LISA data analysis: Doppler demodulation

The orbital motion of the laser interferometer space antenna (LISA) produces amplitude, phase and frequency modulations of a gravitational wave signal. The modulations have the effect of spreading a monochromatic gravitational wave signal across a range of frequencies. The modulations encode useful information about the source location and orientation, but they also have the deleterious effect of spreading a signal across a wide bandwidth, thereby reducing the strength of the signal relative to the instrument noise. We describe a simple method for removing the dominant, Doppler component of the signal modulation. The demodulation reassembles the power from a monochromatic source into a narrow spike and provides a quick way to determine the sky locations and frequencies of the brightest gravitational wave sources.