Parkes observations for project P456 semester 2019OCTS_04

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!

Parkes脉冲星计时阵列（Parkes Pulsar Timing Array, PPTA）项目共有三大核心目标：(a) 探测来自天文天体的引力波，(b) 建立脉冲星时标系统，(c) 加深我们对太阳系动力学的认知。PPTA是三大国际脉冲星计时研究团队中历史最悠久的一支。我们团队拥有的望远镜规模与成员体量均为三者中最小，但却取得了最精准的测量结果与最出色的科研成果。我们给出的非相干引力波背景强度约束，是目前唯一能对相关理论模型形成有效限制的约束条件。我们能够始终保持领先地位的原因在于：我们拥有南天区观测视野；拥有一支精干且目标高度聚焦的研究团队；配备了校准精度最高的接收系统；并且能够以15至20天的近乎恒定观测周期在宽带宽条件下开展观测。本提案旨在维持我们在该领域的领先地位。与多数观测提案不同，这是一项持续性观测提案，其观测工作将持续优化超低频引力波的约束精度，直至最终直接探测到这类引力波。至少在平方千米阵列（Square Kilometre Array, SKA）第一阶段项目能够超越我们的探测灵敏度与观测周期稳定性之前，Parkes望远镜的持续观测仍将具备极高科研价值。即便引力波背景被成功探测，我们仍需继续开展观测，以支撑这一新兴的引力波天文学领域的发展！