What form does a gravitational-wave pulsar signal take at an Earth-based detector?
If a gravitational-wave detector were floating in empty space, far from any massive bodies such as the Sun, Jupiter, or the Earth, gravitational-wave pulsar detection would be very simple. As seen from the detector, the gravitational-wave signal from such a source would be a sinusoidal ‘pure tone’ with a fixed frequency5.1. The signal could be detected using a simple method, known as the Fourier Transform [26]. There is a well-known efficient computer implementation of this method, known as the Fast Fourier Transform, which would make searching for a pulsar signal an easily soluble problem with even a small computer cluster [27]. However, a great deal of complication is introduced because our gravitational-wave detectors (LIGO [6] and GEO [7]) are Earth-based. The Earth’s motion as it spins about its axis and orbits the Sun changes the gravitational wave as measured by the detector. To put it another way, the relative motion of the star and detector “modulates the waveform”. This modul
