Reliability-based models end-of-life satellite disposal

The success rate of end of life disposal currently observed in LEO is well below the 90% required in international SDM standards. The rate is much higher in GEO as telecom operators tend to guarantee sustainability due to limited orbit slots. The population of space debris in LEO is expected to grow because of satellites left in orbit or lost after the occurrence of failures, eventual collisions or explosions in orbit and especially because of future large constellations.

A high Post Mission Disposal success rate will be needed in the near future to stabilize the evolution of the space debris population. One of the main reasons disposals are unsuccessful are in satellites which have been in orbit for a long duration and were just not designed for disposal, or that the decision to initiate disposal is made at the wrong time or too late (i.e. when propellant mass is too low).

Current/future S/C have to be designed for the end of life disposal and operators are no longer allowed to deliberately decide not to deorbit their S/C But how to avoid failures leading to more unsuccessful disposals in the future? An activity with TDE and Thales Alenia Space, France has proposed two solutions to improve satellite reliability and the success of disposals.

A generic reliability model has been implemented in Excel to support and apply the following approaches: Health Monitoring on real operating conditions (e.g. temperature), model updates according to current performance, margins and occurred failures; the return over experience; the prognostic and the Remaining Useful Lifetime (RUL) of units; and finally the enhanced risk assessment analyses.

In addition, new RAMS criteria enabling a better risk awareness decision on end of life of satellites have been evaluated and recommended. The proposed approaches and the developed tool allow for a better risk-awareness decision on the end of life of a satellite and could ideally lead to a high post-mission disposal success rate in the future.

T708-613SY closed in 2021.