NASA Objects To New Mega-Constellation, Citing Risk of 'Catastrophic Collision' (arstechnica.com) 39
NASA has formally commented on a request by a US company to build a mega-constellation of satellites at an altitude of 720km above the Earth's surface, citing concerns about collisions. From a report: This appears to be the first time that NASA has publicly commented on such an application for market access, which is pending before the Federal Communications Commission. "NASA submits this letter during the public comment period for the purpose of providing a better understanding of NASA's concerns with respect to its assets on-orbit, to further mitigate the risks of collisions for the mutual benefit of all involved," wrote Samantha Fonder, an engineer for the space agency. At issue are plans put forth by AST & Science, which intends to build a constellation of more than 240 large satellites, essentially deploying "cell towers" in space to provide 4G and possibly 5G broadband connection directly to cell phones on Earth. The company, based in Midland, Texas, calls its constellation "SpaceMobile" and has raised an estimated $120 million.
Finally! (Score:5, Insightful)
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"What I would like is some simple numbers"
If only astronomy was always so simple... But it ain't.
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I know so little of REAL mathematics, but I've been told that some problems are just not simple. I'm sure it has been compiled. Just not simply. Indeed, figuring out how these satellites will/could fail is by itself, not so simple I bet. Then considering the various failure modes and the effects, and soon you've got too many problems to easily describe or quantify. That is my complaint - we may not really understand the implications, the possibilities, of these constellations of satellites. And the astronom
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Re:No useful data about starlink and astronomy. (Score:4, Informative)
He wants to know *how often* this will happen. There isn't a straightforward answer to that. It depends on where your telescope is located, the direction you're pointing it in, the time of night, and the field of view you need.
If you are looking at a small target area near your local zenith at local midnight, the satellites in your field of view will be in Earth's umbra -- the darkest part of shadow. No problem there, but that's the best possible situation. The further you deviate from that the more likely you're going to see one of these things in your image.
How often this will happen is probably the wrong question. Ground based instruments will continue to operate for the same amount of time every night, but the area of sky they have an unobstructed view of will be reduced.
For professional astronomers, observation time on a major telescope is precious. You only get so much of it over the course of your career. So while ground based astronomy will continue, its productivity is bound to suffer, particularly research areas that require wide angle imagery [lsst.org].
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Actually, orbital mechanics isn't that complex, especially for things stuck in constant velocity orbits. Lots of satellites have well known orbits that it's entirely possible to predict when each satellite will be overhead. (This happens a lot - you can easily find out when the ISS wi
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That's neither here nor there. It's not that astronomers can't calculate where these things might be; it's that astronomers have to work their way around that, which is not always possible.
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So outside of the Earth's umbra (where the Earth's shadow blocks sunlight from glinting off these satellites), and a cone near the poles (I believe the orbital inclination maxes out at 57 degrees), you'll get an average of one visible sa
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If these satellites are fairly bright, surely they can just be removed from the image. I would think that long exposures are actually made up of a number of shorter exposures. You just erase the trace from the exposures that have them.
But what happens when these satellites start smashing into one another, and produce a haze of debris?
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then it will probably be one satellite crossing your field of view every few minutes. We'll probably come up with software which can automatically stop recording any time a satellite transit is predicted,
"stop recording"? That sounds almost like living in the 19th century with silver halide on glass plates.
You don't actually need to predict anything. Modern observations are done not with a single long exposure, but by many frames combined by computer. This solves not just satellites in frame, but also vibration form trucks driving past, stars blinking, etc.
And it is not an exotic technology either. Many mobile phones do it in night mode.
https://ai.googleblog.com/2019... [googleblog.com]
Re:No useful data about starlink and astronomy. (Score:4, Informative)
Are you looking for papers along these lines?
The Low Earth Orbit Satellite Population and Impacts of the SpaceX Starlink Constellation [arxiv.org]
First observations and magnitude measurement of Starlink's Darksat [arxiv.org]
Mitigation of LEO Satellite Brightness and Trail Effects on the Rubin Observatory LSST [arxiv.org]
Optical to NIR magnitude measurements of the Starlink LEO Darksat satellite and effectiveness of the darkening treatment [arxiv.org]
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Being the stupidest person in the room is the best situation... Because you're learning. -Martin Molin
A truly retarded quote; by the same logic, the poorest person in the room is the richest.
