Tuesday, September 27, 2022

ATLAS Shrugged: How Are Dangerous Asteroids Searched?

Время на чтение 6 мин.

Recently, the ATLAS system has included two more telescopes in the southern hemisphere — in South Africa and Chile, adding to the two observatories located in Hawaii. Astronomers can now scan the entire sky around the clock looking for potentially dangerous space objects. While the system was running in test mode, more than 700 asteroids and 66 comets had already been found. How and why ATLAS appeared? Can it warn us of the danger so far in advance that we have time to come up with a plan of action?

The Vigilant Four

ATLAS — Asteroid Terrestrial-impact Last Alert System — is a project of the Institute of Astronomy of the University of Hawaii, which is funded by NASA. Its task is to automatically explore the starry sky, fixing even small bodies and determining how dangerous they are for the Earth. The system should warn mankind about the collision in a few weeks or days (depending on the size of the celestial body).

In 2015, NASA awarded the University of Hawaii a $5 million grant to implement the ATLAS system. By the end of the year, the first telescope was fully operational, and two years later, in March 2017, the second one was connected to it. Both telescopes are in Hawaii, on the islands of Maui and Mauna Loa. In June 2017, Schmidt corrector plates, which increased the resolution of images, were placed on their mirror-optical systems. Since ATLAS must detect even small objects, this refinement was necessary for normal operation. The results of this year’s work were impressive: out of 2057 near-Earth objects, 95% were detected by the ATLAS system.

However, since both telescopes were in the northern hemisphere, about a third of the starry sky was not visible. To solve this problem, it was proposed to install two more telescopes in the southern hemisphere — NASA has allocated additional funding of $3.8 million for this. The South African Astronomical Observatory in Sutherland was chosen to host the instruments, and later the El Sos automatic Chilean observatory in the south of the Atacama Desert. It took four years to implement this stage, but now ATLAS provides full coverage of the starry sky, longer observations and is less dependent on weather conditions in a particular place.

How Does ATLAS Work

The ATLAS system consists of a relatively small telescope — with a mirror diameter of 50 centimeters — and a powerful camera with a 110-megapixel CCD. The telescope has a very wide field of view (7.4 degrees, about 15 times the diameter of the full moon). Each telescope in Hawaii scans 25% of the visible sky four times a night. The camera takes pictures with an exposure of 30 seconds, another five seconds are spent processing the resulting image. In this way, astronomers scan the entire visible sky twice a night.

The next stage of ATLAS work is the search for asteroids against the background of other celestial objects. Stars and galaxies, which move at a speed of 30 arc seconds per hour, are practically motionless compared to asteroids. Four photographs taken overnight from each telescope are immediately downloaded to a computer that analyzes the resulting images and highlights such fast-moving objects.

When the analysis is complete, the computer creates a list of objects that either move quickly or change brightness quickly. The program then determines which of the objects are most likely asteroids and which are other astronomical phenomena such as exoplanets, dwarf planets, supernovae, space debris, and others. If the object is supposed to be an asteroid, then the computer compares its characteristics with a hundred thousand objects, that are already included in the database. If there is no match, then the orbit is calculated, and it is found out, whether the asteroid can be classified as a potentially hazardous object. All this takes a matter of minutes.

We See You

ATLAS is just one of the projects included in NASA’s global Near-Earth Object Observations (NEO) program. This program is a key element of the agency’s strategy to protect the planet from collisions with celestial bodies. The main tasks of NEO observatories are to find, track and catalog near-Earth objects. Thus, astronomers can monitor potentially dangerous objects and predict possible collisions.

So far, NASA has set itself the task of tracking at least 90% of near-Earth objects whose size exceeds 140 meters. Experts believe that these and larger bodies pose a high danger to the planet, because a collision with them can cause enormous destruction. Of all the 25,000 discovered near-Earth objects, less than half are so, and so far none of them, most likely, will collide with the Earth in the next hundred years.

Found. And then what?

If ATLAS or another NEO member finds a potentially hazardous body, they report it to the Minor Planet Center. From there, the information is sent to several scientific teams that calculate the location and time of the collision.

How long will it take for us to know about a possible strike? Alas, the smaller the object, the later it enters our field of vision – as a rule, only a few days before the collision. The only thing that can be done in this situation is to evacuate people from the affected area. Alas, we have no way to counter “minor” threats.

We learn about the larger objects mentioned above several years before the collision. And it’s not all that hopeless. NASA is already developing the DART project, which involves changing the trajectory of a large celestial body by colliding with a spacecraft. All other ideas so far are more or less on the verge of fantasy. Let’s hope we still have enough time to prepare.

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