PORTLAND (AP) _ A ship with two large domes on its deck that was docked in the harbor under a veil of secrecy for three weeks left port, apparently to monitor an Air Force rocket that was scheduled to fly up the East Coast.

The Sage, which left the harbor on Wednesday, is equipped with an antenna to monitor rocket boosters during launches, Lockheed Martin spokesman Doug Sayers told the Portland Press Herald. The Air Force was scheduled to launch a Titan rocket Friday night, and one of its two boosters is expected to drop into the ocean off Newfoundland.

The rocket launch was delayed earlier this month because of worries that one of the Titan’s 204-foot boosters could hit oil rigs off Newfoundland.

But U.S. officials proceeded with the launch after assuring the Canadians the booster would be destroyed if it veered off course.

Lockheed Martin, which made the Titan’s boosters, and Air Force officials have neither confirmed nor denied that the Sage was monitoring the Titan.

Peter Brown, senior multimedia editor for Via Satellite magazine, said the Sage’s departure Wednesday confirms that it was brought to Maine to track the Titan. He said NASA was not preparing any other launches in the near future for this flight path.

“This launch will be scrutinized very closely, and the Air Force is taking additional measures by putting assets into position,” said Brown, who lives on Mount Desert Island.

The 20-story-tall Titan is carrying a military satellite into orbit. Its flight path will take it over the ocean on a trajectory parallel to the East Coast.