Photos: Tuesday’s Atlas 5 rollout

United Launch Alliance crews at Cape Canaveral are finishing final preparations for an Atlas 5 rocket launch Saturday evening to dispatch three U.S. military satellites directly to an orbital perch more than 20,000 miles over the equator.

NASA’s Perseverance rover, set for liftoff Thursday on a journey to Mars, posed some unusual challenges for launch crews working with the robot’s plutonium-fueled power generator, but United Launch Alliance’s Atlas 5 rocket is uniquely suited for the job, the company’s CEO says.

The revised Atlas 5 rocket firing order includes two national security missions this summer before launching NASA’s daring asteroid sampler mission in September as originally planned.