Q&A with Keith Gendreau, principal investigator of the first X-ray space communications experiment (members only)

The first Ariane 5 rocket scheduled for launch in 2018 has been topped off with two communications satellites for SES and Yahsat, moving the European booster closer to liftoff Thursday from a tropical launch pad in French Guiana with payloads to serve commercial and scientific missions.

SpaceX test-fired a Falcon 9 rocket Wednesday afternoon at NASA’s Kennedy Space Center in Florida, clearing a major hurdle before it launches Saturday night — weather permitting — with a four-person crew heading for the International Space Station.

NASA officials said Thursday the launch of the James Webb Space Telescope will be delayed seven months to Oct. 31, 2021, a schedule slip that takes into account work slowdowns caused by the coronavirus pandemic and the amount of testing required on the observatory before its shipment to French Guiana for liftoff on a European Ariane 5 rocket.