Astroscale aced the world’s first rendezvous with a piece of space junk

There's a scene in the film Interstellar where Matthew McConaughey's character flies his spaceplane up to meet a mothership spinning out of control. The protagonist rises to the challenge with a polished piece of piloting and successfully links up with his objective.

Real life, of course, isn't quite this dramatic. Slow down that spin to a tranquil tumble, and replace McConaughey's hand on the joystick with the autonomous wits of a computer, and you'll arrive at an approximation of what Japanese company Astroscale has accomplished within the last year.

Still, it's an impressive feat of engineering and orbital dynamics. Astroscale's ADRAS-J mission became the first spacecraft (at least in the unclassified world) to approach a piece of space junk in low-Earth orbit. This particular object, a derelict upper stage from a Japanese H-IIA rocket, has been in orbit since 2009. It's one of about 2,000 spent rocket bodies circling the Earth and one of more than 45,000 objects in orbit tracked by US Space Command.

"This is the world's first technology that allows any object orbiting the Earth at high speeds to be safely approached from the ground," said Nobu Okada, founder and CEO of Tokyo-based Astroscale. "It has great potential."

Mission success

Like most other space debris, the H-IIA rocket approached by Astroscale is uncontrolled and lacks navigation aids or inter-satellite communication links that could help another satellite safely move in for a close look. This presents a more significant technical challenge than rendezvousing with a "cooperative" object like the International Space Station.

Ars reported on the progress of Astroscale's ADRAS-J mission last August, soon after the spacecraft flew as close as 50 meters (164 feet) from the H-IIA rocket. ADRAS-J is the centerpiece of a public-private partnership between Astroscale and the Japan Aerospace Exploration Agency, which participated with a $13 million contract to co-fund the mission.

ADRAS-J, short for Active Debris Removal by Astroscale-Japan, launched in February 2024 to begin its pursuit of the H-IIA rocket in a polar orbit more than 350 miles (560 kilometers) above the planet. On November 30, ADRAS-J completed its final close approach to the H-IIA upper stage to reach a position just 15 meters (49 feet) from the rocket, using cameras and laser ranging sensors for autopilot navigation before backing away.

With this achievement, Astroscale unlocked its final milestone payment from the Japanese space agency, officials announced Wednesday. Part of Astroscale's demonstration involved completing a 360° fly-around of the H-IIA rocket.

"This was acrobatic and super difficult technology," Okada said last month in a briefing on Astroscale's business outlook. "Please remember the debris is not sitting still. It is traveling around the Earth at seven to eight kilometers per second, which is (nearly) 100 times faster than a bullet train."

Imagery captured by Astroscale showed the H-IIA upper stage to be in good condition, looking much like it did before it launched 16 years ago on a mission to deploy a Japanese climate research satellite. The remnant rocket is about the size of a city bus, while ADRAS-J is a little larger than a kitchen oven.

Is this really for space junk?

It will be up to a future Astroscale mission, named ADRAS-J2, to transit the last 15 meters to the H-IIA rocket. ADRAS-J was a pathfinder and didn't have the equipment to actually latch onto another object in orbit. Last year, Japan's space agency awarded Astroscale a contract worth $88 million (13.2 billion yen) to build and launch ADRAS-J2 to rendezvous and use a robotic arm to attach itself to the same H-IIA rocket, then steer the discarded upper stage back into the atmosphere for a destructive reentry.

ADRAS-J2 is scheduled to launch in 2027, according to Astroscale.

Astroscale's showcase in orbital ballet positions the company as a contender in the commercial satellite servicing industry, where business opportunities may eclipse the market for space debris removal, which Okada founded Astroscale to pursue in 2013. The company has subsidiaries in the United States, United Kingdom, France, and Israel to tailor offerings to customers in different parts of the world.

The US and European governments are now customers for Astroscale. The UK Space Agency and the European Space Agency partnered to award Astroscale approximately $35 million in government support for a demonstration mission named ELSA-M, slated to launch in late 2025 or early 2026 for an attempt to capture and de-orbit a defunct satellite in OneWeb's broadband megaconstellation using a magnetic docking plate. This will differ from Astroscale's work in Japan because the OneWeb satellite will be prepared to receive a visitor, unlike the H-IIA rocket.

Removing space junk from orbit sounds like a wonderful idea. It could reduce the chance of collisions generating more pieces of space debris. Spent rocket stages left in orbit are among the most concerning objects for space debris hawks because they might retain propellants or stored battery energy with explosive potential.

But the big question is who pays for such an undertaking? Removing just the 2,000 rocket bodies from orbit could probably cost tens of billions of dollars. Perhaps it's worth launching a handful of cleanup missions to remove the most hazardous objects in orbit, such as large spacecraft or debris flying too high for atmospheric drag to force reentry for centuries or longer.

Therefore, it's not surprising Astroscale has pivoted to other applications. The rendezvous and proximity operations (RPO) technology proven with ADRAS-J enables several other types of missions, such as satellite servicing and inspection.