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Low Power Proximity Network of Sensors

Eric W Pritchard

Systems Engineering & Assessment Ltd

CCSDS WWG Spring Meeting, May 2010

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802.15.4 LPPNS Wireless Project

• At Santorini we showed the LPPNS module used for RF wireless testing under ESA contract

• This has had propagation testing in a spacecraft model at Astrium Toulouse in nominal 802.15.4 mode of operation, and in a launcher element mock-up at Les Mureaux in a high rate mode.

• Next stage for the LPPNS module is planetary demonstrator testing where we will be trying for maximum range and simulated nominal operation in a planetary context

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Summary of the LPPNS Tests

• One set of tests at Toulouse used a mock-up of a six cavity spacecraft based on the Venus Express spacecraft

• With the spacecraft walls closed the only RF pathways between cavities were holes a few centimetres across

• The tests showed positive link margin over the 802.15.4 specification, which is conservative (receiver sensitivity of -85dBm, whereas commercial systems are achieving -100dBm or better)

• Good correlation with the Astrium model.

Cavity N°1Emitter

Cavity N°3Cavity N°4

Cavity N°6 Cavity N°5

Cavity N °2

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Remaining Tests

To complete the LPPNS work, there is • the test in the launcher module to

complete (two networks, data transfer continuous representing data acquisition in flight)

• The planetary demonstrator tests to do, testing maximum range, multipath effects and simulated operation in a representative environment

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LPPNS NG Demonstrators

• We have progressed from the LPPNS Modules tested in France to a smaller version predominantly aimed at temperature monitoring.

• This is still 802.15.4/Tiny OS based• Presently we have the prototype boards ready to populate

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Module Assembly

• These boards have a flexible middle layer so can be folded, on the top is a chip antenna

• The module size is driven by high density population and battery size for a reasonable life

• This version has the ability to attach 2 thermistors or thermocouples to be positioned externally

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Status of the CAN-BT Bridge

• This has been delivered and the SSC project has been successfully completed.

• Tests demonstrated that the Bluetooth system is compatible with operation as a bridge from a CAN bus on a spacecraft to a CANalyser on an EGSE bus.

• The project used the Bluetooth serial profile which may have other uses in spacecraft for data acquisition.

• Now some thought must be given to how to take this work forward.

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Status of SpaceWire Bridge

In a short test of compatibility, this has been connected to the MARC system and data has been successfully transferred from the MARC EGSE computer through the StarDundee USB- SpaceWire Interface to the MARC SpaceWire Cluster 1, through the backplane to the MARC SpaceWire Cluster 2, out to the SpaceWire EtherNet interface, over EtherNet to the 802.11n Access point, over 802.11n to the other Access point, then back to EtherNet to connect to the RF Wireless test PC.