The first space junk observed during the day

On February 10, 2009, the operating Iridium 33 communication satellite collided with the inactive Cosmos 2251 satellite. The incident took place over Siberia at an altitude of about 800 km above the Earth. The total speed of the collision was approximately 11.7 km / s, thanks to which two satellites produced 2,000 fragments larger than 1 cm.

Over the next few months, the debris spread over the entire Earth orbit, and since then they have threatened other satellites remaining in Earth orbit.

The above event was a warning not only for all satellite operators, but also for politicians.

The problem of the so-called space debris took real shape that day

- says prof. Thomas Schildknecht, head of the Zimmerwald Observatory and deputy director of the Astronomical Institute at the University of Bern.

The ZIMLAT telescope at the Zimmerwald Observatory for measuring the distance to space debris

It starts to get crowded in the space around the world

In some orbits, the risk of a collision with space debris is currently so high that satellites residing there regularly have to perform maneuvers to correct the flight trajectory in order to avoid a collision.

Each year, the European Space Agency receives thousands of collision warnings for each of its satellites, which in turn lead to an average of several dozen orbital maneuvers per year. In most cases, the threat to satellites is one of approximately 20,000 known space debris.

Unfortunately, we know the orbits of inactive satellites, the upper parts of rockets or fragments created after collisions with an accuracy of only a few hundred meters

Says Schildknecht.

For this reason, it is very often difficult to determine whether the orbital maneuver, which in any case is very expensive, is necessary at all and whether it actually reduces the risk of a collision.

Very often, lasers are used to measure the distance to the satellites, which make it possible to assess the distance with an accuracy of several meters.

At the Zimmerwald Observatory, we have been using this technology for years, measuring the distance to objects equipped with special laser retroreflectors. Only a few observatories around the world have been able to determine the distances to space debris using special lasers

- adds Schildknecht.

Until recently, such measurements could only be made at night.

Turn. Daytime surveying with geodesic lasers

On June 24, 2020, researchers from the University of Bern were able for the first time to conduct daytime observations of space debris with a geodesic laser at the Swiss optical ground station at the Zimmerwald Geodynamic Observatory. Geodesic lasers are at least one order weaker than highly specialized lasers for tracing space debris. Additionally, detecting single laser photons reflected from space debris in the photon stream of daylight poses a serious challenge.

The success of the Zimmerwald Observatory was only possible thanks to the combination of active debris tracking with highly sensitive CMOS cameras analyzing real-time images and a digital filter that detected photons reflected from objects in real time.

Being able to observe garbage throughout the day allows you to take many more measurements. There is a whole network of stations equipped with geodesic lasers that can help in the future to create a very precise catalog of space debris orbits. Determining orbits more accurately over time will become an increasingly important issue if we are to continue to safely send satellites, probes and people into space.

The first space junk observed during the day