It is a scientific laboratory orbiting about 250 statute miles above Earth. The International Space Station (ISS) is a cooperative project among 16 nations, led by the United States; the other partners in what is called the most complex science project in history are Russia, Canada, Japan, the 11 nations of the European Space Agency, and Brazil. When completed, the ISS will have a mass of about 1,040,000 pounds, will measure 356 feet across and 290 feet long, and will have almost an acre of solar panels to provide electrical power to six state-of-the-art laboratories.

The ISS was built through a series of missions, the first of which was the U.S.-designed, Russian-built space module Zarya (Sunrise), launched November 20, 1998. The original plan called for completion of the ISS in 2004, but construction was extended into 2006. As of April 30, 2005, the ISS had been in orbit, and a work in progress, for 2,353 days, with a cumulative crew time in space of 1,640 days. (At that time, the United States had sent 11 expeditions to the ISS.) It then measured 240 feet across and 146 feet long, and weighed just more than 404,000 pounds.

Scientists believe that experiments conducted on the ISS will lead to discoveries in medicine and to the development of materials and new science that will benefit people around the world. The space station is also considered a monumental first step in preparing for future human space exploration.

Observers can track the ISS in orbit by using tools at NASA’s Web site (http://spaceflight.nasa.gov/realdata/tracking/index.html). Construction updates and a timeline can be found at the Discovery Channel Web site (http://www.discovery.com/stories/science/iss/iss.html).