The Growth of Space Debris

Global Security Program

Union of Concerned Scientists

The Growth of Space Debris

Space debris is any human-origin object in space that no longer serves a useful purpose.

The following slides show how the amount of space debris orbiting around the Earth has increased since 1957, when the first satellite—Sputnik 1—was placed in orbit and the first pieces of space debris were created.

Source: http://www.secureworldfoundation.org/siteadmin/images/files/file_308.pdf

The Growth of Space Debris

Space debris can stay in orbit for a long time—decades in orbits near the Earth, and essentially forever at very high altitudes.

Over time, the amount of space debris has increased dramatically, as these slides show. It has become dense enough in some parts of space to threaten satellites, which can be damaged or destroyed if they collide with debris.

The Growth of Space Debris

In these slides, you will see debris in two main areas.

(1) The fastest growth is in orbits very close to the Earth, where the first satellites were orbited. These appear to form a fuzzy shell around the Earth in the slides.

This region is known as Low Earth Orbit, or LEO. It contains roughly half of today’s active satellites and half of the known space debris.

The Growth of Space Debris

(2) In the picture for 1970, debris in the Geo-stationary ring (GEO) has become obvious.

In this special orbit, satellites orbit the Earth in 24 hours, so a satellite orbiting above the equator will remain above the same spot on the Earth. This is particularly useful for communication and broadcasting.

Since these satellites must be above the equator, they form a circle around the Earth rather than a shell.

The Growth of Space Debris

Constellations of satellites used for navigation, like the GSP satellites, lie midway between LEO and GEO. Launching these satellites is responsible for some of the debris seen in that region.

The Growth of Space Debris

In LEO, space debris travels at roughly 17,000 mph—some 30 times faster than a passenger jet.

Because of its enormous speed, even small pieces of debris can cause severe damage to a satellite in a collision.

Satellites cannot be shielded against collisions with debris larger than about an inch in size. An object 4 inches in size could completely destroy a satellite in a head-on collision, which could produce thousands of additional pieces of deadly space debris.

The Growth of Space Debris

The United States tracks active satellites as well as large pieces of space debris. It keeps a list of those objects in a debris catalog.

The following drawings are from NASA. They show a “snapshot” of the cataloged objects over time (the debris are not drawn to scale). The debris count on the slides gives the number of objects in the catalog.

Today, only 5-6% of those objects are active satellites—the rest are debris.

The Growth of Space Debris

The rest of the slides will

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Debris count: <100

Debris count: 1,000

Debris count: 2,700

Debris count: 3,800

Debris count: 5,400

Debris count: 6,500

Debris count: 7,300

Debris count: 8,700

Debris count: 9,500

Debris count: 10,000

Debris count: 14,000