- Illustration courtesy DLR: An artist’s impression of ROSAT in orbit.
Dead Satellites are being ‘unwelcome guests’ recently. The 6-ton Upper Atmosphere Research Satellite (UARS) satellite has entered the Earth’s atmosphere early morning of September 24th 2011, but where it has crashed remains unknown. According to NASA, debris would likely have fallen in Ocean, and it may never be found.
Usually satellites’ lifespan depends on their sizes; life span is determined by how much liquid fuel they carry aboard. A satellite that has exceeded its useful purpose has several final resting places. These depend on the amount of fuel available on the satellite, and whether ground control is still able to manoeuvre it. One method is to move the satellite into a ‘graveyard orbit’ (geostationary orbit), which is higher in orbital band and no other satellites are orbiting. Dying satellite can be left to degrade over time, but as it breaks up and potentially shifts in orbit, this could still prove dangerous to other satellites.
Some satellites are merely left in their current orbits if uncontrollable. Other satellites are purposely moved lower into the atmosphere so they burn up and hopefully disintegrate before reaching the Earth. While this is usually the case there have been some notable exceptions, including NASA’s Skylab station in 1979, NASA’s UARS and ROSAT as mentioned earlier.
According to the Federal Communications Commission, any satellite with altitude in geostationary orbit, meaning that satellites just below 36,000 km, must be moved farther away from the Earth at the end of its useful life.
Satellites fall because of frictions and resistance of the atmosphere. In theory, if satellites’ centrifugal force and the Earth’s gravity balance, satellites can circulate the orbit without falling. Scientists probably have worked on different calculations on how satellites work; however, such recent events may appear as lack of preparation and carefulness. There are no clear back-up plans suggested if their expectations are not met. Our lives certainly have become more convenient with satellites, but if what we sent out in the past can come back to hurt us, how meaningful are those techniques? We have to look out for the safety of satellites rigorously.
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European Space Agency: Computer-generated image of the Earth
Not only that, there is a real danger. Concerning that we are sending the dead satellites to outer orbit and keep sending new satellites without proper disposal methods, our planet is turning into the largest dumping ground. Is this what you expect our planet to look like? Would this be what aliens expect the earth to be? They will have problems figuring out whether this Saturn-like planet is the earth!