The Top 50 Most Dangerous Pieces of Space Debris

For the first time, an international team has drawn up a list of the 50 most dangerous space debris in low orbit. This unpublished Top 50 is published online on January 22, 2021 by the journal Acta Astronautica.

PARIS (CNES PR) — It is a landmark article. For the first time, space debris in low orbit (located at an altitude of less than 2,000 km) has been classified according to their dangerousness for operational satellites by a team that includes experts from China, the United States and Russia. France via CNES is one of the signatories of this historic paper published on January 22, 2021 by Acta Astronautica and whose results had already been presented, in October 2020, at the 71st International Astronautical Congress (IAC2020).

Space Debris Impact Factor

This Top 50 of the statistically most worrying debris is based on the aggregation of the lists established by 11 different methods. These 11 methods estimated the risk of new debris generation from formulas taking into account the mass of the object in orbit, its probability of collision with another debris or an operational satellite and the persistence of the new debris generated. One of these methods is CNES stamped and incorporates more than 40 years of work, in particular on the calculation of fragmentation in the event of a collision.

“For the first time, we have a paper signed by Chinese, Russians and Americans listing the 50 most dangerous debris in low orbit. This is remarkable work,” underlines Christophe Bonnal, space debris expert at the CNES launchers department. “This Top 50 does not mean that there are only 50 dangerous debris, the #51 and #52 are just as threatening as the #50 debris. There are more than 5,000 whole objects — and therefore particularly problematic — in low orbit.”

What are the 50 Most Worrying Pieces of Debris?

The vast majority of objects of greatest concern are rocket stages: there are 39 in this Top 50 – the 11 others being out of service satellites. Forty were placed in orbit before the 2000’s. Forty-three are of Soviet or Russian origin, four objects are Japanese, two objects are European and one object is Chinese.

“The first 20 pieces of debris are old stages of Soviet launchers, notably the enormous stages of Zenit rockets which are 9 tons and 9 meters long. Each month, two stages of Zenit pass within 100 meters of each other! If they collide from the front, we double the population of debris in orbit,” explains the CNES expert.

Note that no American debris is present in this Top 50.

“This Top 50 is based on the American public catalog of space debris. This catalog available on space-track.org is by nature biased, because it does not contain debris from the American defense sector,” indicates Christophe Bonnal. “We are currently working at European level to build our own catalog of objects in orbit within the framework of the EU SST program, chaired by CNES. France is a leader in Europe in space surveillance with devices such as the GRAVES radar and the Operational Orbitography Center in Toulouse.”

Clean up Space

For the authors of the article, this Top 50 should serve as a basis for determining which debris should be removed as a priority.

“If we remove 5 to 10 debris per year, we could stabilize the debris population in low orbit. Technical solutions exist. In December 2020, the European Space Agency ordered the 1st deorbiting of debris in orbit from the Swiss startup ClearSpace as part of ESA’s Adrios project, in order to find in 2025 a part of a Vega launcher. of 2 m x 2 m and 110 kg. Each year, around ten satellites are taken out of service, victims of debris.

But the cleaning of Earth’s orbits faces legal and above all financial problems. Removing large debris costs between 10 and 30 million euros. For Christophe Bonnal, more than the idea of ​​cost sharing between international operators, taxes, contribution via insurance (little subscribed), the most promising path is that of the development of commercial services in orbit, in English “in-orbit services”, and satellite inspectors-repairers.

One could imagine that at the end of their life, these “Swiss Army Knife” satellites collect the debris to clean the low orbits. The sustainability of space activities will depend on it.