The ISS is a multinational space station served by the United States (NASA), Japan (JAXA), European Union (ESA), Russia (Roscomos), and Canada (CSA). Continuously occupied since November 2000, this American football field-sized station orbits the Earth at 5 miles per second, making a full orbit after 90 minutes. In the station itself astronauts work on research projects only possible in microgravity that help to advance worldwide understanding of many different technologies.
Containing a central chamber with auxiliary research components, usually with specialized equipment, the ISS has about as much room as a six-bedroom house and weighs about one million pounds, a large portion of it being contained by the eight solar arrays that produce about 84 kilowatts of power to keep the whole structure pressurized at normal sea level—the surface area taken up by the solar arrays is a full acre, enough to make the ISS the second-most visible structure in the night sky besides the Moon. The whole structure is maintained by 44 computers, with the main controllers running 1.8 million lines of software code on 1.5 gigabytes of hard drive space. As a comparison, Microsoft Office is estimated to have about 30 to 60 million lines of code and the smallest common hard drive space for a personal computer is about 128 gigabytes.
The current station crews for Expeditions 42/43 and 43/44, placed in space on November 23, 2014 and March 27, 2015, respectively, is researching topics like cell biology in space, Earth climate and geography, and, most famously, human physical and psychological effects with the Year in Space Project, which has Scott Kelly in orbit on the ISS for one full year while his identical twin retired astronaut brother Mark stays on Earth to better study the more subtle effects of space exploration, radiation, and microgravity.