Fault Tolerant Beam Steering for Cubesats

This proposal is an enabling communication technology for small spacecraft beyond LEO. We propose to adapt real-time coherent combining software for electronically steered arrays recently proven for ground-to-space communications to the computing constraints of small spacecraft. An electronically steered array antenna system must adjust the phase of multiple received signals so they coherently combine, with errors in the process rapidly degrading the output signal. The chief method of mitigating phase errors is to place the radio antenna elements into a robust, high precision mechanical structure. On a moving platform, another mitigation is also used, precise measurements of movement and/or cessation of all movement during antenna usage. The first is at direct odds with the need for small spacecraft to use lightweight, flexible, and deployable structures. The second is an extreme challenge for orbiting craft, especially those navigating in CisLunar or deep space where relative position knowledge is degraded compared to LEO satellite situations.Miles Spacersquo;s coherent combining software continuously adapts to phase differences in radio data streams allowing them to be combined successfully, nearly eliminating grating lobes. Doing so allows flexible, deployable antennas to be used on rotating craft, even those that may have residual antenna vibration due to recent propulsion and attitude control usage. There are corresponding cost and risk reductions in craft mass and machining tolerances with improved tolerance to deployment mechanism issues and on-mission antenna damage.Through a contract with ATLAS Space Operations, Miles Space demonstrated to the US Air Force its coherent combining software operating on a phased array ground terminal downlinking GEO and LEO satellite signals. The algorithm was used on digitized RF data before the data reached a commercial modem for decoding. As judged by the modem, real-time coherent combining eliminated grating lobes.