Space debris: 'grandfather satellite' as it falls to Earth

A pioneering European satellite is set to fall to Earth in a matter of hours.

ERS-2 was a state-of-the-art observatory when it launched in 1995, developing technologies now routinely used to monitor the planet.

The European Space Agency (Esa) says most of the two-tonne satellite will burn up on the way down.

Some of the more robust parts are likely to withstand the extreme heat generated during high-speed diving, but these pieces are less likely to strike and cause damage to inhabited areas.

They could land anywhere in the world, but since much of the Earth's surface is covered by ocean, debris left on the surface is likely to be lost to the ocean.

“And it's worth highlighting that none of the elements that can re-enter the atmosphere (and reach the surface) are radioactive or toxic,” said Mirko Albani of ESA's Earth Observation Ground Division.

The agency launched two identical Earth Remote Sensing (ERS) satellites in the 1990s. They were the most sophisticated planetary observers of their day, carrying a suite of instruments to monitor changes in land, seas and air.

They monitored floods, measured continental and sea-surface temperatures, detected the movement of ice fields and sensed land buckles during earthquakes.

And ERS-2, in particular, introduced a new capability to assess the Earth's protective ozone layer.

“Absolutely,” said Dr. Ralph Korte. “In terms of technology, you can draw a direct line from ERS to Europe's Copernicus/Sentinel satellites that observe the planet today. ERS is where it started,” Airbus Earth Observation Business Development Manager told BBC News.

ERS-2 was home first of the two. Originally placed at an altitude of 780 km above Earth, engineers used up its final fuel reserves in 2011 to lower its altitude to 570 km. The upper atmosphere was expected to drag the spacecraft to destruction in about 15 years.

This prediction will come true on Wednesday evening, GMT.

It is difficult to say exactly when and where. Depends on the density of the upper atmosphere affected by solar activity.

Given the size of the satellite's orbit around the Earth, we can say with certainty that re-entry will occur between 82 degrees north and south.

Those fragments that impact the planet may include internal panels and some metal parts such as fuel and pressure tanks.

The element that has the potential to be created in some form in the atmosphere is an antenna for an artificial aperture radar system built in England. The antenna has a carbon-fiber construction that can withstand high temperatures.

When ERS-2 was launched, space debris mitigation guidelines were very loose. It was considered acceptable to bring the redundant spacecraft home within 25 years of operations.

Isa's new Zero Debris Charter Recommends that the period for disposal not exceed five years. And its future satellites will be launched with the necessary fuel and the ability to propel themselves to de-orbit in a short period of time.

The rationale is obvious: now that so many satellites have been launched into orbit, The potential for conflict is increasing. ERS-1 suddenly failed before engineers could lower its altitude. It is still 700 km above the earth. At that height it can take 100 years to fall down naturally.

SpaceX, the American company that operates the majority of operational satellites currently in orbit (more than 5,400), recently announced that it will take down 100 of them after discovering a bug that “increases the probability of future failure”. It wants to get rid of the spacecraft before any problems complicate the mission.

They said: “The accumulation of massive debris in low-Earth orbit continues unabated; 28% of current long-period massive debris has been left in orbit since the turn of the century.

“These uncontrolled mass clumps show the potential to create massive debris for the thousands of newly deployed satellites that fuel the world's space economy.”