STS-88 (Endeavour / first ISS assembly)

Background

By the mid-1990s, more than a decade of negotiation, redesign, and international diplomacy had produced a detailed plan for a permanently crewed orbital outpost unlike anything attempted before. The International Space Station would draw together the resources and expertise of sixteen nations, with the United States and Russia as the two dominant partners. Each contributed a foundational module: Russia's Zarya — whose name means "sunrise" — was a Functional Cargo Block (FGB) launched atop a Proton rocket from Baikonur Cosmodrome on 20 November 1998, providing early propulsion and power. The American contribution, the Unity connecting node (also called Node 1), would follow aboard the Space Shuttle. It was Unity's job to serve as a passageway, its six berthing ports designed to receive the pressurized modules that would eventually make the station habitable. Before any crew could live aboard the ISS, however, these two modules had to be physically joined in orbit — a task assigned to Space Shuttle Endeavour on its eleventh flight, designated STS-88.

The crew assembled for this historic assignment was led by commander Robert Cabana and pilot Frederick "Rick" Sturckow. Mission specialists Jerry Ross, Nancy Currie, James Newman, and Russian cosmonaut Sergei Krikalev rounded out a team that blended deep experience with precise technical training. Ross and Newman were slated to conduct spacewalks to connect electrical and data cables between the two modules, while Currie would operate the shuttle's robotic arm to maneuver Unity and then grapple Zarya from orbit. Krikalev's presence carried enormous symbolic weight: a veteran of the Mir space station who had once been stranded in orbit when the Soviet Union dissolved, he now represented the partnership that had replaced Cold War rivalry.

Ascent and Rendezvous

Endeavour lifted off from Launch Complex 39A at Kennedy Space Center on 4 December 1998, reaching orbit approximately eight and a half minutes after launch. Unity had been carried in the payload bay since integration, and one of the crew's first tasks was to use the shuttle's robotic arm to extract the node and mate it to the Pressurized Mating Adapter already docked to Endeavour's orbiter docking system — effectively extending the shuttle's forward docking port so Unity would be correctly positioned when the time came to join it to Zarya.

Rendezvous with Zarya required Endeavour to perform a series of carefully calculated orbital maneuvers over two days, closing the gap between the shuttle and the uncrewed module. When proximity operations began, Currie demonstrated exceptional precision in using the robotic arm to grapple Zarya — a module roughly the size of a city bus, free-floating in orbit — and draw it into alignment with Unity. The physical mating of the two modules, achieved at mission elapsed time T+55 hours, 33 minutes, and 20 seconds, marked the moment the International Space Station formally came into existence as a connected structure. Two spacecraft built on separate continents, launched on separate rockets, had become one.

On Orbit Operations

With Unity and Zarya joined, Ross and Newman conducted three spacewalks across the mission, working in the vacuum of low Earth orbit to connect power, communications, and data cables running between the two modules. These extravehicular activities totaled roughly twenty-one hours and were essential: without them, the mechanical link would have been structurally sound but operationally inert. The spacewalkers also installed handrails, tools, and other hardware intended to aid future assembly missions.

After the external work was complete, Cabana and Krikalev opened the hatch between the shuttle and Unity, and then — in a moment that would be widely noted — the two commanders floated together through the connecting modules and became the first human beings to enter the nascent International Space Station. The interior was cold, dark, and stripped of the equipment that would eventually fill it, but its significance was unmistakable. The crew spent time inside both Unity and Zarya, performing inspections, activating systems, and photographing the modules' condition before closing the hatches and preparing to depart.

Endeavour undocked from the station at mission elapsed time T+194 hours, 26 minutes, and 40 seconds, backing away to allow the crew to photograph the newly assembled outpost against the backdrop of Earth. Those images — two modules joined end-to-end, gleaming in sunlight — became some of the most reproduced photographs in the history of human spaceflight.

Legacy

STS-88 stands as one of the pivotal flights in the history of space exploration, not because it completed a grand structure, but because it began one. The assembly of the International Space Station would require more than forty additional flights over the following decade and involve astronauts and cosmonauts from countries around the world. None of that was possible until Zarya and Unity were joined on 4 December 1998.

The mission also demonstrated the maturity of the US–Russian partnership that would define the station's character. Sergei Krikalev became the first cosmonaut to fly aboard the Space Shuttle in the context of ISS assembly operations, a precedent for the crew exchanges and collaborative training that would follow. Jerry Ross, who had already flown five times before STS-88, became one of the most experienced spacewalkers in NASA history in part because of the work performed on this mission.

The ISS has since hosted continuous human presence since November 2000, serving as a laboratory for research in biology, physics, materials science, and medicine that would be impossible to conduct on Earth. That record of sustained habitation traces an unbroken line back to the moment Nancy Currie guided a robotic arm across the orbital darkness and brought two modules together — the sunrise meeting the unity that gave them their names.