## 5 Ground Stations and Region of Interest  
The ground stations remain as the major portion of the constellation and operations. The provision to determine the right location for receiving the aligned data is absolutely crucial for a small satellite constellation scenario. For a global constellation, the ground stations have to be strategically be placed to support satellite data reception effectively. Hence, thorough research was carried out to understand the basic operation of ground  
Figure 8: Apogee and perigee height variation for 90 days under Drag-SRP. Figure 9: Solar flux effect over the satellite for 90 days. stations under a global constellation with small satellite parameters and the necessary propagation conditions. Achieving autonomous ground station operations were one of the primary objectives of this research but are included briefly to show how best the satellites can coordinate with the ground stations to deliver the information/data to the next available ground station. For this, an autonomous methodology is being planned and will be published at a later stage of the project. This paper mainly emphasized the calculated positioning/placement and alignment of these ground stations specifically focusing on the best coverage function scenario for a global constellation. An optimal and strategic approach for the network of ground station positioning would yield cost-effective implementation, saving the unnecessary cost of an extensive number of ground stations and operations. An autonomous system would definitely help in attaining the full coverage with minimum satellites and ground stations with due consideration to all the small satellite constraints and their real-time capabilities. A glimpse of the orientation of the ground station with respect to the constellation in operation is shown in Figure 10 below:  
The communication is planned to include:  
The ground station to the master satellite (with the following satellites communicating and transferring data along the same plane). Individual communication of all the satellites to all the available ground stations (other planes included). These two techniques are depicted as process flow charts in Figure 11. The sequence of the operation is subject to autonomous self-orientation of the satellites with the available ground operation, respectively. This totally depends on the configuration of the designed constellation and the capacity of the satellites to be self-organizing for easy communication and in-orbit problem solving. The essential point is that irrespective of the data relay process, the long pass at each site is to be retained. Figure 10: Ground station positioning for optimal coverage. It has been observed globally that the systems that can define autonomous ground station operations can make a significant difference to seamless data reception with minimum errors and saved time. The long-term reliability of these features and operations remain to be proven, but the scope of research is widely available. This research paved the way for such important features to be included for small satellite constellations, thoroughly solving the majority of data-management issues and support disaster management applications. Hence, considering the above-mentioned possibilities, the ground station-based simulation was made and analyzed thoroughly. Though autonomous behavior is not presented in this paper in detail, a brief idea was shared. The simulation was performed taking one satellite into consideration from the constellation for demonstrating the ground station communication and parametric behavior in real-time situations. This will be replicated to all other satellites in the constellation and relay the data to the respective ground stations using either independent or master-dependent techniques as designed. The six ground stations were located, representing each area of interest as shown in Figure 12 below:  
Figure 11: Strategy for the alignment of autonomous ground stations alignment—1 and 2.