scm teamfields ipdr – scm design 1 solar probe plus fields instrument pdr search coil magnetometer...

SCM team FIELDS iPDR – SCM design 1

Solar Probe Plus FIELDSInstrument PDR

Search Coil Magnetometer SCM

T. Dudok de Wit & G. Jannetand SCM team: C. Agrapart, P. Fergeau V. Krasnosselskikh,

P. Martin, M. Timofeeva-Bouaroua

LPC2E, CNRS and University of Orléans

Contact : [email protected]


Outline

• SCM instrument general description, specifications & performances

• SCM instrument design– Antenna design– Preamplifier design– Electrical interfaces– Mechanical design and interfaces– Thermal design and interfaces– Calibration– Heritage

• Conclusion and main issues


Instrument general description

SCM is a search coil magnetometer (inductive type), consisting of:•2 single-band antennas (10 Hz-50 kHz range)•1 double-band antenna (10 Hz-50 kHz & 1 kHz-1 MHz)•4-channel miniaturized preamplifier inside sensor foot•sensor foot

Analogue outputs are processed by 3 modules from FIELDS-MEP•DFB will routinely compute spectral matrices and on demand capture waveforms from the 3 LF channels•RFS will compute spectra from the MF channel•TDS will capture waveforms from the MF channel

3 search coil antennas

3D preamplifier


Level 3 Requirements

• Measure AC magnetic fields from 9.5 RS to +0.25 AU• 3D magnetic field (LF coil, 10 Hz - 50 kHz)

– Min. sensitivity 10-4nT/Hz-1/2 at 3.5kHz ; Max. field intensity 1000nT at 3.5kHz

• 1D magnetic field (MF coil, 1 kHz - 1 MHz)– Min. sensitivity 3.10-5nT/Hz-1/2 at 100kHz ; Max. field intensity 6nT at 100kHz

LF

MF


Performance expectations

3.16mV/nT

2.51mV/nT

1.78mV/nT

0.09mV/nT

0.35V/nT

1.3V/nT

0.28V/nT

LF frequency bandwidth specification

MF frequency bandwidth specification

SCM frequency response measured with preamplifier and antennas prototype (3000nT @ 3kHz, 6nT @ 100 kHz)

Instrument design


SCM design : Antennas

• Magnetic core consists of 3C95 ferrite: selected for its stable magnetic permeability (µr) at low temperatures

• Coils are performed with the following characteristics :

• Each antenna is inserted inside a carbon fiber tube filled under vacuum with STYCAST resin

• Finished antenna dimensions: ∅20mm length 104mm

100mm

Metallized epoxy flanges for the link

between coiling wire and harness

SCM antennas (TARANIS EM)

MF coil

LF coil

Ferrite mutual reducer

FunctionLF antennas

B1, B2, B3

MF antenna B4 in addition to B3

antennaPrimary coil 13 500 turns 360 turns

Secondary coil 32 turns 3 turnsWire ∅Cu 80µm ∅Cu 90µm

Ferrite coreLength: 100mm

∅coil: 5mm∅max (tips): 14mm

Length: 60mm∅inner: 12mm∅outer: 14mm


SCM design : Preamplifier

• FM preamplifier– Built in 3D technology and manufactured by 3Dplus (compliant with space-

qualified PID reference 3300-0546 rev 7)– 5 stages of electronic circuits + Pin grid array on top (connection to

antennas) and bottom (power supply, signals)– Protection against radiation with 0.5mm of tantalum layers at each tip of

the module and a cylinder around the module– DDD protection implemented inside the preamplifier module (RC structure)

Preamplifier FM example (heritage

TARANIS)SCM preamplifier prototype

Dimensions•Height 32.3mm + 2x5mm for in/out pins•Inside a ∅18.7mm cylinder (PCB with octagonal section, width 16mm)

MF

channel

Power supply regulation

3LF

channels


Electrical interfaces

SCM is connected to

– DFB, TDS and RFS for signal digitization and processing

– LNPS for ±12V power supply & heating


SCM design : Electrical interfaces

• SCM harness definition– 1 shielded and twisted triple (for ±12V) & 9

shielded and twisted pairs – Cables from ESA/SCC 3901 019 series.

