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Groundbreaking manoeuvre provides new images of orbital debris and confirms effective onboard collision avoidance system.

Astroscale Japan announced that its commercial debris inspection demonstration satellite, Active Debris Removal by Astroscale-Japan (ADRAS-J), has successfully taken further images of a debris object in space and demonstrated the effectiveness of its collision avoidance system while conducting a fly-around observation of the debris — a rocket upper stage.

ADRAS-J is the world’s first attempt to safely approach, characterize and survey the state of an existing piece of large debris through Rendezvous and Proximity Operations (RPO). This groundbreaking mission is rendezvousing with an unprepared Japanese upper-stage rocket body that is approximately 11 meters long, 4 meters in diameter, and weighs approximately 3 tons. After demonstrating safe approach and proximity operations with the object that is the size of a city bus, ADRAS-J has been gathering images and other data to assess its movement and structural condition. Unprepared objects in orbit are not designed with any technologies that enable docking or potential servicing or removal, heightening the complexity of the operations.

The fly-around observation involved a complex, autonomous operation to maneuver ADRAS-J around the upper-stage client for continuous image-taking, providing more insights into its characteristics and movement. These operations utilized relative navigation data from the Light Detection and Ranging (LiDAR) sensor, along with custom-developed software algorithms for alignment and control. ADRAS-J maintained a fixed distance of approximately 50 meters during the fly-around operations to capture images of the client, facilitating assessment for potential future removal. When ADRAS-J was approximately one-third through the fly-around observation (~120 degrees), an autonomous abort was triggered by the onboard collision avoidance system due to an unexpected attitude anomaly, and ADRAS-J safely manoeuvred away from the client as designed.

Proximity operations and safe approaches to client objects are critical for on-orbit services, and Astroscale prioritizes safety during all of its mission operations. ADRAS-J in particular is designed to avoid collisions at every phase of this challenging RPO mission, featuring:
  • Fault-Detection, Isolation, and Recovery (FDIR) software that detects anomalies with the spacecraft or within the relative distance to the client and implements countermeasures.
  • If the FDIR system detects an anomaly and the distance to the client is shorter than a certain threshold, an abort manoeuvre is performed to avoid collision.
  • Multiple types of abort manoeuvres are designed for the situation and trajectory, considering positional relationship and directions.
The abort manoeuvre implemented during the fly-around operation demonstrated that ADRAS-J can maintain safety even while performing close approach observations of non-cooperative objects. The autonomous abort manoeuvre performed as designed, validating extensive simulations that were conducted during the spacecraft’s development to verify safety and confirming the effectiveness of the collision avoidance system. There was no impact on ADRAS-J due to the abort, and the spacecraft remains in good health. The cause of the relative attitude control anomaly has been identified, and the team is currently preparing for another close approach to the client.

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