The ability to see Discovery's parting shot (space)

Skywatchers in parts of the United States and Canada have a chance Friday night at NASA's space shuttle Discovery – on its mission last-ever – as it chases the international space station through the night sky.

The shuttle and space station will be visible to the naked eye as a separate entity, appearing as bright "stars" sailing across the twilight sky tonight. With clear skies Skywatchers in the northern and southern United States Canada have the best chances of seeing the two spacecraft.

The ISS can be seen easily in clear nights without a telescope, thanks to its enormous size and solar panels. It is as long as a football field and has enough living space for astronauts like a Boeing 747 jumbo jet.

On good passes, the space station is so intense it can compete with the planet Venus in the sky and appears more than 25 times brighter than Sirius, the brightest star in the night sky.

Discovery launched into space on Thursday and is scheduled to dock at space station Saturday at 2: 16 PM EST. Since Saturday night, both will appear as a singular object moving light.

The international space station makes a complete orbit around the Earth, about once every 91.5 minutes. Initially, after launching Thursday from Kennedy Space Center in Florida, the Discovery space station hauled through the sky from about 37 minutes.

By this evening, this gap will be decreased by around 15 minutes. This means that you will not be able to see the two spacecraft in the sky at the same time; rather, the discovery would appear first, followed by less than half an hour later from the space station traveling along essentially the same path.

Discovery is flying an 11-day mission to deliver a new storage room and humanoid robot to the international space station. This is the final flight of shuttle Discovery because NASA plans to retire the orbiter along with the rest of the shuttle fleet later this year.

NASA's shuttle Discovery is most-flown and is making its ninth trip into space.

Region of visibility
As regards its visibility, it seems that living in the United States of America Central and southern of skywatchers may be out of luck for the discovery or the space station. This is because the trajectories of spacecraft will transmit on paths that are too low or overhead during daylight hours, making them invisible.

More information on final final mission Discovery crew of Discovery: experienced six veteran astronauts and friends are flight of space shuttle Discovery to the international space station during the final voyage of the long and illustrious career of the orbiter. NASA confirms that debris has done evil Robot butler anchor ride shuttle orbit on Shuttle payload includes more closet space by the numbers: basic information about the shuttle scored a big image launch? Please share it

In the northern United States of America, there is the possibility of spotting the discovery and the train station on paths that start in the Western Sky then scroll over the bottom in a direction toward the North and East.

In most cases, the higher the gain the shuttle or space station above the Northern horizon will be about 15 degrees. The closed fist at arm's length measures about 10 degrees. So a pass 15 degrees would be approximately one and a half fists up from the horizon.

From southern Canada, two space vehicles will make a bow even higher across the sky. From Montreal and Calgary, for example, there are estimated passes that are more than 40 degrees above the horizon – almost halfway from the horizon to the point of overhead (called the zenith).

How brilliant are?
Most of the satellites become visible only when they are in the light of the Sun and the observer is in deep dusk or dark. This usually means shortly after sunset or before sunrise.

Because of huge dimensions and configuration of highly reflective solar panels of the international space station, is the brightest object artificial currently in orbit around the Earth.

Some have even caught a glimpse of ISS just before sunset or shortly after sunrise. And as a bonus, in the light of the Sun to directly out of the solar panels can sometimes do seem to flare briefly to ISS superbrilliance.

The space shuttle also appears as a very bright (magnitude 0-1); almost matching Sirius, although nowhere near as dazzling as the ISS.

When and where to look
What are the chances of centering Discovery and space station in your town?

You can easily find trying one of these four popular websites: Chris peat heaven above, Science @ NASA's J-Pass, NASA SkyWatch and Spaceweather.com.

Everyone will ask for your zip code or city, and respond with a list of suggested times. Estimates computed a couple of days ahead of time is usually accurate within a few minutes. However, you can change due to slow decay of the orbit of the space station and periodic reboosts Gurkhas.

Another great site is this one, which provides real-time satellite tracking and shows at any time during the day or night on which part of the land the shuttle or ISS happens to be.

Allows you to check websites often for updates as viewing conditions can sometimes change due to developments of the mission.

Joe Rao serves as an instructor and lecturer at New York's Hayden Planetarium. He writes of astronomy for the New York Times and other publications, and he is also a meteorologist on camera to News 12 Westchester, N.Y., click here for shuttle mission updates and a link to NASA TV.

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