMIS Verification Plan and Environmental Test Specification Compliance. THM-SYS-005 Verification Plan and Environmental Test Specification preliminary draft. Verification matrix to be completed. Mission Requirements

9. THEMIS Instrument CDR 9 UCB, April 19-20, 2004 REQUIREMENTEFI DESIGN IN.EFI-1. The EFI shall determine the 2D spin plane electric field at the times of onset at 8-10 Re. Compliance. Via compliance with IN.EFI-5 and -13. IN.EFI-2. The EFI shall determine the dawn/dusk electric field at 18-30 Re. Compliance. Via compliance with IN.EFI-5 and -13. IN.EFI-3. The EFI shall measure the 3D wave electric field in the frequency range 1-600Hz at the times of onset at 8-10 Re. Compliance. Via compliance with IN.EFI-6, -8, -9, - 10, and –11. IN.EFI-4. The EFI shall measure the waves at frequencies up to the electron cyclotron frequency that may be responsible for electron acceleration in the radiation belt. Compliance. Via compliance with IN.EFI-6, -8, -9, - 10, and –11. Science Requirements

10. THEMIS Instrument CDR 10 UCB, April 19-20, 2004 REQUIREMENTEFI DESIGN IN.EFI-5. The EFI shall measure the 2D spin plane DC E-field with a time resolution of 10 seconds. Compliance. On-board spin-fit of spin plane E-field at 3-s (one-spin) resolution. IN.EFI-6. The EFI shall measure the 3D AC E-field from 1 Hz to 4kHz. Compliance. 3-axis E-field measurement sampled at 8 ksamp/s. See AC Error Budget. Verified through Calibration. IN.EFI-7. The EFI shall measure the Spacecraft Potential with a time resolution better than the spin rate (3 seconds; from ESA to compute moments). Compliance. On-board spin-avg’d sphere potentials at 3-s (spin-rate) resolution; EFI data rate allocation includes single spheres at ¼-rate of E-field data. IN.EFI-8. The EFI DFT Spectra Range shall be 16Hz to 4kHz, with df/f~25%. Compliance. Spectral products from DFB cover 8 Hz to 8 kHz at 5%, 10%, or 20% BW (16, 32, or 64 bins) IN.EFI-9. The EFI shall measure DC-coupled signals of amplitude up to 300 mV/m with 16-bit resolution. Compliance. Analog gain and ADC resolution of DFB set accordingly. Verified through Calibration. IN.EFI-10. The EFI shall measure AC-coupled signals of amplitude up to 100 mV/m with 16-bit resolution. Compliance. Analog gain and ADC resolution of DFB set accordingly. Verified through Calibration. Performance Requirements

11. THEMIS Instrument CDR 11 UCB, April 19-20, 2004 REQUIREMENTEFI DESIGN IN.EFI-11. The EFI noise level shall be below 10 -4 (mV/m)/Hz 1/2. Compliance. Low-noise preamp chosen (OP-15); good analog design practices throughout preamp, BEB and DFB; CBE is 3x10 -5 on AXB, 3x10 -6 on SPB. Verified through ETU testing. IN.EFI-12. The EFI HF RMS (Log power) measurement shall cover 100-500 kHz with a minimum time resolution of the spin rate (on-board triggers). Compliance. CBE of EFI response has gain of 0.8 out to 1 MHz; DFB provides HF-RMS at 1/16 to 8 samp/s. IN.EFI-13. The EFI shall achieve an accuracy better than 10% or 1 mV/m in the SC XY E-field components during times of onset. Compliance. See DC Error Budget Discussion. Performance Requirements

12. THEMIS Instrument CDR 12 UCB, April 19-20, 2004 REQUIREMENTEFI DESIGN DFB FUNCTIONAL REQUIREMENTS IN.DPU-36. The IDPU DFB shall provide an FFT solution for determining the parallel and perpendicular components of E and B in both fast survey and burst modes and produce spectra for each quantity separately. Compliance. DFB design includes FPGA-based projection (E dot B, E cross B) and FFT solutions. Verified through Test and Calibration of ETU. IN.DPU-37. The IDPU DFB shall integrate FGM digital data and EFI data to produce E·B Compliance. DFB design includes FPGA-based projection ( E dot B, E cross B) solutions. Verified through Test and Calibration of ETU. EFI Board Requirements

