Climate effect in space: Expect more satellite collisions

Increasing carbon dioxide levels in the Earth’s atmosphere will result in a long-term decline in air density at high altitudes, according to a new study.

This may extend the lifetime of space debris and intensify the likelihood of satellites running into space debris, stated the findings of the study published in the journal Geophysical Research Letters.

The number of defunct satellites in low earth orbit — altitude up to 2,000 kilometres — had increased by 50 per cent over the last two years, researchers from British Antarctic Survey stated.

Collisions could result in serious issues in a society highly dependent on satellites for navigation, mobile communications and Earth monitoring. Moreover, satellite destruction could cost billions of dollars.

The researchers presented the first accurate assessment of climate change in the upper atmosphere for the next 50 years. The changes in the lower and middle atmospheres have been subjected to several studies. But there has been far less investigation into scenarios at higher altitudes.

There were 5,000 active and defunct satellites in low earth orbit as on March 2021. And various companies are planning to launch more in the next decade.

Satellites continue to orbit even after they are decommissioned. But they gradually slow down owing to atmospheric drag.

Satellite operators should ensure that decommissioned satellites deorbit within 25 years, according to the Inter-Agency Space Debris Coordination Committee guidelines. But the decreasing air density will disrupt debris management by causing planning and calculation errors.

The upper and middle atmospheres have been cooling compared to the lower atmosphere. This causes the density to decrease, which reduces the drag on objects, such as discarded satellites and mission-related debris.

With less drag, these objects’ lifetimes are prolonged. They stay in orbit for longer and have a higher chance of collision with other space junk and operational satellites.

A global model of the entire atmosphere up to 500 km altitude was developed by Ingrid Cnossen, an independent research fellow at the British Antarctic Survey. Using this model, she simulated the changes in the upper atmosphere up to 2070.

She compared her predictions to data from the previous 50 years. Cnossen observed that the expected average cooling and upper atmospheric density reduction are roughly twice the previous, even under a moderate future emission scenario.

“It is increasingly important to understand and predict how climate change will impact these regions, particularly for the satellite industry and the policymakers involved with setting standards for that industry,” said Cnossen.

The changes in the upper atmosphere over the last 50 years and our predictions for the next 50 are a result of CO2 emissions, Cnossen added.

Over 30,000 trackable debris pieces with diameters of more than 10 centimetres and nearly 1 million pieces with diameters over 1 cm are drifting in the low earth orbit, according to the European Space Agency.