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I'm only aware of the ESA and SpaceX incident in 2019. Does this happen more regularly especially now with more active Starlink satellites and other constellations?

More importantly, are there efforts to track these types of near collisions where one or both agencies react (or choose not to) to avoid collisions?

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    $\begingroup$ Do you include the ISS as an "active satellite"? $\endgroup$ Commented May 27, 2022 at 20:29
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    $\begingroup$ @OrganicMarble why would someone not? $\endgroup$
    – Topcode
    Commented May 28, 2022 at 2:14
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    $\begingroup$ @OrganicMarble Also interesting! $\endgroup$
    – Adrian
    Commented May 28, 2022 at 3:54
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    $\begingroup$ @OrganicMarble The ISS is certainly going to be an outlier with regard to the frequency at which it performs collision avoidance maneuvers, for several reasons. (1) The ISS has people on board. (2) The ISS is by far the largest object in space. (3) The ISS is by far the most expensive object in space. (4) The ISS is regularly resupplied with propellant. All of these reasons, and others, make it so the ISS is going to be extremely cautious any time they are warned of anything close to a close approach. $\endgroup$ Commented May 28, 2022 at 4:56
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    $\begingroup$ @DavidHammen pretty much why I made the comment. $\endgroup$ Commented May 28, 2022 at 11:50

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Well, if we want to talk about SpaceX and Starlink, they're obligated by regulation to provide semi annual reports on the operations of Starlink. You can find the reports here (as well as a hilarious amount of very snide back and forth between industry on regulatory approval of Starlink). In the period of 2021 June 1 (~1700 sats) to 2021 November 30 (~1800 sats) they conducted 3,333 maneuvers, although this does number include maneuvers avoiding debris, not just satellite v satellite. There was also 10 occurrences where other operators asked SpaceX not to perform a maneuver because those operators preferred to maneuver their satellites.

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  • $\begingroup$ That is very cool! Do other operators also have to report to the FCC? I'm very new to the regulatory landscape so any help is welcome! $\endgroup$
    – Adrian
    Commented May 29, 2022 at 21:02
  • $\begingroup$ Do they only provide the number of maneuvers and not the individual maneuvers or did I miss this somewhere? $\endgroup$
    – Adrian
    Commented May 30, 2022 at 9:37
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    $\begingroup$ @Adrian Yes, although I'm unclear on how to find them. From this link or here you might be able to get to the document dumps. Looks like you have to register for an FRN. And no they do not report individual maneuvers at this stage. $\endgroup$ Commented May 30, 2022 at 12:49
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Per the most recent (March 2022) Orbital Debris Quarterly News issued by NASA, the International Space Station has conducted 30 orbital debris avoidance maneuvers since 1999. That's a bit over one per year, on average.

The ISS is certainly going to be an outlier with regard to the frequency at which it performs collision avoidance maneuvers, for several reasons:

  • The ISS has people on board.
  • The ISS is by far the largest object in space.
  • The ISS is by far the most expensive object in space.
  • The ISS is regularly resupplied with propellant.

The first three of the above reasons means NASA and Roscosmos have to be very aggressive regarding avoiding potential collisions with debris. The final reason means that NASA and Roscosmos can afford to be very aggressive with regard to avoiding potential collisions. While other spacecraft are expensive, none come close to the value of the ISS. Most spacecraft are not refuelable, so most space operators have to tolerate more risk than the ISS. I suspect that for most spacecraft in low Earth orbit that it's well under one collision avoidance maneuver per year.

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    $\begingroup$ Thank you. Very interesting points. These decisions are exactly what I would like to see in the data. $\endgroup$
    – Adrian
    Commented May 28, 2022 at 16:08
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The Space Data Association (SDA) has, as a part of its reason for being, the role of sharing good quality orbit ephemeris amongst subscribing satellite operators.

Operators own ranging of their satellites is usually rather more accurate than the publically available TLEs. The SDA also have some link (I don't know the details) with JSPOC to access better quality ephemeris than TLEs for uncontrolled objects or those of non-subscribing operators.

How often is a manoeuvre actually a) necessary in one person's view or b) actually performed? I don't think anyone has the big picture - there are ball park estimates in the debris community, its a way of spreading a message about the cost of space debris.

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  • $\begingroup$ Thank you. The SDA data would help to figure out whether collision avoidance might be necessary but it won't be able to determine whether satellites changed course? The space debris community would also mostly say something about collision with debris and not necessarily of two active satellites? Or can you point me in a direction here? $\endgroup$
    – Adrian
    Commented May 28, 2022 at 16:04
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    $\begingroup$ @Adrian OK: re. your second sentence ending "...whether satellites changed course.?" - yes that is my understanding (this bit was aimed at answering the second part of your OP relating to efforts). Re. your third sentence starting "The space debris community would also ..." - I think they are interested in all contributions to the risk whether from debris (tracked or otherwise) or between active satellites. There has been a lot of interest in the growing numbers of collision avoidance manoeuvres implied for Starlink as Barry Jenkins rightly points out. $\endgroup$
    – Puffin
    Commented May 29, 2022 at 19:02
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    $\begingroup$ This researcher has, I think, been putting together close approach prediction rates from celestrak socrates and using that as a starting point for extrapolation forwards in a debris model. twitter.com/ProfHughLewis/status/1522251794293968898 . I understand the approach includes debris and active on active; I get that is not what you want though I presume it would be tractable for that research project to filter down only to the active to active. $\endgroup$
    – Puffin
    Commented May 29, 2022 at 19:06
  • $\begingroup$ this is super interesting, thank you. If you want to put this in a separate answer also pointing to CelesTrak I would accept it. $\endgroup$
    – Adrian
    Commented May 30, 2022 at 8:32

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