π Space
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Defence: the European strategy against spatial collisions

Sophy Caulier, Independant journalist
On April 27th, 2021 |
4 min reading time
Pascal Faucher
Pascal Faucher
President of the European Union Member States Consortium on Space Surveillance and Tracking
Key takeaways
  • Today, one in two low-Earth orbit collisions is due to just two events: the deliberate destruction of a Chinese satellite in 2007 and the collision between two Russian and American satellites in 2009.
  • This debris forces ground crews to conduct avoidance manoeuvres: in 2020, Europeans had to perform 31 such manoeuvres.
  • To address the problem of space debris, Europe will launch the European Union Space Surveillance and Tracking (EU SST) in May 2021.
  • The aim is to protect Europe's space infrastructure from collisions; intentional or accidental.

You are the pres­i­dent of the Euro­pean pro­gram EU SST. What does it con­sist of? 

Pas­cal Fauch­er. EU SST stands for Euro­pean Union Space Sur­veil­lance and Track­ing. It is a civ­il pro­gram man­aged by a con­sor­tium of sev­en Mem­ber States (France, Ger­many, Italy, Spain, Poland, Por­tu­gal and Roma­nia). The fact that the Euro­pean Com­mis­sion asks coun­tries to organ­ise them­selves to man­age and offer a sort of “pub­lic ser­vice” to all Euro­pean users is quite unique. With Europe’s new mul­ti­an­nu­al finan­cial frame­work and the new Space Reg­u­la­tions, ini­ti­at­ed in May 2021, the pro­gram will also be renewed. New part­ner­ships are under dis­cus­sion with 19 oth­er Mem­ber States.

The SST was cre­at­ed to face the increas­ing risk of col­li­sions between space objects. These risks increas­ing­ly threat­en economies and Euro­pean cit­i­zens. Indeed, we depend more and more on nav­i­ga­tion, com­mu­ni­ca­tion and obser­va­tion apps relayed via satel­lites, which can be seri­ous­ly dam­aged by a col­li­sion. Just one of these col­li­sions can gen­er­ate thou­sands of new debris. The role of the con­sor­tium is to pro­vide ser­vices linked to secu­ri­ty, safe­ty and long-term sus­tain­abil­i­ty of space oper­a­tions. In oth­er words, we pro­tect our infra­struc­tures in orbit against haz­ards and inten­tion­al threats.

What are your objec­tives, and what means do you have to car­ry them out? 

We offer sev­er­al ser­vices: eval­u­a­tion of col­li­sion risks in orbit and fol­low­ing return of risky space debris into the Earth’s atmos­phere, as well as the detec­tion and the analy­sis of frag­men­ta­tion in orbit. To that end, we have a net­work of around fifty sen­sors on the ground, radars and tele­scopes of mil­i­tary, sci­en­tif­ic or com­mer­cial ori­gin to track objects in space, but also data pro­cess­ing means. The Cen­tre for Oper­a­tional Orbitog­ra­phy (COO) of the CNES in Toulouse col­lects data and con­stant­ly mon­i­tors the orbits of Euro­pean satellites.

For the past two years, the Mem­ber States have been build­ing a com­mon data­base whose pur­pose is to share thou­sands of mea­sures about objects in space on a dai­ly basis.

The fusion of these data allow us to cat­a­logue orbital objects. Until now, Europe used a lot of mil­i­tary data pro­vid­ed by the Amer­i­can defence agency, which are a bench­mark in that regard. Admit­ted­ly, they have invest­ed heav­i­ly in this field and for a long time: more than half of the active satel­lites – civ­il, mil­i­tary or com­mer­cial – are Amer­i­can. One of the objec­tives of the SST is to raise the capa­bil­i­ty lev­el and to build a strate­gic auton­o­my of Europe in this field, to pro­tect Euro­pean infra­struc­tures, pri­mar­i­ly the flag­ship projects Galileo and Coper­ni­cus and also to offer reli­able ser­vices to its partners.

And it is begin­ning to take shape. For exam­ple, at the end of Feb­ru­ary 2021, a col­li­sion risk was detect­ed between a Galileo satel­lite orbit­ing at 20 000 km and a launch­er stage, a space debris. Thir­teen sen­sors of the SST net­work were acti­vat­ed and con­firmed a very strong col­li­sion prob­a­bil­i­ty. The oper­a­tor decid­ed on 6th March to manoeu­vre the satel­lite in order to pro­tect it.

How, and by whom, is the deci­sion tak­en in such cases? 

SST offers a ser­vice of infor­ma­tion: we show oper­a­tors what is the risk, and where it is found. We cal­cu­late the “Time of Clos­est Approach” and give it to them, it is the moment in which two objects are the clos­est to one anoth­er. We also detect the

“miss dis­tance” and “radi­al sep­a­ra­tion”, infor­ma­tion regard­ing the dis­tance between the two objects and the prob­a­bil­i­ty of col­li­sion, “scaled prob­a­bil­i­ty of col­li­sion”. Thus informed, they can decide to launch an avoid­ance manoeu­vre or not; if the mea­sure is above the thresh­old fixed by the oper­a­tor. A satel­lite is expen­sive, cost­ing sev­er­al €100M, so any respon­si­ble oper­a­tor would pre­fer to avoid a col­li­sion than risk los­ing a satel­lite. Fur­ther­more, it is often pos­si­ble to syn­chro­nise the pro­tec­tion manoeu­vre of the satel­lite with the sta­tion keep­ing manoeu­vre, which is per­formed once a month on average. 

There is always a great deal of uncer­tain­ty. We pro­vide approx­i­ma­tions to locate objects, but these are sub­ject to var­i­ous fric­tions which means that orbits are nev­er per­fect­ly accu­rate. That being said, the more we have infor­ma­tion, the more we can deter­mine pre­cise­ly the orbit of a space object. Today, we have 17 mil­lion mea­sure­ments for 9,500 orbital objects.

How fre­quent­ly are these risks detected?

In 2020, for the fleet of 148 satel­lites we mon­i­tored at the time – we now mon­i­tor 213 satel­lites – we detect­ed 377 “high inter­est events”, name­ly high secu­ri­ty risk events, which led to 31 avoid­ance manoeu­vres. The risks, and there­fore the manoeu­vres, are very rare in high- or medi­um-Earth orbits. They are far more fre­quent in low orbit, where the vast major­i­ty of space objects and debris are found, most being due to two major events cre­at­ed thou­sands of debris in this already con­gest­ed orbit. Half of col­li­sion risks in low orbit are due to debris from the explo­sion of an obso­lete Chi­nese weath­er satel­lite, vol­un­tar­i­ly destroyed in 2007 by Chi­na with an anti-satel­lite mis­sile. The sec­ond cat­a­stroph­ic event is a col­li­sion in 2009 between the deac­ti­vat­ed Russ­ian satel­lite Kos­mos and the active Amer­i­can com­mu­ni­ca­tions satel­lite Iridium. 

Our mis­sion is to ensure the pro­tec­tion of all active satel­lites. How­ev­er, the risk some­times involves inert debris, and we are then pow­er­less. It hap­pened recent­ly. On April 7, we detect­ed a risk in low orbit at 780 km of alti­tude, between two inert satel­lites, one Russ­ian and the oth­er Amer­i­can. The col­li­sion prob­a­bil­i­ty was very high. Final­ly, on April 9, the two objects brushed against each oth­er, only sev­er­al metres apart, but did not col­lide. But they could have explod­ed and cre­at­ed a myr­i­ad of new debris!

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