A limited number of objects orbit Earth. Most eminently, there’s the moon, likely formed billions of years ago when Theia, a Mars-sized body, collided with Earth and hurled vaporized chunks of the young planet’s crust into space. The next cadre of objects are space stations, which currently only include the International Space Station (ISS)—China’s Tiangog-1 disintegrated in the atmosphere over the South Pacific on April 2, 2018. Next, there’s satellites, which number over 1,700.
Most prolifically, however, there’s junk. In fact, thousands of pieces of space debris currently orbit the earth.
It can be said that trash is merely what we leave behind. And, ever since the Soviet satellite Sputnik was launched in 1957, we’ve left a lot of materials just beyond our atmosphere. The below video created by Dr. Stuart Grey, lecturer at University College London and part of the Space Geodesy and Navigation Laboratory, demonstrates the total number of space trash from 1957 to 2016.
There are currently just over 17,000 trackable objects in orbit. Over 40,000 manmade objects have been tracked in Earth orbit since the advent of space travel, but have since burned up. It should be noted, however, that the total amount of detritus orbiting our planet it likely significantly higher than this amount.
NASA and the U.S. Department of Defense (DoD) cooperate and share responsibilities for characterizing the satellite environment. This includes orbital debris. However, NASA only has the capabilities to determine the extent of the population for objects less than 4 inches (10 centimeters) in diameter, and the DoD maintains a highly accurate satellite catalog on objects in Earth orbit that are larger than a softball.
Because of this, the exact amount of space debris orbiting the earth is likely significantly larger. Some estimates have placed it around 500,000. In fact, it was once estimated that the total number of space debris larger than 1 millimeter totaled more than 170 million.
Regardless of the exact count, the presence of space junk surrounding our planet is a problem. Traveling at speeds up to 17,500 miles per hour, even the smallest piece of space trash can damage a satellite or spacecraft. In fact, a number of space shuttle windows have needed replacement due to damage caused by impact with paint flecks.
For handling space debris, NASA has a set of long-standing guidelines that are used to assess whether the threat of close pass with known garbage is sufficient to warrant evasive action or other precautions. NASA also follows policies and standards for limiting orbital debris.
Similarly, ISO has published ISO 16126:2014 – Space systems – Assessment of survivability of unmanned spacecraft against space debris and meteoroid impacts to ensure successful post-mission disposal for assessing the potential impact of artificial, as well as natural (meteoroid), debris and ISO 24113:2011 – Space systems – Space debris mitigation requirements for reducing the likelihood of new space debris being introduced by assuring prevention in the design of unmanned spacecraft systems. ISO has also released several technical reports for handling this subject.
These efforts can help to prevent the introduction of new space debris and allow for safe navigation of spacecraft, but the issue of orbital rubbish persists. Even the introduction of new space debris were to cease entirely (which is unlikely), there would still remain the problem of trash beyond the sky.
Image Source: Eric A. Nielsen, “ARES: Orbital Debris Program Office Photo Gallery,” NASA, accessed April 11, 2018. https://www.orbitaldebris.jsc.nasa.gov/photo-gallery.html