Solid Underconstrained Multi-Frequency (SUM) Deployable Antenna: Built, Measured, and Deployed to Tens of Microns

The Solid Underconstrained Multi-Frequency (SUM) antenna is a new deployable reflector architecture developed for operation at 240 GHz, where solid apertures require sub-63-micron root-mean-square (RMS) surface accuracy to meet λ/20 performance. SUM employs rigid carbon-fiber composite segments guided into position by high-strain rods and precisely seated using kinematic mounts, enabling an under-constrained deployment sequence that decouples actuation from final alignment. Testing has demonstrated deployment repeatability better than 10 microns and composite surface fabrication accuracy near 20 microns RMS, with assembled reflectors meeting the allocated layup and assembly portions of the error budget. Remaining challenges are dominated by thermal deformation and limitations in surface metrology, indicating that improved thermal-control strategies and higher-precision measurement systems will be required to close the final margin for flight. The reflector stows within a compact 0.42-m³ volume and deploys to a 2.4-m aperture, enabling high-frequency solid-surface antennas for ESPA-class spacecraft. This paper presents the SUM architecture, fabrication and assembly methods, deployment and layup accuracy results, and the full surface error budget demonstrating SUM’s potential for next-generation Earth science and communications missions.