Discovery carried out the first exchange of a resident station crew by Shuttle in March 2001, swapping the outpost's first long-duration expedition for its second. The mission delivered a fresh three-person crew and brought home the trio who had opened permanent habitation the previous autumn, establishing the crew-rotation rhythm the station would follow for years.
The flight also debuted an Italian-built cargo module, a reusable "moving van" carried in the bay and berthed to the station to transfer supplies and equipment before being returned to Earth for reuse. Two spacewalks readied the station for future assembly. By rotating a crew and delivering logistics in one visit, STS-102 knit together the two roles — ferry and supply ship — that would define the Shuttle's service to the station.
This was the first crew rotation of the International Space Station's life. Discovery carried up Expedition 2 and brought Expedition 1 home after four and a half months — the handover that turned a station with residents into a station with a permanent programme.
It also introduced the Italian-built logistics modules that would become the workhorses of resupply. Leonardo, a pressurised cylinder carried in the payload bay, was berthed to the station, unloaded, refilled with rubbish and returned — effectively a reusable removal van, and a considerably more civilised arrangement than passing bags through a hatch.
The spacewalks set a record that stood for years: James Voss and Susan Helms spent eight hours and fifty-six minutes outside, the longest EVA ever performed, preparing a berthing port and installing equipment. Helms then stayed aboard as part of the incoming crew, going straight from a record-breaking spacewalk into five months of residency.
