This paper deals with star tracker algorithms validation based on star field scene simulation and hardware-in-the-loop test configuration. A laboratory facility for indoor tests, based on the simulation of star field scenes, is presented. Attainable performance is analyzed theoretically for both static and dynamic simulations. Also, a test campaign is presented, in which a star sensor prototype with real-time, fully autonomous capability is exploited. Results that assess star field scene simulation performance and show the achievable validation for the sensor algorithms and performance in different operating modes (autonomous attitude acquisition, attitude tracking, and angular rate-only) and different aspects (coverage, reliability, and measurement performance) are discussed. 1. Introduction Many spacecraft with accurate 3-axis control requirements are equipped with a star sensor to support attitude determination. In recent years, star tracker technology has had a remarkable evolution. In particular, these sensors have gained significant improvements in their autonomy and capabilities [1, 2]. Modern star sensors are expected to offer new advanced functionalities in addition to the assessed capability of high-precision pointing determination during low angular rate mission phases. They are conceived [3](i)to produce high-accuracy, high-reliability attitude angle, and rate estimates without external support;(ii)to operate in a wide range of mission conditions;(iii)to solve the lost-in-space problem autonomously and in short time;(iv)to deliver angular rate information also when attitude determination is not feasible, as during platform detumbling or slewing. The ultimate goal is the achievement of performance, functionality, and reliability allowing star sensors to be the only attitude sensor onboard the spacecraft [4]. Latest generation star sensor novel and advanced functionalities should be achieved via additional software routines rather than by hardware enhancements, and different operating modes should control sensor operation. As a result, software for system control and management becomes very complex. Due to the widened range of functionality and novel hardware characteristics, new problems arise in testing modern star trackers, both for calibration and performance assessment. Angular and photometric calibration can still be operated following the procedures that have been successfully applied up to now [5, 6]. Differently, all the functions related to processing real star field scenes to platform dynamics effects and estimation and to control
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