Thread by @ProfHughLewis

Important and informative update from @SpaceX in response to widespread concerns about #SpaceSafety & #SpaceSustainability associated with #Starlink. Lots to unpack but worth investing time to do so (it's the Feb 22nd update entry btw) spacex.com/updates/

There's a strong focus on the collision avoidance capabilities of the #Starlink satellites rather than on the services that inform those capabilities. Ryan Hiles and co-authors presented a hugely valuable insight on this aspect at @amoscon last year amostech.com/TechnicalPaper…

The impact of #Starlink on the work of @SpaceForceDoD is explained clearly, as are the steps taken to manage the screening burden that has emerged with growing numbers of #Starlink satellites. That burden is continuing to grow (exponentially by my estimates)

It's also revealing that @SpaceX present the thousands of manoeuvres as successes rather than a signal of a stressed environment. In many respects, the avoidance of collisions should be seen as a success but it's hard to find anything to celebrate in it.

And, as others are starting to point out, it's great that the #Starlink plan A is working, and much of this update from @SpaceX is about things that are working, but what happens when things go wrong? TBH, you can argue a lot has gone wrong already

https://twitter.com/josh_sokol/status/1492159068433227779?t=W_ZAunSvlUmZGpWjF8hBNQ&s=19

There's also a concern that even the 1-in-100,000 collision probability threshold for manoeuvres is not sufficient (even though it is far better than the NASA standard). David Hand talks about rare events (like 1-in-a-million) in his book 'The Improbability Principle'...

...and how the law of very large numbers reveals why rare and seemingly improbable events can and do happen. Given sufficient opportunity (i.e. lots of close approaches) even the conjunctions falling below the manoeuvre threshold can become concerning.

And this is for all the objects we can detect and track. There's a very important and substantial population of lethal non-trackable objects that pose very real risks to #Starlink. Aaron Boley & Michael Byers explored this in their insightful paper nature.com/articles/s4159…