For Yosemite National Park's 120th birthday, a surprise guest is making an appearance 200 miles (322 km) above Earth.
Early birds to the park will be able to spot the International Space Station at 5:03 a.m. PST (8:03 EST) on Friday, Oct. 1, the anniversary of the park's creation.
The space station is often visible in the night sky from wherever you live, and is bright enough to be spotted even from urban areas. [How to Spot Satellites and the Space Station]
And so, of course, Yosemite isn't the only park that the ISS will fly over, and because the space station is more spectacular away from skyline clutter and light pollution, NASA and the National Park Service have released a list that tells national park visitors when to crane their necks skyward to catch a peek at the ISS.
"The space station is an international treasure, the size of a football field, and an inspiring sight in its own right flying through the sky at 5 miles per second," said Mike Suffredini, International Space Station program manager. "But I can't imagine a better way to share the experience with family and friends than during a trip to one of our national parks, where the stars seem to shine brighter whether they're natural or man-made."
The space station appears as a bright light moving steadily across the sky not unlike the nighttime appearance of commercial airplane a few miles out from landing. Details of the orbiting outpost are not visible to the naked eye.
Sighting predictions are available on NASA's SkyWatch website, via the agency's new mobile website, and NASA iPhone and iPad applications.
Sightings depend on lighting, weather conditions and the station's location as it orbits above Earth at 17,500 mph (28,200 kph). With the help of the Park Service, NASA recently imported the coordinates of 507 locations, including national parks and seashores, historic sites, monuments, and wild and scenic rivers into the website that people can use to see sighting information for areas near them. Visitors to the NASA site, http://spaceflight.nasa.gov/realdata/sightings/, can even subscribe to RSS feeds for their state and national parks near them, said NASA spokesperson Stephanie Schierholz.
The station's Mission Control Center at NASA's Johnson Space Center in Houston uses these locations and the orbital path of the space station to predict times when people can see the station zoom across the sky. Park rangers who present night sky programs and park event calendars also will have the information available for park visitors.
"It's a good idea to check the sighting opportunities ahead of time," said Chad Moore, director of the National Park Service night sky program. "Many remote national parks, which offer the best night sky conditions, have limited internet or cell phone coverage."
The space station usually appears over the western horizon and disappears over the eastern horizon in a matter of minutes. The best time to observe the station is near dawn or dusk, when the viewer is in near-darkness, and the passing station continues to reflect light from the rising or setting sun.