> 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 areas (e.g. the pacific ocean), the likelihood of spotting one is very low.
Hope that helps answer your question, even it wasn't necessarily meant seriously :)
>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.
Wow ... is it economical to replace the entire constellation every 5 years? How does the business side work? Or is it just a great money-burning party?
This is a large part of why they're pushing so hard on Starship. Falcon 9 is great and wildly economical, but it's not enough to make Starlink profitable in the long term. They need Starship to make that happen.
They also want to make Starlink satellites bigger, which also requires Starship's much larger diameter.
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.
Starlinks are actually built so that nothing sizeable remains at all after reentry. This even delayed the laser coms a bit, as the original laser mirrors were too sturdy & so pieces of them could theoretically make it through.
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.
Actually the person you replied to somewhat incorrectly. They're not targeted re-entries because the on-board propulsion of Starlink is too low to precisely control the re-entry location. However instead the satellites are designed to be intentionally "demisable" meaning that every portion of the satellite should vaporize/turn to char/dust during re-entry.
Put another way, every kilogram of Starlink spacecraft has as much energy "stored" in it's motion as around 4-5 tons of TNT.
> Actually the person you replied to somewhat incorrectly. They're not targeted re-entries because the on-board propulsion of Starlink is too low to precisely control the re-entry location.
SpaceX says otherwise, see [1]
SpaceX spokesman James Gleeson, when asked about the 10 satellites, said SpaceX is “performing a controlled de-orbit of several first iteration Starlink satellites,” using onboard propulsion.
There's a difference between unscheduled deorbiting (as happened to about 40 satellites after a solar storm in February 2022) and a scheduled deorbiting manoeuvre trigged by ground control. Starlink satellites use electric on-board propulsion (Krypton powered Hall thrusters) that doesn't run out as quickly as chemical or cold gas gas thrusters. There's also not much precision needed to avoid major population centres - Earth is pretty big after all.
Not quite. The spokesman is a talking about controlled deorbit, where propulsion is used to actively lower altitude rather than coasting down due to atmospheric drag. This is in contrast to controlled reentry, which targets an ellipse on the ground where any debris would fall. The latter requires either much more thrust than their electric thrusters have, or a much steeper reentry angle than Starlink's circular orbits.
Starlink satellites are pretty well aerodynamically balanced when in their "ducked" orientation, but are not going to be able to overcome aerodynamic torques below 200 km or so, meaning they will be unable to point their thrusters in target directions. At that point, there are still 1-2 days before reentry will occur. Hour-to-hour variability in tropospheric atmospheric density due to solar flux levels and geomagnetic activity means that the precise reentry time will be unpredictable to within a few hours (which equates to anywhere along the ground track of a few orbits).
And I'm telling you that the statement is incorrect. Starlink is not equipped with propulsion capable of doing that. They use electric propulsion, which means they can't target a re-entry. They can de-orbit it on a time scale, but they cannot do what is conventionally described as a controlled de-orbit. Meaning they cannot precisely target a general area of the Earth. They can target re-entry within a couple hours to days, but that's still all over the world.
Now, none of this is an actual problem as they're entirely demisable, but the statement that they can achieve controlled de-orbit is false.
I think there's a major misunderstanding on what "precision" and controlled de-orbit means here. Precision doesn't mean a targeted landing. It simply means aiming for a certain latitude by adjusting the orbit accordingly, which is sufficient to make the difference between deorbiting over a desert or ocean and potentially densely populated coastlines or other population centres (central Europe comes to mind). Controlled means that it's the operator who decides how exactly and when that happens, i.e. they remain in control of the spacecraft and its orbital parameters throughout the process.
So if you control the orbit, you control the zone of re-entry. It's not a point or an oval in this case, but a "strip" a couple of kilometres wide. This is all that's required if the goal is to avoid major population centres.
This also means that the target is not "all over the world" as you put it - it's a very narrow, well defined stripe/trace (remember the scale we're talking about here!) and that's exactly what a controlled de-orbit is about.
Here's a blog post by ESA that talks about what controlled reentry means. https://blogs.esa.int/cleanspace/2018/11/16/basics-about-con... Controlled requires precise aiming towards a targeted location. Not just the operator deciding to do something. By ESA's definition Starlink de-orbits aren't even "semi-controlled".
This generally involves landing at a precise location of the Earth. It goes by a nickname, Point Nemo. A patch of ocean in the south pacific farthest away from any land. It's also far from standard shipping lanes. If you can't achieve this type of targeting it, definitionally, is not a controlled re-entry.
> It simply means aiming for a certain latitude by adjusting the orbit accordingly
You cannot aim a satellite for a "certain latitude" as orbits cannot follow lines of latitude. That's not how orbital dynamics work. I'm not quite sure what you meant to convey here.
