computers governing command and navigation systems for Russian segments of the station, including two thought to have failed, were back online and would be tested over several days. The cooling system was the first system brought back online. Troubleshooting of the failure by the ISS crew found that the root cause was condensation inside the electrical connectors, which led to a short-circuit that triggered the power off command to all three of the redundant processing units. This was initially a concern because the European Space Agency uses the same computer systems, supplied by EADS Astrium Space Transportation, for the Columbus laboratory module and the Automated Transfer Vehicle. Once the cause of the malfunction was understood, plans were implemented to avoid the problem in the future. 2007 – Torn solar panel On 30 October 2007, during Expedition 16 and flight day 7 of STS-120's visit to ISS, following the repositioning of the P6 truss segment, ISS and crew members began the deployment of the two solar arrays on the truss. The first array deployed without incident, and the second array deployed about 80% before astronauts noticed a 76-centimetre (2.5 ft) tear. The arrays had been deployed in earlier phases of the space station's construction, and the retraction necessary to move the truss to its final position had gone less smoothly than planned. A second, smaller tear was noticed upon further inspection, and the mission's spacewalks were replanned in order to devise a repair. Normally, such spacewalks take several months to plan and are settled upon well in advance. On 3 November, spacewalker Scott Parazynski, assisted by Douglas Wheelock, fixed the torn panels using makeshift cufflinks and riding on the end of the Space Shuttle's OBSS inspection arm. Parazynski was the first ever spacewalker to use the robotic arm in this way. The spacewalk was regarded as significantly more dangerous than most because of the possibility of shock from the electricity generating solar arrays, the unprecedented usage of the OBSS, and the lack of spacewalk planning and training for the impromptu procedure. Parazynski was, however, able to repair the damage as planned, and the repaired array was fully deployed. Also, the OBSS will be left on the International Space Station because of its demonstrated versatility and ability to be left on the station for longer periods of time. 2007 – Damaged starboard Solar Alpha Rotary Joint During STS-120, a problem was detected