STORY WRITTEN FOR CBS NEWS & USED WITH PERMISSION
An unexpected, quickly-planned spacewalk is on tap Monday to troubleshoot a problem preventing the International Space Station’s robot arm transporter from reaching a worksite where it can be locked down, a requirement before a Russian Progress cargo ship can dock later in the week.
The Progress MS-01/62P supply craft is scheduled for launch from the Baikonur Cosmodrome in Kazakhstan at 3:44:39 a.m. EST Monday (GMT-5; 2:44 p.m. local time). It is the first of two planned flights by Russian space freighters utilizing a full suite of upgraded avionics and navigation gear. If all goes well, the new hardware and software will be used aboard piloted Soyuz spacecraft starting next summer.
The Progress launched Monday will dock at the station’s Pirs module around 5:31 a.m. Wednesday, after Russian engineers check out the operation of the new systems during a 34-orbit rendezvous.
But first, a mobile transporter that runs along rails on the forward side of the station’s U.S. power truss must be locked in place. The lab’s robot arm currently is mounted on the mobile transporter and the shaking, or loads, imparted to the station during a docking could damage sensitive systems.
Flight controllers uplinked commands to move the transporter from worksite No. 4 to worksite No. 2 on the power truss last week, but the wheeled transporter stalled after moving about 4 inches. Engineers believe the brakes on one of two so-called CETA carts coupled to the transporter may be engaged, preventing the MT from moving.
To resolve the issue, Expedition 46 commander Scott Kelly and newly arrived flight engineer Timothy Kopra plan to venture outside the station Monday to make sure the brakes are disengaged and, if that fails to fix the problem, look at other possible solutions.
During a spacewalk Nov. 6, Kelly tied down a brake handle on the starboard CETA cart to minimize potential interference and it’s possible the brake somehow became re-engaged.
If that turns out to be the problem, the spacewalkers will simply release the brake and stand by while flight controllers send commands to move the mobile transporter back to worksite No. 4.
If the brake cannot be disengaged, the cart will be uncoupled and secured. Either way, the goal is to get the transporter back to work site No. 4 and firmly locked in place to clear the way for the Progress docking Wednesday.
The spacewalk is expected to take about three hours to complete. Depending on how it goes, flight controllers may add a few “get-ahead” tasks to the crew’s timeline. One possibility is ongoing installation of power and data cables that are part of a long-range plan to add new docking mechanisms to the station.
This will be the 191st spacewalk devoted to station assembly and maintenance since construction began in 1998, the seventh so far this year, the third for Kelly in the past month and a half and the second for Kopra, who carried out an EVA in 2009 during an earlier station mission.
For identification, Kelly, wearing a spacesuit with red stripes, will use the call sign EV-1. Kopra, call sign EV-2, will be wearing an unmarked suit. The spacewalk is expected to begin around 8:10 a.m. Monday.