SIMIS : A space mission simulator

Space systems for earth observation are always complex to analyse. They consist of different types of satellites used in conjunction with data reception and dissemination facilities on the ground. SIMIS is a multimission simulator for space system studies and spacecraft mission planning elaboration. During feasibility and definition studies, engineers have to weigh up the requirements, to size the system and to optimize the solution. This means selection of the appropriate orbit, determination of the revisit time, of the imaging performances taking into account several operational constraints. SIMIS supports the user to make quick and efficient analysis. The structure of SIMIS is composed of models related to space and ground segments, including environment, orbitography, satellite dynamics, different types of payloads and models of data transmission. The genuine modular design allows to build a system with mono or multisatellites configurations and several disseminated ground receiving stations. The user can work on a scenario of imaging requests and simulate the satellite operations. All elements which characterise the mission are entered into the system and results come out thanks to an effective man machine interface. This covers, as a non exhaustive list of capabilities, the onboard recording design specifications (in terms of memory size, downlink throughput), imaging performance sensitivity to the system constraints, visibility for payload data reception and command/control of the spacecraft. Up to now, SIMIS has been involved in main space system studies like Envisat, Spot and more recently for small satellite system evaluations, where it has also been used for high quality demonstrations. SIMIS has been developed on workstation environment using the up-to-date standards and technology, and MATRA MARCONI SPACE followed an original, development approach by involving space system engineers in software coding and validation tasks. The System Simulation department of MATRA MARCONI SPACE is now evaluating the possibility to derive, from SIMIS, a simple configurable new generation simulator which can be used by the engineers on their PC.