page_title: Mir
section_title: Power supply
hierarchical_section_title: Mir / Station structure / Power supply
caption_attribution_description: English: A survey view of the Spektr module of the Russian space station Mir, showing the module's solar arrays prior to the collision with Progress M-34.
context_page_description: Mir was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and later by Russia. Mir was the first modular space station and was assembled in orbit from 1986 to 1996. It had a greater mass than any previous spacecraft. At the time it was the largest artificial satellite in orbit, succeeded by the International Space Station after Mir's orbit decayed. The station served as a microgravity research laboratory in which crews conducted experiments in biology, human biology, physics, astronomy, meteorology, and spacecraft systems with a goal of developing technologies required for permanent occupation of space.
  Mir was the first continuously inhabited long-term research station in orbit and held the record for the longest continuous human presence in space at 3,644 days, until it was surpassed by the ISS on 23 October 2010. It holds the record for the longest single human spaceflight, with Valeri Polyakov spending 437 days and 18 hours on the station between 1994 and 1995.
context_section_description: Photovoltaic (PV) arrays powered Mir. The station used a 28 volt DC supply which provided 5-, 10-, 20- and 50-amp taps. When the station was illuminated by sunlight, several solar arrays mounted on the pressurised modules provided power to Mir's systems and charged the nickel-cadmium storage batteries installed throughout the station. The arrays rotated in only one degree of freedom over a 180° arc, and tracked the sun using sun sensors and motors installed in the array mounts. The station itself also had to be oriented to ensure optimum illumination of the arrays. When the station's all-sky sensor detected that Mir had entered Earth's shadow, the arrays were rotated to the optimum angle predicted for reacquiring the sun once the station passed out of the shadow. The batteries, each of 60 Ah capacity, were then used to power the station until the arrays recovered their maximum output on the day side of Earth.
  The solar arrays themselves were launched and installed over a period of eleven years, more slowly than originally planned, with the station continually suffering from a shortage of power as a result. The first two arrays, each 38 m² (409 ft²) in area, were launched on the core module, and together provided a total of 9 kW of power. A third, dorsal panel was launched on Kvant-1 and mounted on the core module in 1987, providing a further 2 kW from a 22 m² (237 ft²) area. Kvant-2, launched in 1989, provided two 10 m (32.8 ft) long panels which supplied 3.5 kW each, whilst Kristall was launched with two collapsible, 15 m (49.2 ft) long arrays (providing 4 kW each) which were intended to be moved to Kvant-1 and installed on mounts which were attached during a spacewalk by the EO-8 crew in 1991.
  This relocation was begun in 1995, when the panels were retracted and the left panel installed on Kvant-1. By this time all the arrays had degraded and were supplying much less power. To rectify this, Spektr (launched in 1995), which had initially been designed to carry two arrays, was modified to hold four, providing a total of 126 m² (1360 ft²) of array with a 16 kW supply. Two further arrays were flown to the station on board the Space Shuttle Atlantis during STS-74, carried on the docking module. The first of these, the Mir cooperative solar array, consisted of American photovoltaic cells mounted on a Russian frame. It was installed on the unoccupied mount on Kvant-1 in May 1996 and was connected to the socket that had previously been occupied by the core module's dorsal panel, which was by this point barely supplying 1 kW. The other panel, originally intended to be launched on Priroda, replaced the Kristall panel on Kvant-1 in November 1997, completing the station's electrical system.
caption: The four solar arrays on Spektr
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