SpaceX teams are working furiously to keep a modified Falcon 9 rocket on schedule so it can launch a huge communications satellite into orbit. The launch is scheduled to take place on Monday at Cape Canaveral Air Force Station, and the Elon Musk-founded company has a window of about four hours to complete the launch before it might have to get delayed.

The Falcon 9 rocket will be carrying the SES-12, the most powerful commercial communications satellite ever built by a Luxembourg based company. Unlike in previous launches, SpaceX will not use the Of Course I Still Love You drone ship to catch the first stage as it comes back to Earth.

Right now, weather forecasts show a 70 percent favorability rating for the launch window. This launch will be unique because it will feature a second stage rocket called Block 5, a rocket that was first launched from Kennedy Space Center oN May 11.

“A SpaceX Falcon 9 rocket will deliver SES-12 to a geostationary transfer orbit (GTO). The SES-12 satellite will improve communication and connectively in the Middle East and Asia-Pacific regions,” reads a statement from Kennedy Space Center. “For this launch, the first stage of the rocket is flight-proven, meaning it flew in a previous mission. Kennedy Space Center Visitor Complex offers the closest public viewing of launches with the purchase of admission and a launch transportation/viewing ticket. Availability of viewing opportunities and locations is dependent upon the scheduled launch time and is subject to NASA and U.S. Air Force approval.”