Time-delay interferometry and the relativistic treatment of LISA optical links

Abstract

LISA is a joint spae mission of the ESA and NASA for deteting low frequeny gravitational radiation in the band 10−5 −1 Hz. In order to attain the requisite sensitivity for LISA, the laser frequeny noise must be suppressed below the other seondary noises su h asthe optial path noise, a eleration noise et. This is ahieved beause of the redundan y in the data, more spe i ally, by ombining six appropriately time-delayed data streams ontain ingfrational Doppler shifts - time delay interferometry (TDI). The orbits of the spa eraft are omputed in the gravitational eld of the Sun and Earth in the Newtonian framework, while the optial links are treated fully general relativisti ally and thus, e ets suh as the Sagna, Shapiro delay, et. are automatially in orporated. We show that in the model of LISA that we onsider here, there are symmetries inherent in the physis, whih may be used e e tively to suppress the residual laser frequen y noise and simplify the algebrai approa h to TDI.