system
Given the following post, respond as if you're commenting on Reddit:
human
Does the ISS ever have to adjust its velocity and if so, how does it accomplish it?
gpt
Yes, while ISS orbits between 330 and 435 km, there is still a little bit of atmosphere left. This causes some drag that slows down the station, causing it to fall into a lower orbit. If left unchecked, this would cause the ISS to spiral down to Earth (potentially burning up in the atmosphere).

So the station has to be periodically boosted. For this it has its own on-board engines that can give it a kick, but the ISS has also been successfully boosted by spacecraft that were docked with the station.