Gravity Gradient sensor technology for future planetary missions ESA ITT AO/1-3829/01/NL/ND Moons around Jupiter Io Europa ESTEC September University of Twente University of Nantes R&D Programme

Programme for planetary exploration presented by Christophe Sotin

Programme for instrument development Gravity gradiometers based on MEMS and hybrid MEMS orbiter aerial vehicles/balloons (mapping smaller area) Laser cooled atom interferometry Multi sensor multi satellite systems formation flying

MEMS-based GG systems important parameters mass, base line, temperature, quality factor, operating frequency design of prototype with sensitivity in range mE/√Hz further development necessary

MEMS-based GG systems First generation devices: accelerometers and gradiometers with moderate sensitivity fabrication of several devices with different spring approaches material selection for electrodes charge trapping studies by C-V and C-t measurements (pull-in voltage, built-in voltage, temperature effects. electronic readout, force feedback, integration on MEMS-device Second generation devices: Improvement of first generation devices with respect to sensitivity Hybrid systems consisting of MEMS plus additional test mass Study of floating systems Study of modulation of spring constants Inductive readout and the use of high Tc devices

MicroNED activities Several programmes within MicroNed: 250 researchers: 9 knowledge institutes, 23 companies total budget M€ 28 (to be matched) Microsatellite programme MISAT - development of a new generation of microsatellites, with formation flying abilities - payload development: gravity gradiometers, cooling - possible tests of instruments in space UT -development of some prototypes (1 PhD student) -further support necessary: Post Doc, technician, clean room costs -further ESA support would be great

Atom interferometry Conclusions Measurement is performed with the atom cloud in free falling, hence absolute value of gravity determines size, measuring time In space small sizes and long measuring time are possible Rb atoms are favorable with respect to cold collisions frequency shift A sensor for gravity gradient based on atom interferometry could achieve a sensitivity below 1 mE/√Hz using 10s interrogation time. Sizes: 10 cm diameter vacuum chambers, base line 1m Mass: some kg

Source: M. Kasevich, CAMOS Prospects for atom interferometry Waveguides in atom chips

Multi sensor multi satellite systems Programme within Microned - distance sensing (flight configuration) - gravity sensing (accelerometers) large base line systems - magnetic sensing ( GMR, flux gates, high Tc devices) UT 1 PhD student Additional support from ESA?

National Platform planetary research Established on October 29 in 2004 Strengthen the relation between the Dutch potential for planetary research institutions, universities, industries Concentration Astrophysics Instruments (search for live, polarimeter, gravity gradiometers) Focussing on Mars