Temperature range -200°C to +200°C – AWG28 wires for power supply and heaters,

AWG30 for the others (flexible & reduced thermally conductive section)

• SCM connector – HD-sub 26pins, shell size A

• SCM harness accommodation: 30 cm pigtail – 20 cm = 1 turn around the foot inside the

MLI cavity – outside MLI cavity for connection to boom

harnessSCM HD-sub 26 pin connector

10 cm pigtail

Cables•4 for LF (X, Y, Z) and MF (X) signals•1 for calibration•1 for heating power •2 for temperature probe dedicated to heating control •1 for HK temperature probe (sent to telemetry)


SCM design : Mechanical structure

• Mechanical structure inherited from Solar Orbiter design

• SCM mechanical assembly– Orthogonal assembly of 3 antennas (±0.1°)– Preamplifier inside the foot cavity, filled under vacuum with

STYCAST resin– Total mass with MLI 680g

Element individual mass

Double band antenna 72g

Mono band antenna (each)

59g

Closing plates (each) 3g

Centering ring 3g

Anti-rotation pin <1g

Radiation shield 18g

Sensor foot122

g

Insulating bedplate 39g

Preamplifier 25g


• SCM mechanical interface with the boom– The insulating bedplate must be fixed to the boom before the rest of the instrument

N°

Function Element MaterialQty

LocationDimension

(mm) and tolerance

1 Fixing bedplate boom CHC Screw Titanium TA6V4 6 On 38 at 60° M4

2 Centering, Anti-shearing Bedplate pins PEEK 2 Centered on ZURF 10 g6

3 Foolproofing, Anti-rotation Pin Titanium TA6V4 1 On 38 pointing towards YURF 4mm g6

1

2

3

Bottom view Top view

SCM design: mechanical structure


Mechanical design verification

• Current design analysis with Solar Orbiter specifications (simulated with FEM):– First vibration mode: 288Hz– Sinus vibrations: current design can bear

25g sinus with good margins– Random vibrations: Instrument

capabilities already validated up to 1.5g²/Hz

– Shocks: validated up to 2000g

• SCM FEM is ready – analysis shall be performed with

specifications for I-boom units

Mode 1 foot bending (along X axis)


Thermal interfaces

• SCM environment– I-boom: -175°C as a worst case (TBD with EDTRD update)– No solar flux during Sun-pointing phases– Suitable thermal interface is required including insulation and heating

• SCM temperature ranges

element Operating switch-onnon-

operatingsurvival mode

Antennas-100 to +100

°C-100 to +100

°C-100 to +100

°C-100 to +100

°C

Electronics -50 to +80 °C -50 to +80 °C-60 to +100

°C-60 to +100

°C

Harness-200 to +200

°C-200 to +200

°C-200 to +200

°C-200 to +200

°C


SCM design : Thermal interfaces

• Passive thermal control– direct heritage from Solar Orbiter design– protection against radiative losses:

double 15-layer MLI envelope– protection against conductive losses:

insulating bedplate reducing contact surface & decoupling instrument from fixing screws

– conduction through harness reduced by a full turn around the bedplate and increased pigtail length

Contact areafoot / insulating plate: 504mm²

MLI and harness accommodation


SCM design : Thermal interfaces

• Active thermal control– Critical element is preamplifier– Heaters are wrapped around the

preamplifier (Flexible polyimide thermofoil by MINCO, space qualified ESCC 4009 003), powered by LNPS

– Temperature probe for heating control (Lakeshore PT-103)

– 1 HK temperature probe for transmission to telemetry (Lakeshore PT-103 likely)

• Required heating power– Thermal analysis in progress (software

compatibility problems)

heater

T probecontrol T probe

monitoring


SCM design : Accommodation

• Location on I-boom is dictated by EMC requirements– Minimum distance from spacecraft : 3m is acceptable for science if RE-01

requirements are applied on spacecraft bus– Minimum distance from MAG unit : 1m is acceptable (interference tests,

June 2012)

Envelope of MAG drive frequency & harmonics

SCM-MF noise floor with MAG at 1m


Summary of resources

• Power budget – Instrument power supply: 270 mW ±12V– Heating power: TBC (600mW allocated)

• Mass budget – total mass of SCM unit 680g– Instrument: 525g– Harness pigtail: 30g– MLI blanket: 125g– Harness: 55.2 g/m + 15 g/connector

• Overall volume with MLI blanket– diameter ∅110mm – height 165mm

Overall volume with MLI blanket110

16

5

85

∅77


Calibration

• Pre-flight calibration– Frequency response measurement to

have SCM gain in V/nT– Sensitivity measurement to

demonstrate capacity of measuring small fields.

