(CNN) -- Space shuttle Discovery launched early Monday to deliver spare parts and science experiments to the international space station.

Discovery launched at 6:21 a.m. ET from the Kennedy Space Center in Florida

Discovery, with its crew of seven astronauts, is carrying supplies and science equipment for the international space station's laboratories. The 13-day mission includes three planned spacewalks, replacing an ammonia tank assembly and retrieving a Japanese experiment from the station's exterior.

Discovery is scheduled to arrive at the space station on Wednesday, and return to Earth on April 18 at 8:35 a.m. ET.

After this mission, there are only three shuttle missions remaining before the space shuttle fleet is retired.

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NASA said Discovery's mission will mark the first time four women have been in space at one time: Three women -- mission specialists Stephanie Wilson, Dorothy Metcalf-Lindenburger and Naoko Yamazaki -- comprise part of the Discovery's crew, while NASA astronaut Tracy Caldwell Dyson is already at the space station.

The launch comes three days after Russian spacecraft Soyuz TMA-18, carrying Dyson and Russian cosmonauts Alexander Skvortsov and Mikhail Kornienko, blasted off to the International Space Station from a Kazakhstan facility.

The space station, which orbits the Earth at a height of some 250 miles, is due to be finished next year and is about 90 percent complete.