WASHINGTON, May 23 (Xinhua) -- Two crew members of the International Space Station were cleared for a contingency spacewalk on Tuesday to replace a data relay box, according to NASA.
The multiplexer-demultiplexer data relay box failed on Saturday morning for an unidentified reason.
After a review of spacewalk preparations and crew readiness throughout the following day on Sunday, the decision was made to press ahead with the spacewalk by Expedition 51 commander Peggy Whitson and flight engineer Jack Fischer on Tuesday.
The estimated two-hour spacewalk will begin at around 8 a.m. EDT (1200 GMT) or earlier, if the crew run ahead of schedule with its spacewalking preparations.
The data relay box is one of two fully redundant systems housed in the truss that controls the functionality of radiators, solar arrays, cooling loops and other station hardware.
The failure of the box has not disrupted the station's activities or endangered any crew members.
As the 51st and current expedition to the International Space Station, Expedition 51 conducts research on fluid physics, astrophysics and microbiology during April to June this year.