Parkes Pulsar Timing Array (PPTA) is a Pulsar Timing Array, a consortium of Radio Telescopes observatories timing Pulsars. It is an effort to detect Gravitational Waves through comparison of the timing of observed pulsar cycles. It is part of the International Pulsar Timing Array. It is named after the Parkes Observatory of New South Wales.
The array consists of more than twenty pulsars. The term PPTA4 refers to a subset of four Millisecond Pulsars specifically chosen for study because their timings were obtained with very high precision.