# Potential crash in orbit

Two things in orbit may crash. One’s a spent Chinese rocket booster, the other is a Russian satellite no longer in service. Probability is > 10%. They don’t give anything more exact than that, but it almost certainly means less than 20%. So quite likely it won’t happen, although you won’t realize that from all the headlines about it. From the tweets,

miss distance: < 12 meters
relative speed: 14 km/sec
combined mass: 2800 kg
altitude: 991 km.

A similar crash happened 11 years ago:

Hypothetically, how could this lead to someone getting super powers?

So who’s got Kessler Syndrome on their 2020 bingo card?

Supposed to miss by 25 m with the latest update. 15 km/s closing rate is really moving along though. Especially when one object has a lengthy boom sticking out of it.

We’ll know in about 4 hrs from now. (CPA is not quite 1:00 AM, Greenwich time.)

As I understand it, orbital velocity at this altitude is ~7.5 km/s. So a relative speed of 14 km/s would imply they are traveling in opposite directions, right? But aren’t orbiting objects usually launched to take advantage of the earth’s rotation, and would therefore be moving in more or less the same direction?

That would be true if all orbits went due east. They don’t. Instead most orbits are launched generally easterly. Other are even launched polar = mostly north south.

Here’s some pix of how various orbits look laid out over a flat map, not a globe. Imagine one satellite is following along one of those lines and the other satellite is on a different line. Lots of crossing paths there.

I agree I’m having some trouble making 7.5km/s orbital speed and 14km/s closure velocity make sense. That’s too head-on. Which makes me think some news media type got something wrong somewhere.

Had to do a bit of detective work due to weird/multiple naming, but here are the two objects:

The respective orbits:
970 x 1,203 km, 100.4°
970 x 1,013 km, 83.0°

So, near-polar orbits. The thing about polar orbits is that half the time they’re heading north, half the time south. There’s no east-ish preference like low-inclination orbits, so there’s a much greater chance of a head-on collision.

The objects match up on the low part of their orbit, which gives even more of a velocity boost. Velocity-wise, this is nearly a worst-case scenario.

Opposing polars is about the only way for the facts to line up. Excellent sleuthing.

The Kessler-esque consequences for a polar-oriented collision are extra severe. The debris will amount to more of a “doomsday shroud” as encountered by the vastly more numerous equatorial satellites cross-cutting the debris cloud on every orbit.

Thanks, guys, that makes sense.

What complicated the search is that “CZ-4C R/B” refers to the upper stage of a Chinese rocket, and a bunch of them with the same name are currently in orbit–but one of the articles mentioned a launch in 2009, which narrowed it down. Also, I couldn’t find COSMOS 2004 until I tweaked the spelling to Kosmos 2004.

Aside from the velocity, what also makes this bad is that the orbits are low, but not very low–if they were at 500 km, the debris would mostly deorbit through atmospheric drag after a few years. But at ~1000 km, the drag is negligible. So it has the speed of a LEO collision but without the inherent deorbiting of very low orbits.

one hour to go, is there any site where we can check what happened in more or less realtime?

I haven’t really found anything, but this Twitter account appears to run the radar (in New Zealand) that will have the earliest knowledge about a collision. There’s a good chance the first confirmation will come from them.

Yo! Right next to “alien invasion” two up from “cometary impact” .

Thanks!

I just noticed that the encounter shows up in the heavens-above site as well:

Their data comes from the public orbital elements, which isn’t as precise as the radar predictions. So the “minimum distance” they show (of 681 m) should be assumed to have ~1 km error. But the orbital track should be close. If they do collide, it’ll be nearly over Antarctica, with a 167° angle.

Things are getting exciting…

Time is up, no news yet though.

LeoLabs reports no indication of collision:

Damn! No superhero origins today.

Great to see. I look forward to reading their article.

I saw some comments on Reddit criticizing the company, which apparently put a much higher chance of collision from the event than NORAD. LeoLabs claims to have better radars, but they also sell their information, so maybe there’s reason to be skeptical. On the other hand, precise space object tracking is exactly what they specialize in, so why shouldn’t they be better at it? Maybe their article will explain some of the details here.

(I kept wondering why some guy named Leopold or Leonard had put his name to the labs, until I realized it’s for L.ow E.arth O.rbit )