The pieces are coming together for NASA’s first space shuttle launch in more than two years as engineers prepare to roll the Discovery spacecraft out of its protective Orbiter Processing Facility (OPF).

The twin solid rocket boosters and a redesigned external fuel tank that will carry Discovery into orbit later this year stand already assembled in the vast Vehicle Assembly Building (VAB) at NASA’s Kennedy Space Center (KSC) in Florida. They await delivery of Discovery, which is currently set for no earlier than next week, and NASA officials hope the entire assembly will roll out to the launch pad by the end of the month.

“Obviously, those are very important milestones, and we need to keep pushing forward,” said astronaut Wendy Lawrence, a mission specialist for Discovery’s STS-114 spaceflight, in a telephone interview.

NASA is currently targeting a mid-May launch for Discovery’s seven-astronaut crew, with a flight window stretching from May 15 to June 3, though some officials have hinted that preparations are lagging behind, according to an MSNBC.com report Wednesday.