13. THEMIS Instrument CDR 13 UCB, April 19-20, 2004 REQUIREMENTEFI DESIGN BEB FUNCTIONAL REQUIREMENTS IN.DPU-38. The IDPU BEB shall provide sensor biasing circuitry, stub and guard voltage control for the EFI. Compliance. The BEB design provides 3 independent bias channels per sensor (BIAS,GUARD,USHER) and one shared bias channel for the SPB sensors (BRAID). Boom deployment is provided through the IDPU/PCB and DCB. IN.DPU-39. The IDPU BEB shall distribute a floating ground power supply to the EFI sensors. Compliance. The BEB design provides 6 independent floating grounds to the LVPS, and distributes the derived +/-10-V analog supplies to the six EFI sensors. IN.DPU-40. The IDPU BEB shall generate six independent BIAS, GUARD and USHER voltages with an accuracy of 0.1% for distribution to the EFI sensors. Compliance. The BEB design includes matched gain-setting components, along with >12-bit DAC, allowing accuracy of better than 0.1%; Verified through Test and Calibration of ETU. EFI Board Requirements

14. THEMIS Instrument CDR 14 UCB, April 19-20, 2004 REQUIREMENTEFI DESIGN IN.BOOM-5a. Deployed EFI Axials shall be repeatable and stable to  = 1 degree and  L/L = 1%. Compliance. Adequate stiffness and angular alignment of AXB stacers and deploy system included in design; verified by testing of ETU. IN.BOOM-5b. Deployed EFI Radials shall be repeatable and stable to  = 1 degree and  L/L = 1%. Compliance. Proper SPB cable design (stiffness, tempco) along with std. Cable winding procedures included in design; verified by testing of ETU. IN.BOOM-6. EFI Axial Booms shall be designed to be deployed between 2 and 25 RPM about the Probe's positive Z axis. Compliance. Adequate stiffness and angular alignment of AXB stacers included in design; verified by testing of ETU. IN.BOOM-7. EFI Radial Booms shall be designed to be deployed between 2 and 25 RPM. Compliance. Adequate strength margins on cable included in design; verified by proof-loading of cable and testing of ETU. IN.BOOM-8. EFI Axial Booms deployed stiffness shall be greater than 0.75 Hz (1 st mode). Compliance. Part of AXB stacer spec; verified by Testing of ETU. IN.BOOM-12. All deployed booms shall include TBD inhibits to prevent inadvertent release. Compliance. Test/Enable plugs included in design. Red tag door (SPB) and tube (AXB) covers. EFI Boom Requirements

15. THEMIS Instrument CDR 15 UCB, April 19-20, 2004 EFI Block Diagram A High-Input Impedance Low-Noise Voltmeter in Space sensor preamp sheath Floating ground generation Bias channels BIAS USHER GUARD BRAID VBraid Vref VBraidCtrl

16. THEMIS Instrument CDR 16 UCB, April 19-20, 2004 Top-Level Design (1) Diagram of THEMIS EFI Elements

17. THEMIS Instrument CDR 17 UCB, April 19-20, 2004 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).

18. THEMIS Instrument CDR 18 UCB, April 19-20, 2004 Top-Level Design (3) Description of THEMIS EFI Elements Radial booms: –22-m cable length (up to 50 m tip-to-tip deployed; SPB-X to be deployed to 50 m, SPB-Y to be deployed to 40 m). –8-cm dia., Ti-N-coated spherical sensor. –3-m, 0.009-inch dia. fine wire to preamp enclosure. –USHER and GUARD bias surfaces integral to preamp enclosure. –BRAID bias surface of 3-m length inboard of preamp (common between all 4 radial booms). –Sensor is grounded through 10 Mohm 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/safeing and external signal injection.

19. THEMIS Instrument CDR 19 UCB, April 19-20, 2004 Top-Level Design (4) Description of THEMIS EFI Elements Axial booms: –2.8-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 10 Mohm (TBR) 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/safeing and external signal injection.

