Angular and frequency response of LISA

The sensitivity of LISA at frequencies above about 10 mHz is determined by the shot noise of the light together with the decreasing antenna transfer function, finally being limited by mechanical resonances above 1 Hz. In this paper we will investigate the transfer function of laser-interferometric gravitational-wave antennas in the upper frequency range, where the physical arm length of the antenna becomes comparable to or even greater than the wavelength of the gravitational waves. This analysis reveals results which are also interesting for ground-based detectors. Furthermore, we calculate the dependence of the LISA transfer function on orbit azimuth, source azimuth, source declination and polarization, and finally we form the average over these angles in order to arrive at a mean LISA sensitivity curve. It turns out that the resulting response is even better than estimated previously.