16/03 Aerotecnica Missili e Spazio Vol. 83 1/2003 6 AEROSPACE GNC LABORATORY AT THE UNIVERSITY OF NAPLES D. Accardo, G. Rufino, M. Russo, A. Moccia Department of Space Science and Engineering “Luigi G. Napolitano” University of Naples “Federico II” Abstract This paper deals with the activities that are currently carried out at the Laboratory of Guidance, Navigation, and Control of the University of Naples “Federico II”. The two main projects under development are described, presenting objectives, activity planning, achievements, as well as future work and applications. These involve the realisation of an integrated inertial-GPS system for autonomous navigation and flight control of unmanned aerospace vehicles, and of a star tracker for spacecraft attitude determination capable of multi-mode, all-mission-phase operation. In both cases, the activities consisted of theoretical studies, design, and realisation of hardware models. Furthermore, test campaigns results for system calibration and performance assessment are presented. Introduction In the last few years, a laboratory of Guidance, Navigation, and Control (GNC) of aerospace vehicles has been setting up at the Department of Space Science and Engineering “Luigi G. Napolitano” (DISIS) of the University of Naples “Federico II” aimed at carrying out both scientific research and educational activities. This has been carried out thanks to the financial sponsorship of the Italian Ministry of Education, University, and Research (MIUR), the Italian Space Agency (ASI), the Consortium Technapoli, the Consortium Co.Ri.S.T.A., and Italian aerospace industries. Given the wide national and international interest in automatic control of unmanned aerospace platforms and smart integrated sensors, the guidance and navigation laboratory at DISIS has been developed to meet advanced research trends. In particular, the main currently running projects deal with the fusion of Global Positioning System (GPS) receiver and inertial sensor data in strapdown configuration for Unmanned Aerial Vehicles (UAVs) autonomous flight control, and the development of a star tracker for space platform attitude determination. In addition to the benefits for research and development activities, a relevant spin-off results for students who can gain direct experience of state-of-the-art aerospace applications. Autonomous aircraft GNC Following the most recent trends, autonomous GNC of aerial platforms is an investigated topic. In particular, the main purpose is to develop an Autonomous Flight Control System (AFCS) for small Unmanned Aerial Vehicles (UAVs). Available AFCSs for aircraft have some intrinsic limitations such as [1]: − They can be operated only when the aircraft is in a particular mission phase (e.g. cruise flight or landing); − They often need ground aiding (e.g. Radio Navigation or Instrumental Landing Systems); − They are based on high-reel, large, heavy and power consuming hardware that can not be installed on small platforms. However, a major effort has been recently produced to develop fully autonomous, low-cost, and compact AFCS thanks to considerable advances in the fields of electronics and of miniaturised inertial sensors. The aim of the research presented here is to equip an aircraft model with an AFCS based on commercial-off-the-shelf (COTS) devices. This system is essentially composed by four subsystems: processor, sensors, servomotors, and communications. In particular, sensor selection is critical to attain true autonomy. Indeed, inertial sensors are the most appealing ones for autonomous control because they output direct measurement of platform dynamics. In addition, silicon based miniaturised accelerometers and gyros are presently available at low cost. They are usually arranged in small, light-weight boxes that are called Inertial Measurement Units (IMUs). In the strapdown configuration they can be rigidly connected to aircraft platform so that they can measure body reference components of forces and moments acting on the aircraft [2]. An alternative approach to strapdown configuration is the stabilised platform. In this last configuration accelerometers are mounted on a platform that is mechanised to maintain its attitude fixed with respect to the inertial reference frame so that they measure inertial dynamics following Newton’s Laws. This approach requires larger hardware than the one needed for strapdown navigation, with a considerable power consumption. For this reason, strapdown configuration is preferred to stabilised platform in small aircraft applications, even if inertial sensors must face more severe dynamical conditions and the computational load required to processing unit results heavier [2]. Miniaturised inertial sensors have adequate bandwidth and resolution characteristics to manage typical aircraft dynamics [1]. Indeed, these sensors can not be used to perform autonomous navigation because they introduce temporal drifts in the measurement of position and attitude angles. Furthermore, they can not perform autonomous initialisation [3]. For these reasons, they need aiding sensors to correct drifts and to find platform initial position. GPS sensors are one of the best solutions for inertial sensors aiding because they have complementary characteristics. Indeed, GPS receivers can be self-initialised, they have slower data rate (1Hz) with respect to inertial sensors (100Hz), they do not suffer