MELBOURNE, Fla. — The U.S. Department of Justice has cleared the planned merger of ATK and Orbital Sciences Corp., leaving a shareholder vote in January as the final milestone before the merger is completed.

In a press release late Dec. 4, the companies said that the Justice Department “unconditionally cleared” the proposed merger of ATK’s Aerospace and Defense Groups with Orbital. As a result of the Justice Department’s determination, the Federal Trade Commission terminated a waiting period required by the Hart-Scott-Rodino Act before the companies could close the merger.

With the regulatory approvals in place, the companies’ last major steps in completing the merger are separate votes by their shareholders, scheduled for Jan. 27. If shareholders, as expected, approve the merger, the merger is expected to close in February.

The companies had previously scheduled those shareholder votes for Dec. 9. However, on Nov. 17, the companies said they were postponing the votes until January to accommodate reviews of the deal in the wake of the Oct. 28 failure of Orbital’s Antares rocket on a cargo mission to the International Space Station. Those reviews concluded the merger should continue as planned.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...