The delay by one month of the first flight of Spacelab has given the West Europeans who developed it the jitters. They fear that a fault or some minor problem with the space shuttle at this stage could put off the mission for months.
Spacelab is the world's first reusable space laboratory. It will fly piggyback inside the shuttle's cargo bay for up to 10 days at a time at a height of some 250 kilometers (about 155 miles). The 11 nations of the European Space Agency (ESA) have developed Spacelab over 10 years at a cost of some $750 million.
Officials at the Paris-based agency are used to delays with the project. The first flight was to have been in 1980. But NASA has put off the mission because engineers are still not sure that the US's tracking and data relay satellite is working properly. The vehicle will transfer to earth the data that Spacelab experiments will generate.
The launch date is now scheduled for Oct. 28. But ESA officials say they are worried because the launch ''window'' at this time of year is very small - only 15 minutes. And there is only one week in which a launch is possible. On each succeeding day, the window becomes smaller until, by early November, it vanishes altogether.
The window is small because many astronomy experiments depend on the time the laboratory is actually in space.