Tonight, the United Launch Alliance is set to launch one of its Delta IV rockets from Cape Canaveral, Florida, sending a communications satellite into space for the US military. It’ll mark the first Delta IV launch of 2017, and the seventh launch of a certain configuration of the rocket known as the Medium+ (5,4). This version of the vehicle is equipped with four additional strap-on rocket motors at its base, to provide extra thrust during launch.
The satellite going up tonight is the ninth one for the Wideband Global SATCOM (WGS) system, a constellation of satellites that provides high-capacity communication capabilities for the US military all over the globe. Other nations’ militaries, including those of Canada and Australia, also use the system. The satellite launching tonight, called WGS-9, will eventually join the other eight probes in a high orbit above Earth known as geostationary orbit. A total of 10 satellites are planned for WGS, so the constellation will be nearly complete.
Takeoff is scheduled for 7:44PM ET, but ULA has a launch window that lasts an hour and 15 minutes, so the rocket can get off the ground any time until 8:59PM ET. So far, weather looks great for a launch; there’s a 90 percent chance that conditions will be good, according to Patrick Military Air Force Base.
ULA’s coverage of the launch begins about 20 minutes before launch, so check back here at 7:24PM ET to watch the mission live.