Astroscale space janitor attempts fly-around of derelict upper stage

ADRAS-J avoids adding to debris problem with autonomous collision avoidance

Astroscale Japan has shown off images of orbital debris and demonstrated the ability of its spacecraft to avoid adding to the problem thanks to an autonomous collision avoidance system.

The ADRAS-J spacecraft was launched on a Rocket Lab Electron in February – a mission dubbed "On Closer Inspection" – to investigate a derelict HII-A upper stage.

The spacecraft came within several hundred meters of the 11-meter upper-stage rocket body in April and was within 50 meters by the end of May. On June 19, the fly-around operation began while maintaining a fixed distance of 50 meters, the company said today.

Image of a derelict HII-A upper stage in orbit taken by the Astroscale ADRAS-J spacecraft

Derelict HII-A upper stage taken by ADRAS-J (credit: Astroscale)

The purpose of the fly-around was to demonstrate the capabilities of the technology used for the ADRAS-J spacecraft and capture images of the derelict stage, which has a mass of approximately three tons or, by The Reg online standards converter, 1.814 skateboarding rhinoceri.

However, a third of the way through the fly-around, an autonomous abort was triggered "due to an unexpected attitude anomaly," and ADRAS-J backed away from the spent stage.

While unplanned, the automatic abort was a useful demonstration of ADRAS-J's ability to avoid collisions and, therefore, not become part of the debris problem itself that it is trying to help clear up.

Astroscale did not elaborate further on the cause of the abort, saying only that it had had no impact on the spacecraft, which remains in good health. In an update, the company said: "The cause of the relative attitude control anomaly has been identified, and the team is currently preparing for another close approach to the client."

The derelict upper stage was not designed with docking, rendezvous, or removal in mind, and ADRAS-J has been gathering images and other data for a follow-up mission – ADRAS-J2 – which will obtain further images and eventually de-orbit the rocket body "using in-house robotic arm technologies."

The problem of orbital debris is increasing, and while technology such as ADRAS-J can't deal with flakes or paint or bits and pieces shed from disintegrating rocket stages or satellites, bringing down something the size of the HII-A upper stage in a controlled fashion will be quite the achievement. Other space agencies will be monitoring closely after a number of well-publicized incidents of uncontrolled reentries. ®

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