Title: Deployable Cubesat Antenna for Signals of Opportunity (SoOp) Reflectometry in P and I-band 
Presenting Author: James Garrison
Organization: Purdue University
Co-Author(s): Susan Tower; Seho Kim; Jeffrey R. Piepmeier; Manuel A. Vega 

A deployable antenna for signals of opportunity (SoOp) remote sensing in P-band (240-270, 360-380 MHz) and I-band (137-138 MHz), compatible with a U-class (cubesat) platform, is under development. A train of 6-U satellites in high-inclination low-Earth orbit for retrieving Root Zone Soil Moisture (RZSM) is assumed as a relevancy scenario. SoOp operates as an active remote sensing technique in a forward reflection bistatic configuration exploiting pre-existing signal sources outside of protected bands. Antennas at these frequencies present a technical, however, challenge due to the large dimensions. MMA Design is approaching this challenge using a single active membrane antenna and collapsible boom technology to place the antenna away from the spacecraft bus. The proposed ~1.5 m X 1.5 m antenna will stow within a 10 cm square (1U) by 20cm tall (2U) form factor to support CubeSat applications. This high compaction ratio is possible through the use of MMA technologies such as high-strain composite booms, tensioned thin-film membranes, and low-profile launch restraints. A sub-scale model will be built and tested, to validate the design of both the electromagnetic (EM) properties of the antenna and mechanical design of the deployment mechanism. An end-to-end mission simulator is also under development, to both generate the mission error budget as well as validate the feasibility of the systems-level design, including factors such as the attitude dynamics and control of the deployed antenna and the sampling and coverage of the constellation. A preliminary error budget indicates that a low gain (0 dB) wide beam (+/-70 deg) antenna will meet working science requirements. This project was entered at TRL 2, with a measurement concept defined and simulations of the antenna performance. The team will mature the technology during a two-year period of performance (Feb. 2018 to Feb. 2020), and exit at TRL 4.