20. THEMIS Instrument CDR 20 UCB, April 19-20, 2004 Top-Level Design (5) Performance Specification EFI radial sensor baseline will be 40 or 50 m, tip-to-tip (dual- length system). EFI axial sensor baseline will be 7.7 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: +/- 100 mV/m, 3.0 uV/m resolution. AKR log(Power) channel: 1 uV/m to 4.5 mV/m RMS amplitude, 400-kHz bandwidth, 100-500 kHz.

21. THEMIS Instrument CDR 21 UCB, April 19-20, 2004 DC Error Budget (1) The estimated electric field along the direction between the two probes is E=(v1-v2)/2L. Errors arise from and are mitigated by: Errors in baseline (L). Errors in v1 and v2; eg. (v1-v2) or each individually.

22. THEMIS Instrument CDR 22 UCB, April 19-20, 2004 DC Error Budget (2) Errors in baseline (L). Control boom length to 1%, trim deploy length to 4-cm accuracy. Increase fine wire length to reduce boom shorting effect (observed up to 20% on Cluster; predicted 5% on THEMIS (better Lf/L)). SPB-X and SPB-Y have different boom lengths, allowing for examination of L-dependent systematic errors on spin-period time scales (similar to Polar).

23. THEMIS Instrument CDR 23 UCB, April 19-20, 2004 DC Error Budget (3) Errors in v1 and v2; eg. (v1-v2) or each individually. Use TI-N coating on sensors (DAG-213 on AXB) for uniform photoemission. Keep all sensors clean pre-launch. Use high-impedance preamp (10 12 ohm) to reduce DC attenuation. Current-bias sensor to reduce sheath impedance and susceptibility to photoemission asymmetries (20-100 Mohm typ.). Mount sensor on fine wire and reduce emission area of preamp to reduce magnitude and effect of asymmetric photoemission (3-10 times smaller than Cluster). Use USHER and GUARD surfaces to control photocurrents to sensor (>= 20-V bias range, well above bulk of photoelectron energies). Use fine wire and BRAID bias surface to reduce cold plasma wake effects (scale with D/L or 1/L; roughly equivalent to Cluster). Enforce 1.0 to 0.1-V electrostatic cleanliness specification on THEMIS to reduce SC potential asymmetry effects to < 0.1 mV/m on all axes.

24. THEMIS Instrument CDR 24 UCB, April 19-20, 2004 DC Error Budget (4) CG Offset Effect on Systematic Error in Sunward E-Field: Center-of-Gravity (CG) offset from center of SPB boom system drives angular offset between opposing fine wires. Opposing fine wires go through sun- alignment at different spin phases, leading to systematic bipolar error signal. Primary effect is on instantaneous sunward E-field component. CG positioning Requirement of 1 part in 100 of SPB Cable pivot radius (approx. 4 mm, or 0.166 inch) drives magnitude of error below 0.8 mV/m, worst-case. (CG offset)/(pivot radius) 0.001 0.01

25. THEMIS Instrument CDR 25 UCB, April 19-20, 2004 AC Error Budget (1) EFI Spectral Coverage and System Noise Estimates AKR band CDI BBF Preamp and R bias Current Noise Preamp Voltage Noise axial radial Maximum Spectra (DC-Coupled) 1-LSB Spectra (DC-Coupled) flat 1/f 1/f 3 Spin frequency 4-kHz Anti-aliasing roll-off 10-Hz Ac-coupled roll-in

26. THEMIS Instrument CDR 26 UCB, April 19-20, 2004 AC Error Budget (2) RE02 BB Limits set to give S/N of > 3 for expected AKR amplitudes. RE02 NB limits set to drop equivalent BB spectral density below expected amplitudes below 4 kHz on SPB.

27. THEMIS Instrument CDR 27 UCB, April 19-20, 2004 AC Error Budget (3) 7.5 pF input capacitance of preamp has significant effect on gain above 100 Hz: SPB AC gain is 0.65. AXB AC gain is 0.45. Rolloff frequency from DC to AC gain (resistive to capacitive coupling) is predominantly controlled by sheath resistance, which is under direct control via sensor bias current.

