SPP/FIELDS System Engineering Preliminary Design Review

1. SPP/FIELDSSystem EngineeringPreliminary Design Review Keith Goetz University of Minnesota Goetz@umn.edu

2. SPP Level-1 Requirements

3. FIELDS Level-1 Level-1 Flow to FIELDS

4. FIELDS Level-3 Driving Requirements

5. FIELDS Level-4Flowdown – IRD • Requirements are flowed from SPP L3 document to FIELDS subsystems with IRD • APL: 7434-9051_Rev_Dash • SPF_SYS_010_Instrument_Requirements - IRD - SE-001-01B • L3 includes references to the FIELDS QA Matrix, Environmental Spec, EME Spec, Contamination Control, GI ICD, FIELDS ICD, etc. • L3 includes Instrument Functional and Performance Requirements • FIELDS IRD • Requirements linked up to the L3 PAY requirements • Requirements linked down the subsystem L5 or specifications • Subsystem specifications refer to their requirements from the IRD and how the design meets those requirements • Flight and SOC Software Requirements documents flow their requirements from the IRD down to the software modules • IRD specifies how each requirement is to be verified (Test, Analysis, etc) • System Engineer has validated that the subsystem specifications describe an instrument that meets requirements

6. Requirement Flow-down to Subsystems FIELDS Subsystems

7. Example - An IRD snippet – RFS Requirement Flow-down to Subsystems

8. Verification • IRD identifies briefly how each requirement is verified • Verification, Validation, Test, and Calibration Plan describes a plan for how requirements are verified • Discussed in I&T section • Requirements are verified as early as possible at a low level • Verifies subsystems, retires risk • Requirements are verified at the highest level of assembly possible • Often involves verifying a requirement at several levels • System Engineer tracks Verification against IRD • Reports on status at PER, PSR

9. SPP Spacecraft

10. FIELDS MAG Boom

11. FIELDS Block Diagram

12. Interface Control Documents • Spacecraft to FIELDS • General Instrument ICD is at rev - (7434-9066) • FIELDS Specific ICD (7434-9055) • Minor open issues don’t preclude ETU development • MOC-SOC ICD • Well developed and familiar from RBSP and STEREO • FIELDS to SWEAP ICD (SPF_MEP_105_SWEAP_ICD) • Preliminary release signed on both sides • Subsystem ICDs are well along • MEP, CDI, RFS, TDS, DFB, MAG, AEB, LNPS, PA, SCM • Connectors and pin-outs (SPF_MEP_110_Connectors) well defined

13. Software • DCB • Software Development Plan (SPF_MGMT_008_SDP) • Software Requirements (SPF_FSW_002_SRS) • TDS • Software Development Plan (SPF_TDS_002_SDP) • Software Requirements (SPF_TDS_004_SRS) • SOC • Software Development Plan (SPF_MGMT_016_SOC_SDP) • More later

14. Environmental • FIELDS to survive all environments to be encountered during ground operations, launch, and on orbit • FIELDS to operate in spec over all environments to be encountered during ground functional tests, on-orbit commissioning and science phases • Full science performance achieved after MAG boom and FIELDS antennas are deployed (during commissioning) • SPP Environmental Requirements called out in 7434-9039 (dash) • SPP EMC Requirements called out in 7434-9040 • FIELDS Verification Plan described in SPF_IAT_002 • Describes how FIELDS will verify compliance with requirements, including environmental requirements • Plan discussed in more detail in I&T section

15. Environmental Test Matrix

16. Mechanical • Instrument designed to Environmental Specification Requirements • Limit Loads, Stiffness, Venting, Shock • Mechanical Interfaces, mass NTE called out in the FIELDS ICD • Instrument tested per Environmental Spec • Mass Properties at component level • Mass, CG • MOI by analysis • Sine, Random vibration at component level • ETU to qualification levels • FM to acceptance levels • No acoustic test planned (no acoustically sensitive parts) • More mechanical later

