## 1 Introduction
A description of the real-time demonstrations carried out in RAID was provided in [14], which aimed to represent an overview of the project contents but was not specifically devoted to the specification of the features of the DAA system that was tested in the project, i.e., the integrated ADS-B-based automatic separation assurance collision avoidance system (ASACAS) designed by CIRA, the Italian Aerospace Research Center. ASACAS is the specific name (acronym) of the CIRA DAA-designed system integrating both emergency collision avoidance and tactical separation assurance functionalities, as well as TCAS (Traffic Collision Avoidance System) compatibility checks and advanced situational awareness functionalities, into a unique system under unique mission automation logic that is able to manage a unique system that integrates both separation assurance (acting in a time horizon of up to 2-3 min) and collision avoidance (acting in time horizon of lower than 1 min) with a unique software system. For this reason, the CIRA-designed DAA system has been denoted the specific name of the \"automatic separation assurance and collision avoidance system\" and the specific corresponding acronym ASACAS. The aim of this paper was to therefore report on the outcomes and findings from the real-time demonstrations carried out in the RAID project with more detail and a more specific focus, thus complementing and extending the previous reference paper [14]. The novel contribution of this paper is in the fact that it specifically focuses on the DAA system (i.e., the ASACAS designed by CIRA), whereas the previous paper [14] included the DAA system as one aspect of a wider paper addressing a description of the RAID project and the overall real-time simulation campaigns carried out therein. This led to the need to address the ASACAS aspects only in part in [14], whereas in this paper, the ASACAS is the focus of the paper, including therefore aspects not considered in [14], mainly including the background and motivations leading to the design of the system (Section 2.1), the system of the concept of operations (Section 2.2), a high-level description of the implemented functionalities and algorithms (Section 2.4 and all related subsections), and the presentation of further test cases and related results (Section 3). Of course, being limited to real-time demonstration results description and discussion, this paper does not cover flight demonstration results, which will be addressed in future works. The paper is organized as follows. Section 2 first reports a description of the applicable CIRA background and motivations that led to the design of the integrated ADS-B-based automatic separation assurance collision avoidance system. Then, it provides an overview of the system concept of operation and of the implemented system architecture while also providing basic information about the algorithms implemented in the main system functionalities. Section 3 then describes the real-time simulation environment and some relevant tests that have been performed in such real-time simulations, with reference to both collision avoidance and separation assurance experiments, including the related test plan and the obtained results. Finally, Section 4 reports the conclusion of the paper.