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  Plenty of clouds remained Sunday when SpaceX’s Falcon 9 rocket launched. [credit:
  Trevor Mahlmann ]

As a strengthening low pressure system crossed the Florida peninsula on Sunday, weather conditions at Cape Canaveral Air Force Station were poor all day. There were intermittent showers and plenty of lightning.

By mid-morning, SpaceX had already canceled one launch from Florida, a mission carrying five dozen Starlink satellites. But the company held out hope for getting the second flight of a planned doubleheader off on Sunday evening, and by the time the clock ticked down on the SAOCOM-1B mission, weather conditions began to marginally improve.

At 7:18 pm ET (23:18 UTC) launch-site weather had only just turned green, so a thrice-used Falcon 9 first stage took off on its fourth flight. And a historic one it was as SpaceX launched a rocket for the 100th time, and flew a rare polar corridor mission from Florida for Argentina’s space agency.