Space isn’t empty; it’s crowded. And what does up there, might not come back down. Everyone knows that NASA sends science instruments into space, but since the late 1950s, the United States, Russia, China, and lots of other countries have launched thousands of satellites including science satellites, telecommunication satellites, GPS satellites and spy satellites, which orbit at low, medium or high altitudes. These satellites don’t last forever, not even the highest-quality ones. The hardware eventually runs out of fuel or the battery dies or the system simply breaks down after a while.
And that’s not all. There’s old boosters, ballistic missiles left over from testing warheads, insulation, paint chips or other material that flaked off of satellites all floating around up there. On top of all the old broken down satellite bits, some orbital debris is natural, such as meteorites the size of sand grains and larger.
Where does it all go? Does it just stay up there orbiting around in space forever? Can someone go and get it? Does it crash into other space junk? How much is out there? How big are the pieces?
Some space debris re-enters the atmosphere and burns up on its own, but most of it just remains in orbit for years. There have been a few known collisions between satellites over the years. This, of course, creates more debris. Some scientists fear that someday there may be a “chain reaction” in space as more debris causes more frequent collisions. About 15 years ago new regulations and requirements were put into place in order to de-orbit U.S. satellites and prevent future pile-ups. This involves a maneuver to push the satellite out of orbit proactively, driving it into the edge of the atmosphere to burn up.
Space garbage is bad for everybody just like pollution down on Earth. One idea to deal with it might be to send a laser up there to act like a giant broom and push the pieces of debris into the atmosphere to burn up or push them farther out to a higher orbit so they don’t interfere. Another classic design would be like a large net that can capture debris and then either contain it or burn it up in the atmosphere. The obvious question is who will pay for it, manage it and be responsible for it. A space dumpster would cost as much as or more than designing and launching a normal satellite, and no one wants to pay for and pick up someone else’s trash.
For now, a U.S. government agency monitors all orbital debris that’s roughly larger than a baseball. There are about 15,000-20,000 cataloged objects that are monitored on a regular basis. (Spy satellites are generally kept anonymous and identified by a number or a cryptic name because, well … they’re secret.) NASA flight teams usually get a warning three to five days in advance of a possible collision. As the time gets closer and closer and more data and information comes in, they often find that the object will miss by a safe distance and the warning abates. But, when computer analysis tells them that the odds of a collision are greater than about one in ten thousand that’s usually when they consider doing a procedure called a “collision avoidance maneuver” on the satellite to move out of the way. The team uploads a command, which tells the satellite to move its orbit up or down a few hundred kilometers.
It’s a bit like driving in freeway traffic. Before you change lanes to avoid one dangerous driver, you have to look to make sure there’s not another one in the lane you’re moving to. So before performing the maneuver, the team will also need to check where the satellite is going and see if there are any other objects in that new orbit. And just like freeway traffic, not everything stays in its own lane. Some objects have elliptical orbits and cross back and forth over several altitudes and pass over multiple satellite paths.
As I said, space isn’t empty; it’s crowded.