SPP/FIELDS System Engineering Preliminary Design Review Keith Goetz University of Minnesota Goetz@umn.edu

SPP Level-1 Requirements   Trace the flow of energy that heats and accelerates the solar corona and solar wind. 1a How is energy from the lower solar atmosphere transferred to, and dissipated in, the corona and solar wind? 1b What processes shape the non-equilibrium velocity distribution observed throughout the heliosphere? 1c How do the processes in the corona affect the properties of the solar wind in the heliosphere? 2 Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind. 2a How does the magnetic field in the solar wind source regions connect to the photosphere and the heliosphere? 2b Are the sources of the solar wind steady or intermittent? 2c How do the observed structures in the corona evolve into the solar wind? 3 Explore mechanisms that accelerate and transport energetic particles. 3a What are the roles of shocks, reconnection, waves, and turbulence in the acceleration of energetic particles? 3b What are the source populations and physical conditions necessary for energetic particle acceleration? 3c How are energetic particles transported in the corona and heliosphere?

FIELDS Level-1 Level-1 Flow to FIELDS Table 4.1 Baseline Fields and Waves Measurements Req. Measurement Dynamic Range Cadence Bandwidth 4.1.1.1 Magnetic Field 140dB 100k vectors/s DC - 50kHz 4.1.1.2 Electric Field 2M vectors/s DC - 1MHz 4.1.1.3 Plasma Waves 1 spectrum/s ~5Hz - 1MHz 4.1.1.4 QTN/Radio 100dB for QTN 80dB for radio 1 spectrum/4s QTN 1 spectrum/16s radio 10-2,500kHz QTN 1-16MHz radio Table 4.5 Threshold Fields and Waves Measurements Req. Measurement Dynamic Range Cadence Bandwidth 4.1.2.3 Magnetic Field 125dB 256 vectors/s DC - 128Hz 4.1.2.4 Electric Field 4.1.2.5 Plasma Waves 90dB 1 spectrum/10s ~5Hz - 50kHz 4.1.2.6 QTN/Radio 70dB for QTN 70dB for radio 1 spectrum/32s QTN 1 spectrum/32s radio 10-2,500kHz QTN 1-16MHz radio

FIELDS Level-3 Driving Requirements FIELDS Driving Requirements PAY-37 Measurement: Magnetic Field MAG PAY-38 Measurement: Magnetic Field SCM & Plasma Waves PAY-170 Measurement: Electric Field & Plasma Waves PAY-172 Measurement: Plasma Waves (AC Magnetic Field) PAY-174 Measurement: Plasma Waves (Magnetic Field Power Spectra) PAY-272 Measurement: Plasma Waves (Electric Field Power Spectra) PAY-175 Measurement: Electric Field QTN Spectroscopy PAY-176 Measurement: Electric Field Radio Emissions PAY-105 Payload: FIELDS Burst Mode PAY-113 Timekeeping: FIELDS Time Knowledge Accuracy PAY-100 Payload: Minimum Perihelion Hours PAY-101 Payload: Mission Length PAY-104 Payload: Risk Category (single fault tolerant) PAY-109 Payload: Burst Mode Management PAY-112 Payload: Flight Software Modification PAY-277 Compliance: FIELDS to SWEAP ICD (FIELDS) PAY-279 Compliance: FIELDS to Spacecraft ICD PAY-276 Compliance: General Instrument Specification PAY-283 Compliance: MOC to SOC ICD PAY-140 Compliance: EMECP PAY-141 Compliance: EDTRD PAY-148 Compliance: CCP

FIELDS Level-4 Flowdown – 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

Requirement Flow-down to Subsystems FIELDS Subsystems

Requirement Flow-down to Subsystems Example - An IRD snippet – RFS ID Title L4 Requirements TBD Parent ID (Level 3) Parent Title Full Text Verification Method (What test and when) RFS - Radio Frequency Spectromenter and Thermal Noise Receiver RFS-01 Mission Length RFS Components must be selected to withstand the environment of SPP for the duration of the mission   PAY-101 Payload: Mission Length All instruments shall be capable of providing an operational lifetime of at least 7 years after launch. D RFS-02 Measure Quasi Thermal Noise RFS shall be capable of measuring QTN Spectroscopy, as follows: -- frequency range: 10 kHz - 2500 kHz; -- dynamic range: 100 dB; -- maximum field intensity: ±200mV/m at 100kHz -- sensitivity (excluding power converter frequencies): 1 x 10^(-7) V/m/sqrt(Hz) at 100 kHz; 2 x 10^(-8) V/m/sqrt(Hz) at 2 MHz; -- in one direction. PAY-175 Measurement: Electric Field QTN Spectroscopy EFI shall be capable of measuring QTN Spectroscopy (TNR/HFR Survey Mode) from SPP, as follows: -- frequency range: 10 kHz - 2500 kHz; -- dynamic range: 100 dB; -- maximum field intensity: ±200mV/m at 100kHz -- cadence: up to 1 spectrum / 4 seconds; -- sensitivity (excluding power converter frequencies): 1 x 10^(-7) V/m/sqrt(Hz) at 100 kHz; 2 x 10^(-8) V/m/sqrt(Hz) at 2 MHz; -- in one direction. T RFS-03 Measure Radio Emissions RFS electronics shall be capable of handling signals from V1-V4 with -- frequency range: 1 MHz - 16 MHz; -- dynamic range: 80 dB; -- maximum field intensity: ±100mV/m at 2 MHz -- sensitivity (excluding power converter frequences): 2 x 10^(-8) V/m/sqrt(Hz) at 2 MHz and above; -- in two orthogonal components. PAY-176 Measurement: Electric Field Radio Emissions EFI shall be capable of measuring Radio Emissions from SPP, as follows: -- frequency range: 1 MHz - 16 MHz; -- dynamic range: 80 dB; -- maximum field intensity: ±100mV/m at 2 MHz -- cadence: up to 1 spectrum/16 sec; -- sensitivity (excluding power converter frequences): 2 x 10^(-8) V/m/sqrt(Hz) at 2 MHz and above; -- in two orthogonal components. RFS-04 Instrument Calibration RFS shall provide calibration parameters and algorithms so as to allow conversion from telemetry units to physical units (gain and offset per channel) prior to S/C Integration. PAY-102 Payload: Launch Readiness Calibration All instruments shall be calibrated prior to launch. I

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

SPP Spacecraft

FIELDS MAG Boom

FIELDS Block Diagram

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

Software DCB TDS SOC More later 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

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

Environmental Test Matrix

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

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

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

EMC/ESC EMC ESC 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

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

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

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

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

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

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 Antenna brackets 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

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

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

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

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

Picket Fences

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 filtering with 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)

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

FIELDS Synchronized 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

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 vs 10.30W 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

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