ON THE SIMULATION OF THE UPMSAT-2 MICROSATELLITE POWER Carlos de Manuel, Javier Cubas, Santiago Pindado Instituto Universitario de Microgravedad “Ignacio Da Riva” (IDR/UPM) Universidad Politécnica de Madrid, ETSI Aeronáuticos Pza. del Cardenal Cisneros 3, Madrid 28040, Spain Email: c.manuelnavio@upm.es; j.cubas@upm.es; santiago.pindado@upm.es ABSTRACT Simulation of satellite subsystems behaviour is extremely important in the design at early stages. The subsystems are normally simulated in both ways: isolated and as part of a more complex simulation that takes into account inputs from other subsystems (concurrent design). In the present work, a simple concurrent simulation of the power subsystem of a microsatellite, the UPMSat-2, is described. The aim of the work is to obtain the performance profile of the system (battery charging level, power consumption by the payloads, power supply from solar panels…). Different situations such as battery critical low or high level, effects of high current charging due to the low temperature of solar panels after eclipse, DoD margins…, were analysed, and different safety strategies studied using the developed tool (simulator) to fulfil the mission requirements. Also, failure cases were analysed in order to study the robustness of the system. The mentioned simulator has been programed taking into account the power consumption performances (average and maximum consumptions per orbit/day) of small parts of the subsystem (SELEX GALILEO SPVS modular generators built with Azur Space solar cells, SAFT VES16 6P4S Li-ion battery, SSBV magnetometers, TECNOBIT and DATSI/UPM On Board Data Handling –OBDH–…). The developed tool is then intended to be a modular simulator, with the chance of use any other components implementing some standard data. 1. INTRODUCTION Currently, when designing and developing new satellite missions, is common to run some simulations in order to predict, or at least get some information, about the performance of on situation impossible or too expensive to recreate on Earth [1–3]. More precisely, simulation of the Electrical Power Subsystem (EPS), performed over the whole subsystem or some of its different parts, is a good practice for the optimization of the system architecture, as it mostly integrates non-linear systems [3,4]. On the other hand, reliability and troubleshooting analysis are important aspects covered by EPS simulations [5–7]. Reliability of each satellite subsystem during the mission has become increasingly relevant within the last decades, as insurance fees are normally around 50% of the satellite cost. Accordingly, special attention should be addressed to the EPS, as problems regarding this subsystem are translated into a big percentage of the total number of insurance claims regarding satellite failures [8]. Finally, leaving aside the EPS reliability it should be pointed out that simulations of this subsystem allow the satellite users to limit the number of possible configuration adjustments once on orbit [1]. Simulations, even if they are calculations based on simple formulae [1,2,9–11], or assumptions based on interpolation from other mission data [12–15], are performed in all steps of a satellite EPS design. EPS simulations are normally performed based on two different criteria [9]: • Energy balance simulation, it allows to monitor solar array output voltage/current, battery State of Charge (SoC), bus voltage. These simulations are based on balance the average power requirements of the satellite and the EPS power supply on a certain interval (one orbit, one day…). • Voltage quality simulation. It is used to analyse transient behaviour of the electronics. Therefore, the time interval is much smaller than the one from the energy balance simulation. In the present work the simulation of a typical microsatellite EPS is proposed. The main goal of the simulator is to test and check that the EPS, and especially the battery, performance gets no damage and is always within the operative limits set by both manufacturers and the mission requirements. The modelling is adapted to the UPMSat-2 microsatellite, which is being now developed at the IDR/UPM Institute (Instituto Universitario de Microgravedad “Ignacio Da Riva”). This microsatellite represents one more step within the space science and technology carried out at the Polytechnic University of Madrid (UPM - Universidad Politécnica de Madrid). Finally, the pedagogical aspects of the UPMSat-2 should be mentioned. Since 2012, more than 20 final project works of students from the Aeronautics & Space Engineering School of UPM have been completed and marked with good results. Besides, 5 PhD thesis related to the UPMSat-2 design and development are being carried out at present at the IDR/UPM Institute. _______________________________________ Programme ‘European Space Power Conference’ 15–17 April 2014, Noordwijkerhout, The Netherlands