A robot arm in orbit starts assembling an antenna on its own

Caltech's ASTRA payload has spent six months in orbit autonomously joining truss sections, though it did not finish its antenna.

A Caltech team has put a robotic assembly system into low Earth orbit and had it build part of a structure with no astronauts involved. The payload, called ASTRA (Autonomous In-Space Tensioned Reflector Assembly), launched March 30, 2026 from Vandenberg Space Force Base on a SpaceX Transporter-16 mission. It rode aboard Momentus's Vigoride 7 vehicle, which carried 10 payloads, and has now spent six months in orbit.

ASTRA takes up about one cubic meter. It launched with two pre-assembled truss bays plus the machinery and materials to build more. An automated arm pulls structural tubes and joints from storage dispensers and joins them into repeating truss sections. The goal was a reflector antenna 1.4 meters across, made of composite fiber tubes, aluminum connectors and a Kapton reflective surface. DARPA funded the work under NOM4D, and ASTRA is one of two projects chosen for its third phase. Caltech had under 12 months to build, test and deliver the hardware. Sergio Pellegrino leads the effort and co-directs the Space Solar Power Project.

The point is the launch constraint. Rocket fairings cap the size of anything sent up whole. The workarounds today are folding structures that unfold later, or having astronauts assemble launched parts. If a robot can build from compact, dense-packed stock, orbital infrastructure is no longer limited by fairing size. That matters for large antennas, solar power stations and habitats, and so for energy and connectivity. DARPA's program manager says NOM4D targets structures hundreds of meters to kilometers across, which cannot be done today.

The caveats are real. Because of technical difficulties and scheduling constraints, the robot built only an initial section, not the full antenna. Use for much larger telescopes, antennas and power stations is a future possibility, not something shown. The source text was also cut off, so some payload detail is missing. Watch for a completed assembly and the other phase-three project, a University of Illinois Urbana-Champaign test of hardening carbon tubes in space on the International Space Station.

Source: ScienceDaily