ESA GNC Conference Papers Repository

LISA (Laser Interferometer Space Antenna) PathFinder (LPF) is an ESA/NASA mission which aims at demonstrating the technology required for detecting gravitational waves generated by very massive objects such as black holes. Detecting gravitational waves will tell us more about the way space and time are interconnected. The mission consists of placing two test-masses in a nearly perfect gravitational free-fall, and of controlling and measuring their motion with unprecedented accuracy. To do this it will use inertial sensors, a laser metrology system, a drag-free control system and an ultra-precise micro-propulsion system. Additionally the mission will enable the in-flight demonstration of the NASA provided Disturbance Reduction System (DRS). In order to provide the spacecraft with a suitable environment for meeting the necessary science requirements, an operational orbit at the Earth-Sun Lagrange point L1 is selected. The payload mass delivered to the operational orbit is maximised by means of a complex transfer strategy to L1; such a transfer strategy poses many challenges to the spacecraft design in general and to the AOCS in particular. This paper presents a short overview of the mission and the overall AOCS design (excluding the science mode). The design and performance of the AOCS for the transfer phase is then described in more detail, with emphasis on the design features adopted in order to overcome the challenges and constraints imposed by such a complex transfer. The design and performance assessment of the LPF AOCS is now completed. A delta Critical Design Review has been held in May 2013 following the installations of Cold Gas System (CGAS) thrusters in place of the FEEP as the main micro-propulsion on board the spacecraft. Functional testing and Integrated System Testing is now in an advanced phase while the CGAS procurement proceeds; the planned launch date is currently 2015.