Caltech's ASTRA Robot Builds Antenna Module Autonomously in Orbit

ASTRA is a gantry robot that moves in straight lines along three perpendicular axes. It occupies one cubic metre and carries a robotic arm and a motorised dispenser of building materials. It launched on 30 March 2026 aboard Momentus' Vigoride 7 vehicle, on a SpaceX rocket. After commissioning, it began assembling structural tubes and joints into repeating units called bays, which form the truss that becomes the final device.

What it built

The antenna is a test article, not a functional one. ASTRA flew with two modules already assembled and only had to build the third. The result uses composite-fibre tubes, aluminium connectors and a reflective Kapton film, a durable material common on spacecraft.

A minor incident delayed the work, so the antenna will not be fully completed before the mission ends in December. Even so, the team considers the approach proven, as more time would allow it to finish.

Caltech scientists controlled the robot from Earth with minimal intervention, using seven or eight communication windows a day of about 15 minutes each. A twin unit in the laboratory helped them troubleshoot problems.

Part of a DARPA programme

ASTRA belongs to DARPA's Novel Orbital and Moon Manufacturing, Materials, and Mass-efficient Design (NOM4D) programme. It also includes a laser metal-bending project from the University of Florida and a University of Illinois Urbana-Champaign experiment, planned on a module attached to the International Space Station, on hardening carbon tubes in space. Neither has launched yet, so how well they would complement ASTRA remains to be seen.