Snapshots from Atlas 5 launch

The practice countdown began Tuesday night, kicking off a carefully choreographed series of steps to ready the world’s most powerful operational rocket for what amounted to a simulated launch Thursday at 8:42 p.m. EST. Controllers then carried out additional tests to make sure the team can recycle, hold and restart an actual launch countdown as needed to handle unexpected problems.

SpaceX readied a Falcon 9 rocket for takeoff Monday to launch a planet-hunting satellite for NASA that will monitor the light from countless stars to find potentially habitable planets worthy of follow-up studies by more powerful ground- and space-based observatories.

A nearly three-month stoppage of on-site work due to concerns about the spread of the coronavirus at NASA’s Marshall Space Fight Center in Alabama is expected to push back the launch of the IXPE X-ray astronomy satellite from May 2021 until some time later next year, a senior space agency official said.