[image-51][image-94]Two Expedition 36 astronauts wrapped up a successful 6-hour, 7-minute spacewalk at 2:09 p.m. EDT Tuesday, completing the first of two July excursions to prepare the International Space Station for a new Russian module and perform additional installations on the station’s backbone.
Flight Engineers Chris Cassidy of NASA and Luca Parmitano of the European Space Agency began the spacewalk at 8:02 a.m. as they switched their spacesuits to battery power. After the two spacewalkers exited the hatch, Cassidy moved to the top of the Z1 truss to remove and replace a Space-to-Ground Transmitter Receiver Controller. This unit, one of two that allows for two independent strings of Ku-band communication for video and data, failed in December 2012.
In parallel to this, Parmitano headed out to the Express Logistics Carrier-2 on the starboard truss segment and retrieved two experiments that were part of the Materials International Space Station Experiment-8, or MISSE-8. The Optical Reflector Materials Experiment III (ORMatE-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.
While he was out on the on the starboard truss, Parmitano also photographed the Alpha Magnetic Spectrometer-02 (AMS-02) to provide the research team a visual assessment of the condition of this state-of-the-art particle physics detector.
[image-78]Cassidy meanwhile routed power cables to support the addition of the new Russian Multipurpose Laboratory Module scheduled to arrive at the station later this year. Cassidy routed cables from the Unity node to the interface between the Pressurized Mating Adapter-1 and the Zarya module. The station cosmonauts will complete that set up during a future spacewalk. The new module, known as Nauka, will serve as a research facility, docking port and airlock for future Russian spacewalks and will replace the Pirs docking compartment.
The two spacewalkers teamed back up to remove two Radiator Grapple Bars (RGBs) and install one on the port side truss and the other on the starboard side so they will be more strategically located. These RGBs, which are intended to aid in the removal and replacement of failed thermal radiators, were delivered to the station aboard SpaceX-2. While riding at the end of the station’s Canadarm2 robotic arm under the control of Flight Engineer Karen Nyberg, Parmitano transported the RGBs to the worksites where Cassidy bolted them down.
[image-126]As Parmitano rode the arm back from the starboard side to port, he used that 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, was one of the prime viewing systems for monitoring visiting vehicles. Mission managers plan to bring the assembly back to Earth for refurbishment and return it to the station later as a valid spare.
With those tasks complete and the RGBs installed, Cassidy began the installation of two Z1 truss Y-bypass jumpers to provide power redundancy and stability for critical station components. The bypass jumper installation will be completed during the July 16 spacewalk. In conjunction with some cable reconfigurations completed earlier this year inside Unity, the two Y-bypass jumpers will allow the station team to quickly regain critical loads in the event of a loss of one of the external power modules without the need to commit to a spacewalk.
Working briskly ahead of the planned timeline, Parmitano installed a multi-layer insulation cover to protect the docking interface of Pressurized Mating Adapter-2 mounted to the Harmony module.
The two spacewalkers then moved on to a couple of get-ahead tasks -- including the initial routing of cables from the Zarya module to Pressurized Mating Adapter-1 -- before moving back into the Quest airlock to end the spacewalk.
With the completion of his fifth career spacewalk, Cassidy now has a total of 29 hours, 42 minutes of total spacewalking time to his credit. It was the first spacewalk for Parmitano and the first for an Italian. Cassidy and Parmitano are slated to head back out the Quest airlock on July 16 for another spacewalk to complete the Z1 Y-bypass jumper installation and route additional cables.
Tuesday's spacewalk was the 170th in support of station assembly and maintenance, totaling 1,073 hours, 50 minutes.