NASA Findings Underscore LEO Satellite Risks
2020-11-30 | 5 min read
Earlier this year, OneWeb made headlines for filing bankruptcy. Now, it is again in the spotlight for emerging from bankruptcy under new ownership. The company announced near-future plans to launch 36 low earth orbit (LEO) satellites. It revealed plans for an eventual constellation of 650, but it reportedly requested approval for nearly double that number. By comparison, SpaceX has launched around 800 satellites and was granted permission for more than 10,000. Project Kuiper, the Amazon LEO entity, gained approval to launch more than 3,000. As these companies race to keep or take the LEO lead, much data will be gathered around performance over the satellite’s lifetime and how to improve it. NASA, for example, just revealed new findings around LEOs and orbital drag.
According to the NASA article, “Solar Superstorms of the Past Help NASA Scientists Understand Risks for Satellites,” “Extreme storms from the Sun can change Earth’s atmosphere enough to pull a satellite farther off orbit in one day than they’d normally experience in a year. These orbital deviations don’t cause satellites to fall out of the sky, but they can disrupt their communication with Earth, shorten their lifespans, and can even increase the chances of a terminal collision in space.”
Orbital drag is a known issue. NASA has been tracking its effects on LEO satellites used for Earth and weather observations for a long time. What is surprising is that the new research from NASA scientists points to more impact on orbits from longer, less intense storms. Previously, it was assumed that shorter, more severe events would result in worse orbital drag.
Our closest star, the Sun, provides the light to nurture life on Earth. But it also spews dangerous particles and radiation that can affect astronauts and technology in space. Scientists study the many affects from these outpourings, including what happens when such eruptions are extreme. When it comes to the thousands of active satellites in space, however, one of the key concerns is indirect effects from particles and radiation, even from lesser storms.
Understanding Orbital Drag
According to NASA, high-energy particles and radiation from the Sun may heat the Earth’s atmosphere as they collide with common molecules, such as nitrogen and oxygen. As that heated air rises, the atmosphere expands like a balloon. A powerful enough storm will make the atmosphere expand so much that it engulfs LEO satellite orbits.
Typically, these satellites fly through areas with little to no atmosphere. NASA compares the increased atmosphere to running in a headwind. Not only does it slow down, but it also will drop in altitude. One new estimate asserts that the drop from an extreme storm event could result in a satellite going down a third of a mile in elevation. The author of that paper, Denny Oliveira, scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, emphasizes, “That’s a lot. In fact, it’s as much as a satellite would typically lose in a year.”
With the large amount of LEOs expected to launch in the next few years, such research findings are critical. Satellite designers and operators need to clearly understand performance issues over the satellite lifetime, as well as any risks to performance or the mission. By knowing the issues and risks involved, the satellite industry can better predict them and even compensate for them. For LEO satellites, that would mean a much better chance of mission assurance.
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