ESA Wireless Sensor Motes Study

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ESA Wireless Sensor Motes Study

• George Prassinos, SSC, University of Surrey

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Strawman Missions

• Earth observation Satellites
• Science and Technology Enablement
• Vehicular Maintenance
• Astronaut EVA support
• On-Orbit Satellite Reconfiguration
• Formation Flying Spacecraft Missions

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Missions of Interest

• Satellite Cluster in LEO, e.g. plasma bubble
  monitoring, LEO drag monitoring, and upper
  atmosphere (100 200 km) gas species
  identification.
• 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.

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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

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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

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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
• Needs to be autonomous operated

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Mission Requirements

• Minimum Mass and power consumption
• Minimum spacecraft complexity
• Minimum cost
• Maximum reliability and lifetime
• Maximum performance
• Radiation tolerant
• Autonomous operation

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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

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Power Consumption

• Motes operating under the 802.15.4 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.