Middleware Software functionality keeps increasing while CPU throughput remains limited by the space radiation hardened technology, so software may need to be distributed over several processors. Also, the increasing sophistication of sensors, actuators and instruments means that more and more of them are equipped with processors. The associated on-board software must be seen as a whole in a decentralised architecture.       Prototypes   In order to fulfil these needs, several solutions based on middleware are being investigated: Space Advanced Modular Avionics based on fast asynchronous uniform consensus (A3M) Arinc 653, the aircraft integrated modular avionics standard the optimized use of real-time CORBA on-board with a small footprint (RAMA) a distributed, fault tolerant middleware over a network of Spacewire with a router and a Sparc processor (DISCO) a master-slave architecture where the master is radiation hardened and the slaves are commercial components (MOSREM) Unified On-Board Processor Architecture for Spacecraft Avionics, Payload Processing and Data Handling (Unionics)     Study   AXLOG has performed a study on the Optimized Distribution of Real-Time Tasks with Resource Constraint, delivering software that distributes hard real-time tasks on multi-processor systems with resource constraints, with and without optimization criteria. This software was applied to a realistic case of a satellite on-board system. The distribution solver is based upon Constraint Logic Programming (CLP) techniques.       Last update: 19 March 2007 More information  •  A3M (zip) (ftp://ftp.estec.esa.nl/pub/wm/anonymous/wme/Web/A3M.zip)  •  ARINC653 in space (pdf) (ftp://ftp.estec.esa.nl/pub/wm/anonymous/wme/Web/Arinc6532005.pdf)  •  RAMA (zip) (ftp://ftp.estec.esa.nl/pub/wm/anonymous/wme/Web/RAMA.zip)  •  MOSREM (pdf) (ftp://ftp.estec.esa.nl/pub/wm/anonymous/wme/Web/mosrem2003.pdf) Related links  •  Unionics (http://www.sea.co.uk/unionics.aspx?nav=products)  •  AXLOG optimized distribution (in french) (http://www.axlog.fr/rubriquef430.html?id_rubrique=76)