The history of international cooperation in space is much broader than many people realize, there have been several multinational efforts. One of the longest running programs was the international Spacelab missions. These missions were flown with the European-developed Spacelab hardware, flying either a pressurized module or hardware mounted on a pallet – in the Space Shuttle payload bay. There were seven Spacelab missions that best qualify as “International” missions. Three were largely paid for by other countries: Spacelab D-1 and D-2, and Spacelab J, and these three included significant control from a control center in Germany or Japan. Four other missions had major international participation; two even had “International” in their title. Those four were International Microgravity Lab-1 (IML-1) and IML-2, ATmospheric Laboratory for Applications and Science-1 (ATLAS-1) and ATLAS-3. One other Spacelab module mission (STS-9, Spacelab-1) could almost be counted as an International mission, since it had significant payloads from Europe, though it was entirely controlled from the US. It also had a German astronaut (Ulf Merbold) on board, but many non-International flights had International astronauts. Another Spacelab mission, STS-78 (Life and Microgravity Sciences) was also very international and had a French (Jean-Jacques Favier) astronaut on board. Ulf Merbold later went on to fly the IML-1 mission and a mission (Euromir 94) to the Soviet/Russian Mir space station. IML-1 also featured a Canadian astronaut, Roberta Bondar,and LMS had Bob Thirsk from Canada as a part of the crew. Oddly, ATLAS-2 (STS-56) had less International participation. But of the Spacelab missions, seven stood out as stretching the boundaries of the Space Shuttle program to allow international involvement and control.
The years of working on International missions significantly paved the way for the International Space Station – by providing opportunities for International astronauts to fly in a precursor laboratory, giving European companies a significant hardware development effort, and by providing an opportunity for the European and Japanese controls centers to develop their capabilities. Europeans supplied a set of the Spacelab hardware, and this contributed to their ability to produce ISS components. Built by a consortium of European companies led by VFW-Fokker and ERNO based in Bremen, Germany, Spacelab development prepared Europe to later build/integrate the similar Space Station module Columbus and also Nodes 2 and 3. Project management of the European companies which provided many subassemblies for the Spacelab prepared ESA to do the same for ISS. The International control centers pioneered the European and Japanese payload control centers that are used today for payload controls for the Columbus and Japanese Experiment Module (JEM) segments. The Germans had developed their control center, near Munich, for earlier missions but greatly expanded it to accomodate Spacelab. Later, this center would become the hub for European operations on the Space Station.
The years before 1983 were busy as the hardware and software was developed, and then 1993 and 1994 were extremely productive years for the European space science. The final Spacelab mission was in 1998 but European astronauts continued to fly on Space Shuttle missions well after that . Several later missions which did not involve Spacelab or even dedicated science goals, such as STS-99 in Feb of 2000, had significant International participation. The STS-99, Shuttle Radar Topography, mission is just one example of where International astronauts (Gerhard Thiele) got coveted assignments on space missions.
Some of the motivation for the International missions might have been the competition with the Soviets (at the time) since the Soviets had begun flying non-Soviet client cosmonauts to their Salyut-7 space station. The first Western European cosmonaut to fly to the Salyut was Jean-Loup Cretien, in 1982. This was about one year after the first flight of the Space Shuttle, and in about one more year the first Western European astronaut would fly on a Shuttle, in the Spacelab-1 mission. During the time when the International Spacelab missions were being planned and then flown, a series of Western European cosmonauts were flying to the last Salyut and later to the Mir space station.
The one International astronaut that bridged Spacelab and International Space Station is Hans Schlegel. He flew on STS-55, Spacelab D-2, and on STS-122, when the Columbus module was delivered and installed on the ISS. So, as an International astronaut, he had the unique distinction of working in both the Spacelab module and it’s progeny, the Columbus module. Now, several International astronauts did fly on the Shuttle and on the Soviet/Russian Mir, but only Hans flew on both a Spacelab module and the ISS – in the Columbus module.