Exploring Europa with a Surface Lander Powered by a Small Radioisotope Power System (RPS)

Abstract

Europa is a high-priority target for future exploration because of the possibility that it may possess a subsurface liquid ocean that could sustain life. Exploring the surface of this Galilean moon, however, represents a formidable technical challenge due to the great distances involved, the high ambient radiation, and the extremely low surface temperatures. A design concept is presented for a Europa Lander Mission (ELM) powered by a small radioisotope power system (RPS) that could fly aboard the proposed Jupiter Icy Moons Orbiter (JIMO). The ELM would perform in-situ science measurements for a minimum of 30 Earth days. The primary science goals for the Europa lander would include astrobiology and geophysics experiments and determination of surface composition. Science measurements would include visual imagery, microseismometry, Raman spectroscopy, Laser Induced Breakdown Spectroscopy (LIB s), and measurements of surface temperature and radiation levels. The ELM spacecraft would be transported to Europa via the JIMO spacecraft as an auxiliary payload with an extended duration cruise phase (up to 13 years). After arriving at Europa, ELM would separate from JIMO and land on the moon's surface to conduct the nominal science mission. In addition to transportation, the JIMO mothership would be used to relay all lander data back to Earth, thus reducing the size and power requirement of the lander communications system. Conventional power sources were evaluated and found to be impractical for this mission due to the extended duration, low level of solar insolation (-3.7% of Earth's), the low surface temperatures (as low as 85K), and the 1.75 days of eclipse every Europa day. In contrast, a small-RFS would enable the ELM mission by powering the lander and keeping all key instrumentation and subsystems warm during the cruise and landed phases of the mission. The conceptual small-RPS is based on the existing General Purpose Heat Source (GPHS) module using thermoelectric conversion. This would generate 225 Wt (thermal) and 10.1 We (electric) at the end of the mission, and would provide a 145% energy margin. A small rechargeable lithium-ion battery would be used to handle peak load demands during the short-duration communication events and while using the higherpower instrumentation (LIBS and Raman). In summary, small-RPS technology could enable an exciting, scientifically valuable Europa lander mission designed to verify the existence of a subsurface ocean, and to search for signs of past or present life.