Live coverage: Soyuz crew capsule departs station, lands in Kazakhstan

United Launch Alliance called off the planned liftoff of a Delta 4-Heavy rocket and a classified National Reconnaissance Office spy satellite from Vandenberg Air Force Base in California on Wednesday after indications of elevated hydrogen concentrations around one of the launcher’s main engines. Three previous launch attempts were scrubbed by technical concerns and bad weather.

Pettit will fly to the orbiting outpost alongside Russian cosmonauts Alexey Ovchinin and Ivan Vagner on the Soyuz MS-26 mission. Liftoff from the Baikonur Cosmodrome is set for 12:23 p.m. EDT (1623 UTC).

An Orbital ATK Pegasus XL rocket carrying eight hurricane research satellites for NASA fired into orbit Thursday at 8:37 a.m. EST (1337 GMT) off the east coast of Florida.