Forecasting air drag with deep learning helps predict when uncontrolled satellites and rocket stages fall to Earth

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: On May 10, 2025, a spacecraft built in the Soviet Union to land on Venus came home. Launched in 1972, Cosmos-482 was stranded by a failed upper stage of its rocket and circled Earth for 53 years.

In its last days, several space agencies and research groups forecasted when it would fall, and therefore where. Roscosmos later reported that it came down in the Indian Ocean, west of Jakarta. By the end of 2025, low Earth orbit held 25,060 cataloged objects, nearly twice as many as a decade earlier, according to the European Space Agency.

Many old satellites and spent rocket stages will one day fall back without control and may come down anywhere on Earth. In a study published in Acta Astronautica, we combine two tools to predict these falls: a neural network and the laws of orbital motion. Khawariz Andaristiyan of the Research Center for Satellite Technology at Indonesia's National Research and Innovation Agency (BRIN), with Affiani Machmudah and Wahyudi Hasbi of the same center and Ridanto Eko Poetro of the Institut Teknologi Bandung.

An object near the end of its life in orbit still flies at about 7.8 kilometers per second (4.8 miles per second). An error of one minute in the time of its fall shifts the place where it falls by about 460 kilometers (290 miles) along its path, and an error of one hour by about 28,000 kilometers (17,400 miles), two-thirds of the way around Earth. To say where an object will fall, we must first say when.

What brings these objects down is drag, the braking by the thin air of the upper atmosphere. When the sun is active, it heats the upper atmosphere, which swells, so that the air at a given height grows denser and low orbits decay faster. The sun's activity rises and falls in a cycle of about 11 years, and the three falls we studied all came in its recent active years, from 2023 to 2025.

How strongly the air slows an object is measured by its ballistic coefficient: its drag coefficient times its cross-section, divided by its mass. A compact sphere shows the air the same face from every side. A tumbling rocket stage, or a satellite with wide solar panels, shows it a different face from one moment to the next.