Photos: Atlas 5 rocket aims for International Space Station

After a six-week delay for undisclosed reasons, SpaceX raised a Falcon 9 vertical on its launch pad Thursday at the Kennedy Space Center in Florida for another try early Friday to send into orbit the company’s next batch of Starlink Internet relay stations and a pair of commercial BlackSky Earth-imaging microsatellites.

SpaceX test-fired nine Merlin engines Saturday before the company’s next launch from Cape Canaveral, clearing a key readiness test before liftoff as soon as Sunday night with 60 more Starlink internet satellites.

SpaceX’s next launch of satellites for the company’s Starlink broadband network — planned in the final days of 2019 — will carry one spacecraft with an experimental coating designed to make it less reflective in orbit, a first step in assuaging concerns from scientists who say the deployment of thousands more Starlink stations would impede some astronomical observations.