KENNEDY SPACE CENTER, Fla.--An unmanned Russian supply ship successfully docked with the International Space Station Sunday, two days after an interference issue with a television transmitter in a backup docking system triggered an unexpected abort.
For the second attempt, the backup TORU system was not activated, there was no interference, and the KURS automated rendezvous system worked flawlessly, lining the Progress up for a docking at the Zvezda command module's aft port.
After a brief period of station-keeping, the cargo ship resumed its approach, docking on time at 12:17 p.m. EDT as the two spacecraft sailed 220 miles above central Asia. A few moments later, hooks and latches retracted and pulled the Progress firmly into place.
"Congratulations on the successful Progress docking," a flight controller radioed from Moscow.
"Thank you very much," Expedition 24 commander Alexander Skvortsov replied from the station.
Launched Wednesday from the Baikonur Cosmodrome in Kazakhstan, the Progress 38 vehicle is loaded with 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.
During an initial docking attempt Friday, the Progress 38 craft aborted its approach and flew past the station, rotating slowly to keep its solar arrays face on to the sun.
It was the second Progress docking problem in a row for the Russians. During an approach May 1, a problem with the automated KURS navigation system aboard an approaching cargo ship forced Expedition 23 commander Oleg Kotov to take over manual control using the TORU backup system.
Russian engineers concluded the abort Friday was triggered by interference between the KURS system and a television transmitter that is part of the backup TORU system activated around the time of the abort. The result of the interference was a "cancel dynamic operations" command that prompted the Progress flight computers to abort the automated approach.
After tests to make sure redundant KURS components were working properly, Russian managers approved plans for a second docking attempt using the KURS system alone, telling the crew not to activate the backup TORU system. There were no apparent problems.