> This also means that the target is not "all over the world" as you put it - it's a very narrow, well defined stripe/trace (remember the scale we're talking about here!) and that's exactly what a controlled de-orbit is about.
No it's all over the world, definitionally, because low earth orbits cross the entire planet as the Earth rotates. The possible locations the satellite can re-enter span a large portion of the globe from the negative to the positive latitude equivalent to the spacecraft's inclination.
I think you have a major misunderstanding yourself. If there's some term I'm using that you don't understand please let me know so I can help you.
There are so many that I spot them with my telescope while watching the sky with some frequency. In the last year I've probably caught 6 or so. It's just a spot of light passing through the view, nothing spectacular, but I think it would have been virtually impossible 20 years ago.
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 atmosphere), and the satellite - being at high altitude - is still illuminated.
As they pass overhead, you can often see them suddenly vanish as they pass into the Earth's shadow.
The International Space Station is a good one to find, as it's quite bright (very large).
There are various websites and apps; some phone apps use the GPS and magnetometer to show you what direction and time to look, and a search tool to look for visible objects at your location. It used to be really good with the old Iridium satellites, which gave a bright flash due to their large flat antennas.
> Basically this happens just before sunrise, and just after sunset.
I've seen plenty of satellites in the middle of the night, from very dark areas (wilderness). They look like stars, only they move more quickly. These observations go back a decade, at least.
I was mostly referring to the brightest things like the ISS, Starlink and (formerly) Iridium satellites, which are in low Earth orbit.
Higher orbits are visible for longer, due to the angles involved: because they're so high, such satellites can remain illuminated with the Sun further below the horizon. The Moon is the most extreme example: it's almost never in Earth's shadow.
> because they're so high, such satellites can remain illuminated with the Sun further below the horizon. The Moon is the most extreme example: it's almost never in Earth's shadow.
That's a very good question. I'm sure of what I've seen, many times over years:
I can tell you that they look like stars - so much that I need a reference point, an actual star or planet, to verify they are moving and not a 'stationary' star (judging movement being otherwise very difficult at that distance). They move very steadily, horizon to horizon, or as far as I can track them. A wild guess, based on memory, is one might take 5 or 10 minutes to cross between my horizons (usually I'm not on a plain - trees, hills, mountains may elevate my 'horizons' and reduce the distance).
Natural celestial object? No way a star is moving that fast relative to other stars and Earth's horizons. Asteroid? That seems hard to believe, due to size and illumination. Comet? Are there lots of tiny ones? I never see tails. Maybe a meteorite entering the atmosphere that doesn't yet have a tail?
Other human-made objects? Airplanes would look bigger and have colored, blinking lights - I've seen plenty of airplanes at night. Maybe there are higher flying airplanes without the colored and blinking lights? Are they illuminated whitish, and so far away they'd look like stars?
I've seen them so many times, I'm confident that I could take anyone to a wilderness area on a clear night and find one within 15-20 minutes, probably less.
> A wild guess, based on memory, is one might take 5 or 10 minutes to cross between my horizons (usually I'm not on a plain - trees, hills, mountains may elevate my 'horizons' and reduce the distance).
Yup 5-10 minutes is right. It depends on the orbit altitude and the height of the pass.
You can use sat tracker apps to identify which one you're seeing. I do this sometimes because I'm a ham radio operator and I track the one I want to use sometimes with a directional antenna.
> No way a star is moving that fast relative to other stars
No star moves relative to other stars when viewed from earth. They are all so far away they appear static. The starscape rotates as a whole (well it doesn't, the earth does, but to the observer it seems that way), but relative to each other they absolutely don't move.
If they do move, it is definitely a sign to stop drinking :) :)
> Asteroid? That seems hard to believe, due to size and illumination.
Also asteroids move way faster across the sky than a satellite. And they're rare except during that time of the year when they're really common.
> Comet? Are there lots of tiny ones? I never see tails.
Comets are incredibly rare in this galactic neighbourhood.
> and Earth's horizons. Asteroid? That seems hard to believe, due to size and illumination. Comet? Are there lots of tiny ones? I never see tails.
I grew up in a rural area, on a moonless night, without a fire, as well as giving your vision some time to adjust to the darkness, you can see crazy amounts of stars along the Milky Way plane.
I would guess, reflected moonlight (moon over the horizon) would be enough to light up the dot well enough to see unaided.
Between when the sun first disappears below the horizon and when (nearly) all its light disappears, i.e., the end of astronomical twilight when the Sun's center is 18 deg below the horizon, seems to be about 90 minutes.
