Editing Mir (section)

===Orbit control===
[[File:MirOrbitalManoeuvres.svg|thumb|Graph showing the changing altitude of ''Mir'' from 19 February 1986 until 21 March 2001]]
''Mir'' was maintained in a near circular orbit with an average perigee of {{convert|354|km|mi|0|abbr=on}} and an average apogee of {{convert|374|km|mi|0|abbr=on}}, travelling at an average speed of 27,700&nbsp;km/h (17,200&nbsp;mph) and completing 15.7 orbits per day.<ref name="MirBIS"/><ref name="FinalBIS"/><ref name="OrbitCalc"/> As the station constantly lost altitude because of slight [[atmospheric drag]], it needed to be boosted to a higher altitude several times each year. This boost was generally performed by Progress resupply vessels, although during the Shuttle-''Mir'' programme the task was performed by US Space Shuttles, and, prior to the arrival of [[Kvant-1]], the engines on the core module could also accomplish the task.<ref name="SSSM"/>

Attitude<!--It's supposed to be ATTitude, meaning orientation – please don't change this to aLTitude.--> control was maintained by a combination of two mechanisms; in order to hold a set attitude<!--It's supposed to be ATTitude, meaning orientation – please don't change this to aLTitude.-->, a system of twelve [[control moment gyroscope]]s (CMGs, or "gyrodynes") rotating at 10,000&nbsp;[[Revolutions per minute|rpm]] kept the station oriented, six CMGs being located in each of the ''Kvant-1'' and ''Kvant-2'' modules.<ref name="MHH"/><ref name="MirGyros">{{cite report|title=Further Analysis of the Microgravity Environment on Mir Space Station during Mir-16|date=June 1996|url=http://gltrs.grc.nasa.gov/cgi-bin/GLTRS/browse.pl?1996/TM-107239.html|author1=DeLombard R.|author2=Ryaboukha S.|author3=Hrovat K.|author4=Moskowitz M.|publisher=NASA|url-status=dead|archive-url=https://web.archive.org/web/20090507111807/http://gltrs.grc.nasa.gov/cgi-bin/GLTRS/browse.pl?1996%2FTM-107239.html|archive-date=7 May 2009}}</ref> When the attitude<!--It's supposed to be ATTitude, meaning orientation – please don't change this to aLTitude.--> of the station needed to be changed, the gyrodynes were disengaged, thrusters (including those mounted directly to the modules, and the VDU thruster used for roll control mounted to the ''Sofora'' girder) were used to attain the new attitude<!--It's supposed to be ATTitude, meaning orientation – please don't change this to aLTitude.--> and the CMGs were reengaged.<ref name="MirGyros"/> This was done fairly regularly depending on experimental needs; for instance, Earth or astronomical observations required that the instrument recording images be continuously aimed at the target, and so the station was oriented to make this possible.<ref name="SSSM"/> Conversely, materials processing experiments required the minimisation of movement on board the station, and so ''Mir'' would be oriented in a [[Gravity-gradient stabilization|gravity gradient]] attitude<!--It's supposed to be ATTitude, meaning orientation – please don't change this to aLTitude.--> for stability.<ref name="SSSM"/> Prior to the arrival of the modules containing these gyrodynes, the station's attitude<!--It's supposed to be ATTitude, meaning orientation – please don't change this to aLTitude.--> was controlled using thrusters located on the core module alone, and, in an emergency, the thrusters on docked Soyuz spacecraft could be used to maintain the station's orientation.<ref name="SSSM"/><ref name="Dragonfly"/>{{page needed|date=February 2021}}