Optimized communications protocol for low earth orbit cubesat

Abstract

The purpose of this document is to describe and analyze the implementation of a communications protocol to transfer data between a CubeSat and ground station. The mission of the CubeSat is to track debris in low earth orbit (LEO). Data transfers to and from the satellite include images, telemetry, commands, and processed data. The communications channel operates on a half-duplex connection with a single linearly polarized half-wave UHF dipole attached to the CubeSat, and a circularly polarized Yagi-Uda antenna on the ground station. Data will pass through a Software Defined Radio (SDR) and on the ground station over packet radio. The challenges faced in designing the protocol include high packet loss, short and infrequent access times, high delay times, variable signal strength, and limited power. The designed protocol will be implemented and tested on the CubeSat. It is evaluated against other existing communications protocols for performance.