Surrey Space Centre, University of Surrey, Guildford, Surrey, GU2 7XH ESA Wireless Sensor Motes Study George Prassinos, SSC, University of Surrey

Surrey Space Centre, University of Surrey, Guildford, Surrey, GU2 7XH Strawman Missions Earth observation Satellites Science and Technology Enablement Vehicular Maintenance Astronaut EVA support On-Orbit Satellite Reconfiguration Formation Flying Spacecraft Missions

Surrey Space Centre, University of Surrey, Guildford, Surrey, GU2 7XH Missions of Interest 1.Satellite Cluster in LEO, e.g. plasma bubble monitoring, LEO drag monitoring, and upper atmosphere (100 – 200 km) gas species identification. 2.Image transfer between LEO spacecraft such as DMC to another spacecraft of the constellation. This offers a solution for multiple downloads per pass. 3.Nanosatellite inspection, e.g. of communication satellites in GEO, or of the ISS in LEO. 4.Lunar and Mars lander to Mars rover in local area: a few hundred metres max, not necessarily line of sight, may require health data or still images. 5.Lunar orbiter to lunar lander.

Surrey Space Centre, University of Surrey, Guildford, Surrey, GU2 7XH Why consider wireless? S/C fabrication –Manual operation –High costs –Long lead times –Harnessing and electrical interconnects require very complex integration and testing –10% of platform cost –15% of dry mass from harnessing

Surrey Space Centre, University of Surrey, Guildford, Surrey, GU2 7XH Motes for Space Applications Formation Flying (FF) FF enables small inexpensive satellites to fly in formation operating as a “Virtual Satellite” forming a satellite cluster Satellite cluster is a group of satellites within very close range of each other possibly closer than 100m Distributed architecture of the payloads among the satellites One satellite operates as an executive controller of the formation responsible for the Earth - Formation communications

Surrey Space Centre, University of Surrey, Guildford, Surrey, GU2 7XH Motes for Space Applications Satellite Cluster operating as a “Virtual Satellite” Virtual Satellite Advantages: –Each satellite will be smaller, simpler, lighter, simple to manufacture. –Lower total mission risk Reduce total mission failure to instrument failure by distributing the payloads among the satellites of the formation –Increase science data collection Stereo imaging Data of the same location from different angles at the same time –Adds considerable flexibility to the mission If a satellite fails could be possibly be replaced with a new one –Lower mission cost total mass is reduced Satellites can be mass produced Problems: –Complex algorithms for the formation –Difficult to control the swarm from the Earth Need’s to be autonomous operated

Surrey Space Centre, University of Surrey, Guildford, Surrey, GU2 7XH Mission Requirements Minimum Mass and power consumption Minimum spacecraft complexity Minimum cost Maximum reliability and lifetime Maximum performance Radiation tolerant Autonomous operation

Surrey Space Centre, University of Surrey, Guildford, Surrey, GU2 7XH Performance Influenced by: –Size of the spacecraft –Distance of the two spacecrafts –Stabilization of each spacecraft of the formation –Distribution of the nodes on the network –Available power –Operating frequencies

Surrey Space Centre, University of Surrey, Guildford, Surrey, GU2 7XH Power Consumption Motes operating under the protocol have the ability to sleep Example: MICA2DOT –Requires: 24mW active power 3uW standby power –Duty cycle: 0.1% –Supplied by: 3V, 750mAh battery cell –Expected lifecycle of: 27,780 hours equivalent to three years and two months.