Galileo has one section of its orbiter spinning so that it can carry experiments which need to take measurements while rapidly sweeping an area. These experiments are called magnetospheric experiments. The orbiter rotates at three revolutions per minute (rpm), but it can increase its speed up to ten rpm. Some of the cameras, however, cannot be mounted on a spinning orbiter, so they are on the despun section which allows them stability and a fixed orientation. These cameras can then take pictures that are not fuzzy.

Instruments to measure fields and particles, the main antenna, the power supply, the propulsion module, and most of the computers and control electronics are mounted on the spinning section. The scientific instruments include magnetometer sensors, mounted on an 11-meter boom to minimize interference from the body of Galileo itself; a plasma instrument detecting low-energy charged particles and a plasma-wave detector to study waves generated by the particles; a high-energy particle detector; and a detector of cosmic and other dust from Jupiter or its moons. The spinning section also carries the Heavy Ion Counter, an engineering experiment that will assess the danger involved in passing through hazardous charged-particle environments.