• SCM test bench is composed of :– Network/spectrum analyzer – Mumetal shielding to get a

magneticallly clean environment– Helmholtz coil system for magnetic

field generation

• In-flight performance testing– Onboard verification system– Sensor response to a calibration signal

(sine waves) sent by DFB– Exact CAL signal still TBD

SCM frequency response test bench (mu-metal box)

Flux feedback

Main coil

preamplifier

Measmt. signal

CAL signal from DFB

4 layers of µmetal20cm

Helmholtz coils


SCM maturity: heritage

• Strong heritage from TARANIS & Solar Orbiter SCM

• TARANIS heritage – Antenna design: double band concept– 3D Preamplifier design and qualification

philosophy– Full instrument concept with preamplifier inside

the foot has been validated on a fully operational EM

– Assembly process

• Solar Orbiter heritage– Antenna ferrite core and coiling process– Mechanical interface– Thermal interface: conductive and radiative

insulations, heating system implementation

TARANIS EM search coil


Conclusions and open issues

• SCM meets Level 3 requirements

• SCM has good level of maturity thanks to strong heritage from SCM on TARANIS and Solar Orbiter

• Open issues (peer review)

– EMC requirements impose minimum distance from S/C (RE-01 specification) and from MAG magnetometer. Final orientation of the antennas will be set accordingly.

– Thermal model definition and simulation to be done with Solar Probe temperature conditions. Heating power to be set accordingly.

– Mechanical and structural analysis to be updated with I-boom specifications to confirm the design

Backup slides


• SCM sensitivity curves measured with preamplifier and antennas prototype

Performances expectations

10-3nT/Hz-1/2

10-4nT/Hz-1/2

10-5nT/Hz-1/2

L3 specifications


SCM design: antennas

• Antenna internal structure– Dimensions: cylinder ∅20mm, length 104mm– Inner volume is filled under vacuum with STYCAST resin (epoxy)

Ferrite core

Finished antenna with wires and electrostatic shield

MF coilCopper foil separation screen

Internal potting with STYCAST resin

Carbon fiber tube

Harness: 2 twisted and shielded triple

LF coil

Ferrite mutual reducer


SCM design : Preamplifier

• Radiation protection– Ta layers (0.5mm) at each tip inside the module– Ta cylinder (thickness 0.5mm) around the module

• EEE components status – All passive parts are space qualified (MIL-PRF or ESCC)– Active parts

• 2 space qualified: 1 OpAmp, 1 current diode• 5 Commercial parts: heritage from TARANIS and/or Solar Orbiter

– Commercial parts selected for performance and dimensions

• 3D preamplifier qualification– Manufactured by 3Dplus (compliant with space-qualified PID

reference 3300-0546 rev 7)– FM manufacturing lot to be submitted to Lot Acceptance Tests

(LAT), by heritage it will be based on:• burn-in (168h) and life test (1000h at 125°C) on 2 modules and DPA on

1 module• Fast temperature variations (500 cycles -55°C/+125°C) on 2 modules

and DPA on 1 module

– LAT will be adapted to Solar Probe mission


DDD protection

• Injection of DDD at preamplifier output: waveform generated by the model proposed by APL• Implemented design: RC filter, a 4.7nF capacitance is added to the current electrical scheme• Working with 150Ω resistor already present

SCM preamplifier output stage

~5.5V at preamplifier output with 150Ω, 4.7nF config.

in

out

3 pF1500 ohms900 V


DDD protection

• Component selection– 4.7nV capacitor in 1812 package, ESCC 3009 034

admissible DC voltage 1000V, dielectric strength 200% ⇒ 2000V pulse acceptable– Resistor: 2 components in 1206 package added to take margin

• Routing with SCM preamplifier PCB dimensions• Implementation is feasible on a single additional preamplifier stage

Protection structure x7

routing:

3 ½ structures on top and 3 ½ at bottom

Top view of protection routing

16mm


• SCM mechanical interface with the boom: 2nd step– The instrument is fixed to the bed plate

N° Function Element Material Qty LocationDimension (mm) and

tolerance

4 Fixing foot to bedplate CHC Screw Titatium TA6V4 6 On ∅40 at 60° M4

5 Centering, Anti-shearing Ring PEEK 1 Centered on ZURF ∅10 H7

6 Foolprofing, Anti-rotation key Titatium TA6V4 1 On ∅50 pointing towards XURF Width 4mm g6

4

5

6

Top view

SCM design: mechanical structure


• Additional shielding braid option– SCM harness is composed of 10 cables, if an overshield is implemented, required internal

diameter braid is ∅8mm. – AXON reference gives a mass of 52g/m

• Electronic protection option – Using resistor + capacitors to ground to protect the 4 measurement channels and power

supply regulation circuit– Can be implemented on an additional stage inside the 3D preamplifier– This circuit does not protect temperature probes

