The International Space Station crew successfully captured the Progress 38 spacecraft yesterday, after the unmanned Russian supply vessel sailed past the orbiting outpost on Friday.
A telemetry failure 25 minutes before docking prompted last week's unscheduled flyby. The cause was a glitch in the TORU teleoperated rendezvous and docking system, provoked by "the activation of the TORU 'Klest' TV transmitter*, which created interference with TORU itself", NASA explains.
Progress 38 was actually under the control of the KURS autopilot, with TORU in “hot standby”, but the failure of the latter "generated the command 'cancel dynamic operations' which aborted KURS automatic rendezvous mode and switched Progress to a safe, passive flightpath, as designed".
For yesterday's docking (more details here), TORU was "not activated", NASA notes.
Progress launched last Wednesday from Baikonur Cosmodrome in Kazakhstan, carrying "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".
Now suitably resupplied, the ISS's Expedition 24 US astronauts are enjoying their Independence Day holiday today.
*NASA elaborates: "The TORU TV system is designed to provide a view of Zvezda's docking target to station Commander Alexander Skvorstov, if he had to operate a joystick in the service module to dock Progress manually."