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 ringcores Material:6-81-Mo Permalloy band non-ferromagn. NiMo30 alloy  Vector-compensated Ringcore sensor Feedback Coil System Material:Cu - wire, see pickup Coil const.: nT/mA CTE: about 24ppm (Cu and Al) Fixation:by glue (Endfest 300) Pickup Coil systems Material: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 plastics Surface (Al):Alodine 1200 Mass:78g Mechanical Interface mounting:four M4 screws orientation:defined by ground plane and two feed side planes (V) Electrical Interface 10cm 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 Hz:1.5m/s Hz:25g Random Vibration, Grms = 18.07: Hz:+6dB/Oct Hz:0.5 g 2 /Hz 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 Results of the sensor modelling (made by IB - Markus Thiel)

FGM peer CDR FGS - 9 Berlin, April 6, 2004 Test Matrix FGS Assembly Test nameTest description Ringcores Coils only STMFM 1-6 Ringcore selection Long-term test of ringcores (KHF) Criteria: output voltage, offset, noise XX Parts electr. checkout Resistance of all coils before integration (KHF) XX 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 XX Ringcore checkout Test after integration in pickup coils (KHF). Criteria: output voltage, offset, noise XX FGS electr. checkout Test after sensor integration (KHF) Criteria: Resistance + polarity of all coils XX 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 nameTest descriptionSTMFM 6FM 1-5 VibrationAccording to qualification levels (UA) According to acceptance levels With BoomX X TVAccording to qualification levels (WM) According to acceptance levels With BoomX X CalibrationBerlin / 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 range Operation:-100°C … +65°C Survival:-100°C … +65°C Estimation by thermal analysis: -79°C … +35°C

FGM peer CDR FGS - 11 Berlin, April 6, 2004 Harness / Grounding FGSFGE connector close to boom hinge FGS boom harness (2.49 m) CD E F AB 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 insulating outer layer conductive to boom

FGM peer CDR FGS - 12 Berlin, April 6, 2004 FGS Status In time !