Injection of a Body into a Geodesic: Lessons Learnt from the LISA Pathfinder Case

Launch lock and release mechanisms constitute a common space business, however, some science missions due to very challenging functional and performance requirements need the development and testing of dedicated systems. In the LISA Pathfinder mission, a gold-coated 2-kg test mass must be injected into a nearly pure geodesic trajectory with a minimal residual velocity with respect to the spacecraft. This task is performed by the Grabbing Positioning and Release Mechanism, which has been tested on-ground to provide the required qualification. In this paper, we describe the test method that analyzes the main contributions to the mechanism performance and focuses on the critical parameters affecting the residual test mass velocity at the injection into the geodesic trajectory. The test results are also presented and discussed.