[6] The goals of the planned Tianwen-4 Jupiter mission include: study of the interaction between magnetic fields and plasma present in the Jovian system, examination of the compositional variations in the Jovian atmosphere, exploration of the internal structures and surface characteristics of either Ganymede or Callisto, as well as investigation of the space environment surrounding the aforementioned Galilean satellites.
[7] According to reports in the Western media, there are two competing mission profiles as of January 2021[update]: the 'Jupiter Callisto Orbiter' (JCO) and the 'Jupiter System Observer' (JSO).
Finally, presentations by Chinese researchers suggest that the Tianwen-4 Jupiter mission may include an additional probe that would conduct a fly-by of Uranus sometime after 2040.
After 1 or 2 braking passes, the probe will stay in a large elliptical orbit around Jupiter with a period of 30 days, making flybys of irregular moons.
Callisto also has a thin atmosphere with small amounts of oxygen, increasing its scientific allure despite being less glamorous than fellow subsurface ocean moons Europa and Ganymede and volatile, active Io.
JSO would also study the mass, density, dynamics and chemical and isotopic composition of irregular satellites and would provide insights into these unique remnants of Jupiter's formation.
At the end of its tour JSO could be sent to orbit the Sun–Jupiter L1 point, where the planet's gravity balances with the Sun's in a way that spacecraft can remain there for long periods of time.
From this unique perch where no spacecraft has ever visited, JSO could monitor the solar wind outside of Jupiter's magnetic field, and survey the irregular Jovian moons from afar.