The Integrated Science Instrument Module, or ISIM, is the structural heart of the James Webb Space Telescope, what engineers call the main payload. It will house the four main scientific instruments of the telescope. The ISIM is like a chassis in a car providing support for the engine and other components.
Webb will undergo significant shaking when it is launched on the large Ariane V rocket. To be sure the telescope's "chassis" is ready for this "bumpy road," the ISIM is subjected to some extreme testing. During the testing process, the ISIM is spun and shaken while many measurements are taken. Afterwards, engineers compare the measurements with their models of the ISIM. If there are discrepancies, then the engineers track down why, and make corrections.
Webb will be the first next-generation large space observatory and will serve thousands of astronomers worldwide. Designed to detect light from as far away as approximately 14 billion light years, Webb will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of planetary systems capable of supporting life on planets like Earth, to the evolution of our own Solar System. The Webb telescope is a joint mission of NASA, the European Space Agency and Canadian Space Agency.
Explore further: James Webb Space Telescope Begins to Take Shape at Goddard