CommCube 1 and 2: A CubeSat Series of Missions to Enhance Communication Capabilities for CubeSat

摘要

CubeSats and small satellites are becoming a way to explore space and to perform science more affordably. As the goals for these spacecraft become more ambitious in terms of physical distance (moving from Low Earth Orbit (LEO) to Geostationary Earth Orbit (GEO) or further), and of the amount of data to relay back to Earth (from Kbits to Mbits), the communication systems currently implemented will not be able to fully support those missions. Two of the possible strategies to solve this issue are the following: 1. Increasing the time available to communicate to the ground by using existing satellite networks as communication relays. 2. Equipping the satellite with a more powerful antenna compatible with the volume and mass constraints imposed by CubeSats and small satellites. This article describes two CubeSat missions currently under development at the Massachusetts Institute of Technology: CommCube 1 and CommCube 2. CommCube 1 applies the first strategy: the mission aims to test the possibility for a CubeSat to relay data to a satellite constellation, with consequent increase in the throughput capability of the system. The mission is designed for LEO; however the concept could be scaled for interplanetary missions, if a relay infrastructure is available. This is not necessarily true for any celestial body, however it could be the case for Mars which is currently orbited by multiple satellites that could be used in the future as a network of relays for a CubeSat orbiting the planet. CommCube 2 is focused on the second strategy: design and implementation of more powerful antennas. Current antennas for CubeSats are mostly dipole, monopole, or patch antennas with limited gain. Deployable (not inflatable) antennas for CubeSats are currently being investigated, but these solutions are affected by the challenge of packaging the whole deployable structure in a small spacecraft. Hence, CommCube 2 will test the deployment, inflation and functionality of a 1 m inflatable dish for a CubeSats. The dish will increase the gain of the wireless link by approximately 15-20 dB, allowing the communication system to increase the data rate and/or to transmit from a further point in the solar system. The two satellites are currently developed in parallel and they share several commonalities in the avionics, power and structure subsystems. The article presents an overview of each mission together with details on the current status of design and tests.