( 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 . iReport : Did you watch the launch ? Share your photos and video . 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 .
Discovery is on orbit to international space station . Discovery is carrying supplies , back to the space station . Three women planned during 13-day mission . Marks first time four women have been in space at one time .