Scientists have found a new way to monitor space junk surrounding earth, even in daylight.
A novel method of monitoring space junk for virtually 24-hours a day could help protect satellites currently orbiting the earth. With the new system, active satellites can avoid the increasing volumes of materials ranging from discarded spacecraft parts and decommissioned rockets and satellites.
Visualizing Space Debris During Daylight
The new technique, pioneered by a research team from the Austrian Academy of Sciences, is detailed in the journal Nature Communications. The Austrian team proposes utilizing a higher-powered laser to create a space debris laser ranging that detects diffuse reflections for space debris up to 36,000 kilometers away.
At present, space debris laser ranging is only possible for a few hours around twilight. During this narrow window, the satellite ranging stations surrounding Earth are still dark, and space junk is illuminated by the sun's rays. Aside from the time frame available, most discarded space debris were not designed with the foresight of debris detection in mind. These space junk are not usually equipped with a reflective surface to aid in detection once they are discarded and decommissioned.
With the proposed technique, they can potentially expand the observation time for these materials around the world. Furthermore, it can also pave the way for visualizing and mapping the trajectories of each space debris in range.
"The target needs to be lit by sunlight and cannot be in Earth's shadow," said Michael Steindorfer, a researcher in the project and a postdoctoral researcher in Austria's Space Research Institute.
Working Around Excessive Sunlight
To achieve the new detection method, the Austrian research team observed different stars with different levels of brightness and calibrated their telescopes accordingly, ensuring the visibility of debris in orbit.
They then started tracking targets starting at elevations above 15°. With the help of a computer program, they were capable of detecting the illuminated objects, from other light sources, and work around the daylight interferences. It required the researchers to continuously apply corrections to the captured images, based on the target's predicted path and time.
Through their software, they had to apply time biases continuously, center the target on their Satellite Laser Ranging (SLR) telescope, and shift the detector time. The team produced four successful trials with space debris, measured between March and October 2019. Researchers focused on debris from old Russian rockets--identifying them as Zenit, Tsyklon, or Vostok launches that the USSR launched from 1971 to 1995--with their longest measurement holding for about 100 seconds.
The detection method, receiving the photons reflected off the rocket bodies, could also provide additional information about the targets' rotational behavior--direction and period. In the discussion of the study, researchers noted that depending on the season, they could observe these space junk materials from the Graz SLR station at a maximum of six hours a day. With their proposed technique, they peg the potential observation period from the same location to about 22 hours.
Their proposed method will also drastically increase the output of all stations capable of doing space debris measurements. Once implemented, the improved insight regarding space debris will aid in decision-making processes, especially regarding avoidance maneuvers.