欧空局和SpacaX谁先应该移走它们的卫星来避免相撞?Who should have moved their satellite to avoid a possible collision, ESA or SpaceX?

【提问者的问题来自新闻】

【翻译自quora,作者 Jeffrey Naujok,】

Update: turns out SpaceX would have been more than happy to maneuver, but had a bug in their paging system so didn’t get the updated email. For their part, ESA apparently didn’t contact SpaceX until the day before and then immediately chose to maneuver themselves and publish a scathing statement. And rather than SpaceX being “impossible to contact” they had actually repeatedly contacted ESA and decided not to maneuver prior to receiving the updated ephemera.

更新:事实证明,SpaceX会很乐意,但是在其通信系统中存在一个错误,因此没有收到更新的电子邮件。ESA显然直到一天前都没有联系过SpaceX,然后立即选择让自己的卫星回避,并发表严厉的谴责声明。实际上,SpaceX并非“无法联系”,他们实际上已经反复与ESA联系,并决定在收到更新消息之前,不首先进行机动。

【———-以下为推特内容——————】

Loren Grush@lorengrush

Statement from SpaceX on the ESA/Starlink potential collision on Monday

View image on Twitter

73712:04 AM – Sep 4, 2019Twitter Ads info and privacy202 people are talking about this

【———-以上为推特内容——————】

The simple answer: Since ESA defines its own “exclusion zone” size, and felt there was a 1 in a 1000 chance that it would be violated, then it is up to them to preserve their exclusion zone. So, the answer is ESA should have been the one to maneuver.

更简单的回答是,ESA自己定义了卫星“禁区”的大小,并且只要别的卫星有千分之一的机会发生危险,就会保护自己的禁区。所以答案是ESA才是需要改变的那一方。

The expanded answer:

详细版本

We currently don’t know both sides of the story, just that SpaceX refused (in an email, according to ESA) a request from ESA to adjust the trajectory of their Starlink 44 satellite. This happened after ESA determined that there was a 1 in 1000 chance of an “event” and informed SpaceX that they wanted them to move.

我们目前不知道这个故事双方是怎么想的,只是SpaceX公司拒绝(在一封电子邮件中,从ESA得到的消息)从欧空局的要求,拒绝调整自己的 Starlink 44 卫星的轨迹。在欧空局认为有千分之一的概率发生卫星碰撞事件,并通知SpaceX要求后者移开自己的卫星后,发生了上面提到的那件事。

We don’t know why SpaceX chose to refuse, because they did not elaborate, but I have a theory.

我们不知道为什么SpaceX公司选择了拒绝,因为他们没有详细说明,但我有一个理论。

(The Aeolus satellite.)

Aeolus is orbiting at 320 km of altitude, the Starlink constellation is supposed to orbit at 550 km of altitude. This means that Starlink 44 is over 210 kilometers below the main constellation. It’s over 100 km lower than the orbit it was inserted into on launch day, at 440 km of altitude.

Aeolus 是在轨道高度为320公里, Starlink constellation 假定在高度为550 km到轨道。这意味着, Starlink 44要比主要的 constellation 高出210公里。即使在发射当天,它的轨道高度也有440公里,要比主要的 constellation 高出100多公里。

(This chart is a month or so out-of-date, but it shows the Starlink satellite orbital altitudes. Starlink 44’s altitude is the red line that has been descending since early in the mission, after it reached about 485 km in altitude. It’s clear that after that point it appeared to be actively deorbited until day 170 (June 20th), at which point its path becomes more erratic, and is likely either out-of-fuel, or out of control.)

(此图是一个月左右时,但它显示了 Starlink 卫星的轨道高度。 Starlink 44的高度是红线所示,在约在海拔485公里的高度后, 要比早期任务的高度要有些下降。 很清楚在此之后直到170天(6月20日)高度都在下降,此时它的路径变得更加不稳定,并有可能消耗完所有燃料,或失控。

This can only mean one of two things. Either Starlink 44 is being intentionally deorbited, or it is one of the “failed” satellites that is naturally decaying out of orbit. In either case, it represents a set of data for SpaceX that is vitally important.

