International Asteroid Day

The past 30 of June was International Asteroid Day.
Our own Alfredo Escalante, who is studying the navigation of minor bodies such as asteroids, comets or small moons and is working on his thesis entitled “Applying Deep Learning for Optical Navigation of Solar System Exploration and Earth Observation Missions” in collaboration with the European Space Agency – ESA, helps us to understand what they are and why it is important to educate people on this topic.

What is an asteroid?

Asteroids are minor bodies of the Solar System which range from few meters to hundreds of kilometers with a wide variety of compositions. They are considered to be the “building blocks” from which the inner Solar System was formed, so its study is crucial for the understanding of the origin of the Solar System. Asteroid Bennu is currently the best characterized asteroid in the Solar System, it was visited by NASA spacecraft OSIRIS-REX, which took samples from it and is now returning them back to Earth for study. (

What is the purpose of the Asteroid Day?

The highest concentration of Asteroids in the Solar System is located at the Main Belt, between Mars and Jupiter but also there are more than 10000 thousand asteroids larger than 140 meters with an orbit close to Earth (these are called Near-Earth Objects or NEOs). These asteroids suppose a hazard to the Earth in the case of a collision, so they have to be carefully tracked and studied. The Asteroid Day promotes awareness about the reality of Asteroids, how they are investigated and what plans exist to prevent a potential collision.

Gaspra, the first asteroid visited by a spacecraft 1991 (Galileo

How are asteroids related to your thesis?

Small Solar System bodies have been the target of space missions since the ICE (International Cometary Explorer) crossed the plasma tail of Comet Giacobini-Zinner on September 11, 1985, and became the first spacecraft visitor of a comet. The need of taking in-situ measurements, has driven the exploration of various comets and asteroids in the last decades. Spacecraft navigation in the vicinity of these bodies may encounter limitations in robustness and efficiency with traditional landmark matching algorithms. My thesis consist on exploring the application of Deep Learning techniques for accurate and efficient optical navigation around asteroids and comets. These techniques would enable lighter and cheaper missions to reach asteroids and comets for scientific observations, mining or even deflection purposes.

What is the real probability of an asteroid strike?

The asteroids larger than 140 meters which cross the Earth’s orbit are considered hazardous and are carefully tracked and observed (multiple observations help reducing the uncertainty in the trajectory estimation) in order to accurately determine its orbit to estimate the real probability of an impact. The Sentry monitoring system ( scans all the asteroids and comets known to date and estimates the probability of a collision with the Earth for each object. The known asteroid with the highest impact risk is 2010 RF12 with a cumulative probability of 4.7% but luckily is estimated to has a diameter of just 7 meters.

What could be done and what is being done to avoid a collision?

The DART (Double Asteroid Redirection Test) mission by NASA is the first test ever of modifying the trajectory of an asteroid by a kinetic impact. The spacecraft will accelerate using its electric propulsion system until impacting Dimorphos (the moonlet of Didymos) nearly head-on with a velocity of approximately 6 km/s. The impact is expected to take place on the 26th of September this year. The mission HERA (accompanied by two cubesats) by the European Space Agency will later arrive to the binary asteroid to study the results of DART’s impact and the actual change of Dimorphos orbit. This international joint effort will be a milestone in the prevention of a possible future collision with the Earth.

Thank you very much Alfredo for allowing us into your world and especially for helping us to understand what asterioids are and why it is so important to know about them.

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