Title: Solid Underconstrained Multi-Frequency (SUM) Deployable Antenna for Earth Science
Presenting Author: Jonathan Sauder
Organization: Jet Propulsion Laboratory
Co-Author(s): Nacer Chahat, Juan Mejia-Ariza, Grayson Hanes, Tim Rogenmoser, Carlos Jose Garcia-Mora, Brecht Pierreux, Raquel Rodriguez Monje, Shannon Brown

Abstract:
To build the next generation of predictive weather models, we need to measure a storm from space across time over its entire lifecycle, from water vapor to heavy precipitation. The single satellite approaches currently taken can only capture one point in time, not the storm’s lifecycle. To capture the lifecycle across time satellite constellations is required, and the affordable solution are small satellites. While we have demonstrated we can shrink the satellite bus and associated instruments, the antenna’s diameter cannot be shrunk, as this would not provide the resolution required. To enable us to build better weather models this mission needs a broad multi-frequency (10 GHz to 600 GHz), offset-fed, deployable antenna which expands to multiple times the satellite bus size. The Solid Underconstrained Multi-Frequency (SUM ) deployable antenna is 2.4 meters in diameter, can operate at frequencies between 2 GHz and 240 GHz, and can stow in a volume of 0.57x0.61x1.3 m^3. When stowed, the segments stack neatly on top of each other into a compact volume. After launch, launch locks are activated, releasing the segments, and the high strain rods deploy the system into an initial configuration. Two high strain rods arrange each element in its proper orientation, so the system can next be pulled together. After the deployable antenna opens, the cables are then retracted, slowly reeling in each of the segments into the final deployed shape. Kinematic joints precisely locate each segment relative to each other within 20 microns, preloaded in place by the cable, for an overall surface root mean squared (RMS) error of ~60 microns. Because of its under-constrained deployment configuration, unlike hinged antennas, the segments can be stored anywhere on the spacecraft where there is spare volume, maximizing stowed efficiency.