Tune in to NASA TV at 6 a.m. Sunday for the launch of a cargo spacecraft that has important implications for the International Space Station's future.
If the 6:11 a.m. launch of a Soyuz-U rocket and robotic Progress cargo spacecraft isn't successful, it's likely crews would abandon the orbiting research complex next month.
"We're watching it very closely," said Mike Fossum, a NASA astronaut and commander of the station's three-person Expedition 29 crew, this week.
The last Progress launch failed to reach orbit Aug. 24 when the rocket's third-stage engine shut down prematurely. The third stage is almost identical to the one used by the Soyuz-FG booster that launches crews.
A successful launch should clear the way for a new three-person crew to launch Nov. 13. Any problems, and that flight would likely be postponed indefinitely.
The current three-person crew is due to return home Nov. 21, so the station would be left without people for the first time in 11 years if the next crew doesn't arrive before then.
The Progress 45 spacecraft is packed with 2.9 tons of food, fuel and supplies, including 1,653 pounds of propellant, 110 pounds of oxygen, 926 pounds of water and 3,108 pounds of maintenance gear, spare parts and experiment hardware.