Vibration tests on the preloaded LARES satellite and separation system

Vibration testing of payloads is of paramount importance, and is in fact a standard procedure for all satellites, space structures and components. The use of strain gauges during such tests is relatively common. However, in the present study their use had a different aim, induced by the peculiarity of LARES, an Italian Space Agency satellite. The mission of LARES is to test the theory of general relativity and in particular to measure the frame-dragging effect created by the rotation of the Earth. The design of LARES had to meet some stringent scientific requirements and resulted in a satellite without protruding parts (such as bolts or clamps) typically used to interface a separation system. Indeed to maintain and release LARES, four pins are engaged, with an appropriate preload, in four hemispherical cavities manufactured in the satellite body. The paper reports the results of vibration tests on the satellite and separation system and the trade-off analysis performed to select the best technology for reliable monitoring of the preload. The suitability of the required design was proven by the successful separation and orbit insertion of the LARES satellite that is now working perfectly as the best test particle available in the solar system for testing fundamental physics.