Do You Know Where Your Satellite Is Tonight?

Increasingly crowded orbits require transparent modeling practices and data exchange.

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May-June 2024

Volume 112, Number 3
Page 160

DOI: 10.1511/2024.112.3.160

A satellite in orbit around the planet moves at 8 kilometers per second. Right now, there are about 9,500 satellites circling Earth, and about three-quarters of them are classified as small satellites—with a mass less than 500 kilograms and possibly as little as a few kilograms. Space is vast, but orbits most useful to us are either geostationary (in which the satellite rotates with the Earth) or within about 1,000 kilometers of the surface. The likelihood of satellites in these orbits colliding with one another or with debris is very small, but the cost and consequences of such a collision could be very large. Although classical mechanics might have led us to believe that orbits never change, in fact there are physical phenomena on many timescales that can change orbits. We must observe satellites and account for all these factors to track where satellites are now and estimate where they might be in the future.

QUICK TAKE
  • Earth’s orbit is getting more crowded, and it will only become more so with the upcoming deployment of mega-constellations of small communications satellites.
  • Keeping track of the location of satellites, through direct monitoring or modeling, is designed to prevent collisions, but both methods currently lack precision.
  • Space debris is often not depicted at an accurate scale, making Earth’s orbit seem more crowded than it is; still, new methods are needed to minimize the threat of collisions.

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