SpaceX now has 21 successful first-stage touchdowns under its belt, nine of them at Landing Zone 1 and the other 12 on "autonomous spaceport droneships" stationed in the ocean. The two-hour launch window begins at 8 p.m.
Originally scheduled to launch in November, problems with the rocket caused officials to delay plans by several weeks.
It's still unclear where the Zuma mission will be heading.
But now conditions for the mysterious mission are 80-percent go, weather-wise, in Florida.
A Falcon 9 rocket carrying the secretive Zuma spacecraft will lift off from the Kennedy Space Center in Cape Canaveral Sunday night.
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SpaceX successfully sent something into space for the U.S. government, and that may be all we'll ever know about the so-called "Zuma" mission that Elon Musk's commercial space company completed from NASA's Kennedy Space Center in Florida Sunday evening.
After a record 18 launches in 2017, this mission will be SpaceX's first flight of the new year. Aside from its name, little is known about the payload. SpaceX landed the rocket's first stage for reuse in a future launch, a key step in its goal to drive down the cost of access to space.
"As a company, Northrop Grumman realises this is a monumental responsibility and we have taken great care to ensure the most affordable and lowest risk scenario for Zuma", Mr Rains said, declining to comment on the nature of the payload.
Aerospace and defense company Northrop Grumman was responsible for securing SpaceX's launch services for the Zuma mission.