Parkes observations for project P456 semester 2019APRS_15

The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. The PPTA is the oldest of three international pulsar timing groups. We have the smallest telescope and the smallest group, but the best measurements and the best results. Our bound on the strength of the incoherent gravitational wave background is the only bound which significantly constrains theoretical models. We have maintained our leading position because: we have the southern sky; we have a small but well-focussed group; we have the best-calibrated receivers; and we have been able to observe with an almost regular cadence of 15 to 20 days over a wide bandwidth. With this proposal we aim to maintain our pre-eminent position in the field.

Unlike most observing proposals, this is a continuing proposal for which the observations will continue to improve bounds on ultra-low-frequency gravitational waves until they are finally detected. Continued Parkes observations will remain valuable at least until the first stage of the SKA is able to improve on our sensitivity and observing cadence. Even after the gravitational wave background is detected we will want to continue observations in support of the nascent field of gravitational wave astronomy!

帕克斯脉冲星计时阵列（PPTA）项目有三个核心目标：（a）探测来自天文源的引力波（gravitational waves），（b）建立脉冲星时标，（c）深化对太阳系动力学的理解。PPTA是三大国际脉冲星计时团队中历史最悠久的一个。我们拥有最小的望远镜和规模最小的团队，但具备最优的测量数据与成果。我们对非相干引力波背景强度的限制，是唯一能显著约束理论模型的限制条件。我们得以保持领先地位的原因在于：覆盖南天区域；拥有规模虽小但专注度极高的团队；配备最精准校准的接收器；以及能够在宽频带上以15至20天的近乎固定周期开展观测。通过本提案，我们旨在维持该领域的领先地位。

与多数观测提案不同，本提案为持续性提案——观测将持续优化对超低频率引力波的限制，直至最终探测到该引力波。帕克斯的持续观测至少在平方公里阵列（SKA）第一阶段能提升我们的灵敏度与观测周期之前，仍具有重要价值。即便引力波背景被探测到后，我们仍希望继续观测，以支持新兴的引力波天文学领域！