Fraunhofer Institute for High Frequency Physics and Radar Techniques FHRBy analyzing a fragmented debris object in orbit, the TIRA space observation radar successfully mastered an unusual task. Fraunhofer FHR was able to detect, track, and image the object and provided the German Armed Forces Space Command and its inter-agency Space Situational Awareness Center with decision-relevant and operationally usable data on the condition of the object and its surroundings.
Humans have left their mark in orbit: the volume of space debris is steadily increasing. Explosions of rocket upper stages, satellite launches, and uncontrolled collisions of space debris further increase the number of particles orbiting the Earth. This was also the case on July 3, 2022. Shortly before 6:00 a.m. CET, the half-cylinder of a fairing, which protects a payload from external influences during rocket launch and is jettisoned before the satellite is deployed, fragmented: an H-2A Payload Fairing (2018-084D). This raised numerous questions: Are there other debris fragments drifting through orbit in the vicinity of the original object? Is anything left of the original object, or has it been completely destroyed?
Targeting the debris with two different radar settings
These questions needed to be answered using TIRA. A rather unusual task for the space observation radar, as the system is not designed to scan large portions of the sky. “Staring Mode” was used to detect debris along the expected path of the fairing. In this mode, the antenna is pointed at a specific section of the sky and is moved only to compensate for the Earth’s rotation. Previous data provided clues as to when the debris fragments would pass through this observed section of the sky. To ensure that the passage of the fragments was not missed, the observation with the tracking radar began several minutes before the expected time and did not end until 18 minutes later. A total of 50 detections were recorded. A particularly strong echo was detected four minutes after the expected contact.
To better characterize this strong detection, the researchers initiated “tracking” in a second measurement with TIRA: Instead of looking at a constant section of the sky as before, they tracked the object and simultaneously imaged it with the target imaging radar. But how do you find the object again? Since the echo occurred four minutes after the expected contact during the first measurement, the team calculated that the object was delayed by 25 seconds per day. In this way, the researchers extrapolated its reappearance and were able to detect it again with certainty.
Among other things, it was determined that the object was rotating very rapidly, at about 20 degrees per second, and had a geometry similar to that of a half-cylinder. Through its analysis of the H-2A payload fairing, Fraunhofer FHR was once again able to contribute to space situational awareness and thus to improving the basis for decision-making regarding operational and strategic measures in space.