Astronaut James H. Newman waves during a spacewalk preparing for release of the first combined elements of the International Space Station. The Russian-built Zarya module, with its solar array panel visible here, was launched into orbit 15 years ago on November 20, 1998. Two weeks later, on December 4, 1998, NASA's space shuttle Endeavour launched Unity, the first U.S. piece of the complex. Endeavour's forward section is reflected in Newman's helmet visor in this image. During three spacewalks on the STS-88 mission, the two space modules built on opposite sides of the planet were joined together in space, making the space station truly international.
Since that first meeting of Zarya and Unity, the space station grew piece by piece with additions from each of the international partners built across three continents and leading to the largest and most complex spacecraft ever constructed. The space station, now four times larger than Mir and five times larger than Skylab, represents a collaboration between NASA, Roscosmos, the European Space Agency, the Japanese Aerospace Exploration Agency and the Canadian Space Agency, representing 15 countries in all.
In support of station assembly and maintenance, station and shuttle crews have conducted 174 spacewalks totaling almost 1,100 hours — the equivalent to nearly 46 days of spacewalks to build and maintain the complex. The station, with a mass of almost a million pounds and the size of a football field, is second only to the moon as the brightest object in the night sky.
Over the years, a great deal of research has been done on the space laboratory, which has already yielded tremendous results toward various fields. The science of the space station has provided benefits to humankind in areas such as human health, Earth observation and education. Many more results and benefits for both space exploration and life on Earth are expected in the coming years.