• 2 possibilities still in balance – Easiest solution is the additional shielding on harness with the drawback of extra mass and

stiffness– Electronic protection is the best possibility in terms of mass. A way of protecting temperature

probes shall be found

Harness DDD protection


SCM design : EMC test results

• MAG-SCM interference test result– Decrease of MAG drive frequency spike with the separation

Measurements of June 2012


• Frequency response measurement– Measurement for each channel (3LF and 1 MF) with a Helmholtz coil system and a

test bench– Inside a mumetal shield to avoid EMC disturbances– Outside in “free field” to verify “wall effects”– Gives SCM calibration curve (gain in V/nT and phase) used for production of data

in physical unit

Network analyzer

CH1

CH2

source Input signal to Helmholtz coil

µmetal shielding boxes

Gain control nT/V

Power supply

SCM harness

Gain control

4 layers of µmetal20cm Helmholtz

coils

SCM verification: calibration


• Sensitivity measurement– Measurement for each channel (3LF and 1 MF) with the sensor alone in a mumetal

shielding box– Verifies the lowest signals SCM can measure

Spectrum analyzer

CH1

µmetal shielding boxes

Power supply

SCM harness

SCM verification: calibration


SCM verification : in flight test

• In flight performance verification– Onboard verification system– Sensor response to a signal composed of sinus waves – Signal send by DFB during 4s (TBC)– Verify the correct behavior of the instrument (gain and phase) by comparison with ground

measurements

• This system can be used as a functional test on ground• Science measurements can be performed at the same time• Duration of CAL sequences and CAL frequencies

Flux feedback

Main coil

preamplifierMeasurement signal

Calibration signal from DFB


SCM design maturity

• Antennas – Design is fully defined – Coils for ETU model have been received (coiling operation done by

Microspire)– MF coils for the double band antenna will be added at LPC2E

• Preamplifier– Electrical scheme is ready – Issue on DDD protection (additional circuit in the module for

protection) shall be fixed before starting activities with the manufacturer 3Dplus

Ferrite core and coils for SCM ETU antennas


SCM Design maturity

• Mechanical design and assembly– Mechanical structure & machining process (tools and accessories)

are defined– Design shall be confirmed by analysis with I-boom mechanical

specifications– Assembly process is mastered (TARANIS

heritage), necessary tools (vacuum potting, glueing, alignment... ) already exist

• Thermal design– Thermal analysis is ongoing to deliver SCM thermal model and

defined required heating power (SCM urgent issue)– Heaters definition and implementation process are currently being

done (iteration with the manufacturer Minco). Heating power value is needed to finalize the design

SCM mechanical elements kit


SCM PA/QA

C. Agrapart

E. Cocheteau

NASA APL FIELDS


SCM PA/QA

• Package of Product Assurance documents available for PDR:

Document Reference

Product tree, issue 1.0, 03/20/2011 SPP‐SCM‐MNG‐GEN‐PT‐0002‐LPC2E

Product assurance plan, issue 1.0, 11/14/2011

SPP‐SCM‐AQP‐PAP‐PL‐0038‐LPC2E

PAP compliance matrix, issue 1.0, 04/13/2012 SPP‐SCM‐AQP‐PAP‐MT‐0082‐LPC2E

Declared components list, issue 1.0, 06/25/2013

SPP‐SCM‐AQP‐EEE‐LI‐0115‐LPC2E

Declared materials list, issue 1.0, 03/26/2013 SPP‐SCM‐AQP‐MPR‐LI‐0121‐LPC2E

Declared process list, issue 1.0, 03/26/2013 SPP‐SCM‐AQP‐MPR‐LI‐0122‐LPC2E

Failure mode effect analysis, issue 1.0, 04/26/2013

SPP‐SCM‐AQP‐RIS‐TN‐0120‐LPC2E

Documentation management plan, issue 1.0, 04/08/2011

SPP‐SCM‐MNG‐GEN‐PL‐0001‐LPC2E


SCM PA/QA

Product assurance plan update

PAP compliance matrix update

Risks list update

• Work in progress:

• Future work:

scm teamfields ipdr – scm design 1 solar probe plus fields instrument pdr search coil magnetometer...

Documents

scm harness accommodation

scm sensitivity curves

heating power

mli cavity

foot cavity

b3mf antenna b4

mf x signals1

harnessscm hdsub