|Rick Mastracchio and Steve Swanson|
The station's backup computer, or Multiplexer/Demultiplexer(MDM) failed during routine testing on April 11, prompting teams on the ground to plan for today's contingency Extra-Vehicular Activity(EVA) by Mastracchio and Swanson.
Even though the second computer is still functioning normally, the faulty MDM, which is responsible for sending commands to some of the space station's systems including the cooling system, solar alpha rotary joints and mobile transporter rail car, needed to be replaced.
The spacewalking duo, with nearly eighty spacewalking hours between them, began their excursion at 14:26 Irish Time and exited the station's Quest Airlock soon afterwards. The pair soon got to work on the task in hand, as they made their way over to the work site on the station's S0 Truss.
Working harmoniously together, Mastracchio, who now ranks sixth on the all time list of cumulative hours spent on an Extra Vehicular Activity, made light work of removing and replacing the faulty MDM with Swanson. Upon its removal from S0, Mastracchio reported that he had in his possession, "An MDM, slightly used."
|After today's EVA, Mastracchio tweeted this picture saying:|
"In front of the Japanese modules on today's EVA. Not a selfie."
The pair swiflty began the installation of the replacement MDM, which has been stowed inside the Destiny Module of the ISS since April 2001. Altogether there are 45 MDMs aboard the orbiting complex.
With the new MDM installed, teams back on Earth in the Mission Control Center in Houston began conducting preliminary tests of the computer, and not long after, Mastracchio and Swanson were given the good news that the installation had been successful and that everything was working fine.
Just over two hours after beginning today's spacewalk, the pair began to head back to the Quest Airlock, wrapping up today's contingency spacewalk, which lasted just over two hours.
Today's spacewalk comes just hours after the Progress M-21M cargo ship un-docked from the aft end of the Zvezda Service Module to test its KURS automated docking system. The Progress will back away to a distance of 311 miles from the space station, before it redocks with Zvezda early on Friday morning.
This is Irish Space Blog.