Photos: Atlas 5 rocket aims for International Space Station

NASA has narrowed its choices for a new billion-dollar robotic space mission: A plutonium-powered quadcopter to explore the hazy landscape of Saturn’s largest moon Titan, or a probe to scoop up a piece of a comet and return it to Earth.

In the home stretch of nearly a half-year on the International Space Station, four astronauts suited up and rode their SpaceX-owned Crew Dragon “Resilience” spaceship to a new docking port outside the orbiting research lab Monday, a first-of-its kind maneuver for the new generation of commercial crew spaceships.

Japanese space officials have rescheduled the launch of an H-2B rocket and a space station-bound HTV supply ship for Saturday after halting a countdown last week due to a propulsion system problem and bypassing a launch opportunity Friday because of a poor weather forecast.