I was wondering the same thing. But I guest there would be technical problems with that, such as fuel burn off and wear and tear of it solar panels.

Would love someone with more knowledge to answer the question of why this probe cant be kept in Earth orbit until the next windows opens up.

You can't keep a satellite up without expending power, even Geosync satellites need a little power for station keeping, in a low earth orbit you have atmospheric drag to contend with, let alone avoiding all the bits and bobs that are spinning around up there. Send it to the moon, get some sort of work out of it, although I bet that's going to be tricky as the moon has a higher G than phobos.

"Possibly not as NASA is launching a Mars mission on Saturday"

yes, but are they launching into the same orbit as the Russian probe? If not, you need a different thrust vector. Also Curiosity is actually going to Mars, whereas the Russian mission is (was) to Phobos.

SImilarly, perhaps it could be boosted to a higher orbit and hibernate for a couple of years, but again it would then need a different thrust vector, and perhaps would not have enough fuel on board to do that.

@DJ 2

Well, why not send it to the moon and use a gravitational slingshot to whip it towards Mars? Would that not be worth a shot? That said, perhaps they've been planning that all along. And I suppose it's not just the getting-going that's the issue - the thing has to stop at the other end too.

Still, could be cool if it worked - like MacGuyver in space!

There are precedents. The Japanese Venus probe that failed to go into orbit in December 2010. A further attempt is planned in 2015. And Hayabusa which got back to Earth three years later than planned. Space probes seem capable of a lot when pushed.

Phobos-Grunt was intended to land on Phobos and then launch back to Earth again - so it needs to carry enough fuel to wander all the way back to Earth again. Curiosity is only going one way, so needs half as much fuel (for argument's sake, I doubt the planned routes to and from Phobos are identical) - so NASA can afford to go on the slightly more "expensive" route by making their fuel tanks a little bit bigger.

This wiki article gives a fairly good overview of how much "Delta-v" is used for certain transfers: http://en.wikipedia.org/wiki/Delta-v_budget

Interestingly, according to that page, orbit-keeping is fairly cheap (25-100m/s a year) versus the minimum 12,400m/s to Phobos and back. Assuming a couple of percent spare fuel on board, it might actually be possible to wait til the next window, on a fuel basis alone.

But isn't that a long detour just to get to a soundstage in arizona ?