This "Martin Molin" is definitely well-versed on the subject of stupidity.
Re:No useful data about starlink and astronomy. (Score:4, Informative)
Your analogy falls flat though. The quote by Martin Molin doesn't say the stupidest person in the room is the smartest. It says that "being the stupidest person in the room is the best situation" since you have more knowledge to gain than someone that is the smartest. You would have been better to say that by the same logic the poorest person in the room is in the best situation since they have the most room to increase their wealth (percentage wise at least). It doesn't sound as nice but that would be more inline with the original quote.
Crazy Startup doesn't work out details. News @ 11 (Score:4, Informative)
Ok, we have some startup company, probably rushing to be first in the market. Who didn't plan all the details of a proposal in which NASA may have some objection to, do to the fact that they have been studying this stuff for over a half century.
Half of us will Yell "Government is stopping legitimate business!" The other half will Yell "Evil Business is putting people at risk!"
Where the probably correct action, is to work with NASA and see what they may be able to do to help fix their concerns.
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You haven't been reading slashdot lately. This sounds pretty accurate to me.
Is 720 km for 4G/5G reasonable? (Score:2)
An orbital distance of 720 km sounds far too distant for cellular access. The average distance to a satellite would be over 1000 km. Cell phones are not the greatest with regards to transmission strength - the antennas literally have to fit in your hands so there is only so much that can be done. This differs from Starlink which would have fewer users and much better ground based transceivers that are not limited to being powered by a cell phone battery. This proposal sounds like it is technically not
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Satellite dish Internet users will be able to explain ping and return problems... sure it's got bandwidth, but the ping sucks. Most TV guests are now relayed by landline or Zoom. Remember the delays of the 80s.
Re: Is 720 km for 4G/5G reasonable? (Score:2)
720km is 2.4‹ms. The signal has to go up and down and the range will generally be longer than the minimum but the altitude is going to add well under 10ms of delay on average (double for round-trip time). This is very different from geosynchronous birds which are 40 times farther away.
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It all depends on how far away you are putting your satellite(s). Currently most satellite Internet providers and TV satellite relays are using geosync orbits for their satellite(s). At those distances the ping time are quite large. Starlink is using a near earth orbit for their satellites that allows much lower ping times.
About damned time (Score:2)
NASA (and the FCC) needs start thinking ahead a lot further ahead on these. Musk got in there first, ok. Polluting LEO with multiple constellations of future Debris doesn't seem like a wise choice. Maybe the next proposal needs to include viable deorbit and reclamation plans?
Maybe plans B and C (Score:2)
I think they all include de-orbit plans. We all know about plans. As Moltke the Ender famously said:
No plan of operations extends with certainty beyond the first encounter with the enemy's main strength.
Moltke was therefore a strong proponent of having plan B and plan C.
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Sirius' LEO operations crashed into space junk, and all three satellites were destroyed. It was one of the main factors in having to merge with XM, and Sirius-only radios are being served by XM's Rock and Roll geostationary locations fleet on Siruis's frequencies for now, but eventually SiruiusXM will have 3x its original frequency allotment (XM's original bandwidth, space reserved for a third player that never showed up, and Sirius's original allotment) for a unified service that could both ramp up quality
Translation (Score:1)
So what? (Score:1)
Orbit it too high (Score:5, Informative)
It is natural to compare against Starlink. But the orbits are very different.
According to: https://www.spaceacademy.net.a... [spaceacademy.net.au]
At ~340km, Starlink satellites have a life between 1 month to a year without active maneuvers. i.e.: if the satellite "dies", it will fall back to Earth in a short time
At ~720km, the proposed satellites will have a life between 100 to 1000 years. i.e: they will stay there for a very long time, unless someone actively collects the "space junk"
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Starlink isn't at ~340km. Parts are at 500km and 1,200km.
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You are right. It turns out Starlink has multiple different orbits, including higher ones.
https://en.wikipedia.org/wiki/... [wikipedia.org]
But the current ones are at 340 miles (550km):
https://www.spacex.com/updates... [spacex.com]
According to Starlink it should take 5 years to deorbit:
https://spacenews.com/contact-... [spacenews.com].
I could not find a timeline or purpose of the higher orbits. I would speculate they could be for satellite-to-satellite mesh optimizations.
Midland? (Score:3)