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Subcontracted by British Aerospace, AIAI were involved in part of a larger project for EUMETSAT, the European agency responsible for meteorological satellites. Our role was helping in the specification and prototyping of the scheduling component. After an initial feasibility study it was decided to prototype the system using PECOS, an object-oriented constraint programming tool. This approach allowed rapid development while retaining the flexibility to make changes as the problem specification evolved.

A typical problem that the EUMETSAT scheduler has to deal with consists of some 1300 activities over a 14 day period. Activities to be scheduled include regular fixed activities (e.g. image taking every 30 minutes), maintenance activities, and station keeping manoeuvres consisting of series of linked activities which maintain the satellite in its correct position. An important part of the problem was in recognising overconstrained problems (i.e. where it is not possible to meet all the constraints) and dealing with them appropriately.

British Aerospace are now in the process of porting to a C++ version of the tool, in order to integrate the scheduling component with the larger system.

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