Introduction

Raincube is the first active radar in a CubeSat. This introduction provides a brief description of CubeSats and summarizes the innovative work on CubeSat antennas ranging from low‐gain to high‐gain antennas operating at UHF, S‐, X‐, Ku‐, and Ka‐band. It also provides clear examples of high gain antenna (HGA) choices to achieve mission goals and constraints. Selecting a HGA for deep space communication or remote sensing instruments is not an easy task and is of the utmost importance for mission success. A guideline highlighting the advantages and drawbacks of each HGA technologies is provided to help in the selection process is presented. On‐going research concepts are summarized with promising results (e.g. membrane antennas and larger mesh and reflectarray designs). Finally, the chapter describes four major effects related to space environment (radiation exposure, material outgassing, temperature change, and multipacting breakdown) as they are crucial when designing spacecraft antennas.