A secret government satellite mission code-named Zuma launched from Cape Canaveral last night atop a SpaceX Falcon 9 rocket into orbit.
After the 8 pm ET blastoff from Launch Complex 40, the rocket booster returned to Cape Canaveral Air Force Station, producing high decibel sonic booms as it touched down on legs south of the launch site.
Viewers could see the two stages of the rocket separate thanks to the clear skies, and then follow the first stage as it made its way back to Landing Zone1.
This marked SpaceX's 21st rocket landing over two years.
The broadcast of the mission was cutoff a few minutes into the flight to protect its secrecy.
Northrop Grumman had contracted the mission for an unspecified US agency. The mission was known to be headed into a low earth orbit, around 250 miles up, on a northeasterly trajectory angled about 50 degrees relative to the equator.
Amateur satellite trackers who specialise in tracking classified missions suspected Zuma may be an experimental spacecraft testing new technologies, possibly sensors for keeping watch on close approaches between spacecraft.
According to one theory, the mission might have something to do with one SpaceX launched into a similar orbit last May for the National Reconnaissance Office.
The mission was last summer observed to be flying close to the International Space Station, at a time when two US cargo craft arrived or departed.
At one point, when Zuma was scheduled to launch last November, both the National Reconnaissance Office (NRO) satellite and the ISS were on track to fly over Cape Canaveral during or very near Zuma's launch window.
That would place Zuma near the others once in orbit.
The launch was however, delayed. According to SpaceX it needed to review a potential issue with the Falcon 9 rocket's nose cone that cropped up in testing.
For Sunday night's launch time, the orbital tracks of those three spacecraft - Zuma, the NRO satellite and the ISS - were no longer closely aligned, suggesting the missions might not be related after all.
Late January may see two more satellite mission launches by SpaceX: a Spanish Earth observation craft launching from California, and a European communications satellite from Cape Canaveral.