The Space Ranger Around 150 million bits of scrap are circling the earth. Dr. Manuel Metz of the German Aerospace Center (DLR) tidies up the heavens.

“We should, as a matter of principle, ensure that satellites are responsibly disposed of at the end of their working lives.”

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The Space Ranger

 It is the job of Dr. Manuel Metz to tidy up the heavens.

Some of these parts can be seen from earth with the naked eye, others are only a few millimeters across. We’re talking about space debris. Since the first artificial earth satellite Sputnik 1 was launched in 1957, the number of objects humankind has abandoned in orbit has increased dramatically. Burnt out final stages of rockets, decommissioned satellites — and also the debris resulting from explosions or collisions encircle the earth like a metal belt.


The volume of catalogued space debris over 10 centimeters in diameter has increased disproportionately over recent years. Left 1960, right 2010.

With its global network of radar stations and telescopes, the U.S. Military’s Space Surveillance Network has identified and catalogued more than 16,000 bits of debris larger than ten centimeters in size. But equally dangerous to space travel are the estimated 150 million fragments larger than one millimeter. With relative speeds of around 50,000 kilometers an hour, they can develop enormous destructive force on impact.


The simulated impact of a 12 millimeter ball on an eight centimeter thick aluminum sheet. The impact speed was seven kilometers per second.

First Target: Prevention 

At DLR — German Aerospace Center Bonn-Oberkassel — Dr. Manuel Metz of the space travel management department has been responsible for the subject of space debris avoidance since 2009. Metz, who has earned a doctorate in astronomy, accompanies and supports work being performed by research bodies and universities as they search for solutions. In addition, he safeguards German interests in international committees that deal with this problem and draw up guidelines on debris prevention, for all the aerospace nations. “Our major objective is to make sure that this debris isn’t created in the first place. This entails launching the smallest number of objects into orbit and limiting their stay in the orbit regions that are important to space travel. It is our endeavor to design satellites in close proximity to earth in such a way that within 25 years they automatically drop into a lower orbit, where they burn up,” explains the 37 year old.

As opposed to this, communication, television and weather satellites operate at an altitude of 36,000 kilometers. They can be lifted into a graveyard orbit about 300 kilometers further out in space.


Special satellites equipped with grappling arms might serve as heavenly garbage collectors in the future.

Second Target: Cleaning up 

The tasks assigned to this space travel manager also include researching ways to render existing space debris harmless. The highest concentration is to be found where most space activities occur, namely at an altitude of between 800 and 900 kilometers. The denser the “junkyard”, the greater the likelihood that the socalled Kessler syndrome will occur: A collision of two large items gives rise to innumerable pieces of smaller scrap — a fatal chain reaction. “The only thing that will help to prevent this is to systematically bring them back to earth,” says Manuel Metz. Being considered are satellite missions where a space vehicle is directed safely to the larger chunks of debris, which it then picks up with robotic grapplers, nets or harpoons. They are then brought back to earth along a defined reentry trajectory.  “As yet none of these options has proven to be feasible. We will have to investigate several approaches because, for example, retrieving satellites is a lot different than collecting the upper stages of rockets. And there still is, of course, the question of finances,” emphasizes Metz.

The challenges are manifold. “To get a grip on the problem, politicians, partners  from the nations involved in space travel, and researchers all sit at one table and search for solutions,” the scientist notes. “Working in this team and the vital common goal both make my job exciting.”


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This article was first published in Spring 2015.

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Tell us, Dr. Metz …

… what do you see as your greatest strength?

I have always been interested in technical and scientific subjects — even those beyond my area of expertise. This has proved very helpful with interdisciplinary topics like those I pursue.

… how would you characterize yourself in a few words?

I am a quiet person who thinks analytically. And I am a family man.

… where do you get your energy?

Time spent with my loved ones is precious to me. There I can easily switch off and recharge my batteries. And then, my work in an international setting is very diversified and motivating.

… what would you take with you to the proverbial desert island?

A sturdy tent, a pressurized alcohol cooker — both from a Swedish company I won’t name — and my family.

… what dream would you like to make come true in your life?

I would love to go on another trekking tour in the Scottish Highlands. But there are also other remote regions of the world I would like to visit.

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