NASA astronauts Peggy Whitson and Jack Fischer are getting ready to perform the emergency spacewalk outside the International Space Station (ISS) on Tuesday, May 23 to replace a relay box, known as a multiplexer-demultiplexer (MDM), that failed on May 21.
There are two MDM devices installed outside ISS, and their job is to control exterior systems like solar arrays, radiators, cooling loops, radiators, etc. The MDM that was upgrade in March failed on May 20th.
According to NASA, the cause of this failure is not known yet.
After the failure, the space MDM started functioning, although NASA wants to replace the failed unit as earliest as possible.
According to NASA spokesman Dan Huot, the failure of MDM device will not have any impact on launch of SpaceX Dragon cargo ship to ISS scheduled for next week.
On Sunday, Whitson spent her day assembling the new MDM, measuring 10.5 x 14.9 x 16.4 inches and this is the unit that will be installed by astronauts on Tuesday.
The last spacewalk by astronauts on board was conducted by Fischer and Whitson on May 12.
Apart from these two astronauts, French astronaut Thomas Pesquet and two Russian cosmonauts are also present on ISS.
A press release from NASA HQ said:
NASA astronauts Peggy Whitson and Jack Fischer are preparing for an unscheduled spacewalk outside the International Space Station Tuesday, May 23. Live coverage will begin at 6:30 a.m. EDT on NASA Television and the agency’s website.
Whitson, Expedition 51 commander, and Fischer, flight engineer, will replace a critical computer relay box that failed May 20. The relay box, known as a multiplexer-demultiplexer (MDM), is one of two units that regulate the operation of radiators, solar arrays and cooling loops. They also route commands to other vital station systems.
Because each MDM is capable of performing the critical station functions, the crew on the station is in no danger and station operations are not affected.
The failed relay box was installed in the space station truss March 30 during a spacewalk by Whitson and Expedition 50 commander Shane Kimbrough. Whitson prepared a spare data relay box May 21, and tested components installed in the replacement. She reported the spare MDM is ready to be brought outside to replace the failed unit.
The spacewalk to replace the failed box is planned to last about 2.5 hours. While Whitson is replacing the MDM, Fischer will install a pair of antennas on the U.S. Destiny Laboratory module to enhance wireless communication capability for future spacewalks.
The spacewalk will be the 201st in support of space station assembly and maintenance, the sixth spacewalk conducted from the Quest airlock this year, the 10th for Whitson and the second for Fischer.
Whitson, who already is the leading female spacewalker in history, will be designated extravehicular crew member 1 (EV-1) wearing a suit with red stripes. Fischer will be designated as EV-2, wearing a suit with no stripes.
Get NASA TV streaming video, schedule and downlink information at: https://www.nasa.gov/nasatv
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