in the starboard Solar Alpha Rotary Joint (SARJ). This joint, together with a similar device on the port side of the station's truss structure, rotates the large solar arrays to keep them facing the Sun. Excessive vibration and high-current spikes in the array drive motor were noted, resulting in a decision to substantially curtail motion of the starboard SARJ until the cause was understood. Inspections during EVAs on STS-120 and STS-123 showed extensive contamination from metallic shavings and debris in the large drive gear and confirmed damage to the large metallic race ring at the heart of the joint. The station had sufficient operating power to carry out its near-term programme with only modest impacts on operations, so to prevent further damage, the joint was locked in place. On 25 September 2008, NASA announced significant progress in diagnosing the source of the starboard SARJ problem and a programme to repair it on orbit. The repair programme began with the flight of the on STS-126. The crew carried out servicing of both the starboard and port SARJs, lubricating both joints and replacing 11 of 12 trundle bearings on the starboard SARJ. It was hoped that this servicing would provide a temporary solution to the problem. A long-term solution is a 10-EVA plan called 'SARJ-XL', which calls for the installation of structural supports between the two segments of the SARJ and a new race ring to be inserted between them to completely replace the failed joint. However, following the cleaning and lubrication of the joint, the results that have been noted so far have been extremely encouraging, to the point that it is now believed that the joint could be maintained by occasional servicing EVAs by resident station crews. Nevertheless, the data from the SARJ will require some time to fully analyse before a decision as to the future of the joint is made. 2009 – Excessive vibration during reboost On 14 January 2009, an incorrect command sequence caused the Zvezda service module orbital altitude maintenance rocket propulsion control system to misfire during an altitude re-boost manoeuvre. This resulted in resonant vibrations into the station structure which persisted for over two minutes. While no damage to the station was immediately reported, some components may have been stressed beyond their design limits. Further analysis confirmed that the station was unlikely to have suffered any structural damage, and it appears that "structures will still