这只能意味着两件事情之一。 Starlink 44要么是在控制下脱离轨道,或者它无法被控制而脱离轨道下降。在任何情况下,它表达的信息对SpaceX至关重要。

If it is being intentionally deorbited — and this is the most likely case — then it is entirely possible that the amount of fuel the satellite was launched with was made to reflect an expected “end-of-mission” low fuel amount, and that most of that fuel was expended intentionally deorbiting out of the main constellation.

如果它是被有意控制脱离轨道 – 这是最有可能的情况下 – 那么它是完全有可能的是,卫星的燃料量在发射时预先计算好,以在“完成任务”时仅剩很少的燃料量,而且这些仅剩燃料的大多数还在到达主 constellation 之前的脱轨中被有意消耗掉了。

Even if they did have fuel aboard, it’s entirely possible that they are trying to simulate an end-of-life event precisely, and in an end-of-life event, there would be no fuel aboard, and the satellite would be incapable of movement. In such a case, they would have to know that non-SpaceX satellites can maneuver to avoid their satellite. Additionally, changing the orbit at this point could invalidate all of their ongoing deorbit data that they are collecting on Starlink 44.

即使在卫星上确实有燃料,他们可能正试图精确控制卫星完成任务事件,并且在结束仍无时恰好消耗完所以燃料,由于卫星不能运动。在这种情况下,他们必须知道,其他非SpaceX公司的卫星可以机动以避免他们的卫星。此外,如果Starlink 44在这个时候改变了轨道,那么SpaceX在之前收集的所有数据都没用了。

It’s also possible, although less likely, that this is one of the satellites that had a battery failure, and lost communication, in which case, SpaceX would be incapable of telling it to move out of the way.

这也可能是有一个电池失效,失去了通信功能,在这种情况下,SpaceX公司将不能让它的卫星移动。但这种可能性很小。

In either case, we know this much just because it’s in a 320 km orbit and on its way lower.

在这两种情况下,我们知道这么多,只是因为它在320公里的轨道上并且还在降低。

Finally, there exists one more option. When travelling in orbit, each satellite has an operator-defined “safe zone” around it that they don’t allow other satellites into. For Aeolus, that safe zone might be 5 km wide, and thus, with a chance that Starlink 44 might enter that 5 km safe zone, they chose to maneuver to keep their safe zone clear. SpaceX may have simply defined their safe zone as 4 km, and by their calculation, the Aeolus spacecraft would not enter their exclusion zone, so they saw no reason to adjust their course.

最后,还有一个选择。当在轨道上运行,每颗卫星都有运营者定义的“安全区”范围,他们不允许其他卫星进入。对于 Aeolus ,安全区可能是宽5公里,由于 Starlink 44可能进入这宽5公里的范围 , Aeolus 选择了移动,以保持自己的安全区没有危险的东西。SpaceX公司可能已经定义为自己的安全区为4公里,按他们的计算, Aeolus 还没有不进入他们的禁区,所以他们认为没有理由调整自己的卫星。

There is no particular reason for one satellite operator to respect the exclusion zone of another satellite operator. If that were a requirement, then I would simply make my exclusion zone the size of the Earth, and demand that all the other satellites move out of my way, giving me a monopoly on space. The idea is ludicrous. If you want a 100 km exclusion zone around your satellite, then it’s your responsibility to maintain it, not mine.

一个卫星运营者没有特别的理由要尊重其他卫星运营者所划定的禁区。如果这是一个要求必须被遵守的话,我会让我的禁飞区大小与地球一样,并且要求所有其他卫星离开我的禁飞区,让我的卫星独自在太空飞行。这个想法很可笑,如果你想保证你的卫星周围100公里的禁飞区是安全的,那么你应该移动你的卫星来避免危险,而不是我的。

The kicker, of course, is that Iridium almost immediately responded with the fact that they’ve had to adjust their satellites weekly to avoid other satellites[1] , but they’ve never put out a press release about it…

The kicker,当然,铱星不得不每周调整自己,以避免其他卫星[1]回应,但他们从来没有拿出一个例子当成它的新闻发布…

It’s almost like ESA, the world’s former largest launcher of commercial satellites until SpaceX came along, has a vested interest in making SpaceX look bad.

