Parkes observations for project P456 semester 2018OCTS_01

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（PPTA）项目有三个核心目标：（a）探测来自天文源的引力波；（b）建立脉冲星时间尺度；（c）深化我们对太阳系动力学的理解。PPTA是三大国际脉冲星计时研究组中历史最悠久的一个。我们拥有最小的望远镜和规模最小的团队，但却取得了最佳的测量数据与最优的研究成果。我们对非相干引力波背景强度设定的约束上限，是目前唯一能对理论模型构成显著限制的约束。我们能保持领先地位，原因在于：我们覆盖南天区域；拥有规模小但专注度极高的团队；配备校准最精准的接收器；并能以15至20天的近乎规律周期，在三个不同波长上开展观测。本提案旨在维持我们在该领域的卓越地位。

与多数观测提案不同，本提案为持续性提案——观测工作将持续推进，不断收紧超低频引力波的约束上限，直至最终探测到引力波。帕克斯的持续观测将保持其价值，至少在平方公里阵列射电望远镜（SKA）第一阶段建成并能超越我们的观测灵敏度与周期之前。即便引力波背景被探测到后，我们仍将继续观测，以支持引力波天文学这一新兴领域的发展！