Space.com - An unmanned Russian cargo ship that missed its first chance to dock at the International Space Station last week tried again Sunday – this time successfully linking up with the orbiting lab.
The Progress 38 cargo ship docked flawlessly while flying without the safety net of a remote control system that allows cosmonauts inside the space station to take command of incoming supply ships using a joystick should they veer off course.
The successful docking comes two days after the Progress 38 cargo ship's first failed docking attempt on Friday, in which the spacecraft sailed clear past the space station after aborting its delivery run.
"No doubt a sigh of relief on the part of the Russian control team," NASA commentator Rob Navias said in a NASA TV broadcast after today's smooth docking.
The orbital rendezvous occurred 220 miles above Earth as both spacecraft flew over the point where the borders of China, Kazakhstan, Mongolia and Russia meet. The Progress 38 supply ship launched Wednesday and delivered 2.5 tons of new equipment, fresh food and other supplies for the space station's six-person crew.
Russian engineers suspect it was interference between the Progress vehicle remote control system on the International Space Station and a TV camera on the space freighter that forced the incoming spacecraft to abort its first approach on Friday.
Instead of docking to an aft berth on the station's Russian Zvezda module, the Progress 38 cargo ship flew by at a range of about 3 miles to a point about 186 miles in front of the space station until another attempt could be made.
For Sunday's docking, Russian flight controllers opted to forgo any use of the remote control system, called the Telerobotically Operated Rendezvous Unit (TORU). Instead, they checked and rechecked the Progress 38's autonomous Kurs navigation system, as well as its backup system, to make sure the spacecraft was completely ready to dock itself at the space station.
Like Russia's crew-carrying Soyuz spacecraft, the unmanned Progress freighters are designed to fly themselves to the space station using the Kurs navigation system. Soyuz spacecraft can be flown manually by cosmonauts from inside the vehicles, while Progress can be guided in using the TORU system.
Both spacecraft have a long track record for reliability, though some have had to be guided in by cosmonaut every now and then. The last Progress to be docked under cosmonaut control arrived at the station on May 1.
"It is a bit surprising," former NASA astronaut Leroy Chiao, a former space station commander, told SPACE.com of the recent Progress malfunction. "These vehicles are very reliable, and the operations for getting them to stations are quite mature."
Packed aboard the spacecraft are 1,918 pounds of propellant for the station, 110 pounds of oxygen, 220 pounds of water and 2,667 pounds of dry cargo – including spare parts, science equipment and other supplies.
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