Re: 3.6AU per year
How much is it decelerating by? Since it's in (mostly) vacuum, there wouldn't be much in the way of friction against other particles. And I wouldn't think collisions with micro-meteorites, etc. would make much of a dent in its speed. Other parts of it, yes, but not its speed! The sun's rays would presumably push it along by a tiny amount, collisions from behind by other space particles might do the same slightly, but unless it's been slowed down a lot by hitting the heliosheath / edge of the healioshpere, then what's been slowing it down? Oh, and the slingshots around planets (which the ISS obviously hasn't benefited from unless you count its orbit as a permanent slingshot around Earth) is another reason why I'd have thought it would be a lot faster than twice ISS's speed.