There are only sixty days left before the American space probe Dart.Double asteroid redirection test) fails to achieve its goal. Launched in November 2021 from the Vandenberg base in California, the half-ton, cube-shaped machine flies through space at a speed of 24,000 km/h. And on September 26, 2022, the asteroid will hit Dimorphos, which will then be 11 million kilometers from Earth.
This approximately 160 meter wide asteroid orbits Didymos, an 800 meter diameter rocky object, in just 11 hours. And by measuring, after the collision, the change in Dimorphos’ orbital period (estimated to decrease by about 10%) the DART mission will test the effect of a dynamic impactor on the trajectory of an asteroid… A maneuver that could deflect a near-Earth cruiser heading straight for our planet. And thus a regional catastrophe could be avoided if such meteors were one day detected.
Figure representing the binary asteroid targeted by the DART mission. Credit: DART
A two step mission
The results of the impact on Dimorphos (orbital period changes, crater formation, debris extraction, etc.) will be analyzed by the Italian nano-satellite LICIACube (Lightweight Italian CubeSat for asteroid imaging) boarded with DART and ejected ten days before the collision. And in 2024, the European probe HERA will fly to the binary asteroid to enter orbit, map the surface of Dimorphos and collect very precise data for a battery of instruments (camera, radar, infrared imager, gravimeter, altimeter, etc.).
China wants to play a role
But within a few years, the United States and Europe will no longer be the only space powers working on planetary defense and experimenting with such technologies. Because China wants to play a role and is also building an asteroid deflection mission. First announced last April, the project was detailed during a conference given by Chinese engineer Long Lehao who designed the Long March launchers as well as piloted the Chinese lunar exploration program. Developed by the Chinese Space Administration, the mission will be launched in 2026 by a Long March 3B rocket.
New details of China’s asteroid deflection mission: launch on Long March 3B rocket in 2026, targeting Earth-crossing, near-Earth asteroid 2020 PN1 (~40m diameter). It will combine an orbiter and impactor, according to a slide from Long March designer Long Lehao’s lecture. pic.twitter.com/GRWpRDCbgy
—Andrew Jones (@AJ_FI) July 12, 2022
Engineer Long Leha also presented the concept of the Chinese mission.
A small goal from Dimorphos
Just as the DART and HERA programs are integrated into the AIDA consortium (Asteroid impact and deflection assessment), it will test a projectile’s ability to deflect a threatening celestial object. But the Chinese mission will include both an impactor, a full-speed launcher toward an asteroid, and an orbiter that will study the consequences of the collision. The target will also be smaller than Dimorphs. It is about 40 meters in diameter for asteroid 2020 PN1. Discovered two years ago by Hawaii’s Haleakala Observatory, it is part of the “Aton” type asteroid and will be 19 million kilometers from Earth in 2026.
These objects would destroy a city like Lyon
Only NEOs larger than one kilometer wide can cause a planetary catastrophe, and those larger than 140 meters in diameter – such as dimorphs – can cause a regional catastrophe. 2020 PN1 is therefore below this threshold. By hitting Earth, asteroids of this size can however cause significant damage, for example destroying a city like Lyon. They are much more numerous and difficult to identify than dimorphous-like asteroids. The Chinese mission will provide valuable information to try to protect itself from such threats.
Because of their small size, most of the asteroids, measuring about 25 meters across, have yet to be detected. Credit: DART/NASA/APL