1. SPP/FIELDS System Engineering Preliminary Design Review
Keith Goetz
University of Minnesota

2. 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?

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

4. 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

5. FIELDS Level-4 Flowdown – IRD
Requirements are flowed from SPP L3 document to FIELDS subsystems with IRD
APL: _Rev_Dash
SPF_SYS_010_Instrument_Requirements - IRD - SE B
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. 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 kHz; -- dynamic range: 100 dB; -- maximum field intensity: ±200mV/m at 100kHz -- sensitivity (excluding power converter frequencies): x 10^(-7) V/m/sqrt(Hz) at 100 kHz; 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 kHz; -- dynamic range: 100 dB; -- maximum field intensity: ±200mV/m at 100kHz -- cadence: up to 1 spectrum / 4 seconds; -- sensitivity (excluding power converter frequencies): x 10^(-7) V/m/sqrt(Hz) at 100 kHz; 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): 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): 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

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 - ( )
FIELDS Specific ICD ( )
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 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

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 (dash)
SPP EMC Requirements called out in
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 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

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 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

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 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)

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 ( 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. 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

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 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

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