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This paper presents the new architecture of the satellite simulator software for the third China-Brazil Earth Resources Satellite (CBERS-3). This architecture is flexible and scalable to comply with the new challenge imposed of making software reusable to reduce cost. The article discusses previous solutions adopted at INPE since the 90's. Advantages and disadvantages of past simulator solutions are summarized, from simple satellites, like the Brazilian data collection SCD's, up to the more complex earth resources observation satellites (CBERSs). The experience of purchasing a COTS (Commercial Off-The-Shelf) product to accelerate the simulator development for scientific satellites is also reported. The new simulator architecture, for CBERS3, is intended to serve as a framework also for the development of the scientific satellite simulators. Furthermore, the simulator development is to comply with INPE's policy of improving and giving priority to the national space software industry. To achieve this, the architecture includes a common, reusable, real time command monitoring core software, which is based on software engineering concepts of objectoriented modeling and design patterns.

Research of automatic solutions for space operations is a real need for all space agencies in order to reduce space mission costs. Nowadays, a significant parcel of satellite operation activities at the National Institute for Space Research (INPE) is still performed manually. Thus, finding automated alternatives for the satellite operation activities at INPE is of capital importance, in order to maintain the currently satisfactory performance of these activities, despite the scarcity of financial resources. This paper proposes the architecture of an Intelligent Planning System for the automatic generation of satellite flight operation plans (PlanIPOV). The proposed system employs temporal planning techniques of artificial intelligence (IA) in the automatic flight operation plans (FOP) generation for a satellite routine operational phase, with the aim of opening the way toward a higher degree of automation for satellite operation activities of INPE. The main reason for the application of the planning system in the routine operational phase of the satellite lifespan is that this phase is composed of very repetitive and well defined tasks which have lower programming costs. In addition, this phase is the longest comprising practically the entire lifespan of the satellite. The PlanIPOV system uses the Planning Domain Definition Language (PDDL2.2) to model the knowledge base of INPE satellite operations. It is based on the automatic generation of problem files, i.e., the initial state of the satellite control environment and the goal to be reached by executing the generated FOP timeline. The system uses information extracted from the following files: tracking knowledge domain; prediction of future satellite passes of the involved ground stations; and configuration parameters of the satellites and the ground stations. This paper also presents a prototype of the proposed planning system. This prototype was implemented using the PDDL2.2 language and LPG-TD planner (Local Search for Planning Graphs -Time Initial Literal and Derived Predicates). It was tested for the tracking domain of the satellites currently being controlled by INPE (SCD1, SCD2 and CBERS2). These results are presented along with the limitations that have been observed in the planning technique application. The solutions adopted to overcome these limitations are outlined. The obtained results may be considered satisfactory.

This paper presents the comparison between the numerical and analytical results of a spacecraft attitude propagation for a spin-stabilized satellite. Some external torques are introduced in the equations of the motion and the comparisons are done considering that these torques are acting together, which are: gravity gradient, aerodynamic, solar radiation, magnetic residual and eddy current. In the numerical approach it is used the quaternion to represent the attitude. This numerical approach can be applied for any kind of satellite. The analytical approach is applied directly for a spin-stabilized satellite and the equations of motion are described in terms of the spin velocity, spin axis right ascension and declination angles. An analytical solution of these equations is presented and valid for one orbit period. Applications are developed considering the Brazilian spin-stabilized satellites SCD1 and SCD2. The comparisons are important to validate some simplifications that are required in

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