Photos: Atlas 5 rolls out for launch

A balky interplanetary seismic instrument that ran into technical problems in 2015, forcing a two-year delay in the launch of NASA’s InSight lander to Mars, cleared a major test last week after engineers redesigned part of the sensor package, boosting confidence that the mission will be ready to blast off in May 2018.

The United Launch Alliance Delta 4 rocket, standing 206 feet tall and and weighing 720,000 pounds, unleashes 1.1 million pounds of thrust from its main engine and two side-mounted boosters at 12:52 a.m. EDT (0452 today to launch the GSSAP No. 3 and No. 4 satellites for the Geosynchronous Space Situational Awareness Program from Cape Canaveral.

The 200th Atlas-Centaur rocket, history some 52 years in the making, will blast off Tuesday from Cape Canaveral to deliver a U.S. Navy mobile communications satellite into orbit.