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NASA’s NEOWISE mission, launched in 2011, was in Earth orbit until last weekend. It discovered more than 3,000 near-Earth objects, or NEOs (asteroids or comets), whose orbits could
NASA’s NEOWISE mission, launched in 2011, was in Earth orbit until last weekend. It discovered more than 3,000 near-Earth objects, or NEOs (asteroids or comets), whose orbits could bring them close to Earth, even if they could collide. NEOWISE was shut down on August 8.
Studying the NEO population is central to the new concept of planetary protection: understanding and reducing the risk of collisions with asteroids large enough to cause serious damage to Earth.
NEOWISE has made a fundamental contribution to the knowledge base for planetary defense, with more than 200 of the 3,000 objects studied in ways we did not know before. Once the mission is complete and NASA orders its shutdown, NEOWISE will reenter Earth’s atmosphere by the end of this year. What does it take to protect our planet?
NEOWISE began as another mission, simply called WISE (Wide-field Infrared Survey Explorer). It was designed to study infrared radiation from distant galaxies in the universe. Infrared means “beyond the red”; infrared light is just beyond the red end of the color spectrum that humans can see. We know infrared radiation better as heat from the sun, for example, or the heat from a radiator that warms us in the winter.
After the coolant on the WISE mission ran out and these sensitive observations of the galaxies could no longer be made, NASA allowed the mission to continue under the name NEOWISE. They realized that the telescope system was still sensitive enough to detect asteroids and comets approaching the Earth and the Sun, and therefore had a very strong infrared signal.
NASA has a remarkable history of taking extra lives from completed missions, and in this case, NEOWISE represented a whole second life in a completely different area of research.
In addition to discovering and studying thousands of NEOs, NEOWISE has laid the foundation for a new dedicated mission to protect the planet. NASA’s NEO Surveyor is set to launch in 2027. NEO Surveyor’s goal is to detect about two-thirds of all NEOs larger than 140 meters in diameter during a five-year baseline survey. This is a major step toward fulfilling NASA’s Congressional mandate to detect 90% of all NEOs of this size.
Asteroids of this size could cause mass casualties if they collided with Earth and hit a major metropolitan area. You might think shutting down NEOWISE three years before NEO Surveyor launch was a bit risky. What would happen if one of these large asteroids hit us in the next few years?
The risks are very small, as estimates suggest that asteroids with a diameter of 140 meters only collide with the Earth once every 20,000 years or so. So we would have to be extremely unlucky to hit a place that would do particularly much damage in any three-year period. Only 3% of the Earth’s surface is occupied by urban areas.
After NEOWISE ends, NASA doesn’t have much of a choice. The Sun’s 11-year activity cycle is intensifying, causing the Earth’s upper atmosphere, the ionosphere, to thicken. NEOWISE flies through this ionosphere and can’t raise its orbit, so the ionosphere will inevitably pull NEOWISE back toward Earth.
NEO Surveyor began construction in 2023, so a launch in 2027 is impressively fast and minimizes the gap between NEOWISE and NEO Surveyor. NEOWISE is scheduled to enter Earth’s atmosphere by the end of the year, but we don’t know exactly when.
Some of NEOWISE, which weighs about 700 kg, will likely collide with the Earth’s surface. Hopefully, it will avoid populated areas; some recent re-entry events have caused space debris to land quite close to populated areas.
Knowing that an asteroid is on a collision course with Earth is one thing. Doing something about it is quite another. Giant steps toward protecting the planet came two years ago when the DART mission flew by an asteroid, collided with it, and changed its orbit. This showed that it is possible to change the course of asteroids that could be used to protect Earth from collision in the future.
Predicting potential impact on Earth as far in advance as possible, preferably years in advance, gives DART technology a chance. NEOWISE’s pioneering work and NEO Surveyor’s future comprehensive observations will deposit a large amount of information into our scientific bank that will never become obsolete and will form the basis for protecting the planet for perhaps hundreds of years into the future.
Source: Port Altele
As an experienced journalist and author, Mary has been reporting on the latest news and trends for over 5 years. With a passion for uncovering the stories behind the headlines, Mary has earned a reputation as a trusted voice in the world of journalism. Her writing style is insightful, engaging and thought-provoking, as she takes a deep dive into the most pressing issues of our time.
