8:50pm ET / 01:50am Update: Everything lined up perfectly for SpaceX on Monday evening. The Florida sunset provided a backdrop of pink and purple hues. The weather cleared. And the rocket was good to go. Until it wasn't. Almost exactly like Sunday's initial launch attempt, the rocket's onboard computers halted the launch attempt at T-9 seconds on Monday evening. The technical cause of the scrub was not immediately clear.

SpaceX does have another launch opportunity on Tuesday, July 4th, during the evening hours. It is not clear, however, whether the company will have resolved this technical issue in time to launch on the holiday. Certainly, if it does, there will be no shortage of "fireworks" in headlines about the launch.

Original post: SpaceX's Falcon 9 rocket almost made it off a Florida launch pad on Sunday evening—but with just nine seconds to go before liftoff the on-board computers detected an issue within the rocket's guidance, navigation, and control system. The launch was scrubbed and now the attempt has moved to Monday evening, with the 58-minute launch window opening at 7:37pm ET (00:37am UK). (Note: Due to weather issues, launch time is now 8:35pm ET, at the end of the launch window).

With a mass of 6,761kg, the Intelsat 35e communications satellite is the heaviest payload 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, will be expended.

This will be SpaceX's 10th launch of 2017, and the company has been especially busy as of late. A launch Monday would be the company's third flight in just 10 days, and fourth since June 3. By way of comparison, the most successful launches the California rocket company has had in any year, prior to this one, is eight. And it's only July.

After the Intelsat 35e mission, SpaceX will slow its roll 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 the range 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. SpaceX's next launch is planned for no earlier than August 10, a supply mission to the International Space Station.

The weather forecast for Monday evening in Florida is pretty good, with a 70 percent chance of acceptable conditions at launch time. The webcast below should begin about 15 minutes before the launch window opens.