Building operability into the Jupiter Europa Orbiter design to endure a high radiation environment

Abstract

The Europa Jupiter System Mission (EJSM) has been prioritized as the next Outer Planets Flagship Mission that would be devoted to exploring the emergence of habitable worlds around gas giants. This joint NASA and ESA endeavor would focus on the Galilean moons Europa and Ganymede but would also investigate Io, Callisto, and the Jupiter system as a whole. The NASA-contributed Jupiter Europa Orbiter (JEO) and the ESA-contributed Jupiter Ganymede Orbiter (JGO) would be launched on separate launch vehicles in 2020. Here we focus on JEO. After 2-3 years of performing science in the Jovian system, JEO would orbit Europa and would operate in a high radiation environment. The life-limiting radiation environment complicates hardware and software performance as well as operations strategy. These challenges would require the Europa science goals to be met in an efficient duration of 9 months. To maximize the science while in orbit at Europa, JEO needs to develop strategies to make the system easily operable and robust to radiation degradation. In addition to radiation tolerant hardware and software designs along with robust margins, the project has already been considering operability features in its baseline design for JEO. Operability is the combination of aspects of a system that make it simple and inexpensive to operate, robust to changing system behavior, responsive to modified goals, and adaptive to deviations in expected environments or operating conditions. For JEO, being robust and flexible to meet science goals in the face of a harsh environment is paramount. The mission must be designed to have multiple means of meeting critical science goals; accommodate operation in the face of radiation-based noise, degradation and failure; and be flexible to changing science goals based upon discoveries. As a result, JEO has kept science goals and operability in mind for all system design processes and trade studies. The most stringent and driving operational requirements and constraints for the JEO concept are encountered during Europa Science orbit phase. Some of the key operability issues incorporated from the earliest concept studies include: (1) Make the flight and ground systems operable and survivable for a high intensity, rapid turn-around operations environment in Europa orbit in the presence of radiation based anomalies. (2) Use modern system engineering methods to model the system behavior as early as possible to balance mission scope with system capability, complexity, risk, and cost. Systems design based on behavior models allows for accommodation of changing behaviors in operating the systems. (3) Use lessons learned from previous applicable missions to guide design philosophy and trade studies specifically for operability issues. In this paper, we discuss the key flight system design trades, operations scenarios and lessons learned developed in recent JEO mission studies.