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GOCE Satellite Makes Fiery Fall to Earth

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Bill Chater: GOCE Re-entry

As captured – and tweeted – by skywatcher Bill Chater in the photo above, the European Space Agency’s Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) re-entered the atmosphere on Sunday, making an uncontrolled fall after running out of fuel last month.

Launched in 2009, GOCE mapped variations in Earth’s gravitational field to help scientists better understand how gravity affects phenomena like ocean circulation and sea level. As Slate reported, the satellite only spent about a quarter of its time over land, so the odds were high for a safe crash into the ocean, but when an object weighing over a ton is in a free-fall to Earth, the risk is noteworthy.

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While scientists knew that most of the satellite would burn up during approach, its 25 to 45 pieces of debris weighing up to 200 pounds each pose a significant threat. Without any means of controlling where it would land, officials from the ESA, Inter-Agency Space Debris Coordination Committee and United States Strategic Command closely monitored the massive “space debris” until it fell into the South Atlantic off the tip of South America, south of the Falkland Islands.

Since 2008, United Nations guidelines have attempted to reduce the danger of space debris, and scientists now build extra fuel and thrusters into space-bound objects to help control re-entry.

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GOCE had already been designed when the guidelines were issued, but future iterations would likely include these failsafes.

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The risk of uncontrolled space debris is increasingly common, however. On average, one piece of tracked “space junk” falls every day and one intact defunct spacecraft or old rocket body comes back every week, BBC reported. Renowned astrophysicist Neil Degrasse Tyson was quite thorough in pointing out that major space debris disasters like the one depicted in Gravity are scientifically questionable at best, but the everyday risks merit serious consideration as increasing what we send into space increases what we can expect to fall back. There are currently about 750 live satellites circling Earth and an estimated 500,000 pieces of space debris in orbit, dating as far back as the 1958 Vanguard 1 research satellite.

The Next Frontier of Risk: Space Debris

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You may remember back in February 2009 when the Iridium 33 and Russia’s Cosmos 2251 satellites collided in orbit somewhere above Siberia. The crash of the two objects resulted in more than 600 pieces of debris larger than a tennis ball being strewn about in space, adding to what scientists and researchers call space debris or space junk.

The problem with the collision of satellites (many of which are non-working and have been abandoned in space to drift freely for eternity) is that it creates added debris in an already cluttered lower earth orbit, creating a hazard to operational satellites. The debris can also pose a threat to space stations — in March of last year, the crew of the international space station was forced to take cover in its escape capsule after learning that a piece of debris moving at 20,000 mph was heading towards them. Though the object missed the space station, it won’t be the last close call.

We covered space risk in our May 2009 issue, stating that scientists are concerned about the “dangerous and possibly irreversible cycle of wreckage.” The worst case scenario for the problem of space debris is known as the Kessler Syndrome (named after NASA scientist Donald J. Kessler), a scenario in which the volume of space debris in lower earth orbit is so high that the risk of further collisions increases to the point where launches become nearly impossible.

A space so cluttered with junk that the U.S. military (or any military for that matter), NASA or any weather, cable or GPS satellites cannot launch? Scary indeed.

The latest issue of the Economist explores the ongoing problem of space pollution, stating that:

At orbital velocity, some eight kilometers a second, even an object a centimeter across could knock a satellite out. According to the European Space Agency, the number of collision alters has doubled in the past decade.

But there are possible solutions to clearing the massive amount of space junk out there. The following are a few ideas put forth in the aforementioned article:

  1. Use ground-based lasers to change the orbits of pieces by vaporizing their surfaces. Apparently, the American armed forces claim one laser facility could complete the job in a matter of three years.
  2. Alliant Techsystems has proposed building special satellites enclosed in multiple spheres of strong, lightweight material. Debris that came into contact with the satellite would lose momentum and velocity with each collision. “As a bonus, many object large enough to cause damage would be shattered by the collision into fragments too small to cause serious harm.”
  3. Robots. That’s right — robots. Many space agencies are considering the option of sending robots into space to dock with dead satellites and fire rockets to either boost them into an uninhabited orbit or deorbit them completely.

Whatever these agencies decide, something should be done quickly to remedy the situation. For every day that passes, more space junk accumulates. Let us not come to realize the dreaded Kessler Syndrome.

From the August 21st - 27th, 2010 issue of the Economist.

From the August 21st - 27th, 2010 issue of the Economist.