Parkes observations for project P456 semester 2018APRS_10

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 at three different wavelengths. With this proposal we aim to maintain our pre-eminent position in the field.\r\n\r\nUnlike 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（Parkes Pulsar Timing Array，PPTA）项目拥有三大核心目标：（a）探测来自各类天文源的引力波；（b）建立脉冲星时标系统；（c）深化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组中历史最悠久的一个。我们虽拥有最小的望远镜与规模最小的团队，但却斩获了最优质的观测数据与最出色的研究成果。我们针对非相干引力波背景强度给出的约束，是目前唯一能够显著限制相关理论模型的约束结果。我们能够始终保持领域领先地位的原因在于：一是坐拥南天区观测优势；二是拥有一支规模小巧但目标高度聚焦的科研团队；三是配备了经过最优校准的接收设备；四是能够以15至20天的近乎规律的观测周期，在三个不同波段开展观测工作。通过本次提案，我们旨在巩固本领域的领先地位。

与绝大多数观测提案不同，本提案属于持续性观测项目，其观测工作将持续优化对超低频引力波的约束精度，直至最终实现这类引力波的直接探测。帕克斯望远镜的持续观测至少将在平方千米阵列（Square Kilometre Array，SKA）第一阶段项目实现灵敏度与观测周期的升级之前，始终保有其科研价值。即便引力波背景被成功探测，我们仍将持续开展观测工作，以支撑这一新兴的引力波天文学领域的发展！