GPS-Based Relative Navigation during the Separation Sequence of the PRISMA Mission

Kurzfassung

PRISMA is a Swedish-led micro-satellite mission that serves as a test platform for autonomous formation flying and rendezvous of spacecraft. It comprises two satellites which are launched together in a clamped configuration and separated in orbit after completion of all checkout operations. The challenge of the subsequent early operations phase is to maintain the formation safety and in particular to minimize the risk of collision using only a reduced subset of the overall guidance, navigation and control functionalities. While not specifically designed for safe mode operations, the PRISMA GPS-based relative navigation system is still considered the best source of relative orbit information during this mission phase. A comprehensive simulation of the separation sequence has been therefore conducted that demonstrates the robust operation of the GPS navigation system under the adverse conditions of the separation event and the subsequent non-nominal spacecraft attitude. While initially based on offline Simulink/C++ software simulations, the employed test approach makes use of the prototype flight software for the GPS navigation system and enables a seamless transition to real-time software simulations as well as hardware-in-the-loop simulations.