# Tianwen-4 by CNSA

Canonical page: https://technooptimist.io/spaceflight/tianwen-4
Frontier: [Spaceflight](https://technooptimist.io/spaceflight.md) · Field: Planetary missions · Company: [CNSA](https://technooptimist.io/companies/cnsa.md)
Stage: Research (1 of 5: Research → Proto → Pilot → Deploy → Scaling)
Updated: last update 2023-12-21, facts checked 2026-10-11
Goal: Learn how Jupiter and its large moons formed by orbiting Callisto, an old, heavily cratered moon that may hide an ocean, and send a second probe past Uranus, a planet visited only once.
Status: In design; plans call for a September 2029 launch on a Long March 5.
Next milestone: Mission design and instrument selection

## Milestones

| Status | Milestone | Date | Slip |
| --- | --- | --- | --- |
| Done | Two-spacecraft plan presented at IAC in Paris | 21 Sep 2022 |   |
| Done | Callisto focus and 2029 launch presented | Dec 2023 |   |
| Done | Preliminary instrument list published | May 2024 |   |
| Current | Mission design and instrument selection |   |   |
| Planned | Launch on a Long March 5 from Wenchang | Sep 2029 |   |
| Planned | Venus gravity assist | 2030 |   |
| Planned | Earth gravity assists | 2033 |   |
| Planned | Arrive in orbit around Jupiter | Dec 2035 |   |
| Planned | Uranus flyby by the small probe | Mar 2045 |   |

## Upcoming events

- **Sep 2029**: Launch on a Long March 5 from Wenchang
- **Sep 2029**: Tianwen-4 launch
- **2030**: Venus gravity assist
- **2033**: Earth gravity assists
- **Dec 2035**: Arrive in orbit around Jupiter
- **Mar 2045**: Uranus flyby by the small probe

## Most important updates

- **21 Dec 2023**: Tianwen-4 plan: launch September 2029, Jupiter orbit 2035, Uranus flyby 2045. At a UN and China space exploration workshop, Zhu Xinbo, deputy chief designer of the Tianwen-1 Mars orbiter, set out a Callisto-focused Tianwen-4. ([our story](https://technooptimist.io/stories/tianwen-4-plan-launch-september-2029-jupiter-orbit-2035-uranus-flyby-aaedfa15.md) · [original source](https://www.planetary.org/articles/Chinas-plans-for-outer-solar-system-exploration))
- **21 Sep 2022**: CNSA presents a Jupiter and Uranus mission: two spacecraft on one Long March 5 around 2030. Wang Qiong of CNSA's Lunar Exploration and Space Engineering Center presented Tianwen-4 at the International Astronautical Congress in Paris. ([our story](https://technooptimist.io/stories/cnsa-presents-a-jupiter-and-uranus-mission-two-spacecraft-on-one-long-f7d7e98f.md) · [original source](https://interestingengineering.com/innovation/tianwen-4-jupiter-and-uranus-two-spacecraft-one-rocket))

## Current obstacles

- **Power far from the Sun**: At about 800 million km from the Sun, sunlight is weak; Chinese engineers named generating enough power as work in progress.
- **Goals and approval still being set**: Published plans list a launch date and instruments, but science goals were still under discussion and no final go-ahead has been announced.

## Physics limits

- **Sunlight is 25 times weaker at Jupiter**: Light falls off with the square of distance; at 5.2 times Earth's distance a solar panel gets about 4% of the power, so panels must be huge or a nuclear source used.
- **Messages take most of an hour**: Radio signals take roughly 35 to 50 minutes to reach Jupiter, so the craft must fly itself through orbit insertion and flybys.

## How it works

### Slingshots: Borrowing speed from Venus and Earth

The rocket alone cannot throw the craft to Jupiter, so it flies past Venus once and Earth twice, picking up speed from each planet's gravity.

### Split up: Two craft, two destinations

Before reaching Jupiter, a small probe separates and keeps going toward Uranus, while the main craft brakes into orbit around Jupiter.

### Callisto: Why Callisto, not Europa

Callisto lies outside Jupiter's harshest radiation, so electronics last longer, and its ancient surface records how the moon system formed.

### Impactor: Hitting the moon to look inside

Plans include an impactor, letting the orbiter watch the crash and study material thrown up from below the surface.

## Spec sheet

| Spec | Tianwen-4 | Provenance |
| --- | --- | --- |
| Spacecraft | Jupiter–Callisto orbiter + Uranus flyby probe | reported |
| Uranus probe mass | A few hundred kg | reported |
| Rocket | Long March 5 (one launch for both) | reported |
| Launch to Jupiter orbit | About 6 years | estimated |
| Distance from the Sun at Jupiter | About 800 million km | reported |

Provenance: reported = stated by the company; estimated = our estimate; sample = a sample figure.

## About CNSA

The China National Space Administration (CNSA) is China's government civil space agency, established in 1993. It manages the country's lunar and planetary exploration programs, including the Chang'e lunar missions and Tianwen deep space exploration projects.

- China's civil space agency founded in 1993. Operates the world's most active lunar program, deploying hardware constantly.
- Chang'e missions map south pole ice; Tianwen explores asteroids and comets for sample return.
- Manages lunar, planetary, orbital and space station programs in parallel.

- Founded: 1993
- Headquarters: CN
- Status: government
- Website: https://www.cnsa.gov.cn
- Partners, customers, investors: China Aerospace Science and Technology Corporation (CASC) (supplier)

Company page: https://technooptimist.io/companies/cnsa.md

## Related programs

More from CNSA:

- [Chang'e 7](https://technooptimist.io/spaceflight/change-7.md) (Proto)
- [Tianwen-2](https://technooptimist.io/spaceflight/tianwen-2.md) (Deploy)
- [Tianwen-3](https://technooptimist.io/spaceflight/tianwen-3.md) (Proto)

Everything in Spaceflight: https://technooptimist.io/spaceflight.md

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