Four identical satellites that will study the interactions between solar winds and the Earth's magnetic fields blasted off into space on Thursday and settled into orbit begin a two-year study, NASA said.
The Delta V rocket of the United Launch Alliance lifted off from its launchpad from Cape Canaveral in Florida at 22:44 local time (2:44 GMT Friday) as planned at the beginning a 30-minute window of opportunity.
The quartet of spacecraft weighing 1.2 tonnes known as "Magnetospheric Multiscale" or MMS, will fly in a pyramid formation.
They later eased away from each other successfully.