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The End of the Night Sky?


I've been reading recently about Starlink, The constellation of satellites planned by SpaceX, the American company associated with Elon Musk, to provide satellite internet access.


This is a phenomenally ambitious project, and the physics associated with is really interesting.


It involves an investment of 10 bn dollars, and aims to put 12,000 satellites - each one a few hundred kg in mass - into orbit by the mid 2020s. There was a time in the not-distant past where such plans could be filed under science fiction, but this looks like it might really happen: there are already nearly 200 of them in orbit - including a batch launched just last Monday, Jan 6th. They will eventually form 3 shells around the earth, at altitudes of 340 km, 500km and 1150km.


Amongst the proposed benefits are, obviously, improved internet availability - including the provision of a service that might survive earth-based crises such as hurricanes and therefore provide service when it is most needed. Also, their relative proximity to the earth would make systems such as satellite phone calls more practical: at the moment the journey to and from the surface of the earth means that such calls have a latency (a delay) of about 600 ms - which is enough to make conversation uncomfortable. Starlink claim they could reduce that to 25 or 35 ms - a delay most of us wouldn't notice in conversation.


But there are a few problems. Very obvious problems, I would have thought.


Firstly, this is an enormous increase in the number of satellites up there: the total of functional devices up to last summer was about 2,000. This proposal would increase that 7-fold. These devices have a life span - of about 5 - 7 yrs - after which they have to be disposed of by guiding them down to a low earth orbit and allowing them to burn up as they re-enter the atmosphere. Three of those launched last year are failing to respond to communications from controllers so are already space junk, but we are told not to worry because their orbits will eventually decay to the point where they burn up anyway. Hmmm......


And then there is what seems to me to be the biggest issue: they are going to be visible. Indeed to the trained eye, they already are. Various astronomical bodies have already voiced concern at this and say it will affect their ability to take readings. The effect could be dealt with to an extent by reducing their reflectiveness (or albedo) - but so far this hasn't happened. Starlink say that will co-operate with astronomers by sharing information about flight paths etc, so that readings can be taken in between their passing. That looks to me like something that would be hard to manage, but it totally fails to deal with a simpler point: this is going to change the night sky: the constellations with which we are all so familiar could soon be indistinguishable from the geometric net of industrial hardware that will surround us.


Its important to note too, that this might only be the beginning. Samsung, Amazon and Telesat have all announced comparable systems.


Who has allowed all of this? The answer seems to be that nobody is there to stop it. The US fcc is licensing the bandwidth that will be used and I think there is some international co-operation on that. But that seems to be the limit of the regulation involved: you may need planning permission to build an extension to your house, or even to put in a new window, for fear of intrusion on your neighbours. But you don't need any permission to change the sky above us for ever.


various links below...


https://www.theguardian.com/science/2020/jan/09/spacewatch-spacex-elon-musk-launches-60-more-satellites-into-starlink-constellation


https://www.forbes.com/sites/startswithabang/2019/11/20/this-is-how-elon-musk-can-fix-the-damage-his-starlink-satellites-are-causing-to-astronomy/


https://www.space.com/spacex-starlink-satellites-megaconstellation-surprise-astronomers.html


https://en.wikipedia.org/wiki/Starlink_(satellite_constellation)







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