FGS Mechanical Design HansUlrich Auster Institut fr Geophysik

FGS Mechanical Design Hans-Ulrich Auster Institut für Geophysik und Meteorologie TU Braunschweig FGM peer CDR FGS - 1 Berlin, April 6, 2004

Fluxgate Sensor (FGS) § Sensor design § Summary of PDR presentation § Response to findings § (F 13) Degrading of coating § (F 14) Glue properties § (F 15) CTE of FGS coil system, see presentation of test facilities § (F 16) quasi static vibration levels § FGS test matrix § FGS Harness / Grounding § FGS status FGM peer CDR FGS - 2 Berlin, April 6, 2004

Sensor Design (1) § Vector-compensated Ringcore sensor Two crossed ringcores Material: 6 -81 -Mo Permalloy band non-ferromagn. Ni. Mo 30 alloy Pickup Coil systems Material: Sensitivity: Cu wire isolated by polyesterimid and covered by bond coat (polyamid) about 1, 5 … 3µV/n. T Feedback Coil System Material: Coil const. : CTE: Fixation: FGM peer CDR Cu - wire, see pickup 13 -17000 n. T/m. A about 24 ppm (Cu and Al) by glue (Endfest 300) FGS - 3 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: 78 g Mechanical Interface mounting: orientation: four M 4 screws defined by ground plane and two feed side planes (V) Electrical Interface 10 cm pigtail with HD-26 P connector FGM peer CDR FGS - 4 Berlin, April 6, 2004

(F 13) Degrading of coating (F 13): 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 90 min 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 - 5 Berlin, April 6, 2004

(F 14) Glue properties (F 14): Glue is qualified by similarity with another unit which was qualified to 2000 gs. 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. § 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 FGM peer CDR FGS - 6 Berlin, April 6, 2004

(F 16) quasi static vib. levels Vibration Specs (Qualification): Rosetta - Ariane 5 Venus Express - Sojus/Fregat Sinusoidal Vibration: 5 - 20 Hz: 12 mm 20 26 - 26 Hz: 100 Hz: 1. 5 m/s 25 g Random Vibration, Grms = 18. 07: 20 - 100 Hz: 100 - 400 Hz: 400 - 2000 Hz: +6 d. B/Oct 0. 5 g 2/Hz - 6 d. B/Oct Quasi static acceleration: 25 g (F 16): Stated vibration levels seem very high, but the quasi-static level looks low (25 g). Recommend you set limit loads for the design: if the instruments “are designed to” 100 g, then you are in good shape for levels which fall out of the coupled loads analysis late in project. FGM peer CDR FGS - 7 Berlin, April 6, 2004

(F 16) quasi static vib. levels Results of the sensor modelling (made by IB - Markus Thiel) FGM peer CDR FGS - 8 Berlin, April 6, 2004

Test Matrix FGS Assembly Test name Test description Ringcore selection Ringcores Coils only STM FM 1 -6 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 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 FGM peer CDR FGS - 9 X X Berlin, April 6, 2004

Test Matrix FGS Test name Test description Vibration TV Calibration STM FM 6 According to qualification levels (UA) According to acceptance levels With Boom X According to qualification levels (WM) According to acceptance levels With Boom FM 1 -5 X X X 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 Required temperature range Operation: Survival: Estimation by thermal analysis: FGM peer CDR -100°C … +65°C -79°C … +35°C FGS - 10 Berlin, April 6, 2004

Harness / Grounding § Harness § A/B connector bracket on the boom § C/D connector bracket on the spacecraft FGS sensor pigtail (10 cm) FGS boom harness (2. 49 m) AB FGS electr: harness (1. 2 m) C D connector close to sensor E F FGE connector close to boom hinge § 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 - 11 Berlin, April 6, 2004

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