Second Docking Attempt for Station Cargo Craft Successful
The ISS Progress 38 cargo resupply ship successfully docked to the aft end of the International Space Station’s Zvezda service module at 12:17 p.m. EDT Sunday. The docking was executed flawlessly by Progress’ Kurs automated rendezvous system.
The Progress spacecraft carries 1,918 pounds of propellant, 110 pounds of oxygen, 220 pounds of water and 2,667 pounds of experiment equipment, spare parts and other supplies to the station. It launched from the Baikonur Cosmodrome in Kazakhstan on June 30.
An attempted docking Friday, July 2, was aborted when telemetry between the Progress and the space station was lost about 25 minutes before its planned docking. As a result, the Progress vehicle continued on its trajectory and glided past the space station. At the time of the communication loss, the vehicle was approximately three kilometers from the station.
Progress conducted two successful firings of its engines Friday night to put the craft in a parking orbit around 300 kilometers from the space station. Another engine firing conducted Saturday morning began the process of returning the spacecraft back to the station for Sunday’s docking attempt.
Russian specialists told program officials the cause of Friday's aborted docking was what they termed a “cancel dynamic operations” command that instructed Progress’ computers to fly the vehicle past the station on its final approach for docking, as it is intended to do if the internal guidance system receives conflicting commands or commands that do not comply with its pre-programmed commands.
The Russian flight controllers said the command to cancel was caused by the activation of the "Klest" TV transmitter for the TORU manual rendezvous system in the Zvezda service module, which created interference with TORU itself, causing a loss of the TORU command link between Progress and the space station. TORU is used to override the Kurs automated rendezvous system, which Progress normally uses for docking, in the event Kurs experiences a problem. The TORU TV system is designed to provide a view of Zvezda's docking target to the station crew to dock the Progress manually.
The Russian flight control team confirmed that the Kurs system operated normally Friday and did not fail, as was initially believed. Kurs uses radio beacon signals beamed back and forth between the approaching spacecraft and the space station to measure distance between the two vehicles and the rate of closure by Progress to Zvezda.
The TORU system was not activated Sunday for the second docking attempt as a precautionary measure.
To make room for the new Progress supply ship, the Expedition 24 crew relocated the Soyuz TMA-19 spacecraft to the Rassvet module June 26. With fellow Flight Engineers Doug Wheelock and Shannon Walker aboard, Fyodor Yurchikhin undocked the Soyuz TMA-19 from the aft end of Zvezda, then manually piloted the vehicle to the Rassvet module where it docked successfully. It was the first docking to Rassvet, which was delivered to the station in May on the STS-132 mission of space shuttle Atlantis.