Special Report (Revised and Updated):Unplanned ISS Spacewalk Needed - rail car got stuck

The Mobile Transporter rail car,or "space train," that moves along with the attached Canadarm2 robot arm along a truss on the outside of the International Space Station has gotten stuck.It got within 10 cm of its target work site directly above the US laboratory,NASA said,but would go no further,perhaps because of a faulty brake handle.The MT must be checked out and repaired by the astronauts;moved to a work site;latched into place and electrically mated to the complex as a precaution for the docking of the new ISS Progress 62 cargo spacecraft on Wednesday following its Monday launch.
The unplanned spacewalk for the urgent repair will be made by American astronauts Scott Kelly,the ISS commander,who is currently on a one-year mission aboard ISS with Russian cosmonaut Mikhail Kornienko,and his colleague,flight engineer Tim Kopra,who just arrived at the ISS on Thursday.Kelly is a veteran of two ISS spacewalks,one of them just weeks ago,and Kopra had performed one during the Space Shuttle era.They began preparing their spacesuits on Friday.Kopra was aware before his Soyuz launch that he might have to make a repair spacewalk at any time during Expedition 46.The four other ISS crew members will be available to assist in preparing and monitoring the spacewalk,which it is estimated will take between three and three-and-a-half hours for the rail car repair.
NASA mission managers will meet on Sunday morning Eastern time to give the final go-ahead and decide if the walk will be made on Monday or Tuesday.The astronauts have been instructed to inspect the repair area to see if there are any other repairs they can make while they are out there.It will be the 191st spacewalk for ISS repair or assembly.Actually,they look forward to such challenges.
Update:The ISS Mission Management Team has approved the spacewalk for Monday morning beginning at 7:10 am Central time,or 8:10 am Eastern.It may be delayed,however,as astronaut Tim Kopra has to perform a fit check on his spacesuit before the spacewalk begins.If the repair is made expeditiously,the astronauts may then go ahead and route cables in advance of installation of the International Docking Adapter for the new US commercial crew vehicles;they may also open a door housing a power distribution system relay boxes just above the worksite to facilitate robotic replacement of modular components.