Flight Engineer Kononenko photographs commander Volkov operating the manual Strela crane holding him. The commander stands on Pirs and has his back to the Soyuz spacecraft. Zarya is seen to the left and Zvezda across the bottom of the image.
The Strela (Russian Стрела, means Arrow) cranes are four Russian built cargo cranes used to move cosmonauts and components around the exterior of the Soviet/Russian space stationMir and the Russian Orbital Segment of the International Space Station. Mir featured two cranes mounted to its core module (delivered by Progress spacecraft), and the ISS also possesses two cranes, mounted to Pirs (they were carried to the ISS on Integrated Cargo Carriers, the first on STS-96, the second on STS-101). The cranes are structurally telescopic poles assembled in sections, which measure around 6 feet (182 cm) when collapsed but, when extended using a hand crank, measure 46 feet (14 m) long. This means that the cranes on Mir could easily reach all of the main modules of the complex, and those attached to the ISS can be used to transfer objects the full length of the ROS, from Zvezda to Zarya.
The largest robotic arm on the ISS, Canadarm2 weighs 1,800 kilograms and is used to berth and manipulate spacecraft and modules on the USOS, and hold crew members and equipment during EVA's. The ROS does not require spacecraft or modules to be manipulated, as all spacecraft and modules dock automatically, and may be repositioned or discarded the same way. Each strela crane weighs 45kg and can perform all necessary tasks, with substantial weight savings, less complexity and less maintenance than the Canadarm2.
An EVA planned for February, 2012 will see one Strela crane relocated to the docking compartment Poisk. Shortly afterwards another Strela crane will be relocated to Zarya. These moves are required because Pirs will be detached soon after and deorbited to allow the MLM Nauka to dock to the Pirs current location in mid-2012.
Strela cranes mount on opposite sides of the Pirs module.