Space Waste: Debris in Space – Part One

When you look up at the night sky, you can see stars, planets and, occasionally, the reflected glint off the International Space Station (ISS) or another satellite as it passes over your location. What you can’t see are the tens of millions of particles of space debris in orbit, including most of the nearly 16,000 objects which are 10 centimeters in diameter (baseball size) or larger.  There are two types of space debris — natural and artificial. Natural space debris includes objects such as micrometeoroids, comets and asteroids. Artificial debris — also known as orbital debris or “space waste” — is any human-made and non-functional object, including: derelict spacecraft, spent rocket stages, mission-related debris (such as a lost tool bag) and fragmentation debris from satellite break-ups and deterioration. ¹ The oldest known piece of space debris still in orbit is the Vanguard 1 satellite, launched by the United States in 1958; as of 2011, the satellite — which stopped operating in 1964 — is expected to naturally remain in orbit for another 187 years. ²

All of this space debris puts the Space Station and other crewed vehicles in increased danger, as well as threatening the 957 operational communications, research and surveillance satellites currently in orbit around the Earth. ³ So far this month, the Station’s crew and their ground support teams have had to respond to two distinct threats of orbital debris passing at uncomfortably close range. According to one report, the ISS typically “has to dodge such debris four to five times each year,” so two independent encounters in one week is somewhat noteworthy.

Late in the evening on April 1st, ground controllers adjusted the Space Station’s orbit to avoid debris created by the accidental collision of two communications satellites in 2009 – Russia’s Cosmos 2251 (Космос-2251) and one of the United States’ many Iridium satellites, Iridium 33. This particular debris had been tracked for more than several hours, allowing ample time to adjust the Station’s orbit and avoid disrupting the crew’s activities; in fact, the debris avoidance maneuver (NASA acronym? You guessed it, DAM!) took place during their sleep period. ⁴ Detailed, real-time observations and calculations are used to determine the probability of a debris strike, and thereby determine whether or not the ISS will perform a debris avoidance maneuver. ^{5  6}

Less than a week later, on the morning of April 5th, NASA began monitoring a new debris threat. There was not enough time to coordinate another debris avoidance maneuver, so Mission Control advised the crew to be ready to evacuate to their Soyuz TMA-20 spacecraft as a safety precaution. ⁷ This debris threat was due to a 2007 anti-satellite missile test conducted by the Chinese space agency. China’s destruction of their weather satellite, Fengyun-1C, resulted in the largest recorded creation of space debris in history, adding at least 2,317 golf ball-sized or larger objects as well as over 35,000 objects measuring more than 1 centimeter. ⁸ Especially worrisome, the test resulted in “the majority of the debris…thrown into long-duration orbits, with lifetimes measured in decades and even centuries.” ⁹

Ultimately, the April 5th debris encounter ended without incident. About 1.5 hours prior to the closest approach of the debris, NASA obtained sufficient data to confirm the object would harmlessly pass the Station, albeit at fairly close range (approximately 3.5 miles). With this knowledge, NASA relayed an “all clear” to the Station crew, allowing the astronauts to resume their normal tasks without having to seek shelter in their Soyuz. ¹⁰ According to Space.com, NASA and its international partners try to maintain a safety perimeter around Station that is fairly wide (15 miles), but shallow (.5 miles above and below) — like a pizza box.

At orbital velocity (17,500 miles per hour or more), colliding with even a very small object — like a grain of sand or a flake of paint — can cause significant damage. Unfortunately, there are many millions of pieces of space debris that measure less than 1 centimeter in diameter, and none of these objects are trackable with currently available technology and resources. Any object in orbit is at risk of being impacted by MMOD (NASA’s acronym for MicroMeteoroid/Orbiting Debris). Even Space Shuttles, which aren’t in space for more than 10 to 14 days at a time, have sustained some damage on orbit. The first documented example of damage to a Space Shuttle from an orbital debris impact was on STS-7, when a paint flake impacted one of Space Shuttle Challenger‘s windows. Another example of damage occurred during STS-115, when a small fragment of circuit board material damaged a payload bay door radiator on Space Shuttle Atlantis. ¹¹

The scale and complexity of the orbital debris issue can make it difficult to grasp. The Waste in Space infographic does a good job of surfacing important details. For example: Two incidents — China’s anti-satellite mission and the 2009 satellite collision — increased the total amount of orbital debris by more than 60%. ¹² If just two collisions can increase space junk that much, all space-faring nations must take heed. Each successive debris-creating event magnifies the risks to orbiting satellites significantly, putting humanity’s efforts in Low Earth Orbit (LEO) and beyond at ever-greater risk. ¹³

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Part Two of this series will explore how orbital debris is tracked and by whom, as well as methods for reducing space waste.