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 http://satlab.org/wiki/doku.php 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 @es.aau.dk)

Pyxis concept

Pyxis Blue Box

Blue Box rdy for assembly