<blockquote><font class="small">In reply to:</font><hr /><p>because it have to be serviced by the russian who launch from baikonur... in fact Mir was on the same altitude/inclination.<p><hr /></p></p></blockquote><br /><br />To elaborate a bit, it's because it has to be serviced by Soyuz rockets from Baikonur <i>and</i> Shuttles from Florida. The altitude is actually lower than what the Russians would prefer. It's more efficient to get to ISS from Baikonur (which is at 51 degrees north latitude, and it's not a coincidence that that's the same as the ISS's orbital inclination) so they can afford to fly a bit higher into that inclination. If the ISS is higher, it doesn't need to be reboosted as often. For this reason, while the Shuttle was unavailable for the last two years, they pushed the ISS into a higher orbit, out of the Shuttle's reach. They allowed it to drop back down in time for STS-114, of course.<br /><br />So the orbit is basically the best compromise between Soyuz rockets from Baikonur and Shuttles from KSC.<br /><br />The Russians actually originally intended Mir-2 (the core of which ultimately became Zvezda, during its greatly extended planning phase) to be in an orbit which Shuttles cannot acheive. It would've been a polar orbit, servicable by Soyuz rockets launched from the far north site of Plesetsk. This was intended to resolve the problem of renting space from a foreign country after the breakup of the Soviet Union and the loss of Kazakhstan. But for a variety of reasons this never became a reality. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em> -- The Tenth Doctor, "Blink"</font></p> </div>