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Starlink's laser system is beaming 42 petabytes of data per day

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Re: Starlink's laser system is beaming 42 petabytes of data per day

#151

Post by WanderPanda »

HPsquared wrote: post #134
gnrlst wrote: post #103

Earlier quoted context omitted.

How do you spot a satellite? I've never seen one.

1. The satellite needs to be passing overhead at an angle where you can see it, and clear skies etc. 2. The sky needs to be dark enough to see it (so twilight or night) 3. The satellite needs to be illuminated by the sun. 4. The satellite needs to reflect enough light that you can see it. Basically this happens just before sunrise, and just after sunset. So the ground and sky are dark (allowing you to see through the…

I remember chasing one of the iridium flares and it was very bright, even during the day

Re: Starlink's laser system is beaming 42 petabytes of data per day

#152

Post by carlosjobim »

HPsquared wrote: post #134
gnrlst wrote: post #103

Earlier quoted context omitted.

How do you spot a satellite? I've never seen one.

1. The satellite needs to be passing overhead at an angle where you can see it, and clear skies etc. 2. The sky needs to be dark enough to see it (so twilight or night) 3. The satellite needs to be illuminated by the sun. 4. The satellite needs to reflect enough light that you can see it. Basically this happens just before sunrise, and just after sunset. So the ground and sky are dark (allowing you to see through the…

In short: after sunset.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#153

Post by krisoft »

m2fkxy wrote: post #125
latchkey wrote: post #120

Earlier quoted context omitted.

I actually see them disappear long before they get to the horizon. My guess is just less reflected light on whatever is shiny on the satellite.

that and/or entering the Earth penumbra.

In higschool we did an experiment with one of our science teachers based on this fact. We measured the duratuon of the iridum flares and could use some basic geometry to estimate how high their orbit is based on where the shadow of the earth is.

I don’t remember the details anymore, but it was one of the coolest practical experiments we did.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#154

Post by versteegen »

why_at wrote: post #147

Random thought I just had: What are the odds of a rocket launch crossing through one of these laser links on its way to a higher orbit and disrupting traffic for a fraction of a second? I know space is really big and so the odds of a rocket hitting a satellite on its way up are incredibly low, but now we're talking about lots of lines between each satellite rather than just the satellites themselves. Are the odds sti…

> the odds of a rocket hitting a satellite on its way up are incredibly low

Aside, but it's not left to chance. They only launch when there's a gap in the space traffic.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#155

Post by oconnor663 »

aetherspawn wrote: post #139
qayxc wrote: post #104

Earlier quoted context omitted.

> Which also makes me wonder how many of the shooting stars I've seen recently are just old starlinks burning up. Probably close to none. The lifetime of the satellites is about 5 years give or take. According to this page [1], a total of 355 satellites have deorbited over the past roughly 5 years. That's an average of about 71 per year or about one every 5 days. Since planned disposals are done over uninhabited area…

If someone makes a mistake and the satellite deorbits in the wrong place, am I likely to be impaled by a satellite screw or something travelling at terminal velocity?

No, they burn up. You can think of how much work goes into the heat shields on spacecraft that are supposed to survive reentry. Satellites have none of that.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#156

Post by lxgr »

moffkalast wrote: post #113
nightpool wrote: post #105

Earlier quoted context omitted.

In the context of the full article ( https://en.wikipedia.org/wiki/Iridium_satellite_constellatio... ), it's clear they're talking about the polar orbits used by the Iridium constellation, which have "seams" around the Atlantic and the Pacific as the "first" set of satellites passing north-to-south overlap with the "last" set of satellites coming back south-to-north on the other side of their orbits. So of the 6 orbi…

Ah I didn't realize they have all of their stats in polar orbits, that's interesting. Starlink is mostly equatorial afaik, the higher latitudes aren't very well covered.

Most of Starlink's orbits have an inclination of 53 degrees, which I wouldn't really call equatorial anymore.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#157

Post by bdamm »

versteegen wrote: post #154
why_at wrote: post #147

Random thought I just had: What are the odds of a rocket launch crossing through one of these laser links on its way to a higher orbit and disrupting traffic for a fraction of a second? I know space is really big and so the odds of a rocket hitting a satellite on its way up are incredibly low, but now we're talking about lots of lines between each satellite rather than just the satellites themselves. Are the odds sti…

> the odds of a rocket hitting a satellite on its way up are incredibly low Aside, but it's not left to chance. They only launch when there's a gap in the space traffic.

Fair, but they don't compute and probably can't know the laser paths between Starlink nodes.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#158

Post by MeImCounting »

ortusdux wrote: post #33
heeton wrote: post #22

Don’t you mean 42million Gigabytes?

I was going to put 336,000,000,000,000,000 bits/day, but it seamed a bit overkill.

*seemed

I dont think theres anything having to do with seams or fabric in this conversation

Re: Starlink's laser system is beaming 42 petabytes of data per day

#159

Post by scottlamb »

oconnor663 wrote: post #155
aetherspawn wrote: post #139

Earlier quoted context omitted.

If someone makes a mistake and the satellite deorbits in the wrong place, am I likely to be impaled by a satellite screw or something travelling at terminal velocity?

No, they burn up. You can think of how much work goes into the heat shields on spacecraft that are supposed to survive reentry. Satellites have none of that.

I also think a screw at terminal velocity might not be particularly dangerous, similar to the popular "will a penny dropped off the empire skyscraper kill you?" question.

...which I suppose is closely related. The deorbiting satellite burns up because all that potential energy goes into heat because of the ~friction~ [edit: compression, thanks for the correction] that limits it to that low terminal velocity.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#160

Post by lxgr »

Scoundreller wrote: post #26
Symmetry wrote: post #20

Earlier quoted context omitted.

Right. The Iridium network had communication between satellites in different orbital planes passing each other but that was a pretty unusual capability.

I wonder how iridium actually handles the tracking (or if it’s just slow enough and lack of attenuation in free space just lets them blast it). And if they have zones where they don’t go to adjacent orbits, but instead go up or down within their orbit for the handover between orbits.

Supposedly they use steering, since the horizontal azimuth to adjacent-plane satellites varies from 0 to 65 degrees across an orbit: https://apps.dtic.mil/sti/tr/pdf/ADA348174.pdf
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