Parkes observations for project P456 semester 2020APRS_03

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.\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。我们拥有规模最小的望远镜与最小的研究团队，但却取得了最优质的观测数据与研究成果。我们针对非相干引力波背景强度给出的约束，是目前唯一能对理论模型构成有效限制的约束条件。我们能始终保持领先地位的原因在于：我们拥有南半球天空的观测优势；拥有一支精干且目标明确的研究团队；配备了经过最佳校准的接收系统；并且能够以15至20天的近乎固定观测周期，在宽带宽范围内开展观测。通过本提案，我们旨在维持本领域的领先地位。 与多数观测提案不同，本提案属于持续性观测提案，相关观测将持续优化超低频率引力波的约束精度，直至最终探测到该引力波信号。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）第一阶段完成灵敏度与观测周期优化前保持其科研价值。即便在引力波背景被探测到之后，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！