By CBS3 Staff

PHILADELPHIA (CBS) — A second chance at history. After the first attempt was scrubbed, NASA will once again try to launch two astronauts into space aboard the SpaceX rocket.

Derrick Pitts, chief astronomer at the Franklin Institute, joined Eyewitness News to talk more about this mission.

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He says that there are actually 14 weather parameters that are looked at very carefully to make sure that it is safe for the astronauts to launch.

“It ranges everywhere from how high the winds speeds are, to how much electricity is in the air due to nearby thunderstorms,” Pitts said.

Saturday’s launch is scheduled for 3:22 p.m. So how do they have an exact time for launch?

“It’s what’s called an instantaneous launch window,” Pitts said. “They don’t have a lot of time, they have to go at that moment. The reason why is, because they need to leave Earth at a specific time to arrive at the International Space Station at a specific time.”

He also explained that the specific time allows the astronauts to have all of the resources available along the flight path in case there is an emergency.

Watch the video to hear more from Derrick Pitts