CAPE CANAVERAL, March 16 -- Just over a day after launching, a SpaceX crew capsule arrived at the International Space Station on Sunday, bringing the replacements for NASA's two stranded astronauts.

The four newcomers - from the U.S., Japan, and Russia - will spend the next few days getting acquainted with the station's operations from Butch Wilmore and Suni Williams. Afterward, the two will board their own SpaceX capsule later this week to wrap up an unexpectedly extended mission that began last June.

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Wilmore and Williams had anticipated being gone for only a week when they launched on Boeing's first astronaut flight, but they marked the nine-month milestone earlier this month.

Th...