1. Introduction Low mass, high speed impacting projectiles, performing science investigations from below surface. Objectives: ground truth, unique science not possible from orbit, future missions support Science capabilities: geophysics, chemistry, astrobiology, environment. Developments Update ESA ‘Jovian Moons Penetrators’ study performed. Paper (‘Penetrators for in situ subsurface investigations of Europa’ ) written and accepted for publication (http://dx.doi.org/10.1016/j.asr.2010.06.026)http://dx.doi.org/10.1016/j.asr.2010.06.026 Engaged in ESA Instruments TDA (Technical Development Activities) Program. ESA Jovian Moons Penetrator Study - Context ESA study with special provision for UK. Astrium UK [prime](descent system), MSSL(penetrator), QinetiQ UK(shell, comms), UCL(impact sites & materials) Initially focused on Ganymede then on Europa Study did not include science instruments development Study constraints: 2 planetary orbits operational lifetime, battery only power, high TRL solutions, 100 kg total mass limit. →Included model payload selected from candidate instruments PDD (Payload Definition Document) →Just within ~100 kg mass limit for single penetrator for Ganymede (too high for inclusion in JGO reference payload) →Performed evaluation to determine minimum mass solution (using ‘floor’ single instrument payload micro-seismometer only payload for Europa) Europa Surface Element Penetrators MSSL Penetrator Shell: Detailed modelling shows Steel or Titanium alloy shell can survive impact into 40Mpa solid polycrystalline ice (cf baseline 10MPa compressive strength). Broader body design reduces over-penetration into more porous ice. (QinetiQ, UK) Inner: Vacuum flask concept limits thermal losses to enable 1 week lifetime with batteries only power; and decouples thermal environment which could enable feasible use of RHU to extend lifetime or reduce mass. Communications system: rear mounted UHF (High TRL) with 10dB margin for transmission through pure ice; proximity-1 enables large range of dynamic signal attenuation. 120  cone patch antenna allows for considerable range of post impact orientations. Power: Potentially suitable primary battery alternatives identified, but require detailed low temperature and impact assessment. Descent System Delivers penetrator to surface from orbiter Monopropellant system Orbiter visible throughout descent Estimated Mass -Includes maturity and system margins -micro-seismometer only payload (penetrator mass not particularly sensitive to payload)] (a)For steel shell penetrator. (see Table) (b) Minimum Mass System:  ~60 kg (Titanium alloy shell reduces penetrator mass to 10.8 kg) Additional mass saving options possible (packing, RHU, bespoke batteries) ESA Europa Penetrators Study Results Impact materials characterisation and hazards assessment Impact survival testing of all elements Assess impact crater morphology Batteries (low temperature performance, bespoke design) Europa Penetrator Conceptual Design Europa Penetrator Descent Module [Design by Astrium Ltd.] Way Forward Develop TRL for science instruments Develop TRL for access to external materials Detailed study of planetary protection and radiation assessment Europa SEPMass Penetrator~14.3 kg Descent Module~49.8 kg Total system mass~64.1 kg Rob Gowen (MSSL/UCL) on behalf of The Penetrator Consortium EJSM 4 th Workshop, July 26-29 2010. Universal City, LA. U.S.A. Estimated Penetrator System Mass (steel penetrator), including margins Penetrator Shell Battery & Control Electronics Bay Instrument Bay Release stud Abutment Ring Back Plate Front snubber support system Spacecraft interface Radome housing antenna Rear axial snubbers (not visible) Communications Bay Radial snubbers positions