在SpaceX出现之前,欧空局是世界上最大的商业卫星发射商。如果他们现在能压制住SpaceX的话,就能保持自己的既得利益。

Footnotes

[1] Matt Desch on Twitter

【评论区】

@ Jim Lux

CSpOC sends the satellite operator an email when the expected closest approach in the next 5–10 days is <1000 meters. You’ll get emails 2–3 times a day as they update the predicts. The SpaceTrack website has the information on the two spacecraft and the time/date of closest approach. There’s a Pc (collision probability) field that is typically zero, but rises as the model predictions get more certain.

当未来5-10天最接近处<1000米时,CSpOC向卫星运营商发送电子邮件。由于他们更新预测,您每天会受到2~3份电子邮件。SpaceTrack网站会记录这两个航天器和最接近的时间/日期的信息。这两个航天器的PC( collision probability ,碰撞概率)字段通常为零,但是根据预测这个概率将会上升。

I have a satellite in a 500km orbit, and I get a “Conjunction Alert” series of emails about once a month. Most recently with a Starlink, as it happens. But typically, the miss distance is something like 400–500 meters and the Pc stays at zero, or is tiny (1E-10 or something like that). The probability is a combination of the size of the spacecraft, how sure they are of the position and velocity, and how close the approach will be. For my satellite the closest predicted approach I’ve seen has been <100 meters, and even there Pc was still tiny.

我在500km的轨道上有个卫星,我大概每个月会受到一次“接触警报”之类的邮件。最近一次时是与一颗 Starlink 卫星。但通常情况下,会发生的碰撞的距离是在400-500米内,所以PC是零或很小(1E-10或类似)。碰撞的概率要根据航天器的大小,位置和速度,以及两个航天器要多接近来确定。对我的卫星来说,与其他卫星最接近的一次小于100米,但碰撞概率仍然很小。

答主:

Exactly, SpaceX and ESA both got a notice that the range was 2.2E-5 and decided to do nothing. Then a new alert went out moving it to 1.69E-3, and that should have triggered an alert on both sides.

没错,SpaceX公司和欧洲航天局都得到了通知,碰撞概率为2.2E-5,他们决定什么也不做。然后新的警报是1.69E-3,双方都应该警觉起来。

Now you have one satellite that you’re watching. The guy (or girl) at SpaceX has 60 of them to keep an eye on. If you get 2–3 emails a day on 60 satellites, you want to have a system to automatically ignore the ones with a Pc below some threshold, and only get paged for the important ones.

现在你有一个需要关注的卫星。但SpaceX公司的那些小伙子(或姑娘)需要注视着60颗卫星。如果60颗卫星每颗卫星每天都要收到2~3份电子邮件,你肯定想有个可以忽略那些Pc低于某一特定值的邮件的系统,只关注那些比较重要的。

Clearly, in this case, that system failed. Meanwhile at ESA, the guys who have only one satellite got the update and took action.

显然,在这种情况下,这个系统没有及时通知到SpaceX。同时在只有一个卫星的欧空局,那些家伙得到了警告,并采取了行动。

This is like being on the highway driving next to your friend that has just had octuplets that are strapped into the car screaming at him. If he swerves a little into your lane, you honk, and if he doesn’t notice, you take action to avoid him. You then call him up and tell him, “hey, pay attention to your driving, I’ve got my kid in the car!”

这就好像你和你的朋友在高速公路上驾驶,而你的朋友的车子上有8个在狂喊乱叫不安宁的孩子。假如朋友的车稍微挡住你了你的路并且没有注意到,你采取行动避开它,然后告诉你的朋友:“小心一点,注意驾驶,我的车子上有一个孩子!”

What you don’t do is send out a press release saying what a horrible driver he is and demanding that the state take away all his children.

但你不应该在忽略了他车上有8个孩子的情况下,向他施加压力说他是一个可怕的驾驶员。

The way most of the articles are written, the guy was white-knuckling the wheel, barreling down the interstate in the wrong direction and heading straight for Aeolus while flipping the bird.【??最后一段看不懂】

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