Updated 8:00 p.m. Eastern with NASA statement.

WASHINGTON — SpaceX has filed a protest over the award of a launch contract to United Launch Alliance for a NASA planetary science mission, claiming it could carry out the mission for significantly less money.

The protest, filed with the Government Accountability Office (GAO) Feb. 11, is regarding a NASA procurement formally known as RLSP-35. That contract is for the launch of the Lucy mission to the Trojan asteroids of Jupiter, awarded by NASA to ULA Jan. 31 at a total cost to the agency of $148.3 million.

The GAO documents did not disclose additional information about the protest, other than the office has until May 22 to render a decision. NASA said that, as a result of the protest, it’s halted work on the ULA contract.

“NASA has issued a stop work order on the agency’s Lucy mission after a protest of the contract award was filed with the Government Accountability Office,” agency spokesperson Tracy Young said Feb. 13. “NASA is always cognizant of its mission schedule, but we are not able to comment on pending litigation.”

SpaceX confirmed that the company was protesting the contract. “Since SpaceX has started launching missions for NASA, this is the first time the company has challenged one of the agency’s award decisions,” a company spokesperson said in a statement to SpaceNews.

“SpaceX offered a solution with extraordinarily high confidence of mission success at a price dramatically lower than the award amount, so we believe the decision to pay vastly more to Boeing and Lockheed for the same mission was therefore not in the best interest of the agency or the American taxpayers,” the spokesperson added. ULA is a joint venture of Boeing and Lockheed Martin.

NASA said at the time of the award that it was a competitive procurement, but did not disclose the number or identity of bidders. SpaceX did not comment at that time if it submitted a bid, although industry sources, speaking on background, said that SpaceX proposed launching the mission on a fully expendable Falcon 9 rocket in order to maximize performance.

A key factor in the decision to award the contract to ULA was schedule certainty. Lucy has a complex mission profile with a series of flybys in order to visit several asteroid either leading or following Jupiter in its orbit around the sun. That results in a launch window that is open for only about 20 days in October 2021. Should the launch miss that window, the mission cannot be flown as currently planned.

ULA emphasized its adherence to schedule in its announcement of the contract. “This mission has a once-in-a-lifetime planetary launch window, and Atlas V’s world-leading schedule certainty, coupled with our reliability and performance provided the optimal vehicle for this mission,” Tory Bruno, president and chief executive of ULA, said in a Jan. 31 statement about the launch award.

“ULA entered into an open competition for NASA’s Lucy spacecraft and was honored to be awarded this important science mission,” ULA said in a Feb. 13 statement to SpaceNews. “This interplanetary mission has an extremely narrow launch window in order to reach all of the desired planetary bodies and accomplish the science objectives. If Lucy misses this launch window, the full mission cannot be accomplished for decades.