Caltech's ASTRA robot assembled a third truss bay in orbit, in what the university describes as the first autonomous construction of a structure in space.
The robot was developed by researchers at the California Institute of Technology, known as Caltech, with funding from the US Defense Advanced Research Projects Agency (DARPA). It is part of DARPA's Novel Orbital and Moon Manufacturing, Materials and Mass-efficient Design (NOM4D) programme.
Caltech's 1.4-Metre ASTRA Antenna Remains Incomplete
ASTRA was designed to build a 1.4-metre reflector antenna from composite fibre tubes, aluminium joints and a reflective film. Caltech says the spacecraft carried two truss bays built on Earth; after deploying them, ASTRA assembled a third bay in orbit.
The planned truss contains 11 bays. The demonstration did not complete it: Caltech says the team ran into time limitations and unforeseen problems and was only able to build the initial section. The mission is expected to end in December 2026, and the team says the test showed the approach was feasible while identifying a need to simplify and refine the design.
ASTRA's Orbital Assembly Relied on Engineers on Earth
Caltech calls the manipulator autonomous, but its account describes an operation that still relied on commands and troubleshooting from the ground. Engineers sent instructions through the Vigoride vehicle and checked the assembly's progress using images returned from orbit.
When the team encountered problems, it tested possible fixes using a flight spare in Caltech's laboratory, then relayed workarounds to the spacecraft. Caltech reports that communication windows were limited to about seven or eight periods of roughly 15 minutes each day.
That distinction sets the boundary of the result: ASTRA assembled a section on board, while the overall mission remained ground-directed. Caltech's account does not describe the robot independently planning or managing the construction sequence.
DARPA's NOM4D Programme Envisions Much Larger Structures
NOM4D is investigating whether large structures could be built from components in orbit instead of being folded into a rocket fairing or assembled manually from sections sent up on separate launches.
DARPA programme manager Andrew Detor said the programme aims to support structures hundreds of metres or kilometres in scale, adding that 'nothing approaching that scale can be achieved today'.
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DARPA lists possible future uses including space depots, habitats, solar arrays and radio antennas. These are programme goals, not capabilities tested by ASTRA. Caltech has also identified large telescope reflectors and communications antennas as potential applications of in-space construction.
The result is a small-scale demonstration with a specific limit: one bay was assembled in orbit, while the full 11-bay antenna was not completed. Further engineering would be needed before the approach could support the much larger systems described by DARPA and Caltech.
