Saturday night (or whichever night it actually launches), Space Shuttle Discovery should be visible from the New York area as it roars up the eastern seaboard for its rendezvous with the International Space Station. Launch is scheduled for 8:47 PM ET. The shuttle should appear in the New York sky about seven minutes later, and remain visible for approximately 90 seconds.

To accommodate our Russian partners, as well as to maximize the area of the Earth it can observe, the ISS was placed in an orbit inclined 52 degrees to the equator. The shuttle -- which is bringing materials needed to rewire the space station's solar-powered electrical system -- has to reach a similar orbit to dock with ISS, so as soon as it leaves the Florida launchpad it rolls northeast, up the Atlantic coast (coincidentally following the Gulf Stream) until it turns due east around the latitude of London.

For us in New York, if weather conditions are right we'll see a bright starlike object, brighter (and yellower) than any airplane, appear to rise out of the southwest horizon about 7 and a half minutes after launch. It will arc across the southern sky to the east, reaching an altitude of about 8 degrees (about two extended fists) above the horizon. Near its peak, the bright glow of the Shuttle's main engines will cut off, and the shuttle will probably no longer be visible to the naked eye as it heads into orbit.

Night launches are the only time we New Yorkers can see the shuttle ascend to orbit, and for a multitide of safety reasons NASA now tries to avoid night launches as much as it can. Shuttle schedules aren't laid out very far in advance, so we don't know when (or if) there will be another night launch. However, with the projected retirement of the fleet in 2010 this might be the last time to see this sight.