Reliability Model Supporting Satellite Life Extension and Safe Disposal

Spacecraft that survive their nominal mission lifetime are generally proposed for a mission extension to maximize their return on investment. Currently, the remaining lifetime estimates to support mission extension decisions are largely based on consumables (e.g. remaining propellant). However, more accurate quantitative reliability-based lifetime assessments are needed to demonstrate compliance to the probability of successful disposal requirements imposed by Space Debris Mitigation (SDM) standards and regulations [1]-[8] which are in place to limit the growth of hazardous human-made objects in protected orbital regions. Remaining lifetime predictions should take into account wear out mechanisms impacted by environmental stresses (e.g. radiation) or use conditions (thermal and power cycles), limited resources (e.g. propellant, power degradation over time), and the minimum configuration needed for disposal. Although wear-out mechanisms or spacecraft limitations are covered for the most part by design margins these generally only apply to the nominal mission lifetime. In order to address this challenge and in line with the European Space Agency's (ESA) system safety and dependability roadmap [9], a generic reliability model is proposed combining systems engineering and reliability aspects by integrating units degradation, diagnostic, and prognostic information. The approach is proposed to be validated at unit, subsystem, and satellite level using in-orbit field data.