Cluttered space: Orbiting debris poses increasing threat, scientists say
Scientists are warning people about orbital junk. These leftover parts and old satellites have been left in orbit around planet Earth. The orbital junk could be a danger to future missions in space.
The scientists spoke at a conference in Germany. In less than 25 years, the scientists said, the number of orbiting fragments large enough to destroy a spacecraft has more than doubled.
The estimated tally of tiny objects is now around 150 million. The smaller parts can harm or damage spacecraft if they run into each other, and they are hard to track.
"We are very much concerned," said Rolf Densing, director of operations at the European Space Agency, or ESA. He begged for a worldwide effort to tackle the mess.
"This problem can only be solved globally," he said.
Risks Rise Along With Litter
The junk is dangerous because it moves incredibly fast, around 17,500 miles per hour. Even a very small object can hit with enough force to damage the surface of a satellite or manned spacecraft.
In 1993, ground-based radar showed about 8,000 manmade objects in orbit that were larger than 4.5 inches across. These objects are big enough to cause catastrophic damage, said Holger Krag. He is in charge of ESA's space junk office. He explained that there are about 5,000 objects in space larger than 3.25 feet across, as well 20,000 4-inch-long objects and 750,000 objects half an inch across.
"For objects larger than 1 millimeter, 150 million is our model estimate for that."
According to researchers' mathematical calculations, the risk of a crash is not very likely. However, the chances rise as the litter increases and more and more satellites are sent into space.
Krag warned that the amount of junk in space is not merely rising at a steady pace. It is growing at an increasingly rapid rate.
Experts Seek Ways To Reduce Junk
The conference is being held in Darmstadt, Germany, and it broadcast its opening speeches on the internet. It is the biggest-ever gathering dedicated to space junk.
Experts will spend four days discussing the problem. They will consider measures to reduce space litter, such as by "de-orbiting" satellites at the end of their working lives.
Krag pointed to two events that have made the problem much worse by creating junk fields. These fields may create more junk as pieces smash into each other.
The first was in January 2007, when China tested an anti-satellite weapon on an old Fengyun weather satellite. At the time, the move sparked an outcry by orbital junk experts.
The other was in February 2009. An Iridium telecoms satellite used for cellphone and internet communication and a Russian military satellite, accidentally collided.
Space Station Crew Needs Notice
Given enough warning, satellites can move a little bit to avoid a crash. However, this uses up fuel and potentially shortens the satellite's working life.
ESA receives a "high risk of crash" alert message every week on average for 10 of its science satellites in low-Earth orbit, Krag said. Each has to resort to "one or two" avoidance actions per year.
French astronaut Thomas Pesquet delivered a message to the conference from the International Space Station, or ISS. He said the manned outpost in space was shielded for objects less than half an inch across.
The ISS often has to move to avoid junk but needs 24 hours' warning to be able to do this, he said.
If there is less time, Pesquet explained, the crew has to close the hatches and enter the safe zone of the ISS. The safe zone is a smaller Russian spacecraft that can leave the ISS in the case of a crash. "This has happened four times in the history of the ISS program," he said.