International Space Station Astronauts Perform Spacewalk: Watch it Live

Two astronauts aboard the International Space Station (ISS) began what is planned to be a more than six hour spacewalk at 8:02 EDT today in order to prepare the orbiting lab for a new Russian module as well as perform additional installations on the station's back bone.

The spacewalkers include Chris Cassidy of NASA and Luca Parmintano of the European Space Agency, both of whom are flight engineers for the crew that arrived at the ISS on May 13. And while Cassidy is a spacewalking veteran with four previous excursions to his name, the task marks the first of its kind for Parmitano who is making history as the first Italian astronaut to walk in space.

According to NASA, after the two astronauts exited the hatch, Cassidy moved to the top of the Z1 truss to remove and replace a Space-to-Ground Transmitter Receiver Controller that failed back in December 2012.

Meanwhile, Parmitano headed out to the Express Logistics Carrier-2 on the starboard truss segment where he retrieved two experiments that were part of the Materials International Space Station Experiment-8, or MISSE-8.

The Optical Reflector Materials Experiment III and the Payload Experiment Container, which assessed the impacts of the space environment on materials and processor elements, are scheduled to return to Earth aboard the SpaceX-3 commercial cargo craft later this year, NASA reports

While on the starboard truss, Parmitano also photographed the Alpha Magnetic Spectrometer-02 in order to provide the research team a visual assessment of the condition of the state-of-the-art particle physics detector.

Later, the two spacewalkers will team back up to remove two Radiator Grapple Bars (RGBs) and install one on either side of the truss. Designed to aid in the removal and replacement of failed thermal radiators, these RGBs were delivered to the station aboard the capsule SpaceX-2. Parmitano will ride at the end of the station's Canadarm2 robotic arm under the control of Flight Engineer Karen Nyberg in order to transport the RGBs to the worksites where Cassidy will bolt them down.

As Parmitano rides the arm back from the starboard side to port, he will use this opportunity to remove a failed camera assembly - the Mobile Base Camera Light Pan-Tilt Assembly, which failed back in May 2012 just before the arrival of the Japanese H-II Transfer Vehicle. Before it broke down, the assembly was one of the prime viewing systems for monitoring visiting vehicles. 

As Parmitano does this, Cassidy will route power cables to support the addition of the new Russian Multipurpose Laboratory Module scheduled to arrive at the station later this year. Known as Nauka, the lab will serve as a research facility, docking port and airlock for future Russian spacewalks and will replace the Pirs docking compartment.

Once these tasks are complete, Cassidy will begin the installation of two Z1 truss Y-bypass jumpers to provide power redundancy and stability for critical station components, though it will not be completed until a spacewalk scheduled for July 16. In conjunction with some cable reconfigurations completed earlier this year inside the Unity node, the two Y-bypass jumpers will allow those aboard the ISS to quickly regain critical loads in the event of a loss of one of the external power modules without having to complete a spacewalk.

Finally, the two spacewalkers will round out the event by installing a multi-layer insulation cover to protect the docking interface of Pressurized Mating Adapter-2 mounted to the Harmony module.

During all of this, Astronaut Shane Kimbrough at Houston's Mission Control Center will be providing ground support. 

To watch NASA's live streaming of the event, click here.