It's been awhile, but I'm pretty sure I've seen these much later than that. I'm talking about lying in a sleeping bag, looking up at the amazing starfields of pitch-black wilderness nights (tip: never use a tent except in extremis - look what you're missing!).
To me, they look like little white dots moving across the sky. Brightness can change as they move too. It'll start off bright and then as it goes away it eventually disappears entirely. Since I usually sit in the same position in the hot tub, I've come to notice that I usually see one of them cross a pretty specific path from north to south, so I've gotten used to looking in that part of the sky as I'm sitting there. It happens so frequently, I get a little disappointed if I don't see one!
Planes are similar, but tend to have flashing or colored lights and obviously aren't as far away.
I'm in a big city, but close to the ocean so I have a bit less light pollution. The city is also heavy military, so that could be part of the frequency.
Update: if you're near any of the spacex launches, you can watch the rocket too. I'm house sitting in Irvine, CA and saw the Monday launch go right near the house. Amazing to watch the plume from the rocket!
Just throwing this out there, but has anyone else seen 'formations' of satellites? I've only seen them once but there were about 5 to 10 (it was a while ago) of what I'm assuming are satellites moving in a line formation at high speeds across the night sky. They're too distant and too fast to be planes so I'm assuming they are some sort of military formation of satellites?
That's often a recently launched StarLink formation -- the bunch up in a line when deployed, and have to be maneuvered over several weeks to spread out and take different orbits.
I don’t know how you would know that. People are very bad at seeing distances at these scales.
If they were indeed satelites they could be starlink satelites. They are put into orbit as a bunch together and then they spread along their orbital path as they take up their position.
If you could recall more details then maybe we can figure out more exactly what this might have been. (Such as where you were, which direction you were looking at, when did this happen, how fast did they cross the sky and how far the dots were from each other. Were the line spread in the direction they were moving or sideways?)
I saw ISS in formation with visiting spacecraft a couple times - once with Space Shuttle back in the day and at least once with Dragon. Looks pretty interesting. :)
My impression was that you can only see them as they reflect sunlight in your direction. As the angle formed between you, the satellite and the sun changes, you will first not see the satellite, then see, then not see it again.
And of course, if it is 3am, and there is no sunlight at any altitude because the sun is on the other side of the world, no satellites are visible.
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.
My tip is that the very central part of your field of view has worse night vision than the rest (trading off for higher resolution instead), so if you spot something moving in your peripheral vision, don’t try to look straight at it or it’ll disappear; instead, look slightly to the side, and it’ll be easier to see (although maybe blurrier).
You probably just thought it was a star or a plane. They move but relatively slowly (even a fast LEO sat will cover the sky in about 5 minutes). They look just like a star apart from moving slowly. Depending on angles they can look pretty dim, especially the latest SpaceX sats. But the ISS is usually really bright because it's so huge and technically it's also a satellite.
You can tell them apart from a plane because they don't flash.
Edit: But yes there are several conditions that need to be met to see them like the other posters have mentioned. But every clear night near dusk or dawn you will see sats for sure. There are just so damn many in LEO now.
It depends where you live certainly - if you live close to a big city you will probably never see them. But there are places - like New Zealand - where you can see them fairly often. There are some online trackers you can use.
The easiest satellite to see is the ISS. NASA provides times when it can be seen from any given place. I subscribe to the SpotTheStation mailing list.
In general, you can see a satellite when it is overhead and illuminated by the sun. In the evening, it will appear in the west, moving towards the east ( almost all satellites go this way, not just ISS ). As it goes farther east, heading towards darkness, it will fade away. The ISS is bright enough to see a reddish tinge as it passes through sunset light.
Yeah. With Starlink satellites, you need a lot of luck with the conditions to see them. I've seen them a handful of times and I'm in a relatively dark sky location.
ISS is often visible in the middle of the day even in bright midday Southwest sun, if you know where & when to look.
It takes several minutes for your eyesight to adjust enough to spot them with the naked eye. You can use websites to know when one is likely to pass overhead. Choose a suitable time (see: everyone else, basically right after dusk), and then lie down and stare up about 15-minutes ahead. Mushrooms are optional, they increase the chances of seeing something but decrease the chance that what you saw was real.
https://james.darpinian.com/satellites/ Put in your location and it will tell you when and where to look at the sky to see one. Works great for me and hopefully it will work for you.
If the seeing is good it's actually possible to spot up hundred satellites with the unaided eye. Due to light pollution, it's unlikely to spot one in most places, though. The ISS at least should be easily visible due to its size, even in places that aren't particularly dark.
Which also makes me wonder how many of the shooting stars I've seen recently are just old starlinks burning up.