FGM peer CDR FGS - 1 Berlin, April 6, 2004

FGS Mechanical Design

Hans-Ulrich Auster

Institut für Geophysik und Meteorologie

TU Braunschweig

FGM peer CDR FGS - 2 Berlin, April 6, 2004

Sensor design Summary of PDR presentation

Response to findings (F13) Degrading of coating (F14) Glue properties (F15) CTE of FGS coil system, see presentation

of test facilities (F16) quasi static vibration levels

FGS test matrix FGS Harness / Grounding FGS status

Fluxgate Sensor (FGS)

FGM peer CDR FGS - 3 Berlin, April 6, 2004

Sensor Design (1)

Two crossed ringcoresMaterial: 6-81-Mo Permalloy band

non-ferromagn. NiMo30 alloy

Vector-compensated Ringcore sensor

Feedback Coil SystemMaterial: Cu - wire, see pickupCoil const.: 13-17000nT/mACTE: about 24ppm (Cu and Al)Fixation: by glue (Endfest 300)

Pickup Coil systemsMaterial: Cu wire isolated by polyesterimid and covered by bond coat (polyamid)Sensitivity: about 1,5 … 3µV/nT

FGM peer CDR FGS - 4 Berlin, April 6, 2004

Sensor Design (2)

Sensor Hut Interface Material Hut & base plate: Aluminium Isolation: glassfibre reinforced plastics Screws: titanium

Washers: glassfibre reinforced plasticsSurface (Al): Alodine 1200Mass: 78g

Mechanical Interfacemounting: four M4 screwsorientation: defined by ground plane and two feed side planes (V)

Electrical Interface10cm pigtail with HD-26P connector

FGM peer CDR FGS - 5 Berlin, April 6, 2004

(F13) Degrading of coating

(F13): Question coating on wire: polyesterimid, covered by bond coat (polyamid). Is anyone concerned about thermal cycles Themis will experience degrading this coating (especially the innermost probes)? Recommend you compare thermal predictions of # of cycles to environments to which similar coils have been tested/flown.

Experiences onboard MIR station. One year operation in 90min orbit without thermal isolation. All sensor parameter in nominal range.

Extended test program for spare coils added into test matrix. (5 times between -190°C and +120°C)

FGM peer CDR FGS - 6 Berlin, April 6, 2004

All similar space qualified sensors (Rosetta, Venus Express) are fabricated with the same glue

Surface finishes/treatment has changed between Rosetta (aluminium pure) and Venus Express (aluminium irridite) sensors

liquid nitrogen immersion test will be done with GRM sensor (see test matrix)

Tension tests with glued parts at Bundesanstalt für Materialprüfung

(F14) Glue properties

(F14): Glue is qualified by similarity with another unit which was qualified to 2000gs. Compare glue patch extents with those of qualified unit. Also, are surface finishes/treatments similar between this unit and the qualified unit? Recommend that the FGM team perform a “liquid nitrogen immersion” test on the flight configuration, with flight-like surface finishes/coatings.

FGM peer CDR FGS - 7 Berlin, April 6, 2004

Vibration Specs (Qualification):Rosetta - Ariane 5 Venus Express - Sojus/Fregat

Sinusoidal Vibration:  5 - 20 Hz: 12mm

20 - 26 Hz: 1.5m/s  26 - 100 Hz: 25g

Random Vibration, Grms = 18.07:20 - 100 Hz: +6dB/Oct100 - 400 Hz: 0.5 g2/Hz400 - 2000 Hz: - 6 dB/Oct

Quasi static acceleration: 25g

(F16) quasi static vib. levels

(F16): Stated vibration levels seem very high, but the quasi-static level looks low (25g). Recommend you set limit loads for the design: if the instruments “are designed to” 100g, then you are in good shape for levels which fall out of the coupled loads analysis late in project.

