During its time in space, the European Space Agency’s Gravity Field and Steady-State Ocean Circulation Explorer, or GOCE, has mapped Earth's gravitational field in great detail.
But GOCE ran out of propellant last month and has been slowly dropping 2.5 miles a day. As of Wednesday, the satellite was 113 miles up as it circled the Earth every 88 minutes.
About 25 to 45 fragments of the spacecraft are expected to make it all the way to Earth's surface after the fall. The biggest fragment could weigh up to 200 pounds.
"It’s rather hard to predict where the spacecraft will re-enter and impact,” said GOCE mission manager Rune Floberghagen. “Concretely our best engineering prediction is now for a re-entry on Sunday, with a possibility for it slipping into early Monday.”
GOCE was always designed for a so-called "uncontrolled re-entry" as it lacks traditional thrusters, and was instead equipped with ion engine to help it maintain a low orbit.
But this planned fall is just one of a string of recent and upcoming uncontrolled entries as our many man-made orbital objects, some decades old, fall to Earth.
About 100 tons of space debris are expected to fall from the sky this year alone. So far, there have been no reported instances in which anyone has been injured by falling space debris.