Spacecraft Missions to Jupiter

China is planning to launch the country's first spacecraft to Jupiter and its satellites around 2030. The space mission has organized a series of discussions for scientists and engineers. Proposals of scientific objectives and engineering techniques are being collected. To help formulate the scientific goals of the Jupiter mission, the authors review past missions to Jupiter conducted by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). Among the nine space missions that explored Jupiter and its satellites so far, seven are flyby missions. The two others particularly for Jupiter, Galileo and Juno, carried many suites of instruments. Observations are not limited to Jupiter's atmosphere. Rather, they extend to the magnetosphere, ionosphere, and internal structures. In this paper, the authors focus on observations of the Jovian atmosphere. The authors introduce the flyby missions briefly, while the Galileo and Juno spacecrafts are summarized in greater details. The authors also discuss some of the outstanding questions.