Videos: Atlas 5 caps a generation of GPS launches

This is will be the fourth pair of O3b mPOWER satellites launched to a medium Earth orbit. Liftoff from Launch Complex 39A is set for 5:26 p.m. EST (2226 UTC).

Culminating years of construction and testing, a $1.2 billion satellite designed to spot and track enemy missiles threatening the United States homeland, its deployed military forces abroad or allied nations will ascend to a surveillance post in space Thursday.

The United Launch Alliance Atlas 5 rocket carrying NASA’s InSight lander toward Mars will have a roughly two-hour predawn launch window each day from May 5 through June 8 to boost the science probe into space from Vandenberg Air Force Base, California.