## 1 Introduction
Figure 2 shows this and other feasible topologies, with the full-duplex ISL being represented by double arrows. By including reactive components into the architecture, ISL allows the DSS operations to be enhanced and data to be processed on-board the satellite for timely operation, which makes intelligent DSS (iDSS). The ground station network and/or geostationary satellite service can be used to facilitate communications between satellites of different formations, which may be useful to perform constellation reconfigurations and process collision avoidance alarms from external objects [16]. As the communications become part of the control loop, a complete infrastructure to validate autonomous orbit control shall be able to emulate the inter-satellite links, as proposed in [23]. ISL is an essential component of the DSS astrictics architecture. They make it possible for rapid data sharing between satellites and AI-based on-board data processing [24; 25; 26], which relieves some of the tasks that were previously carried out by the ground segment. In this way, the information generated within each formation can be combined on-board (for instance, processed on one satellite and distributed within each formation using a Star ISL, as shown in the following figure) and delivered directly to the user, which is crucial on a surveillance application as MDA. We propose a single pass and on-board generation of the interferogram created by the combination of the SAR acquisitions of all the satellites of each formation, which will allow to obtain a timely high-quality product. This improves both the efficiency of the downlink and the operational effectiveness of the system, as measured by a decreased amount of work for human operators and more streamlined mission management. Figure 2: Inter-Satellite Link (ISL) topologies within the DSS, adapted from [22]. In this research work, a _constellation of formations_ is proposed to combine the benefits of the repeat cycle given by the constellation with the single-pass products allowed only by the Formation Flying distribution. An example of a monolithic SAR satellite was the Envisat [27], which provided a repeat cycle of 35 days. To perform interferometry, the product constructs the interferogram from different acquisitions of the same scene, which in this case is separated for 35 days. The constellation solution reduces the revisit time to a few days as the Satellite System for Emergency Management (SIASGE) system (Satellite Argentino de Observacion COn Microondas (SAOCOM-1) and Cosmo-Skymed SAR constellations). However, this could not be enough for applications needing real-time generation of the interferogram. In this study, a real-time interferometry is required for the MDA application, which needs to be computed on every single pass over a given target zone or area of interest (AOI). This requirement may be derived from two main motivations: the need for a fast determination of the interferogram, and the need for high coherence in the interferometry, in order to avoid artifacts caused by differences in the background of the scene due to the atmospheric changes or other effects not related to this specific application. Furthermore, as a new DSS architecture type, a constellation of these formations is considered to keep this feature and reduce the revisit time. This work also investigates the possibility of allocating control accelerations among satellites on each formation as a function of the formation objective (relative geometry) and the constellation objective (ground track repetition cycle period). The following contributions were made:  
* A safe multi-baseline shifted-Helix Formation Flying is proposed for Along-Track Interferometric Synthetic Aperture Radar (AT-InSAR) Distributed Satellite Systems (DSS), in the context of a Maritime Domain Awareness (MDA) mission over Australia. * Autonomous orbital control is evaluated for reconfiguration and maintenance of this DSS formation.