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When operating LEO (low earth orbit) satellites the short duration for a pass is a problem.

For a standard cubesat in 800 km height a pass last 4-8 minuttes. In lower orbits this time decreases.

To be able to get enough ... data down over a low speed link(9600 baud, 19200 baud) cooperative ground stations are suggested.

The first inititative at lower levels has been taken for AAUSAT3 - Pyxis homepage. (initiative by old students)

The big customer (us) and hopefully QB50

The Project

Design a distributed data package system for ground station use

  • Can forward bit streams for online aligment and voting
  • Can do hand over, fault detection, ...
  • Proper routing
  • Pass and communication planning
  • Modelling, simulation, measurement, verification
  • Security models
  • Generic for different protocols (ax.25,fx.25, pyxis/csp,...)

An Invariant

Communication with satellites like cubesats has many problems due to the weak and unreliable link. A cubesat typically transmit with less than 1W and have quite small antennas.

We propose a protocol development project which can take a take off on AAUSAT3 CSP Protocol.

  • Analysis of strength and weakness of CSP
  • Analysis of characteristics for communication (link budget, error rate)
  • Analysis of communication needs for application (client-server, broadcast, groupcast, (un)reliable, adaptive correction
  • Design and implementation of a solution

It is important to take into consideration:

  • Message size (do you really want to move 4 MByte)
  • Multi layer protocol definition acc to ISO skeleton
  • What is to be left to handled at next protocol level (fragmentation, re transmit)
  • Error modelling - whatif loss of packages, retransmit,...

Additional features is usage of more ground stations with intelligent re assembly of packages.

See for additional information about our embedded own devloped transciever and first trial on a distributed ground system.

for further information contact Jens or Jesper (jdn, jal

Pyxis concept

Pyxis Blue Box

Blue Box rdy for assembly
Page last modified on February 01, 2013, at 01:05 PM EST