Planetary Defense: A New “Asteroid Hunter” to Spot Threats to Earth

NASA gives the top to build a future space lookout. Her name? NEO Surveyor. His role? Detect NEOs that are in the vicinity of the Earth and identify those that would be really dangerous.

These are news headlines that you come across regularly, and which often turn out to be exaggerated. Each time, they say that such and such an asteroid will “graze” the Earth. Their trajectory is even sometimes “threatening”, suggesting a possible risk of collision. But so far, these nearby NEOs have proven harmless. Fortunately.

This work of detecting and tracking space bodies that move around near the Earth is made possible thanks to a battery of telescopes that scan near space. It is also thanks to these tools that we manage to catalog these objects and we can determine if they are threatening or not. That’s good, a new “asteroid hunter” is in the works.

A new space lookout: NEO Surveyor

Her name? NEO Surveyor, for Near-Earth Object Surveyor. This is not a completely new program: it had been in the cards for years. In 2019, the green light is given to the principal of this future space lookout. Today, the construction of the machine has just been approved.

NEO Surveyor recently passed a rigorous technical and programmatic review. The mission is now moving into the final design and manufacturing phase and establishing its technical basis, cost, and schedule,” the US space agency wrote in a December 22 update. In other words, we will move on to practical work.

NEO Surveyor is part of a larger planetary defense program. According to NASA, the craft will help track down “the hardest-to-find asteroids and comets that stray into Earth’s orbital vicinity” This knowledge of the immediate environment will help to anticipate possible dangers and, if necessary, to act against them to deflect them.

Artist’s impression of the giant impact hypothesis. Atmosphere. // Source: YouTube SciChief screenshot

This was the whole purpose of the DART mission: to hit an asteroid very quickly and very hard ( it was not at all threatening: it was selected because its characteristics are close to those that a really threatening NEO would have) to test a change in its trajectory. The test was successful, giving Earth a first defense solution.

Today, the Planetary Defense Strategy requires NASA to discover, track, and characterize more than 90% of near-Earth objects greater than 140 meters in diameter and within 48 million kilometers of Earth’s orbit. This size was chosen considering the major damage that would be caused by a collision.

There is also tracking for smaller objects, but those that have very small dimensions sometimes go unnoticed. They also sometimes end up in the form of meteorites. The good news is that the smaller these bodies are, the less dangerous they are. Missing it is not as critical as not seeing a 3-kilometer diameter asteroid.

Leaving NEO Surveyor in 2028

Sending a space telescope like the NEO Surveyor demonstrates how difficult it is now to do tracking work with Earth-based telescopes. Indeed, certain wavelengths are blocked by the atmosphere, whereas they would be very useful in the search for these near-Earth objects. Hence the deployment of the telescope in space, for an unobstructed view.

One question remains: when will NEO Surveyor leave? The current schedule sets a start at 2028, but postponements are not uncommon: a few years ago, NASA was rather hoping for take-off around 2025 or 2026. Fortunately, it’s not too serious: the near-Earth cruisers that would directly threaten the Earth are extremely rare. The larger they are, the lower the probability of impact.

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