Optimising LISA orbits: The projectile solution

Abstract

LISA is a joint spae mission of the NASA and the ESA for deteting low frequeny gravitational waves (GW) in the band 10−5 − 0.1 Hz. The proposed mission will use oherent laser beams whih will be exhanged between three idential spae raft forming a giant (almost) equilateral triangle of side 5×106 kilometres. The plane of the triangle will makean angle of ∼ 60◦ with the plane of the elipti. The spaeraft onstituting LISA will be freely oating in the ambient gravitational eld of the Sun and other elestial bodies. To ahieve the requisite sensitivity, the spaeraft formation should remain stable, one requirement being, the distanes between spaeraft should remain as onstant as possible - that is the exing of the arms should be minimal. In this paper we present a solution - the projetile solution - whih onstrains the exing of the arms to below 5.5 metres/se in a three year mission period. This solution is obtained in the eld of the Sun and Earth only, whih prinipally a et the motion of the spaeaft, espeially the exing of LISA's arms.