China is planning a Voyager-like mission to the outer solar system that includes a flyby of Neptune, measurements of the electrically charged gas bubble surrounding our solar system, and a journey to interstellar space.The mission is currently named IHP, which stands for Interstellar Heliosphere Probe. It consists of two spacecraft that would explore the heliosphere, the solar-wind-created region around our Sun that separates us from interstellar space as the solar system travels through the Milky Way.
Zong Qiugang, the director of the Institute of Space Physics and Applied Technology at Peking University in China, said the mission “will allow us to discover, explore, and understand fundamental astrophysical processes in the largest plasma laboratory—the heliosphere.” Zong gave an overview of the mission at EPSC-DPS 2019, an international gathering of planetary scientists in Geneva, Switzerland.
The first spacecraft, IHP-1, would launch towards the head of the heliosphere in 2024. A second probe, IHP-2, would go in the opposite direction to explore the tail. The heliosphere is hypothesized to resemble a comet’s tail, but whether or not the tail “closes” behind the Sun is an open question. The Voyagers exited the heliosphere on the head side, and the tail has never been explored.
The IHP spacecraft will carry magnetometers, energetic neutral atom and particle payloads, dust and plasma detectors, and optical cameras. Phenomena of particular interest to the mission include Anomalous Cosmic Rays. These are slower versions of galactic cosmic rays from the local interstellar medium that become ionized once inside the heliosphere. The mechanism behind this process is not understood, and studying the ACRs could provide insights into the heliosphere and the nature of interstellar material itself.
The “hydrogen wall,” where interstellar material interacts with the edge of the heliosphere, is also of interest. As a structure that can be observed around other stars as well as our own, studying the hydrogen wall will aid the understanding of physical processes in the heliosphere and inform models of other stellar systems.
Getting to the Heliosphere
Before IHP-1 and 2 can explore the far reaches of the solar system, they will use flybys of Earth and Jupiter to gain speed. IHP-1 would fly past Earth in 2025 and 2027, and then Jupiter in 2029. It would reach the heliosphere around 2049.
IHP-2 would have additional targets. After a flyby of Jupiter in 2033, it would set course for Neptune, making the second-ever visit to the ice giant in 2038. The spacecraft would release a smaller probe shortly before arrival at Neptune, and observe the impact as the probe plunges into the atmosphere.
The IHP concept has not been formally approved but feasibility studies have long been underway. The formal go-ahead could be granted in 2021 or 2022, with the formation of the next Chinese Five Year Plan. Mission proposers have also noted that the IHP spacecraft would reach a distance of about 100 AU from Earth by 2049, in order to mark the 100th anniversary of the founding of the People’s Republic of China.
A couple of criticisms of this article: the diagrams do not accurately depict the Earth flybys. The flybys will involve revolutions about the sun, with periodic encounters with the Earth. Also, the article says the craft will reach “the heliosphere”. We are IN the heliosphere right now! The heliosphere is the region of space dominated by the sun. Presumably they just meant heliopause.
Obviously, this would be the first non-NASA mission sent on a trajectory out of the solar system. It would also, incidentally, be the first flyby mission to Neptune since the Voyager era.
Not mentioned in this article but elsewhere the possibility for incidental flybys of post-Neptunian objects has been discussed.
https://meetingorganizer.copernicus.org/EPSC-DPS2019/EPSC-DPS2019-1986-1.pdf
https://www.planetary.org/articles/china-voyager-like-interstellar-mission