17. Thermal • SPP – of course – presents its thermal challenges • FIELDS interface temperatures called out in the EDTRD and ICD • MEP Operational: -25ºC to +55ºC • FIELDS components conductively coupled to spacecraft structures • FIELDS’ various thermal designs to be verified by analysis and thermal vacuum testing • Analysis to include launch transients (heating) • Modeling and Analysis performed cooperatively between FIELDS and APL • Boom verification testing (Thermal Balance) described in I&T section • Verification testing (Thermal Vacum) described in I&T section • More thermal later

18. EMC for FIELDS • FIELDS is a driver for EMC/ESC/MAG requirements • Power supply conversion control • Limited radiated and conducted noise • Electrostatics – S/C exterior an equipotential surface • ΔV from point to point must be small (less than ~1V) • Spacecraft must be magnetically clean • STEREO and RBSP are good models • Spacecraft EMC testing plan needs to be worked • FIELDS antennas and radiated emissions

19. EMC/ESC • EMC • MEP box design includes EMC closeout • stair-step joints, vent shielding, connector close-out • DC-DC converter frequency is 150kHz synchronized • DC-AC MAG heater is 150kHz synchronized • RF receiver is synchronized to a multiple of 150kHz chopping frequency • All sampling is synchronized to 150kHz chopping frequency • Supply has front end filtering, soft start • Verification by EMC tests: • ETU (CE on bench) • FM (CE, CS, RE, RS, BI, On/Off transients) • ESC • Exterior surfaces are conductive and connected to chassis ground • ESC Verification at the component level • surface resistance measurements

20. DDD/Radiation • Components inside boxes are generally immune • Harnessing is not immune • Components connecting to external harnesses have considered DDD issues • For example – in peer reviews • Immunity will be demonstrated by analysis • Immunity will be tested with ETU • Radiation environment inside spacecraft is fairly benign (20kRad) • Most EEE parts have no problem • Some parts require additional screening – possibly latch-up circuitry • PMPCB in the loop • Electronics outside the spacecraft analyzed separately • PMPCB providing guidance and assistance • Spot shielding may be added in some locations • Planned for SCM preamplifier

21. Resources – Mass FIELDS mass tracking Shows 11.9% CBE to NTE

22. Resources – Power • FIELDS power summary • MEP Power shows ample contingency: 27% • At room temperature • New power estimates at 55C show much higher power needs • Contingency is negative • Heater power has been an issue • Operational heating • Below .25AU is reasonable • Above .25AU needs work • But is apt to be ok • Limited heating on MAG sensor has caused problems

23. Resources – Power Detail • FIELDS power tracking • Power broken out to indicate dissipation location • Heating broken into • Operational and survival • Above .25AU and below

24. Resources – Telemetry • Telemetry bit-rate allows us to meet our science requirements • Survey data goes to S/C C&DH SSR – 15Gb/perihelion • Select data goes to large FIELDS internal flash storage • Selected data comes down during cruise – 5Gb/perihelion • More bits is always more good! • Telecommand requirements are modest

25. Trades and Changes • Survival/operational heating additions • RTAX4000 selection – implemented on daughter boards (3 places) • FIELDS MAG boom to be built at APL • Accept virtual PPS from S/C • V1-4 Antennabrackets will accommodate one TPS shift • FIELDS Clocks – synchronized to power supply • Split FIELDS into two halves to enhance reliability • Open Trades • Location of FIELDS boom sensors • Length of FIELDS boom • Length of FIELDS whips

26. FIELDS/TDS Evolution FIELDS was proposed as a single string instrument Within FIELDS, TDS was proposed as a single science board

27. TDS Evolution • In early 2013, we recognized that FIELDS was central to meeting threshold science – occupying 4 of 9 threshold blocks • A single failure would mean a failure to meet threshold science • LNPS or DCB failure

