A passing gravitational wave will affect the local space-time metric on the travel path of a radio pulse and can lead to observable fluctuations in its arrival time at Earth. There is an international effort in using pulsar timing arrays (PTAs) to detect gravitational waves.
The Parkes Pulsar Timing Array (PPTA) in Australia observes 20 millisecond pulsars at 2-3 weeks interval with regular monitoring commenced early 2005. PPTA offers the most regularly monitored millisecond pulsars among all efforts. The UWA Gravity Group uses data from the Parkes telescope to search for gravitational waves from binaries of supermassive black holes. They design optimal detections and localization method for individual gravitational wave sources and set stringent astrophysical limit on detectable sources.