Constraints on LISA Pathfinder's self-gravity: design requirements, estimates and testing procedures

Abstract

LISA Pathfinder satellite has been launched on 3th December 2015 toward the Sun-Earth first Lagrangian point (L1) where the LISA Technology Package (LTP), which is the main science payload, will be tested. With its cutting-edge technology, the LTP will provide the ability to achieve unprecedented geodesic motion residual acceleration measurements down to the order of $3 \times 10^{-14}\,\mathrm{m/s^2/{Hz^{1/2}}}$ within the $1-30\,\mathrm{mHz}$ frequency band. The presence of the spacecraft itself is responsible of the local gravitational field which will interact with the two proof test-masses. Potentially, such a force interaction might prevent to achieve the targeted free-fall level originating a significant source of noise. We balanced this gravitational force with sub $\mathrm{nm/s^2}$ accuracy, guided by a protocol based on measurements of the position and the mass of all parts that constitute the satellite, via finite element calculation tool estimates. In the following, we will introduce requirements, design and foreseen on-orbit testing procedures.