1. FGM peer PDR Magnetsrode - 1 Braunschweig, October 8-9, 2003 MAGNETOMETER CALIBRATION Ingo Richter Institut für Geophysik und Meteorologie TU Braunschweig

2. FGM peer PDR Magnetsrode - 2 Braunschweig, October 8-9, 2003 Magnetsrode - MCF

3. FGM peer PDR Magnetsrode - 3 Braunschweig, October 8-9, 2003 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. FGM peer PDR Magnetsrode - 4 Braunschweig, October 8-9, 2003 Sensitivity S= {S ii },S ii = S ii (T ) MisalignmentM= {M ij },M ij = M ij (T ) Offset B O = { B ox (T ), B oy (T ), B oz (T ) } Frequency Response Parameters _ _ _ _ A magnetometer can be characterized by the following entities:

5. FGM peer PDR Magnetsrode - 5 Braunschweig, October 8-9, 2003 B c = F -1 B m Sensor Model B c = {R -1 M -1 S -1 } ( B r - B off - B res ) _ _ _ _ _ _ _ _

6. FGM peer PDR Magnetsrode - 6 Braunschweig, October 8-9, 2003 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. FGM peer PDR Magnetsrode - 7 Braunschweig, October 8-9, 2003 Parameters - Offset

8. FGM peer PDR Magnetsrode - 8 Braunschweig, October 8-9, 2003 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. FGM peer PDR Magnetsrode - 9 Braunschweig, October 8-9, 2003 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. FGM peer PDR Magnetsrode - 10 Braunschweig, October 8-9, 2003 Sensitivity (Results) Geometrical correction factor

11. FGM peer PDR Magnetsrode - 11 Braunschweig, October 8-9, 2003 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. FGM peer PDR Magnetsrode - 12 Braunschweig, October 8-9, 2003 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 1

13. FGM peer PDR Magnetsrode - 13 Braunschweig, October 8-9, 2003 Misalignment (Results) The correction matrix is given by: Finally we get the desired Misalignment Matrix : and

14. FGM peer PDR Magnetsrode - 14 Braunschweig, October 8-9, 2003 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. FGM peer PDR Magnetsrode - 15 Braunschweig, October 8-9, 2003 Frequency Response

16. FGM peer PDR Magnetsrode - 16 Braunschweig, October 8-9, 2003 Documentation Report: RO-IGM-TR-0002 DC-Analysis: RO-IGM-TR-0003 AC-Analysis: RO-IWF-TR-0001