The People’s Republic of China will be launching the Chang’e-4 lunar probe on Friday. This will mark the world’s first mission to land on the far side of the moon. (There is no “dark side” of the moon, Pink Floyd notwithstanding.)
The Chinese will be landing at the lunar south pole, in the Aitken Basin, which is the oldest, deepest impact basin on the moon. This is especially significant because it is believed to contain one of the largest deposits of frozen water on the moon, in parts of the crater that are in permanent darkness. The mission will entail the landing of a probe and the deployment of a small rover to take soil samples.
The mission is enormously significant, for several reasons.
In the first place, it is a major scientific advance. Despite being Earth’s closest celestial neighbor, much of the moon remains unexplored. The far side of the moon, for example, has only been photographed, but has never been physically examined. The images make clear that the far side looks very different from the near side, and while there are a variety of theories about it, only now will physical data be collected.
The rover aboard an earlier Chinese lunar probe, Chang’e-3, discovered a new type of lunar rock on the near side, so the possibility of further discoveries by the new probe is high.
Part of the reason there have been no missions to the far side of the moon is that communicating with any lander is very difficult. The far side of the moon is permanently faced away from Earth, so any communication requires the deployment of a relay satellite.
China has deployed the Queqiao relay satellite to Lagrange Point-2 (L-2) to allow the Chang’e-4 to report back its results. This relay satellite is not only a key part of the mission, but reflects a long-term Chinese interest in the Lagrange points, as it is the third Chinese satellite to have gone to L-2.
The five Lagrange points are a key part of the Earth-sun gravitational system. They are the points where the various gravitational forces interact to produce a kind of “parking spot” in space. A satellite placed at one of these points can remain in place for a long time while expending minimal amounts of fuel, thereby maximizing its lifespan.
Moreover, the Lagrange points are beyond the geosynchronous belt (where a satellite would stay over a fixed spot on Earth). As the lower orbits become more congested and contested over time, there has been growing interest in moving to higher orbits.
Some research has suggested that the combination of such outer orbits and a shift to new frequencies—which would allow greater data transmission rates—may revolutionize space communications. China appears to be positioning itself to exploit this potential.
But equally important is the fact that opening up this vast volume of space would exacerbate demands on the U.S. Air Force, NASA, and other U.S. space agencies to keep track of all the various space objects and systems in orbit. The U.S. Air Force Space Command, for example, is already heavily burdened as it seeks to maintain surveillance over some 24,000 objects in space on a 24-hour basis.
This is yet another reminder that the United States faces growing challenges in space. Where China is actively moving to deploy communications and relay satellites in higher orbit, the U.S. has shown only limited interest in doing the same. Thus far, most American and Western satellites deployed to this region carry scientific payloads. Similarly, China’s decision to deploy a lander to the far side of the moon indicates a commitment to space exploration that now rivals the U.S. in some ways.
Over the next decade, Beijing and Washington will likely intensify their efforts to exploit this new strategic high ground. China is making clear that it intends to win this competition.