28. System-6 • FIELDS then suggested a number of alternatives • increasing reliability • Eventually, we settled on System-6 • Split • FIELDS1/2 • LNPS • LNPS1/2 • AEB • AEB1/2 • DPU function • DCB/TDS

29. FIELDS Clocks • FIELDS instrument to use unified clocking • Receivers, sampling, power supplies, clocks • FIELDS LF instruments to operate in sync • FIELDS HF instrument relies on picket-fence for RF sensitivity • Power supplies chop – making lines noise as a function of frequency • Un-avoidable but controllable chopping at controlled frequencies • All S/C power supplies must be controlled • N * 50 kHz with N starting at 3 – e.g. 150 kHz, 200 kHz and so on • Frequencies are crystal controlled (±100PPM) • Make RF observations as a function of frequency in between lines of noise • In earlier analog super-heterodyne receivers, we used sharp crystal filters to create the picket fence • Observing in between lines of noise

30. Picket Fences

31. FIELDS HF Clocks • In the past, we used sharp crystal filters to create the picket fence • With our new all-digital receiver, we implement sharp picket-fence filteringwith simple high speed time series and poly-phase filtering • Samples must be in sync with FIELDS’ and S/C power supplies • FIELDS/HFR high end is about 20 MHz – sampling at ~40 MSa/s • Exact frequency must fall on the picket fence with room for an FFT • Master RFS sampling frequency is thus of the form 150 kHz * 2^N • Master sampling frequency is 150,000 * 256 Hz is 38,400,000 Hz • (±4 kHz)

32. FIELDS LF Clocks • Other FIELDS instruments will be operated in synchronization with power supply chopping frequency (SWEAP too) • Power supply chopping frequency is 150,000 Hz • For lower frequencies we’ll shift down by powers of two • For lowest sample rates we’ll shift down by powers of two to ~293 Sa/s • 150,000 Hz / 512 (292.968750 Sa/s) • However, making convenient and compressible packets still requires a packet sizes and cycle times corresponding to a power of 2 samples • A standard packet should start with 256 samples • Giving a FIELDS internal cycle time of .87 seconds/cycle • 131,072 / 150,000 Hz • FIELDS’ New York second

33. FIELDSSynchronized Sampling • MAGs produce samples at ~293 vectors per second • MAGs produce chunks/packets at 256 vectors per cycle • Out-board MAG survey data down-sampled at ~36.3 vectors/second • In-board MAG survey data down-sampled at ~2.3 vectors/second • DFB can sample from all 4 SCM axes and all 5 electric axes • Sampled at 150,000Sa/s • Low frequency DFB packets • DFB samples in sync with DC MAGs • 256 vectors at 293Sa/s covering .87s and 1 cycle in duration – lowest resolution • DFB mid-frequency spectra • DFB mid-frequency select time series • TDS time series triggered bursts – V,E, B and SWEAP • ~2MSa/s (1.92MSa/s = 38,400,000 / 20) • RFS spectra • Sampled in sync at ~40MSa/s

34. Issues • Mass margin is tight • +11.9% (16.51kg CBE vs 18.48kg NTE) • Power margin is tight – especially when operating hot • -0.7% (22.71W CBE vs 22.56W NTE) • +27.8% (17.66W CBE vs 22.56W CBE) at 20C • Heater power has been an complex issue • DC MAG sensors should be warmer • +53.4% (3.98W CBE vs 6.10W NTE) in the best operational case • -29.0% (8.59W CBE vs 6.10W NTE) in the worst operational case • +2.5% (10.05W CBE vs10.30W NTE) in the worst survival case • LVDS over-voltage protection solution has proved elusive • DCB and TDS • Monitoring non-op FIELDS Boom sensor temperatures remains open • MAGi, MAGo, SCM

35. Conclusion Issues are workable Requirements are understood Preliminary FIELDS system design meets requirements Documentation is in place FIELDS is ready to move into ETU development