月球偏振技术帮助世界上最大的射电望远镜测量木星上每小时900英里的风
Portions excerpted from Popular Science
一个国际天文学家小组使用了月球技术，他们第一次测量了木星猛烈的平流层风，他们使用了一颗27年前的彗星。
科学家们已经测量了木星对流层的风速，在那里，行星标志性的条纹在其电离层中不断上升。但是这项新的研究首次使用超灵敏的Atacama大毫米/亚毫米阵列（ALMA）对木星平流层进行风速测量。他们测量了赤道附近和两极附近的风速。
一些风速测量结果并不太令人惊讶——研究人员发现赤道的风速大致与模型预测的一样。“但我们在两极附近看到的东西是完全出乎意料的，”研究作者蒂鲍特·卡瓦利说，他是波尔多实验室的行星科学家，他领导了这项实验。研究小组发现，每秒300到400米的风速——大约每小时700到900英里的风速在没有预料的方向上横过两极。
For decades, the easiest way to figure out planetary wind speeds was to simply take a snapshot of the planet, then another one some time later and see how far the clouds moved between the two frames, Cavalié says. But at higher altitudes this doesn’t work, because the winds are invisible. There are no clouds to track.
But ever since the Shoemaker-Levy 9 comet impacted on Jupiter back in 1994, researchers have kept tabs on two compounds the comet delivered there: hydrogen cyanide and carbon monoxide. The team was able to trace the unique spectral fingerprints of the chemicals. Since they could track winds using the movement of clouds, perhaps they could use these molecules to do the same, by detecting their frequencies with ALMA.
然后,他们利用多普勒效应,means those frequencies change depending on whether the molecules are moving toward us or away from us. So, on Jupiter, as the molecules blew towards the telescope, they would produce slightly different spectral signals than those moving away. By measuring the difference — how much the frequencies got bumped — the team could measure the speed at which the molecules (and the wind) were moving.
Luna的技术是如何帮助的
阿尔玛是目前世界上最大的射电望远镜，它使用的是Luna Innovations long-range polarization-stabilized fiber stretcher assembly要更正ALMA的定时，以便消除温度变化和天线运动影响。该定制模块结合了Luna的几个（以前是通用光子学）专利技术：光纤拉伸器用于光路匹配，偏振控制器动态控制偏振，以及一个偏振计分析偏振并用作反馈信号。它是国家射电天文观测站（NARO）的一个特殊产品，它在高达100Hz的情况下产生高达4mm的光延迟，这是一种由自定义偏振控制和监测电路实现的极为精确的控制水平。
为了向天线提供最精确的振荡器定时信号，ALMA采用的方法使用非常精确的尺度来探测光纤延迟对每个天线的微小变化。这是通过一个超稳定的“主激光器”与光电光纤线拉伸器一起使用的，该光纤拉伸器可连续调整每个天线的总光纤长度。
Read the full article“研究人员刚刚首次测量了木星平流层的风，他们是个倒霉的家伙”at Popular Sciencehere.