Leonard David's INSIDE OUTER SPACE

Photo illustration by Thomas Gaulkin for the Bulletin of the Atomic Scientists’ January 2022 issue (used with permission)

Active spacecraft face greater chances of collision with space debris as a result of reduced density in the upper atmosphere.

A new study released by the British Antarctic Survey, published in the journal Geophysical Research Letters, presents a projection of climate change in the upper atmosphere for the next 50 years.

Increasing levels of carbon dioxide in the Earth’s atmosphere will result in a long-term decline in air density at high altitudes. Such decreased density will reduce drag on objects orbiting in the upper atmosphere, between 90 and 500 km altitude, therefore, extending the lifetime of space debris and elevating the risk of collisions between debris and satellites.

Credit: NASA/Goddard

Space pollution problem

Ingrid Cnossen, a NERC independent research fellow at the British Antarctic Survey, used a global model of the whole atmosphere up to 500 km altitude to simulate changes in the upper atmosphere up to 2070. She compared her projections to the last 50 years of data and found that even under a moderate future emissions scenario the predicted average cooling and decline in upper atmosphere density is about twice as strong as has been seen in the past.

“Space debris is becoming a rapidly growing problem for satellite operators due to the risk of collisions, which the long-term decline in upper atmosphere density is making even worse,” Cnossen stated in a British Antarctic Survey statement. “I hope this work will help to guide appropriate action to control the space pollution problem and ensure that the upper atmosphere remains a usable resource into the future.”

Space debris impact on functioning satellite.
Credit: The Aerospace Corporation

Mean decline

As noted in the paper, “the global mean decline in thermosphere density is a concern for the future exploitation of the LEO environment due to its impact on atmospheric drag and the lifetime of space debris.”

Cnossen’s research points out that climatic changes in the upper atmosphere will have important consequences for the build-up of space debris in the low Earth orbit (LEO) environment and may also impact on the long-term stability of satellite-based measurements.

“The projection presented here offers the first realistic insight in the quantitative long-term changes to expect in the upper atmosphere during the next roughly 50 years in order to prepare for these effects,” Cnossen explains in the paper.

To access the full research paper – “A Realistic Projection of Climate Change in the Upper Atmosphere Into the 21st Century” – go to Volume 49, Issue 19, October 16, 2022 of Geophysical Research Letters at: 

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL100693