FGM peer CDR FGS - 8 Berlin, April 6, 2004

(F16) quasi static vib. levels

min. safety margin

5.4416.3123.4927.04

109.02Support structure to base plate 3.24Table 3.1: Safety margins for relevant parts / connections

The calculated safety margin is sufficient for all parts and connections within the Flux Gate Sensor. The smallest margin (S=3,24), calculated for the screwed joint of the support structure to the base plate is still significantly higher than required (S=

From the results of this strength analysis it can be conluded that the FGS can withstand a static acceleration of 100g.

A summary of the calculated safety margins at an acceleration of 100g is given in table 3.1 for all relevant internal parts and connections:

Part / connection

Internal coils to Al-adapterInternal coil system to support

Outer coil system to supportSupport structure

Secondary z-coil

Results of the sensor modelling (made by IB - Markus Thiel)

FGM peer CDR FGS - 9 Berlin, April 6, 2004

Test Matrix FGS Assembly

Test name Test description Ringcores Coils only

STM FM 1-6

Ringcore selection

Long-term test of ringcores (KHF) Criteria: output voltage, offset, noise

X X

Parts electr. checkout

Resistance of all coils before integration (KHF)

X X

Coil qualification

-190°C / +120°C five times each (BS)Criteria: visual inspection, resistance

X

Coil aging acceptance

-40°C / +80°C three times each (BS)Criteria: visual inspection, resistance

X X

Ringcore checkout

Test after integration in pickup coils (KHF). Criteria: output voltage, offset, noise

X X

FGS electr. checkout

Test after sensor integration (KHF)Criteria: Resistance + polarity of all coils

X X

FGS aging qualification

-190°C / +120°C five times each (KHF) Criteria: visual inspection, resistance, output voltage, offset, noise

X

FGS aging acceptance

-40°C / +80°C three times each (KHF) Criteria: visual inspection, resistance, output voltage, offset, noise

X

FGM peer CDR FGS - 10 Berlin, April 6, 2004

Test name Test description STM FM 6 FM 1-5

Vibration According to qualification levels (UA)According to acceptance levels

With Boom XX

TV According to qualification levels (WM)According to acceptance levels

With Boom XX

Calibration Berlin / Braunschweig:Offset, noise at room temperature, versus electronics temperature, versus time

Graz:Offset, noise, transfer function versus temp

Magnetsrode:Scale value, orthogonality versus temp

Test Matrix FGS

Required temperature rangeOperation: -100°C … +65°CSurvival: -100°C … +65°CEstimation by thermal analysis: -79°C … +35°C

FGM peer CDR FGS - 11 Berlin, April 6, 2004

Harness / Grounding

FGS FGE

connector close to boom hinge

FGS boom harness (2.49 m)

C D E FA B

connector close to sensor

FGS electr: harness (1.2 m)

FGS sensor pigtail (10 cm)

Harness A/B connector bracket

on the boom C/D connector bracket

on the spacecraft

Grounding Overall shielding connected to S/C ground (chassis) via connector back shells Sensor aluminum housing, connected to pin 11 of the sensor connector MLI:

inner layer insulatingouter layer conductiveto boom

FGM peer CDR FGS - 12 Berlin, April 6, 2004

FGS Status

Nr. Task Name Start End36 FGM Sensor incl. Harness (FGS) ETU & FM 01.09.03 14.05.0437 FGS coils Fab. 01.09.03 21.11.03

38 FGS STM Fab 01.12.03 23.01.04

39 FGS F6 Ringcore Integration 02.02.04 06.02.04

40 FGS F1 Ringcore Integration 23.02.04 27.02.04

41 FGS F2&F3 Ringcore Integration 08.03.04 19.03.04

42 FGS F4&F5 Ringcore Integration 05.04.04 16.04.04

43 FGS F6 Fab 16.02.04 20.02.04

44 FGS F1 Fab 15.03.04 19.03.04

45 FGS F2 Fab 29.03.04 02.04.04

46 FGS F3 Fab 12.04.04 16.04.04

47 FGS F4 Fab 26.04.04 30.04.04

48 FGS F5 Fab 10.05.04 14.05.04

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In time !