Yeah, you can feel the bad blood behind the press release.

Basically ESA nicely asked SpaceX to maneuver their sat and shorten its lifetime - they don't have a legal basis or enforcement mechanism anyway. SpaceX pretended not to hear until it was too late and ESA went ahead with their contingency plan of burning their own sat's fuel and lifetime instead.

ESA said they didn't ask spacex to move their sat, they just said they let them know. Spacex replied they had no intention to move their sat, since it was in deorbit testing.

If it was really about burning fuel, ESA would not have waited until half an orbit before. The longer you wait, the more you have to burn.

Not really.

a. They did an altitude increase. There's no real gains from an earlier burn that one might get when doing something like a hohmann transfer.

b. Half an orbit before out means more/better telemetry to work with.

c. They are from a quick google, well within the range where atmospheric drag plays a role, and you need to do station keeping. leaving it this late means you don't "waste" fuel from drag.

Admittedly, my only credentials for this are a few thousand hours in KSP and reading around the subject. Anyone with a proper degree on this is welcome to correct me.

In that case they were simply adjusting their station keeping schedule and minimum (if any) fuel would be wasted.

If that wasn't the case, they could raise or lower the altitude slightly several orbits before the "event" causing them to arrive at the intersection point earlier or later. For a desired time delta, the sooner your perform your altitude change the smaller the changed required.

Sure, but I'm positive the ESA's argument is their fuel burn should have been zero.

I haven't seen any mention of ESA "nicely asking" SpaceX to maneuver. Is that referenced in another article?

The sat in question was in deorbit testing, it's lifetime was already short.

Yeah, but ESA message is clear that space needs some regulation, now there is no rule who should do the avoidance, with more and more satellites you need some defined rules and coordination on handling this incidents. Also I am wondering if some cheap satellite destroys a expensive scientific one is there a law that could apply for recovering some damages and act as a incentive to prevent such a thing?

As far as I know, everything that is sent into space is the responsibility of the nation that launched it and governed by its laws. So if two satellites were owned by organizations from the same country, that country's legal system would have to deal with the damages. I am not sure if the space treaties actually cover the case where multiple nations are involved. I wouldn't bet on it.

As for the second question yes, the Space Liability Convention contemplates joint launches, see article V here: http://www.unoosa.org/pdf/gares/ARES_26_2777E.pdf

> I am not sure if the space treaties actually cover the case where multiple nations are involved. I wouldn't bet on it.

I would.

https://en.wikipedia.org/wiki/Space_Liability_Convention

> States (countries) bear international responsibility for all space objects that are launched within their territory. This means that regardless of who launches the space object, if it was launched from State A's territory, or from State A's facility, or if State A caused the launch to happen, then State A is fully liable for damages that result from that space object.

So for cars we have clear rules like on intersection who has the priority, on an incline, etc . It seems that in this case there are no rules, the SpaceX was following the rules but ESA thinks it was to risky or SpaceX are incompetent and could not do anything and couldn't even produce a response in time.

Yeah, at the moment, this sort of issue is an after-the-fact thing. Determining fault would probably be a diplomatic and multi-national legal fuss that stretches for years.

ESA felt no such thing. What you are recalling here is Jonathan O’Calaghan’s opinion that whoever was in an orbit first automatically has right of way.

ESA’s take on the matter is that it was annoying that they couldn’t contact SpaceX, and that relying on email and phone calls between humans is not going to work when there are tens of thousands of satellites in orbit.

The Twitter thread which started this was about ESA’s plans to automate their entire collision detection and avoidance process, and a call for an industry consensus on processes and protocols for communicating facts and intentions between satellite operators, and a set of rules and policies for managing space traffic, similar to what is done for international air traffic today.