International Space Station Celebrates 15 Years in Orbit

Thursday, Nov. 20, marks 15 years since the first piece of the International Space Station was launched into orbit. The space station's completion saw great triumphs as well as tragedy, the end of one era in human space exploration and the beginning of another. The ISS stands as a critical platform for advancing humanity's presence beyond Earth's orbit, and is, according to senior NASA scientist Harley Thronson, "the essential demonstration site and steppingstone for a sustained future in space with humans."

The station's construction was the result of unprecedented feats of engineering and ushered in a new era of international cooperation in space. On Nov. 20, 1998, the Russian Zarya Control module became the first component of the station to be sent into orbit. The first American-constructed piece of the station, Unity, was launched on Dec. 4, 1998. Two years later the Russian Zvezda module was installed and featured the station's first lab and living quarters. This allowed astronaut Bill Shepherd and cosmonauts Yuri Gidzenko and Sergei Krikalev to become the station's first crew members in November of 2000.

More components were added over the next several years including the US Destiny laboratory module and the Canadian Canadarm2 robotic arm, which further aided construction. The project came to a halt in 2003 following the Columbia shuttle disaster. For three years the station continued to be resupplied by Russian Soyuz spacecraft but construction would not resume until 2006 after the space shuttle moratorium.

The Discovery shuttle returned to the station in July of 2006 to deliver supplies and test safety procedures and in 2008 the Atlantis shuttle installed the European Space Agency's Columbus Laboratory. Nov. 2, 2010 marked the 10th anniversary of continuous human occupation on the ISS. The station has now seen a total of 202 occupants since Expedition 1 in 2000.

The final launches of the United States' space shuttle program were in support of the space station. In February of 2011, Discovery began its last mission to deliver the Leonardo Permanent Multipurpose Module. It contained the advanced humanoid robotic torso known as the Robonaut2 which was designed to assist astronauts during spacewalks. Later that year, the Atlantis shuttle was sent to the ISS to deliver supplies and to complete its construction. This would be the end of the shuttle program, 30 years after the first launch in 1981.

By the end of 2011, the station was more or less complete with all of its scientific and habitable modules successfully installed. The project has involved contributions from the US, Russia, the ESA, Canada and Japan including over 100 rocket and space shuttle launches, 160 spacewalks and an estimated price tag of $100 billion, making it one of the most expensive objects ever built.

Since then the space station has served as a zero-gravity environment for over 400 scientific experiments in fields ranging from biology, robotics, oncology, physical and materials science and Earth science studies. Already, research aboard the ISS has provided some remarkable findings. In April of 2013 the station's Alpha Magnetic Spectrometer observed particles that could confirm the existence of dark matter in the universe.

The space station is slated to get its own 3D printer in 2014 and in 2015 the U.S. and Russia plan to send a pair of astronauts to the station for an entire year to further study the long-term effects of space on human physiology. Much of the research done on the space station will be invaluable as human space exploration extends further away from low earth orbit to asteroids and even Mars.

The ISS represents an unprecedented coordinated effort on the part of many countries and agencies. It also provides a model for the future of space exploration with countries and private companies like SpaceX and Orbital Sciences working together to achieve common goals, building off of existing technologies and creating new ones in the process.

Currently, the station is supposed to be deorbited and dropped into the ocean after 2020, though there are ongoing discussions about whether or not its lifespan can be extended further. Either way, the ISS is a remarkable achievement, and 15 years later we are only beginning to see what it is capable of.

Robyn Johnston is a freelance science and technology writer, her online portfolio can be found here.