论文标题
星形通信下行链路
A Starshot Communication Downlink
论文作者
论文摘要
突破性的星光图是将帆船推向下一代Alpha Centauri的一项举措。当Sailcraft在0.2 C上移动Alpha Centauri时，它通过成像行星和收集其他科学数据来寻找生命的迹象。过境后，4.1米直径的帆船将其数据下链接到基于地球的接收器。目前的工作估计了1.02μm，100瓦激光器的原始数据速率，该速度以1.25μm的速度接收到30米高的望远镜。望远镜在考虑到光学增长（+296 dbi），常规损失（-476 dB），相对论效应（-3.5 dB）之后，望远镜每秒收到288个信号光子（-133 dBM），并接收链接（-3.0 dB）。对于这个具有0.1 nm等效噪声带宽的光子释放的泊松通道，检测器量子效率为90％，1024-ARY PPM调制和10^-3原始位错误率，原始数据速率为260位/s（硬命令）至1.5 kbit/s（理想）的原始数据速率，哪些是8-50 GBIT/年。噪音会减慢此速度，尤其是来自Alpha Centauri A的星光，随着帆船靠近恒星，大气和接收器光学散布在检测器中。因为这是一个飞行任务（Sailcraft（Sailcraft）在半人马座系统中没有停止），所以Alpha Centauri相对于地球的适当运动将其带离帆船后，而噪音在几天到几周内就消失了。下行链路可以在运输后的第二天恢复，从7-22位/s开始，在4个月后几乎全速达到全速。通过在接收望远镜上使用冠状动脉，可以更快地达到全率下行链路速度。
Breakthrough Starshot is an initiative to propel a sailcraft to Alpha Centauri within the next generation. As the sailcraft transits Alpha Centauri at 0.2 c, it looks for signs of life by imaging planets and gathering other scientific data. After the transit, the 4.1-meter diameter sailcraft downlinks its data to an Earth-based receiver. The present work estimates the raw data rate of a 1.02 μm, 100 Watt laser that is received at 1.25 μm by a 30-meter telescope. The telescope receives 288 signal photons per second (-133 dBm) from the sailcraft after accounting for optical gains (+296 dBi), conventional losses (-476 dB), relativistic effects (-3.5 dB), and link margin (-3.0 dB). For this photon-starved Poisson channel with 0.1 nm equivalent noise bandwidth, 90% detector quantum efficiency, 1024-ary PPM modulation, and 10^-3 raw bit error rate, the raw data rate is 260 bit/s (hard-decision) to 1.5 kbit/s (ideal) raw data rate, which is 8-50 Gbit/year. This rate is slowed by noise, especially starlight from Alpha Centauri A scattered into the detector by the atmosphere and receiver optics as sailcraft nears the star. Because this is a flyby mission (the sailcraft does not stop in the Centauri system), the proper motion of Alpha Centauri relative to Earth carries it away from the sailcraft after transit, and the noise subsides over days to weeks. The downlink can resume as soon as a day after transit, starting at 7-22 bit/s and reaching nearly full speed after 4 months. By using a coronagraph on the receiving telescope, full-rate downlink speed could be reached much sooner.
