The minivan-sized ROSAT satellite, shown in an artist's rendering, is expected to re-enter the atmosphere sometime between Friday and Monday. The minivan-sized ROSAT satellite, shown in an artist's rendering, is expected to re-enter the atmosphere sometime between Friday and Monday. (EADS Astrium/Associated Press)

A retired satellite is hurtling toward the atmosphere and pieces of it could crash into the Earth as early as Friday, the German Aerospace Center says.

Scientists are no longer able to communicate with the dead German satellite ROSAT, which orbits the earth every 90 minutes, and experts are not sure exactly where pieces of it could land.

Parts of the satellite, which is the size of a minivan, will burn up during re-entry but up to 30 fragments weighing a total of 1.7 metric tonnes could crash into the Earth sometime between Friday and Monday, centre spokesman Andreas Schuetz told The Associated Press.

"All countries around the globe between 53-degrees north and 53-degrees south could possibly be affected," Schuetz said Wednesday — a vast swath of territory that includes much of the earth outside the poles.

The scientific satellite was launched in 1990 and retired in 1999 after being used for research on black holes and neutron stars and performing the first all-sky survey of X-ray sources with an imaging telescope.

The largest single fragment of ROSAT that could hit into the earth is the telescope's heat-resistant mirror, which weighs 1.6 metric tonnes alone.

The satellite will re-enter the atmosphere at a speed of 28,000 kilometres per hour.

As it nears the Earth in coming days, scientists will be able to more accurately estimate exactly when it will land to a window of about 10 hours.

A dead NASA satellite fell into the southern Pacific Ocean last month, causing no damage, despite fears it would hit a populated area and cause damage or kill people.

The German space agency puts the odds of somebody somewhere on Earth being hurt by its satellite at 1-in-2,000 — a slightly higher level of risk than was calculated for the NASA satellite. But any one individual's odds of being struck are 1-in-14 trillion, given there are seven billion people on the planet.