The number of satellites in orbit is expected to rise considerably in the upcoming decade. More satellites mean more debris and that means a greater risk of collisions. The space industry is therefore looking for ways to safeguard space operations for years to come. Keeping Space Tidy: Industry Steps Up
When India’s Prime Minister Narendra Modi proudly announced that his country successfully shot down one of its Low Earth Orbit (LEO) satellites with an anti-satellite missile in March, many in the global space community were quick to condemn the action. Though considerably less damaging than the infamous 2007 Chinese anti-satellite missile test, the Indian demonstration created a cloud of debris fragments, some of which might remain in orbit for years.
More clutter in orbit is exactly the last thing the space community needs. According to the European Space Agency (ESA) Space Debris Office, there are currently about 30,000 out of control objects larger than 10 centimeter (cm) in diameter hurtling around the Earth, including defunct satellites and fragments generated in collisions and in-orbit explosions. In addition to that, ESA’s scientists estimate a further 900,000 fragments larger than 1 cm and a staggering 130 million pieces larger than 1 millimeter (mm).
The smaller objects are impossible track. Still, they have the ability to destroy a satellite.
“These collisions occur at impact speeds of around 40,000 kilometer (km) an hour,” Holger Krag, head of ESA’s Space Safety Program Office, tells Via Space. “A 1 cm object has the ability to terminate a mission. If a satellite is hit by something larger than 10 cm, the impact will not only terminate the mission but also generate a huge number of fragments.” Keeping Space Tidy: Industry Steps Up
In August 2016, a fragment only a few millimeters in size hit the Earth-observing Sentinel-1A satellite, operated by ESA as part of the European Union (EU)-funded Copernicus program. Although the fragment created a 40 cm hole in the spacecraft’s solar panel, the spacecraft was able to make up for the resultant power loss, and the mission could continue without changes. Krag, however, admits the impact could have been far worse.
“If we were just two or three milliseconds earlier, we would have had an impact into the main body and that definitely would have had an effect,” he says. “We would have probably lost one of the instruments or, if the tank was hit, we might have lost the whole mission.”
Krag says that most satellites would experience a collision with an object about a millimeter in size during their lifetime. Depending on the area of the impact, such a collision could degrade the satellite’s performance. A collision with a larger, 1 cm, object could happen about every few hundred years per each satellite. With thousands of satellites in orbit, such an incident is statistically likely to occur every few years. A collision with a 10 cm object might happen every five years, according to Krag. Smaller fragmentation events are, however, far more frequent.
“Most of the debris pieces that we have in space are a result of explosions,” says Krag. “We have had more than 200 break-up events of rocket stages and satellites that happen because the spacecraft are left in space for too long after the mission ends and suffer from the aggressive space environment as a result. Residual fuel and pressure in the tanks can then lead to a break-up.” Keeping Space Tidy: Industry Steps Up
Such an event, Krag says, happens about five times per year. And so, the amount of space debris fragments is gradually rising. The math is simple — the more objects in space, the greater the likelihood of collisions. And since the number of objects in space is expected to rise greatly as mega-constellations of small satellites are moving from plans to reality, the experts worry about the future.
Since the launch of the Soviet Sputnik 1 in 1957, around 8,400 satellites have been lofted into space. Out of the nearly 5,000 still orbiting the Earth only about 2,000 are operational. Over the past few years, new space companies have filed plans to launch a combined 14,000 satellites. Even if not all of these satellites make it into orbit, the environment around the Earth is without a doubt set to become much busier.