1. Ingo Richter Institut für Geophysik und Meteorologie TU Braunschweig MAGNETOMETER CALIBRATION

2. Magnetsrode - MCF

3. Magnetsrode – Characteristics • Compensation: Dynamic v fixed (user defined) • Fields - Range: -100000 nT ... +100000 nT • Direction: any, 3 components • Type : DC, AC, Arbitrary • Field-Sequence: arbitrary, user defined • Accuracy: < 0.8 nT • I/F to DUT: Analog (16 Bit) v Digital (EGSE) • DUT TC: yes, via RS232 (user defined) • Successful calibrations have been performed for: • CLUSTER, DS 1, MARS 96, ØRSTED,ROSETTA, • CASSINI, CHAMP, ROMAP, DOUBLE STAR,....

4. Parameters A magnetometer can be characterized by the following entities: _ _ • Sensitivity S = {Sii } ,Sii= Sii (T ) • MisalignmentM = {Mij } ,Mij = Mij (T ) • Offset BO = { Box(T ), Boy(T ), Boz(T ) } • Frequency Response _ _

5. Sensor Model B c = F-1 Bm _ _ B c ={R-1M-1 S-1}( B r -Boff - Bres) _ _ _ _ _ _

6. Calibration Method • Offset: • Perform 2 measurements. One at 0° orientation and one at 180° • orientation. Boff = (B1 +B2) /2 . Bres = (B1-B2) /2 • Sensitivity & Misalignment: • Two methods: • a) Pure linear steps in subsequently x,yz direction • b) Spike spheres: apply randomly distributed B-Field on sphere • Generate least-square fit model to calculate S,M. • Possible models : up to 5th order polynome in x,y,z (mixed) • Frequency response: • Apply sine-signals at different discrete frequencies at constant amplitude. Calculate response function

7. Parameters - Offset

8. Parameters – Offset(T): Plot These parameters have been measured using thermocycles. OB & IB were placed at off-center positions in the thermal test box.

9. Sensitivity (overview) (FS / FM-IB) Reference Measurements: T1 = 17.39°C, CoC : (Spike sphere) Sensitivities obtained from the temperature calibration at the off-center position: (linearity measurements at varying Temperature) Wanted: Temperature dependent Sensitivity at CoC: with The temperature dependent sensitivity at CoC can be derived from the off-center measurements using a geometry coefficient k

10. Sensitivity (Results) Geometrical correction factor

11. Parameters – S(T): Plot These parameters have been measured using thermocycles. OB & IB were placed at off-center positions in the thermal test box.

12. 1 Misalignment (overview) Reference Measurements: T1 = 17.39°C, CoC : (Spike sphere) Misalignment angles obtained from the temperature calibration at the off-center position: (linearity measurements at varying Temperature) The off-center Misalignment Matrix is given by: Wanted: Temperature dependent Misalignment Matrix at CoC. It can be derived from the off-center measurements using a geometry correction Matrix K

13. Misalignment (Results) The correction matrix is given by: Finally we get the desired Misalignment Matrix : and

14. Alignment Angles (T) : Plot These angels have been measured using thermocycles. OB & IB were placed at off-center positions in the thermal test box. The plots show the deviation from The nominal value of 90° 00´.

15. Frequency Response

16. Documentation • Report: RO-IGM-TR-0002 • DC-Analysis: RO-IGM-TR-0003 • AC-Analysis: RO-IWF-TR-0001