Russian cosmonauts Oleg Kotov and Sergei Ryazanskyi have ventured outside the International Space Station (ISS) on Monday for a second attempt to install two commercial Earth-observing cameras on the exterior of the Russian Zvezda service module. The cosmonaut duo - donning their Orlan suits - egressed the Pirs airlock at 8:00 AM central time for what is planned to be a six hour spacewalk.

The main objective of the EVA, designated EVA-37a, is to install a high resolution camera and a medium resolution camera on a biaxial pointing platform on the Zvezda service module.

The two cameras are part of a joint project of the Russian space agency and a Canadian company, which aims to provide high resolution views of the Earth to internet subscribers.

Other objectives include the retrieval of a material science experiment container mounted on the Pirs module.

The previous EVA, conducted on December 27, shared most of its objectives with EVA-37a.

Kotov and Ryazanskyi first installed a foot restraint to help them stabilize themselves at the biaxial pointing platform.

Then, they installed and connected the high resolution camera, which was followed by installation of the medium resolution camera.

After the cosmonauts finished routing power and data cables along Zvezda's hull and connecting the cables to the camera platform, controllers in the MCC in Moscow (MCC-M) proceeded with activation of the two cameras.

However, they discovered they were unable to receive telemetry from the cameras. Without telemetry, the controllers had no way of telling if the cameras were receiving power.

As discussions and attempts to activate the cameras went on in MCC-M, the spacewalkers continued with the planned tasks of the EVA. Finally, MCC-M controllers, along with the camera engineers, decided to uninstall the cameras and bring them inside the ISS for troubleshooting.

The rationale for returning the cameras inside the ISS related to the fact that the camera's internal heaters would not function without power, exposing the cameras to the extreme temperature differences of the day and night side of the station's orbit.

This led to deferring the remaining tasks to a later EVA, so that the cosmonauts had enough time and consumables to bring the cameras back inside.

Even with some of the tasks replanned for EVA-37a, EVA-37 still broke the Russian record of the longest spacewalk, with its eight hours and seven minutes duration.

In the weeks following the EVA, RSC Energia and MCC-M - with the help of the Russian crew - conducted troubleshooting of the problem, which was eventually attributed to a cabling issue inside the ISS.

"On January 2nd, the crew found a badly docked cable connector inside the Zvezda module," noted source information in L2's RS-37 section. The source information also noted that the only way to verify that the issue is resolved is to connect the cameras on the outside.

The EVA crew egressed the Pirs airlock at 8:00 central time. They first retrieved the two cameras from the airlock and took them with them to the Zvezda service module.

On the service module's plane IV is a universal work platform, called URM-D, on which the biaxial pointing platform (DPN) is installed.

The crew is in the process of installing the high resolution camera on the DPN, and the medium resolution camera on the URM-D base.

After they complete the camera installation task, the spacewalkers will proceed with tasks that were deferred from EVA-37.

The cosmonauts will also uninstall a cassette container (SKK2-SO) which exposes different material samples to the space environment, from the Pirs module, and bring it back inside.

After these primary objectives are completed, the crew will conduct a photo survey of the exterior of the Russian segment, if time permits. Crew

This is Kotov's 6th and Ryazanskyi's 3rd EVA, the third for the pair during Expedition 37 and 38. Both are wearing Russian Orlan suits, with Wireless Video System cameras borrowed from the US segment installed on their helmets.

The rest of the Expedition 38 crew is remaining inside the ISS, but are separated, as the transfer compartment between Zvezda and Zarya has to be sealed in case the spacewalking crew run into problems with the Pirs airlock and have to use the backup airlock - Poisk.

Mike Hopkins who arrived on Soyuz 36 with the spacewalkers, is isolated in the Soyuz for the duration of the EVA.

The rest of the crew - Rick Mastracchio, Koichi Wakata, and Mikhail Tyurin, are free to move around the US segment and the Zarya and Rassvet modules

Source: Voice of Russia