— Ch. 1 · Origins And Naming —
Tianwen-4.
~5 min read · Ch. 1 of 6
The mission carries the name Tianwen-4, a title that signals its place in China's expanding interplanetary fleet. Before adopting this designation, planners referred to it as Gan De. This earlier name honored an astronomer from the fourth century BCE who made early planetary observations. Some historical accounts suggest he first observed the Galilean moons with the unaided eye. The choice of name reflects a strategic desire to build upon centuries of Chinese astronomical tradition while launching into modern space exploration. In 2018, Pei Zhaoyu served as deputy director of CNSA's Lunar Exploration and Space Program Center. He stated that China planned four major interplanetary missions before the end of the 2020s. These included Tianwen-1 for Mars, Tianwen-2 for asteroid sample return, Tianwen-3 for Mars sample return, and the Jupiter system mission now known as Tianwen-4. The agency had already launched Chang'e 1 and Chang'e 2 robotic lunar orbiters. They followed these with Chang'e 3, which landed on the Moon. By the 15th of October 2003, China had successfully sent its first independent crewed orbital mission into space. These achievements formed the foundation for more ambitious projects beginning in the 2020s.
Competing Mission Profiles
Western media reports describe two competing mission profiles under consideration: the Jupiter Callisto Orbiter and the Jupiter System Observer. The Jupiter Callisto Orbiter would conduct flybys of Jupiter's irregular satellites before entering a polar orbit around Callisto. This profile may include a lander or impact probe to study the moon's surface directly. In contrast, the Jupiter System Observer would forgo an attempt to orbit Callisto. Instead it focuses on intensive studies of Io, Jupiter's volcanic moon. The spacecraft would perform several flybys to examine how Jupiter's gravity powers Io's eruptions. It might also release small satellites to study the dynamics of the Jovian magnetosphere from multiple points. At the end of its tour, this profile could send the craft to the Sun, Jupiter L1 point. There the planet's gravity balances with the Sun's allowing long-term observation of solar wind outside Jupiter's magnetic field. Presentations by Chinese researchers suggest that the Jupiter Callisto Orbiter combined with a Uranus flyby probe may have been selected by mission planners during 2023 and 2024. Reports published in China Space Science and Technology support this direction as of early 2024.