类似哈勃的卫星有多繁忙呢?每天都被安排得满满的吗?How busy is a satellite like Hubble? Does it have downtime or is it scheduled 100%?

【文章来源quora】

Hubble is BUSY!

The telescope is scheduled to the second, weeks in advance. If you are an astronomer who wants to use Hubble, you have to submit a proposal months before, explaining why the telescope should be used for your work rather than someone else’s. Hubble is massively overbooked. There are about twenty times as many serious requests for observations as there is time to make them.

使用望远镜之前必须在两周前就计划好。如果您是想使用哈勃望远镜的天文学家,则必须在几个月前提交建议,以解释为什么应该将望远镜用于您的工作而不是别人的。哈勃望远镜已经严重超额预定。请求进行观察的时间大约真正能进行观察时间的二十倍。

And yet, Hubble is not collecting data 100% of the time, even if everything is going to plan.

但是,即使一切都按计划进行,哈勃也不会100%地收集数据。

To explain how the telescope is spending a normal day, let’s look at its schedule for the remainder of today (11 October 2019):

要了解望远镜如何度过正常的一天,让我们看一下今天(2019年10月11日)剩下的的时间表:

Image: Part of Hubble’s weekly schedule for 7–14 October 2019.[1]

If you look at the observation begin and end times, there are sometimes a few minutes between the end of one observation and the beginning of the next one. This happens when the telescope needs to switch between instruments, or when it moves to point at another part of the sky, which takes time.

如果您看下观察的开始和结束时间,就会发现这次观察结束和下次观察之间会有几分钟空隙。当望远镜需要在仪器之间切换时,或者当它需要指向天空的另一部分时,这种情况会发生。

But there are also longer gaps. For example, there will be no data recorded between 16:39:43 and 19:00:00, and again between 21:34:51 and 23:00:00. There are several reasons why this happens. Sometimes there is maintenance to be done (remotely, of course). More interestingly, there are orbits when Hubble passes over the South Atlantic Anomaly (SAA for short), a region where Earth’s magnetic field is weaker than elsewhere. Cosmic radiation can penetrate into the higher layers of the atmosphere there. NASA has decided that it is too risky to operate the space telescope when it passes over this part of the Earth.

但有时候时间间隔很长。例如,在16:39:43和19:00:00之间以及在21:34:51和23:00:00之间都不会记录任何数据。发生这种情况有几个原因。有时需要进行维护(当然是远程的)。更有趣的是,哈勃越过南大西洋异常(SAA)时会绕轨道飞行,该地区的地球磁场强度比其他地方都弱。宇宙辐射可以穿透那里的大气高层。 NASA认为,当太空望远镜经过地球的这一部分时,操作太空望远镜的风险太大。

Image: The South Atlantic Anomaly is the red region, covering parts of South America, South Africa, and much of the southern Atlantic Ocean. The space telescope is routinely switched off when it flies over this part of the Earth. Image shows the SAA at an altitude of 560 km above the Earth.[2]

图片:南大西洋异常是红色区域,覆盖南美,南非和南部大西洋的大部分地区。太空望远镜飞过地球的这部分时,通常会关闭。该图显示了SAA在地球上方560公里的高度。[2]

As a space telescope, Hubble orbits the Earth once every 95 minutes, at an altitude of 540 km. It experiences 15 sunsets and 15 sunrises every day. The telescope is in sunlight half of the time. A telescope on the ground could not be used at those times (most telescopes only work at night), but Hubble is unaffected by this. It only needs to avoid pointing too close to the Sun, so sunlight does not get into the main body of the telescope, but apart from that, there are few constraints. To avoid damage from bright light, the telescope cannot point

作为太空望远镜,哈勃望远镜每95分钟在540公里的高度绕地球一周。每天经历15次日落和15次日出。望远镜一半时间都在阳光下。当时无法使用地面望远镜(大多数望远镜仅在夜间使用),但哈勃不受此影响。它仅需避免过近地指向太阳,因此太阳光不会进入望远镜的主体,但除此之外,几乎没有任何限制。为避免强光损坏,望远镜无法指向

  • within 50 degrees of the Sun
  • within 15.5 degrees of any illuminated portion of the Earth
  • within 7.6 degrees of the dark limb of the Earth, or
  • within 9 degrees of the Moon.
  • 在太阳50度以内
  • 在地球任何被照亮的部分的15.5度以内
  • 地球dark limb的7.6度内
  • 在月球9度以内。

There is always enough sky to find a target, 24/7 (well, apart from the down times I mentioned earlier).

总是有足够的天空来找到目标。(嗯,除了我之前提到的停机时间)。

There are two things I’d like to add:

First, even when Hubble is operational, it is not recording science data for much of the time. If you look at the schedule I posted, there is a column called “Target”. Many of those runs are dubbed “dark”, “bias” or something similar. The telescope needs to spend a lot of time recording calibration images. That’s something every astrophotographer has to do, and the space telescope (like every other professional telescope on the ground) needs to do it, too.[3] Hubble actually spends about as much time (if not more) recording calibration images as it spends on science targets.

首先,即使哈勃望远镜在运行,它不记录科学数据的时间也很多。如果您看一下我发布的日程表,会有一个名为“目标”的列。这些项目中有许多被称为“dark”,“bias”或类似名称。望远镜需要花费大量时间来记录校准图像。这是每位天文摄影师必须做的事情,太空望远镜(就像地面上的其他专业望远镜一样)也需要这样做。[3]实际上,哈勃花在记录校准图像上的时间与花在科学目标上的时间差不多(也有可能更多)。

Second, Hubble is, unfortunately, showing signs of old age. The telescope has been in orbit since 1990. Some of its instruments have failed, the orbit is decaying (Hubble will inevitably burn up in the atmosphere some time in the 2020s or 2030s), and most importantly, its controls (the gyroscopes and the computers) have caused trouble in recent years. There have been times when Hubble was not operational for weeks because some system didn’t work correctly. The last time this happened was in October 2018.[4] It can happen again at any moment. If you are a scientist and you’ve been waiting for years to get your two hours with Hubble, and the telescope has technical difficulties when your observations were scheduled, you are having a bad day. You don’t get your data.

其次,不幸的是,哈勃正显示出老年迹象。该望远镜自1990年以来一直在轨道上运行。它的某些仪器已经失效,轨道正在衰减(哈勃望远镜将不可避免地在2020年代或2030年代的某个时间在大气中燃烧),最重要的是,它的控件(陀螺仪和计算机) 在最近几年出了很多问题。有时候,由于某些系统无法正常运行,哈勃有数周时间都无法运行。上一次发生在2018年10月。[4]它随时可能再次发生。如果您是科学家,并且已经等了多年才能获得哈勃望远镜的两个小时,并且在安排观测时间时望远镜遇到了技术难题,那么您会很难过——您没有得到任何数据。

You can follow what Hubble is currently doing on their Twitter account, Space Telescope Live.

Since its launch, Hubble has collected about 1.5 million scientific images, resulting in the publication of almost 20,000 scientific papers.[5] Fingers crossed the telescope keeps going for many more years!

自发射以来,哈勃收集了约150万张科学图像,出版了近20,000篇科学论文。[5]转瞬间望远镜继续前进了很多年!

Footnotes

[1] Index of /ftp/observing/weekly_timeline

[2] File:ROSAT SAA.gif

[3] The Types of Images

[4] NASA’s Hubble Space Telescope Returns to Science Operations

[5] About the Hubble Space Telescope

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