Sat Track Cam is an amateur satellite observer's blog tracking spacecraft, debris, reentries, and classified or military satellites.
HN commenters recommend it as an example of amateur satellite trackers, and link it for coverage of the Zuma launch and Kosmos reentry.
That figure of 10 to 15 kJ can be very misleading about what it takes to propel something to such speeds. Put into 'TNT equivalent', it would take the entire energy of 50g of TNT to boost a 100g bolt by just 2 km/s. It's difficult to concentrate that much energy per mass in an explosion (which is leaky). To add further, most ASATs (including the Indian test) doesn't use explosives, but make a direct hit (hit to kill) from a suborbital trajectory (one that has much less energy than an orbital interceptor). The boosting comes mostly from fragmentation mechanics.
The satellite will still fragment with some fragments getting boosted up to a higher velocity. In addition, the propellants on the satellite and the kill vehicle might add velocity to the fragments too - though arguably less energy than if it was TNT. So, previous studies on US and Chinese ASAT debris cloud can be considered for a fair assessment. The Chinese test was at a higher altitude of 865km and US test was at a similar altitude. 'Gabbard plot' of these debris show the maximum altitude to be only around 3900 km for both tests. There could be untracked particles at higher orbits, but remember that the velocities of the debris is a random distribution (not sure which one) that tapers at extreme values. Odds of any debris crossing geostationary orbit is very low.
There is one additional significant point to consider. Boosted orbits mostly retain the altitude at interception (it's the diametrically opposite part of…
The fuel dump is to prevent explosions before reentry that could damage the spacecraft it just delivered or create unnecessary space debris.
https://sattrackcam.blogspot.com/2018/01/fuel-dump-of-zumas-falcon-9-upper-stage.html
> Rocket stages always carry excess fuel, as you don't want the engine to cut out prematurely by running out of fuel. So it always has a sufficient fuel margin. Once its work is done, this excess fuel is often vented, also known as "depressurization".
> Depressurization and fuel venting avoids the risk of the rocket stage blowing up, for example as a result of static electricity building up in the rocket stage. You do not want your rocket stage to blow up, as it creates an uncontrolable swarm of debris and includes the risk that particles are ejected into orbits where they do not decay quickly, adding to the space debris risk.
As for burning up, it's a bit of both. Some material burns up, some larger chunks splash into the ocean. Same thing happened a while back when the US dropped bits of Skylab on Australia. https://www.abc.net.au/news/2020-05-31/nasa-skylab-fell-to-earth-esperance-retrofocus/12282468
No, this is not true. First of all, every nation is required by space law to publish the initial orbits of every object they launch, as part of that taking responsibility I mentioned earlier.
The US Government further publishes tracking on pretty much every single thing in orbit of the earth larger than a few centimeters, to help satellite operators avoid space debris. They do obfuscate the current orbit of their own spy satellites (only publishing their initial orbit), but other countries and even private citizens around the world keep obsessive tabs on these things (e.g. https://sattrackcam.blogspot.com/). This sort of thing is easily within the reach of even a medium sized nation state that was interested in the investment: just need a couple of big ole radars and you can do it just like the US does. So if you do try and hide the resources of a nation-state can easily counter.
The solution to oppressive government is not technological, it's political. Prevent countries from going bad, retrieve the ones that have gone bad, it works out a lot better for everyone.
Not really, McDowell says it most likely is, but he's "not fully convinced". Langbroek says it's plausible his blog goes on the explain why and show other debris was found in the region, references McDownell, the anonymous Twitter account, Arianespace's doubt.
Langbroek even simulated the situation (in TU Delft Astrodynamics Toolbox[0]) with known information about recent flights. His blog post is pretty thorough.[1]
It's a shame Arianespace (who.. you know, may be worried about reputation or liability) hasn't just posted an image of the SYLDA shell they say it isn't.. that would clear up the speculation.
[0]: https://docs.tudat.space/en/latest/
[1]: https://sattrackcam.blogspot.com/2025/01/possible-space-debris-impact-in-kenia.html
There is a link buried on this page that goes into more detail:
http://sattrackcam.blogspot.dk/2011/11/lacrosse-5-disappearance-trick-captured.html
The key questions:
> Is it a matter of strongly differing reflectance properties of the satellite body with illumination angle? Is it some brightly reflecting appendage on the satellite disappearing from view? Is it a dark appendage on the satellite starting to block view of the illuminated satellite body, or casting a shadow on it? Is it due to some moving part of the satellite, e.g. a moving dish antenna?
It's all rather fascinating. Presumably having a stealth satellite is somewhat redundant as the objects will eventually be seen or tracked by other spacecraft or satellites?
Article says ±3.1 days, but the author wrote a newer entry (go to homepage, click on latest article, click through to space.com link¹) that says May 10, ±2.2 days.
Starting to get to the range where a timezone would be helpful!
Via Wikipedia², which will probably also get updated fast, this page says they'll stay updated with the latest estimate: https://sattrackcam.blogspot.com/2025/04/kosmos-842-descent-craft-reentry.html
¹ https://www.space.com/space-exploration/launches-spacecraft/new-images-of-soviet-venus-lander-falling-to-earth-suggest-its-parachute-may-be-out
² https://en.m.wikipedia.org/wiki/Kosmos_482