The Zimmerwald Laser and Astrometry Telescope (ZIMLAT) in Zimmerwald, which is used for distance measurement to space debris objects.
Credit: University of Bern, AIUB

Possible collisions between orbital debris and satellites can be detected at an early stage and evasive maneuvers can be initiated – that’s the promise of a new ability to spot space clutter during the day.

According to researchers at the University of Bern’s Zimmerwald Observatory they are the first in the world to succeed in determining the distance to a space debris object using a geodetic laser in daylight.

Geodetic laser systems are at least one order of magnitude less powerful than highly specialized space debris lasers.

The orbits of disused satellites, rocket upper stages or fragments of collisions and explosions are not known with sufficient accuracy, i.e. only to a few hundred meters.

The measurement of distances to such objects using the satellite laser ranging method is an effective technology to improve the trajectory accuracy to a few meters, say university specialists.

Example of a “string of pearls” of photons reflected by the target debris object in the “sea of sky background photos.”
Credit: University of Bern, AIUB

Reflected photons

“We have been using the technology at the Zimmerwald Observatory for years to measure objects equipped with special laser retroreflectors. Only a few observatories worldwide have succeeded in determining distances to space debris using special, powerful lasers to date,” explains Thomas Schildknecht, head of the Zimmerwald Observatory and deputy director of the Astronomical Institute at the University of Bern. “These measurements were also previously only possible at night,” he adds.

The success at Zimmerwald Observatory was made possible using a combination of active tracking of the debris using a highly sensitive scientific CMOS (short for complementary metal-oxide-semiconductor) camera with real-time image processing and a real-time digital filter to detect the photons reflected by the object.

Schildknecht told Inside Outer Space that the observation was an abandoned launcher upper stage. “Pretty large, of the order of [26 feet] 8 meters long. Precise orbits of such large objects are particularly important to avoid catastrophic collisions (laser ranging allows for higher accuracy orbits than, e.g., radars).”

During night time objects with sizes of the order of 1 meter have been tracked with lasers, Schildknecht says.

Thomas Schildknecht of the Astronomisches Institut der Universität Bern (AIUB).
Credit: Manu Friederich

Network of stations

In 2018, two additional domes extended the observatory ultimately making it the world’s largest observation station for space debris.

“The possibility of observing during the day allows for the number of measures to be multiplied. There is a whole network of stations with geodetic lasers, which could in future help build up a highly precise space debris orbit catalog,” Schildknecht points out. “More accurate orbits will be essential in [the] future to avoid collisions and improve safety and sustainability in space.”

Leave a Reply