Platzhalter für Bild, Bild auf Titelfolie hinter das Logo einsetzen Electrical Sounding on Ganymede A. Przyklenk, A. Hördt IGEP TU Braunschweig Ganymede Lander Colloquium and Workshop 06. March 2013 | Electrical Sounding on Ganymede [nasa.gov]

Motivation Open questions:  Composition of Ganymede‘s subsurface?  Which non-ice materials occur?  Is there a regolith layer? 06. March 2013 | Electrical Sounding on Ganymede | 2 [modified after Placky, 1988]

Motivation Open Questions:  Composition of Ganymede‘s subsurface?  Which non-ice materials occur?  Is there a regolith layer? Measurement of electrical parameters with ERIC (Electrical Resistivity Imaging via Capacitive Electrodes) 06. March 2013 | Electrical Sounding on Ganymede | 3 [Kuras, 2002]

Outline 1.Motivation 2.Quadrupole and its impedance 3.ERIC  Operating Modes  Measurements on Earth  Integration on a Lander 4.Conclusion 06. March 2013 | Electrical Sounding on Ganymede | 4

Quadrupole and its impedance 06. March 2013 | Electrical Sounding on Ganymede | 5 A V A V [after Kuras, 2002] c ccc

Quadrupole and its impedance 06. March 2013 | Electrical Sounding on Ganymede | 6 A V A V [after Kuras, 2002] c ccc

4-Point-Array over a half-space:  Sensitivity ranges Quadrupole and its impedance 06. March 2013 | Electrical Sounding on Ganymede | 7 displacement current → ε conduction current → ρ ρ crit

Operating Modes A cccc V 06. March 2013 | Electrical Sounding on Ganymede | 8 Main Mode:  Impedance Z  4 electrode array  Sounding depth: array size

Operating Modes Main Mode:  Impedance Z  4 electrode array  Sounding depth: array size Potential option 1:  Contact impedance Z C [Hördt et al., 2013]  2 electrode array  Sounding depth: electrode size A cc V A cccc V 06. March 2013 | Electrical Sounding on Ganymede | 9

Operating Modes 06. March 2013 | Electrical Sounding on Ganymede | 10 Potential option 2: combine E- and B-field measurments  Jupiter rotation: magnetic field variation on Ganymede  10hrs  Electromagnetic impedance Z EM  Penetration depth: 100km-scale  Derive information on conductive ocean  Expected electic field signal: 1Ωm (conductive ocean): 1µV Method is very attractive but 1MΩm (no ocean): 1mV not tested untill now!

Measurements on Earth Determining electrical parameters of ice  Sounding depth:  Z ~ 0.5m  Z C ~ 0.05m  ρ=1MΩm  ε r =120 [Sheshadri et al., 2008] Transmitter Receiver Potential electrodes Current electrodes 06. March 2013 | Electrical Sounding on Ganymede | 11

Integration on a lander V A Configuration as proposed for the Phobos Grunt Mission: Main Mode: Impedance measurement: sounding depth 2m 06. March 2013 | Electrical Sounding on Ganymede | 12

Integration on a lander V A Configuration as proposed for the Phobos Grunt Mission: Potential option 1: Contact impedance measurement: sounding depth 0.2m 06. March 2013 | Electrical Sounding on Ganymede | 13

Integration on a lander V A Configuration as proposed for the Phobos Grunt Mission: Potential option 2: Electromagnetic impedance measurement: sounding depth 100km-scale + magnetometer 06. March 2013 | Electrical Sounding on Ganymede | 14

06. March 2013 | Electrical Sounding on Ganymede | 15 Data processing in FPGA  Controlling of AD and DA conversion  Calculating of physical units  Pre-calibration  Packaging  Timing  HK processing data interface power interface ADC DAC ADC DAC excitation measuring dB/dt feedback active E-field measurement stimulation Integration on a lander Using existing structures:

06. March 2013 | Electrical Sounding on Ganymede | 16 Data processing in FPGA  Controlling of AD and DA conversion  Calculating of physical units  Pre-calibration  Packaging  Timing  HK processing data interface power interface ADC DAC ADC DAC excitation measuring dB/dt feedback active E-field measurement stimulation Integration on a lander Using existing structures: ComponentWeight Cables150 g Electrodes200 g Preamplifier150 g Sum500 g Power200 mW

Conclusion  Electrical parameters are adapted to determine Ganymedes surface/subsurface composition.  ERIC appoints transfer and contact impedance. Combined with the magnetometer also the electromagnetic impedance.  We are experienced in measuring on earth.  There is already a concept to integrate ERIC on the lander (proposal for the Phobos Grunt Mission). 06. March 2013 | Electrical Sounding on Ganymede | 17

Thank you for listening! I also want to thank the for funding. 06. March 2013 | Electrical Sounding on Ganymede | 18

2. Quadrupole and its transfer impedance 06. March 2013 | Electrical Sounding on Ganymede | 19 h A V A V [after Kuras, 2002] c ccc

Determine permittivity

Determine resistivity