China has established a satellite network consisting of three satellites conducting scientific research in the space between Earth and the Moon. The orbits of these satellites coincide with routes used by the United States for manned lunar exploration, raising attention about how China's first-mover advantage may impact future competition between the two countries in deep space exploration.
On the 15th, the Space Application Center of the Chinese Academy of Sciences (CAS) announced at a symposium held in Beijing that it has successfully deployed the DRO-A and DRO-B satellites in the distant retrograde orbit (DRO) between Earth and the Moon and established a communication and observation network with the DRO-L satellite orbiting in low Earth orbit (LEO).
The region between Earth and the Moon, known in English as 'cislunar,' is emerging as a launchpad for recent lunar exploration as well as deep space exploration, including Mars. The United States and China are pursuing plans to train in this orbit and establish key supporting infrastructure for communication, navigation, and supply to send humans to the Moon and Mars.
The distant retrograde orbit (DRO) where China has deployed its satellites is one of several orbits from Earth to the Moon. It corresponds to an area stretching up to 2 million kilometers beyond the orbit near the Moon. As the term 'retrograde' suggests, it is an orbit that flies in the opposite direction to the Moon's orbit around the Earth. Wang Wenbin, a researcher at the Space Application Center, explained, 'It provides an optimal environment for scientific exploration, infrastructure development, and support for manned deep space missions in the space between Earth and the Moon.'
To seize the Silk Road of space exploration, China launched the DRO-L satellite into low Earth orbit (sun-synchronous orbit) from the Sichuan Satellite Launch Center in southwest China in February of last year. Subsequently, in March of the same year, the DRO-A and DRO-B satellites were launched. However, due to an issue with the launch rocket carrying the satellites, the two satellites did not enter the planned orbit.
The Space Application Center provided a relatively detailed overview of the rescue operation that lasted for 123 days from March 13, the day of the launch, to July 15. The research team found that the satellites were spinning at high speeds based on data from remote observations immediately after the launch. Upon reporting an anomaly with the satellites, the team promptly began rescue operations. Despite the extreme conditions, they successfully adjusted the satellites’ positions after five attempts for orbital control and five modifications.
After nearly five months of traveling together over 8.5 million kilometers, the two satellites finally arrived at their designated orbit. After separating in August of last year, the two satellites began work to establish a communication link transmitting K-band microwaves, a type of radio widely used in space communications and scientific research, and also succeeded in entering their assigned orbits. According to the Space Application Center, the DRO-A satellite is currently in the distant retrograde orbit, while the DRO-B is flying in the lunar orbital trajectory between Earth and the Moon.
Chinese scientists regard the constellation of satellites deployed between Earth and the Moon as a groundbreaking case demonstrating significant advancements in deep space exploration and autonomous navigation technology. Zhang Jun, a chief engineer at the Micro Satellite Innovation Academy of the China Academy of Space Technology (CAST), noted in an interview with Xinhua News Agency, 'Through the construction of the satellite network, we have proven flexibility and adaptability in complex missions and opened the door to low-cost deep space exploration.'
Scientists liken the distant retrograde orbit to the 'Himalayas' of space. Similar to the high mountains of the Himalayas, it possesses a very large gravitational potential energy, allowing spacecraft to be sent with relatively much less energy to Earth, the Moon, and deep space. Once in this orbit, the gravitational forces of Earth and the Moon balance out, requiring almost no fuel for the spacecraft to enter and remain there. The fact that it spatially holds 'infinite beauty' is also why it is compared to the Himalayas.
Scientists believe this orbit has the potential to become a transportation hub linking Earth, the Moon, and deep space, as well as an attractive location for disposing of or long-term storage of derelict satellites and spacecraft surrounding Earth. Some scholars identify it as a potential final storage site for asteroids captured in plans by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) to alter the trajectories of asteroids threatening Earth.
The United States has also emphasized the need for research in the space between Earth and the Moon. The distant retrograde orbit has gained public attention because it is the orbit used by the Orion spacecraft in the Artemis program, which is America’s lunar manned exploration initiative, during its mission to the Moon in November 2022. The United States has identified the distant retrograde orbit as a potential location for a lunar orbital space station, the Lunar Gateway, within the Artemis program. The U.S. Space Force also announced last year plans to expand its reconnaissance jurisdiction all the way to the Moon. The Space Force stated at that time, 'Previous space missions were limited to an altitude of 22,000 miles (about 35,400 kilometers), but that is in the past. In the future, we will expand our mission range tenfold and our operational area one thousandfold, extending to the far side of the Moon.'
Since 2017, China has been paying attention to the unique characteristics and strategic value of the distant retrograde orbit in the space between Earth and the Moon, initiating full-fledged research. In 2022, it announced plans to deploy three experimental satellites in this space. By successfully establishing the satellite constellation first, China has put the United States at a disadvantage.
Since its unmanned lunar probe Chang'e 6 became the first in the world to visit the unexplored region of the far side of the Moon last year, China has been breaking records in space. During the process of building this satellite constellation, the country also deployed the satellites to their target orbits using the least energy ever. The Space Application Center reported that 'by applying innovative design technology, we used only one-fifth of the fuel typically needed to place the satellites in orbit.' This means a revolutionary reduction in the cost of accessing space, and it has been evaluated that China is now in a favorable position in the impending large-scale space development competition between Earth and the Moon.
China has built a stable communication network and observation network between a satellite 1.17 million kilometers away and the ground station. Using three hours' worth of inter-satellite measurement data, it achieved the precision of satellite orbital tracking that previously took two days with ground tracking. There are also evaluations that this has resolved key technical limitations necessary for building large-scale cluster satellites in the space between Earth and the Moon and have reduced satellite operational expenses.
China emphasizes that the achievement of this satellite constellation was not the result of overnight success but rather the outcome of perseverance and a hunger for achievement. Wang Chang, deputy director of the Space Application Center, noted in an interview with the China Science Daily, 'While it usually takes a decade of sharpening a knife in a laboratory for foundational research to bear fruit, our research is the result of 20 years of honing.' He added that 'the research team strove to be the front-runners, endured loneliness, was unafraid of setbacks, and worked together to solve core issues,' highlighting that 'the items the team most frequently relied on in the lab were instant noodles, sausages, and bottled water.'
The Chinese Academy of Sciences stated that the satellites deployed in the retrograde orbit will be utilized as research infrastructure to study the foundational science and technology necessary for lunar exploration and deep space exploration. Wang noted that 'by building the satellite network in the retrograde orbit, various cutting-edge scientific and technological experiments are underway, promoting research in space between Earth and the Moon.'
Plans are in place to conduct research to understand the laws of evolution of the space environment between Earth and the Moon and to deploy atomic optical clocks, which have an error margin of one second over 7 billion years, to advance various fundamental studies in quantum mechanics and atomic physics, as well as validation of general relativity. This process is expected to yield a substantial amount of top-tier scientific papers that will impact the global scientific community.
As investment in the space between Earth and the Moon increases, a first-mover advantage is also expected. The vast amounts of information collected by Chinese satellites have a high likelihood of being sold as high-value products to countries and corporations seeking to enter this space. The U.S. administration projects that from 2024 to 2040, corporations will generate a market worth approximately $63 billion (89 trillion won) in the space between Earth and the Moon. China plans to explore various orbits connecting Earth and the Moon to pioneer new routes to deep space.