28. THEMIS Instrument CDR 28 UCB, April 19-20, 2004 Summary of EPR Findings Radial Boom design ( 1,2,3,9; Draft findings, 3 Nov 2003 ): Dynamic stability issues (spin/trans MOI ratio) (Bus EPR) Dual-length/longer-length designs Axial Boom design ( 6,10 ): Deploy force margin Length vs. noise margin, whip vs. sphere sensors. Attitude information and jitter requirements ( 14 ). Miscellaneous mechanical findings ( 15,18,5 ): Deploy sequence modeling. Boom deployment temperature. SPB miter gear life testing. Hot parts and thermal stresses Gain and Filter Specifications of EFI and SCM on DFB ( 4,8,12 ). BEB FPGA specification and programming ( 20 ). Preamp electro-mechanical design ( 11 ). Electrostatic Cleanliness Specification (RFA UCB-8)( 7,17 ). EMI/EMC Specification (RFA UCB-9)( 13 ). Detailed I&T plan development (RFA UCB-10)( 19 ).

29. THEMIS Instrument CDR 29 UCB, April 19-20, 2004 EPR Findings—Radial Booms Dynamic stability issues: Bus and Instrument team analysis of dynamic stability not in accord; question is proper spin/transverse MOI ratio for non-rigid boom systems on THEMIS. Swales analysis indicates shorter AXB (60%) or longer SPB required to achieve stable configuration (Bus EPR finding). Longer-length/Dual-length designs (science-driven): 56-m (2x(25+3)m system) tip-to-tip SPB possible with current mechanical design. Direct improvement in DC error budget (30%). Allows for dual-length (21/28 m) system that would allow the detection of ES wake effects (not mission critical, however). Mass hit (56 g/SPB) for 7-m cable addition; fuel hit (~60%, 452 g increase) for final spin up. Resolution: Must be resolved by Jan ’04 (EFI F1 Cable Assy); Cable Assy schedule margin allows push back to Apr ’04, if necessary. Dynamic stability analysis is ongoing at Swales and UCB.

30. THEMIS Instrument CDR 30 UCB, April 19-20, 2004 EPR Findings—Axial Booms Deploy force margin and AXB length repeatability: AXB design may not have enough deploy force margin to ensure dL/L = 1% repeatability of deploy length. Resolution: AXB ETU testing (Feb ’04). Length vs. Noise Margin; whip vs. sphere sensor response Current AXB length (~9-m effective, 10-m tip-to-tip) allows only factor of 3 S/N margin at 4 kHz (CBE of system noise level). SC perturbations will strongly affect DC E-field in AXB (several mV/m, dependent upon SC potential (plasma conditions). AXB whip sensor may have different response para/perp to B than SPB sphere+wire sensor. Resolution: AXB length can not be reduced significantly without compromising 3D AC measurement. AXB lengths will be trimmed based on simulation results to reduce DC offset due to SC potential (final length Feb ’04 (AXB F1 Mach)). Literature on antenna response to be investigated to determine significance of whip vs. sphere effect (no mitigation planned; different capacitance of SPB and AXB sensors already known, and part of electrical Calibration plan).

31. THEMIS Instrument CDR 31 UCB, April 19-20, 2004 EPR Findings—Attitude Attitude knowledge and jitter requirements are modest, and achievable by Bus and Instrument designs. 5.6 degree (10%) knowledge required; better than 0.1 to 1.0 degrees achieved via post-processing of FGM and EFI data. Better than 3-degree accuracy and jitter in spin phase required for accurate on- board spin fits of E-field data; current IDPU design provides 0.9 degrees.

