NASA astronauts emergency spacewalk outside ISS at 5:30 PM; failed MDM data relay box to be replaced

NASA has called for an emergency spacewalk outside its International Space Station (ISS) following the failure of some equipment. Two NASA astronauts – Expedition 51 Commander Peggy Whitson and Flight Engineer Jack Fischer – are all set to go on a spacewalk on Tuesday to replace a data relay box that controls some key hardware on the ISS.

They will be replacing the multiplexer-demultiplexer (MDM) data relay box on the S0 truss that suffered a failure last week. However, the cause of the failure of the MDM is not known yet.

The programme managers of the ISS gave a go ahead to the spacewalk after reviewing preparations and crew readiness on Sunday.
The truss is home to the data relay box along with another system and controls the functionality of radiators, solar arrays, cooling loops and other station hardware.

However, the other MDM housed in the truss is working perfectly and providing uninterrupted telemetry routing to ISS’ systems. NASA said that there is no danger to the ISS crew and the failure of the MDM has created no impact on the activities on the space station.

A spare data relay box has been prepared by Whitson, who has also tested components installed in the replacement. She has confirmed that the spare relay box was ready to be used as a replacement for the failed MDM.

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Tuesday’s spacewalk is likely to begin around 8 am EDT (5:30 pm IST) and will last about two hours in duration to replace the failed box.

Also, Fischer will install a pair of wireless communications antennas on the Destiny Lab while Whitson replaces the failed data relay box. The antenna installation task was originally planned for the last spacewalk on May 12.

The contingency spacewalk will be the 201st in support of space station assembly and maintenance and the sixth conducted from the Quest airlock this year.

This will be the 10th spacewalk in Whitson’s career and the second for Fischer. On March 30, a spacewalk was conducted by Whitson and Expedition 50 commander Shane Kimbrough to install the same MDM with upgraded software.

In April 2014, Expedition 39 crewmembers Steve Swanson and Rick Mastracchio went on a similar MDM replacement spacewalk.

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(With inputs from PTI)