Parkes observations for project P456 semester 2018OCTS_37

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）项目设有三大核心目标：(a) 探测来自天文天体的引力波；(b) 建立脉冲星时标系统；(c) 深化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为悠久的团队。尽管我们拥有的望远镜规模与团队体量均为三者中最小，但却斩获了最精良的观测数据与最顶尖的研究成果。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观测约束。我们能够始终保持领域领先地位的原因在于：我们坐拥南半球天区的观测优势；我们拥有一支规模精简但目标聚焦的研究团队；我们配备了校准精度最高的接收机；并且我们能够以15至20天的近乎规则观测频次开展持续观测。凭借本提案，我们旨在巩固并维持在该领域的领先地位。

与绝大多数观测提案不同，本提案属于持续性观测项目，相关观测将持续优化对超低频引力波的探测约束，直至最终成功探测到引力波信号。帕克斯望远镜的持续观测至少将保持其科学价值，直至平方公里阵列（Square Kilometre Array, SKA）第一阶段项目能够在观测灵敏度与观测频次上实现对我们的超越。即便在引力波背景被成功探测之后，我们仍将持续开展观测，以支持这一新兴的引力波天文学研究领域！