Progress 39 liftoff from Baikonur.
The crew of the ISS always needs resupply. The Russian Progress supply spacecraft are tailor-made for this mission, lifting such necessities as oxygen, food, spare parts, experiments and propellant for the station's thrusters.
Progress 39 blasted off from its base in Kazakhstan on Friday after a 2-day weather delay. After another 2-day journey, it arrived at the ISS this morning at close to 6 a.m. MDT. Using the Kurs automated rendezvous system, it was safely docked and the crew of ISS will begin unloading supplies.
On approach for docking, picture from ISS.
After the spacecraft has been unloaded, it serves as a container for waste and trash from the ISS. When full, or when the docking port is needed, the Progress craft is undocked and de-orbited to burn up in the atmosphere over the ocean.