Welcome to the future. Satellites reentering Earth's atmosphere are the reality of living in the space age. In fact, it happens fairly regularly nowadays. We have expected this as we’ve been launching thousands of satellites over the last 50 years. See 1957 up until 2010 below.
It is actually a great thing that one of the dead satellites is reentering. Just like everything else, satellites eventually stop working. Ideally, they use their remaining fuel to lower their orbit so much it ensures a very quick reentry, or they raise their orbit so that they don’t interfere with active satellites. Unfortunately, for various reasons, that is not always possible and a dead satellite becomes another piece of space junk. In the UARS case, we have a piece of junk the size of a bus that could pose a real threat to hundreds of other active satellites that we use on a daily basis.
There is sometimes the option of shooting down a satellite but that is a touchy subject. In 2007, China tested an anti-satellite (ASAT) missile against one of its older satellites. This resulted in thousands more pieces of debris in orbit dense with active satellites. This was criticized as a very irresponsible act because it created a much worse debris situation for low satellites. Many of these pieces are small, but even a golf ball traveling at 18,000 mph could pulverize another satellite. See video below.
The United States also recently shot down a dead satellite in a cleaner fashion that resulted in debris reentering. However, shooting down satellites is a last resort for obvious political reasons. See video below.
So if we can’t shoot something down, we just have to leave it up in orbit and let physics run its course. Space is a big place and these things will never hit, right? In 2009, physics and statistics met when an old defunct satellite collided with an active Iridium satellite, again resulting in increased space junk. See video below.
Why didn’t we just steer the active satellite out of the way of the dead one? If you are aware of the situation, you can. In 2010, a zombie satellite could have hit critical active geostationary satellites but they were able to maneuver out of the way.
Unfortunately we don’t always have a clear understanding of everything going on in space. But we are getting there. Right now this is the primary desire of the entire global space community. This is typically referred to as Space Situational Awareness (SSA) and it is extremely necessary.
The challenges at hand are extremely complicated physics and computing problems and they will require an unprecedented level of cooperation between many governments and companies. The Space Data Association
is a trailblazing, nonprofit association that brought together many commercial satellite operators who are currently sharing data on more than 300 active satellites. The basic concept is that each operator knows the location of their own satellites much more accurately than they know the location of the other operators’ satellites. So they essentially share info with each other without giving away any propriety information.
Thousands of other very smart people in various other organizations are looking into methods of ensuring a safer space for satellites and human missions. Ideas range from refueling satellites to debris-collecting sweeper satellites. But the solution is not immediate. Here at AGI, we’re very proud of our role in this challenge. We’ve been making software for SSA since 1989
So when one bus-sized piece of space junk re-enters on its own, it is one less problem we have to worry about.