The arrival of NASA astronaut Kevin Ford and Russians Oleg Novitsky and Yevgeny Tarelkin on Thursday will bring to six the size of the crew at the orbiting outpost.
The trio blasted off Tuesday from a Russian-leased facility in the southern Kazakhstan town of Baikonur.
Cargo on the Soyuz includes 32 Guppy-like fish that will be used to test how conditions in space impact on living organisms.
A spacewalk to repair a minor ammonia leak from the station's temperature control system is planned for the coming days.
Another task for the incoming crew's first week in orbit will be the departure of a commercial Dragon cargo vehicle.
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