The International Space Station arcs across the night sky at five miles a second. A great place to follow its glittering path is in the "dark skies" of a national park beyond the reach of urban light pollution and skyline clutter.

Since the first space station was launched in 1971, a total of nine have been placed in low earth orbit and occupied by astronauts over varying periods of time, mostly for purposes of scientific research (including the effects of zero-gravity on the human body). Eight of these structures have since been destroyed through reentry into the earth's atmosphere. The one still up there is the International Space Station.

Launched on November 20, 1998, the International Space Station is a multinational project conducted for peaceful research and designed for completion in stages over a period of more than a decade (last module scheduled for 2011). Before the end of this month the ISS will have established a new record for uninterrupted human occupancy, extending the tally to more than ten years. It is a truly amazing piece of technology.

The ISS orbits the earth at an average altitude of about 200 miles and an average speed of 17,239 mph. At this great speed -- about five miles a second -- it can complete 15.7 orbits each day. Some of those orbits carry it across the nighttime sky, and because the ISS is so large (about as big as a football field) it reflects a good bit of light and can be seen with the unaided eye under ideal conditions. Of course, you need to know when and where to look.

Weather conditions, lighting, and orbiting schedule permitting, the ISS normally makes its appearance above the western horizon and is visible for a few minutes before it disappears over the eastern horizon. The best time to see it is near dawn or dusk when near-darkness prevails at the earth surface while the space station passing high above reflects direct light from the rising or setting sun.

Most Americans live in places where space station viewing is very difficult. A whopping 99% of the U.S. population resides in areas that scientists consider light polluted. Sadly, two–thirds of Americans cannot even see the Milky Way from their backyard.

Viewing the space station can be an especially delightful experience for people overnighting in national parks with "dark skies" that favor stargazing. With this in mind, the National Park Service has partnered with NASA to provide helpful space station-spotting information to park visitors.

Knowing park locations in relation to the orbital path of the ISS, the Mission Control Center at NASA’s Johnson Space Center in Houston can precisely predict the times when visitors in various national parks people can watch the station arc across the night sky. Sighting predictions are available through several sources, including NASA's SkyWatch website, the agency's new mobile website, and the NASA iPhone and iPad applications. The information may also be available in park event calendars or conveyed via ranger night sky programs.

Obtaining the sighting schedule for any given U.S. national park is a simple matter for Internet users. Go to NASA's Satellite Sighting Information website, click on the state, and then click on the park. There you will find several week's worth of scheduling information for the relevant park. For example, the sighting schedule for October 1-16 at Yellowstone National Park indicates that there will be a three minute-long passage at 6:17 a.m. on Tuesday, October 5. Maximum elevation and approach/departure directional information is also provided.

If you need to obtain sighting schedules for non-listed places, such as your residence or favorite stargazing site, you can click to obtain a NASA Skywatch applet for that at the Satellite Sighting Information website.

Chad Moore, who manages the Park Service's night sky program, cautions that people who want to watch the space station in remote parks should be sure to check the sighting opportunities well in advance. Internet and cell phone coverage is apt to be unavailable or very limited in the remote parks with the best night sky conditions.

Park Service director Jon Jarvis has applauded the NASA/NPS space station viewing partnership, remarking that "The night sky is one of many spectacular resources national park visitors enjoy. Coordinating park locations with the space station flight schedule gives visitors another opportunity to reflect on human connections with the world and beyond."

International Space Station program manager Mike Suffredini wholeheartedly agrees: "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."

For further information, contact Jeffrey Olson (NPS) at 202-208-6843, Kelly Humphries (NASA) at 281-483-5111, or Stephanie Schierholz (NASA) at 202-358-1100.

Postscript: On Friday, October 1, a space station passage at 5:03 a.m. PST became part of the celebration of Yosemite National Park's 120th birthday. On October 2, a space station passage in the pre-dawn darkness helped mark the 120th birthday of Sequoia and Kings Canyon National Parks as well as the 42nd birthday of Redwood National Park.