China advances plans for dual solar system boundary missions

HELSINKI — China has published coordinated papers outlining dual missions to the solar system’s edge, suggesting the long-studied project is nearing formal approval.

A lead paper on the design and key technologies for a solar system boundary exploration mission published in the Journal of Deep Space Exploration (JDSE) outlines a pair of missions to the head and tail of the heliosphere and the boundaries of the solar system. The two spacecraft are scheduled to launch in 2033 and 2032 respectively on Long March 5 rockets along with kick stages for further propulsive power. A key author is senior Chinese space official Wu Weiren, head of the national Deep Space Exploration Laboratory (DSEL).

Further papers focus on energy and power systems required for long duration missions, science objectives for solar system boundary exploration, ultra-long communications needs and challenges, and an intelligent payload management and processing system, with authors arguing that such a project would drive leapfrog advances in key fields, including space nuclear power systems, ultra-long-life spacecraft design and deep space communications.

The missions would use Jupiter for a gravitational assist to accelerate their respective journeys to the head and tail of the heliosphere, with the former including an extra Earth flyby.  The head-direction mission would reach the heliosphere’s nose around 2053, while the tail-direction mission would not arrive at the far edge of the longer heliotail until about 2059, despite launching earlier.

While the missions echo the NASA Voyager 1 and 2 missions, those spacecraft were designed to make a “grand tour” of the solar system, making unprecedented visits to and studies of the outer solar system planets. Returning data from the farther reaches of the solar system was a secondary objective, and one for which the spacecraft’s sensor suite was not optimized.

China’s missions would be focused primarily on heliospheric physics, along with planetary science and astrophysics. It would aim to provide an unprecedented “panoramic view of the heliosphere” to determine how the solar wind interacts with the interstellar medium, and provide new insights into the evolution of the solar system. Key objectives include characterizing the heliopause, termination shock, and IBEX-discovered neutral-atom ribbon; measuring pickup ions, energetic particles, magnetic fields, and turbulence; and constraining cosmic-ray modulation. 

The overall mission design paper also notes the possibility of a visit to Neptune for the mission to the heliosphere’s head, while the tail mission could make a flyby or either Saturn or Uranus, but not both. Studies of other celestial bodies, such as Centaurs, which are small objects with unstable orbits located between Jupiter and Neptune, and Kuiper Belt objects, are also noted as matters of strong scientific interest. The spacecraft would conduct opportunistic observations of giant planets, small bodies, and background astrophysical sources

The mission architecture paper proposes a comprehensive 11-instrument payload suite aimed at closing long-standing gaps in heliophysics. Core instruments include magnetometers and wave analyzers, charged-particle, neutral-atom and dust sensors, and long- and wide-angle cameras, complemented by infrared, ultraviolet and terahertz spectrometers, a high-energy photon detector and a passive hydrogen maser for astronomy and fundamental physics.

At the boundary of approval?

China has previously outlined early conceptual roadmaps for a mission to explore the boundaries of the solar system, with earlier, tentative plans for launches in 2024 and 2027. The new outline, however, commits to using the Long March 5 to launch the identical spacecraft, each to be powered by 1 kWe-class nuclear heat-pipe reactors to enable more than 30 years of continuous operation. Each spacecraft would have a mass of no more than 8,200 kilograms. The development of nuclear power for space is likely a strategic consideration for China’s overall space efforts.

While there is no indication of a final, formal approval for the solar system boundary exploration mission, there are a number of indications that this could follow soon. 

Along with the scope and depth of the papers, representing an ecosystem of expertise, and involvement of international scientists among the authors, there are two prior notes suggesting its progression. First is that studying plans for solar system boundary exploration was noted in the most recent space white paper as a key planetary exploration task for the 14th Five-year plan period (2021-2025), and second is that solar system boundary exploration was noted as an advanced space mission for the 2028-2035 period in China’s long-term space science roadmap, published in fall 2024. 

China is scheduled to approve its 15th Five-year Plan (2026-2030) in March 2026 during its annual political sessions in Beijing, which could provide a pathway for formal approval of the mission, along with the announcement of other key space priorities for China in the five years ahead.