Which spacecraft was designed to take direct measurements of Jupiter's atmosphere?

The Galileo spacecraft is the correct choice for this question as it was specifically designed to study Jupiter and its moons. Launched in 1989, Galileo was equipped with a variety of scientific instruments that enabled it to conduct detailed observations of Jupiter's atmosphere, including its composition, temperature, and dynamics.

During its mission, Galileo performed multiple flybys of Jupiter while also deploying a probe that entered Jupiter's atmosphere. This probe was instrumental in taking direct measurements of atmospheric pressure, temperature, and chemical composition, providing valuable data that enhanced our understanding of the planet's complex atmosphere.

Other spacecraft listed, such as Giotto, were focused on different missions—Giotto, for instance, was designed to study Halley's Comet. Cassini was primarily sent to study Saturn and its system. The Pathfinders, while a term that may refer to various missions, do not specifically relate to Jupiter's atmospheric measurements. Thus, Galileo stands out as the dedicated mission for Jupiter's atmospheric exploration.