SpaceX conducted a static fire test of the Falcon 9 rocket April 25 in preparation for an April 30 launch to carry NROL-76 into orbit. Credit: SpaceX

WASHINGTON –  Preparations are underway for SpaceX’s first big launch for the National Reconnaissance Office, a classified mission slated to lift off early Sunday from Florida.

The  SpaceX Falcon 9 rocket that will carry the hush-hush payload dubbed NROL-76 completed a static-fire test Tuesday, setting the stage for a morning liftoff from Kennedy Space Center’s Launch Complex 39A. The planned two-hour launch window is set to open at 7 am, but NRO has not announced what the exact planned liftoff time will be.

Neither SpaceX nor the spy agency has disclosed much information about the launch. However, satellite observers speculate that, based on the rocket’s trajectory, it may be carrying a data relay satellite to operate in a so-called Molniya orbit designed for increased dwell time over the Earth’s  north and south poles.

While Sunday’s mission will be SpaceX’s first for the U.S. spy satellite agency since Elon Musk’s rocket shop was certified by the Air Force in 2015 to carry national security satellites to orbit, it might not be the first time the company has flown an NRO spacecraft.

A tiny NRO cubesat is believed to have flown as a secondary payload aboard a Falcon 9 as part of a NASA-funded demonstration flight of SpaceX’s Dragon cargo spacecraft.

The NRO is responsible for building and operating U.S. spy satellites, and reveals very little about their work. Previous NRO launches – usually aboard United Launch Alliance rockets – have also been shrouded in secrecy, with live broadcasts cut off shortly after liftoff. The agency does not disclose the purpose or location of their satellites, nor when they achieve orbit and enter operation.

SpaceX confirmed on Twitter that they had test-fired the rocket Tuesday in preparation for the launch. The current plan is to recover the Falcon 9’s first stage booster by landing it back at Cape Canaveral.

Sunday’s launch also stands to be the first national security launch for SpaceX since successfully launching and landing a previously flown Falcon 9 booster March 30 on a mission for commercial satellite fleet operator SES. The U.S. government has yet to certify launches using reused boosters for national security spacecraft..

Respected amatuer satellite sleuth Ted Molczan speculates that NROL-76 is part of a delivery-on-orbit deal between the NRO and Boeing involving several of Boeing’s  BSS-702SP spacecraft platforms. That would explain how SpaceX got tapped for the mission before achieving the Air Force certification it needed to compete against United Launch Alliance for contracts to launch military and intelligence satellites.

“How could Falcon 9 have been procured in 2013 for an NRO payload? It could have been included in a package deal with Boeing for the BSS-702SP,” Molczan wrote online. “It seems reasonable to assume that Boeing won a competition for the three payloads and launch vehicles. The low-cost Falcon 9 would have provided a competitive advantage. Assuming the contractor is paid only for delivery of a functioning payload to orbit, the only risk to the NRO of a payload or launch failure is a delay in its program.”

In 2016, NRO Director Betty Sapp said that her agency had “bought launches from SpaceX,” implying this might be the first of several NRO launches for SpaceX.

Likewise, Loretta DeSio, an NRO spokesperson, said in a May 2016 e-mail sent to SpaceNews that “the NRO is anticipating the possibility of SpaceX supporting additional missions based on future competitions.”

Phillip Swarts is the military space reporter for SpaceNews. He previously covered space and advanced technology for Air Force Times, the Justice Department for The Washington Times, and investigative journalism for the Washington Guardian;...