A lot of the debris won't stay in the same orbit. It'll be like a mini-explosion, spraying out debris in every direction, but then add the existing velocity to

A lot of the debris won't stay in the same orbit. It'll be like a mini-explosion, spraying out debris in every direction, but then add the existing velocity to that. So yes, the debris will be in another orbit. The question is, how much of a change occurs. In the twitter thread, there is a Gabbard diagram that shows a prediction of the orbits that the pieces will end up in. The satellites currently have a reasonably circular orbit, with apogee (highest point) and perigee (lowest point) about 800km. After the collision, the apogee is likely to be higher and the perigee is likely to be lower, so the orbits won't be circular any more. The way this happens is - if the debris piece is knocked directly backwards, then its apogee will be about the same, but its perigee will be lower. If it is knocked forwards (yes, that can happen), then the apogee will be raised, and the perigee will be about the same, and the piece could remain in orbit for a long time. If it is knocked up or down, then both the perigee will be lowered and the apogee will be raised. If the perigee is low enough, then the pieces will scrape through the upper levels of the atmosphere, and de-orbit eventually. It looks like the prediction is for the lowest perigee to be about 200km. It may take a long time for even those pieces to de-orbit.