Parkes observations for project P456 semester 2018OCTS_20

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. 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（Parkes Pulsar Timing Array，PPTA）项目拥有三大核心目标：（a）探测来自天文天体的引力波，（b）建立脉冲星时标系统，（c）加深对太阳系动力学的认知。PPTA是三大国际脉冲星计时合作组中历史最悠久的一个。我们的望远镜规模与团队体量均为三者中最小，但却取得了最优的测量结果与科研成果。我们针对非相干引力波背景强度给出的约束边界，是目前唯一可对理论模型形成有效制约的关键观测限制。我们能够始终保持领先地位的原因在于：坐拥南天球观测天区；拥有一支精干且聚焦核心研究方向的团队；配备了经过最优校准的射电接收系统；并且能够以15至20天的近乎恒定观测周期，在三个不同波段开展观测。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，本提案属于持续性科研项目，相关观测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（Square Kilometre Array，SKA）第一阶段项目能够实现比我们更优的灵敏度与观测周期之前，帕克斯天文台的持续观测仍将具备极高科研价值。即便在引力波背景被成功探测之后，我们仍需持续开展观测，以支撑新兴的引力波天文学领域发展！