7:45pm ET (00:45am UK) Sunday update: The weather cooperated just fine on Sunday evening, near sunset in Florida, but the rocket did not. With just 10 seconds to go before liftoff, the on-board computers detected some issue within the rocket's guidance, navigation, and control system. At that point the flight computers stopped the countdown just before the engines were ignited. This forced a 24-hour scrub.

If it can diagnose and fix the problem, SpaceX will make a second attempt to launch the Intelsat 35e satellite on Monday, with the launch window opening at, or around, 7:37pm ET (00:37am UK).

Original post: SpaceX will look to continue its high launch cadence later on Sunday with its third mission in just nine days, and fourth in a month. For the launch, a SpaceX Falcon 9 rocket will attempt to deliver the Intelsat 35e communications satellite to geostationary transfer orbit. The launch window opens at 7:36pm ET (00:36am UK) and spans 58 minutes. The primary concern is weather, with just a 40 percent chance of favorable conditions at launch time.

With a mass of 6,761kg, this is the heaviest satellite SpaceX has ever launched to geostationary orbit, about 36,000km above the Earth's surface. For this reason, the rocket will not have enough fuel reserves to attempt a safe return to Earth—even to a drone ship in the Atlantic Ocean. This booster, therefore, is being expended.

If the Falcon 9 does fly Sunday, it would cap a remarkably productive period for SpaceX. Already, the company has successfully launched nine missions in 2017, and this would be the company's fourth flight since June 3. Should inclement weather preclude a launch Sunday, a backup opportunity will come Monday, at 7:37pm ET.

After the Intelsat 35e mission, SpaceX will step back from its furious cadence for about a month. This is partly because the US Air Force needs time to upgrade some of its assets on the "Eastern Range," which tracks rocket launches along the entire US East Coast. This purpose of this update is to ensure the safety of shipping lanes and residents beneath the flight path of launches.

As a result, no launches are planned from Kennedy Space Center or Cape Canaveral Air Force Station in Florida until August 3, when United Launch Alliance will lift a communications and data relay satellite for NASA into space. SpaceX's next launch is planned for no earlier than August 10, which will be its next supply mission to the International Space Station.

So it's best to enjoy today's attempt, because it will be awhile before there's another US launch. The webcast for the Intelsay 35e mission should begin about 15 or 20 minutes before the launch window opens.