Editing Mir (section)

===Power supply===
[[File:Spektr before collision - cropped.jpg|thumb|The four solar arrays on ''[[Spektr]]'']]
[[Photovoltaic system#Photovoltaic arrays|Photovoltaic (PV) arrays]] powered ''Mir''. The station used a 28&nbsp;[[volt]] [[direct current|DC]] supply which provided 5-, 10-, 20- and 50-[[Ampere|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 battery|nickel-cadmium storage batteries]] installed throughout the station.<ref name="SSSM"/> The arrays rotated in only one degree of freedom over a 180° arc, and tracked the Sun using [[Sun sensor]]s 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&nbsp;[[Ampere hour|Ah]] capacity, were then used to power the station until the arrays recovered their maximum output on the day side of Earth.<ref name="SSSM"/>

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&nbsp;m<sup>2</sup> (409&nbsp;ft<sup>2</sup>) in area, were launched on the core module, and together provided a total of 9&nbsp;kW of power. A third, [[Dorsum (anatomy)|dorsal]] panel was launched on ''Kvant''-1 and mounted on the core module in 1987, providing a further 2&nbsp;kW from a 22&nbsp;m<sup>2</sup> (237&nbsp;ft<sup>2</sup>) area.<ref name="SSSM"/> ''Kvant''-2, launched in 1989, provided two 10&nbsp;m (32.8&nbsp;ft) long panels which supplied 3.5&nbsp;kW each, whilst ''Kristall'' was launched with two collapsible, 15&nbsp;m (49.2&nbsp;ft) long arrays (providing 4&nbsp;kW each) which were intended to be moved to ''Kvant''-1 and installed on mounts which were attached during a spacewalk by the [[Soyuz TM-11|EO-8]] crew in 1991.<ref name="SSSM"/><ref name="MHH"/>

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&nbsp;m<sup>2</sup> (1360&nbsp;ft<sup>2</sup>) of array with a 16&nbsp;kW supply.<ref name="SSSM"/> Two further arrays were flown to the station on board the {{OV|104}} 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&nbsp;kW.<ref name="SSSM"/> 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.<ref name="SSSM"/>