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US issues first ever fine for space junk to Dish Network
(www.bbc.com)
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I don't think they need much fuel in this case unless they want to be absolutely sure that they deorbit in the right place. The satellites are so small that might not even be needed.
Yes, it takes little fuel to destabilize one's orbit and eventually enter the atmosphere to burn up. It's more difficult if you need to make sure that the craft doesn't take others down during the procedure.
The satellites are in LEO so the orbit will decay on its own because of the atmospheric drag.
I don't think they really have to worry about taking down other satellites.