MOSCOW, September 11 (RIA Novosti) - The...

The space agency was forced to miss two landing windows on Thursday due to the weather.

"Two more Discovery landing opportunities are available Friday at Kennedy Space Center. The first begins with a de-orbit burn at 4:41 p.m. EDT and ends with landing at 5:48 p.m. The second opportunity begins with a de-orbit burn at 6:17 p.m. with a landing at 7:23 p.m.," NASA said.

If the weather does not improve, the shuttle may have to land at Edwards Air Force Base in California.

The Discovery spent nine days docked at the International Space Station, and delivered a freezer for storing research specimens, a sleeping compartment, and other equipment.

The shuttle carried ISS flight engineer Nicole Stott to the station, and is bringing home U.S. Army Colonel Timothy Kopra.