# Trusted Autonomous Operations of Distributed Satellite Systems Using Optical Sensors +
## 2 Distributed Satellite Systems
This research work establishes a constellation of Low Earth orbit (LEO) satellites [37; 38; 39; 40; 41; 42] for EO [43] disaster event management such as droughts [44], sandstorms [45], rising sea levels [46], tornados [47], volcanic eruption [48], wildfires [49], etc. In particular, wildfire is chosen because one of the Sustainable Development Goals (SDG:13) is climate action, and among the primary catastrophe events that have an impact on climate is wildfire. In Australia and other countries, large-scale forest fires have dramatically grown in rate of recurrence and size in recent years. In the past 15 years, there have been 18 wildfire events in Australia [50]. For the same, an iDSS, i.e., a constellation of satellites, is proposed as shown in Figure 6 with ISL to provide near-real-time disaster management. Figure 5: (**a**) ISL relationship between the orbits and the ground station; (**b**) proposed iDSS constellation with ISL. Figure 6: An instance of the proposed EO constellation illustration with inter-orbital plane ISL and ground link. **Coverage Analysis:** An imprint in the shape of a circle or rectangle is left on the surface of the Earth whenever a satellite is used to observe a particular area. The separation between the spacecraft and a targeted point within the satellite's field of view region (also known as the imprint region) at a specific point in time is referred to as the instantaneous coverage of the satellite. The value of the Earth central angle \(\lambda\) is determined by the following equation where \((\Theta_{\rm s},\ \Lambda_{\rm s})\), denotes the latitudes and longitudes of the sub-satellite point and \((\Theta_{\rm t},\ \Lambda_{\rm t})\) denotes the latitudes and longitudes of the target [51]. \[\cos\lambda\ =\ \sin\Theta_{\rm s}\!\sin\Theta_{\rm t}+\cos\Theta_{\rm s}\! \cos\Theta_{\rm t}\cos\lvert\Lambda_{\rm s}-\Lambda_{\rm t}\rvert \tag{1}\]  
Then, the nadir \(\eta\) is computed, which is then utilised to obtain the maximum Earth central angle \(\lambda_{\rm max}\). \[\sin\eta_{\rm max}=\cos\ \epsilon_{\rm min}\!\left[\frac{\rm R_{E}}{\rm R_{E} +h}\right] \tag{2}\]  
\[\lambda_{\rm max}=90^{\circ}-\epsilon_{\rm min}-\ \eta_{\rm max} \tag{3}\]  
**System-Wide Access:** It is essential to determine the period that at least one spacecraft's camera can perceive the Area of Interest (AOI) during this timeframe in order to compute the coverage and system-wide access. The corresponding percentage quantity is referred to as the system-wide access percentage, and it is calculated by using the following equations:  
\[\rm SWAD=n\!\cdot\!S_{\rm c} \tag{4}\]  
Figure 5.0  
Figure 5.1  
where SWAD stands for \"system wide access duration\", n represents the number of elements in the system-wide access status whose value is \"true\", i.e., 1, which means that the satellite has a full view of the AOI; \(S_{\rm c}\) denotes the sampling time of the spacecraft; and SWAP stands for \"system wide access percentage\". The above-mentioned equations, which relate to the nadir pointing, can also be applied to systems that have reconfiguration capabilities:  
Figure 5.2  
Figure 5.3  
Figure 5.4  
where \(\rm SWAD_{T}\) is the system-wide access duration with reconfiguration; N is the number of elements in the system-wide access status with reconfiguration whose value is true, which means the satellite has full view of the AOI; \(S_{\rm c}\) is the spacecraft sample time, which is considered to be 30 s for both of these scenarios; and \(\rm SWAP_{T}\) is the system-wide access percentage with reconfiguration [35].