As the world waits for six-ton satellite UARS to crash to Earth this week, we can reveal that a second giant piece of space junk is set for a similar fiery demise within weeks.
It wasn’t always junk. The latest doomed craft, called ROSAT, is a German space telescope, partly built in the UK and controlled by NASA, that observed in X-ray light from 1990 to 1999 in an orbit 575 km above the Earth.
But atmospheric drag has already brought ROSAT – it stands for the ROentgen SATellite – to a height of less than 327 km and it has no on-board propulsion system to control its descent.
NASA experts are warning that as many as 30 fragments, weighing a total of 1.6 tons, could survive re-entry to hit the ground, including the largest chunk, the observatory’s hefty glass mirror.
It will re-enter the atmosphere at a speed of around 28,000 km per hour and disintegrate in early November. There is currently an error of plus or minus five weeks in this prediction, so the crash landing could occur in early October.
Fluctuations in solar activity which can cause variation in the density of the fringes of the atmosphere add to the uncertainty.
Most of the inhabited world lies under the track of ROSAT which flies in an orbit that carries it from 53 degrees north to 53 degrees south. Experts expect most of the debris to impact the ground in a compact region but fragments could fall within an 80 km wide path.
NASA’s Upper Atmosphere Research Satellite is also hurtling out of control at 8 km (5 miles) per second and space scientists have no way of predicting where it will land. Virtually the entire populated world is at risk because the satellite flies between a zone stretching as far north as Edinburgh and as far south as Cape Horn in Chile.
The 35-ft long satellite, which was put into orbit by space shuttle Discovery in 1991, will disentegrate as it makes a fiery re-entry which is predicted to happen on Friday, give or take a day.
Debris is expected to be scattered across a 800 km area with the biggest surviving chunk weighing 300 lb – about the same as a fridge-freezer. NASA admits that could strike anywhere but says there is only a one in 3,200 chance of it hitting anyone.
The biggest piece of space junk to fall from orbit was America’s first space station Skylab in July 1979. The 75-ton outpost, which had been home to several visiting astronauts, broke up in a massive fireball, scattering debris over a sparsely populated region of western Australia.
Chartered mechanical engineer and space enthusiast Lucy Rogers is an expert in the dangers of orbiting debris and has recently blogged about it. She told Skymania News: “Uncontrolled re-entries of satellites are just the tip of the iceberg of the problem caused by space debris.
“Catastrophic collisions will cause fragmentation and each fragment has the potential to cause further collisions. If we do not do something soon, we will no longer have safe corridors to space, and all the services on the earth that rely on space – systems such as financial transactions, search and rescue and sat nav – will no longer be available to us.”