32. THEMIS Instrument CDR 32 UCB, April 19-20, 2004 EPR Findings—Misc. Mech. UCB should initiate kinematic and dynamic modeling of the boom deploy sequences. Resolution: Kinematic model of boom deploy already exists (Th_booms3d.xls; D. Pankow) at UCB as tool for understanding timing, spin-up requirements, mechanical loads, boom/SC modes, coriolis displacements, etc. Resolution: Algor product will be taken under advisement as part of on-going resolution of dynamic stability question (see Radial Booms; Jan ‘04). Boom deployment temperature range should be defined. Resolution: Boom deployment temperature range will be defined as part of I&T test flow (Dec. ’03-Jan. ‘04). SPB miter gear life testing under worst-case load required. Resolution: Such testing will be included in SPB I&T test plan (Dec ’03 – Jan ’04).

33. THEMIS Instrument CDR 33 UCB, April 19-20, 2004 EPR Findings—Gain/Filter DC/AC-coupled dynamic range and solitary waves Large-amplitude (>=100 mV/m) solitary waves have been observed at frequencies from 1-1000 Hz on Polar and Cluster in the THEMIS observation region. Such waves will saturate the AC-coupled (10 Hz-6 kHz) E-field channels with a dynamic range of +/- 50 mV/m. Resolution: Other channels can handle the large-amplitude events, although not simultaneously. DC-coupled (0-4 kHz) channels have a dynamic range of +/- 300 mV/m. Dc-coupled sphere/whip voltages have +/-60-V range (3 V/m on SPB, ~13 V/m on AXB). AC-coupled gain may be reduced to allow higher rate sampling of large-amplitude signals (TBR, Nov-Dec ’03, DFB ETU design). Filter specifications SCM channels use Butterworth, EFI uses Bessel. Difference means non-trivial phase differences and time-domain responses over entire 0-4 kHz range, maximizing between 1-4 kHz, preventing direct comparison of time-domain signals. Resolution: Trade between filter types underway (TBR, Nov-Dec ’03, DFB ETU design).

34. THEMIS Instrument CDR 34 UCB, April 19-20, 2004 EPR Findings—BEB FPGA BEB FPGA specification and programming Resolution: BEB FPGA requirements are modest and now well-defined (CDI interface, DAC control, Analog housekeeping), and common to most IDPU boards, allowing FPGA programmer (R. Abiad, UCB) to work on design and programming within BEB ETU schedule (Build/Test, Dec ’03).

35. THEMIS Instrument CDR 35 UCB, April 19-20, 2004 EPR Findings—Preamp Bootstrapping and guarding of preamp inputs Bootstrapping and guarding of preamp electronics in the current electromechanical design should be reviewed. Potentials of all conductors need to be defined (can, shields, etc.). Resolution: Current design does not include input guard, based on estimated input capacitance of preamp enclosure. Preamp ETU Assy and Test begins early Dec ’03 to characterize input capacity, and allow for changes and re-evaluation before FLT fabrication begins (Jan ’04).

36. THEMIS Instrument CDR 36 UCB, April 19-20, 2004 EPR Findings—ESC Electrostatic Cleanliness Specification and Enforcement Resolution: Rev. B of the THEMIS ESC Specification has been posted for review and will be signed off in Nov ’03. It is is available via the THEMIS ftp site (URL), and includes a complete specification of electrostatic cleanliness requirements as well as verification procedures. The specification sets a 1-V potential uniformity requirement under an 8 nA/cm 2 current density, with 0.1-V potential uniformity as a goal (see DC Error Budget for discussion).

37. THEMIS Instrument CDR 37 UCB, April 19-20, 2004 EPR Findings—EMI/EMC Electromagnetic Interference/Cleanliness Specification Resolution: A Draft of the THEMIS EMI/EMC Specification has been posted for review and will be signed off in TBD. This specification is modeled on that for the FAST mission, adapted to the instrument properties on THEMIS (SCM/EFI system noise levels and expected wave amplitudes). Testing and verification of compliance with EMI/EMC TBD, and requires some work, due to low frequencies of interest (0-4 kHz).

38. THEMIS Instrument CDR 38 UCB, April 19-20, 2004 EPR Findings—I&T Plan I&T test flow needs to be defined to include development, ETU, qualification and acceptance testing. Resolution: An EFI I&T plan will be developed in Dec ’03 to support qualification and acceptance testing of the EFI ETU in Jan-Mar ’04.