Europa tomography probe (ETP) mission feasibility – spacecraft design

Europa Tomography Probe is proposed as a European contribution to NASA’s mission to Europa. ETP is a small probe to be released by the main spacecraft, Europa Clipper, during its nominal mission. The probe will complement the goals of Clipper in the determination of the deep interior structure of the moon by combining magnetic and gravity field measurements. Hosting just one scientific instrument (a magnetometer) and a transponder required for the Inter-Satellite Link with the mother spacecraft, ETP could also enhance the accuracy of Clipper’s radar altimeter (REASON), thereby improving Clipper’s orbit determination. After arriving in the Jovian system with Clipper, the probe will attain a nearly circular, polar orbit around Europa at an altitude of 250 km by means of an autonomous guidance system. The minimum mission duration has been set to 6 months although, as a goal, it should be the same as that of the main spacecraft. The spacecraft design has been pursued by considering the main mission requirements and how they affect the overall system in terms of mass, power, and volume. Furthermore, the major design issues concerning each subsystem have been assessed to satisfy the strong constraint imposed by the maximum mass allowance on the main spacecraft (250 kg). Since ETP will be able to autonomously reach its final orbit, the propulsion system has been one of the primary focuses in this feasibility study. An accurate radiation analysis has also been essential because its results affect both the mission duration and the mass budget, which must include the radiation shielding. This feasibility study has been carried out under the design philosophy of determining the minimum required total mass and volume that allows to meet the mission requirements. The goal has thus been to assess which system architecture is needed to determine Europa's deep interior structure with the best possible accuracy, rather than what science return could be obtained with preassigned system constraints.