# The Impact of Space-Based AIS Antenna Orientation on In-Orbit AIS Detection Performance
## Materials and Methods
### Analysis Method
#### 2.3.1 Data Preparation  
In daily operation, in case no specific maneuver is required according to the mission, the orientation of LAPAN-A2 is set to default position i.e., nadir position, as provided in Figure 4a. In this condition, the continuous \(D_{0}\) dataset will be recorded as long as the AIS system is working properly. However, for the maneuvered condition (\(D_{45}\) or \(D_{90}\)), the satellite maneuvering has been performed for a certain time range. After the maneuvering, a specific procedure was then applied in order to set  
Figure 4: Illustration of LAPAN-A2 maneuvering configuration. (**a**) nadir, (**b**) 45\({}^{\circ}\)-maneuvered, (**c**) 90\({}^{\circ}\)-maneuvered. Figure 5: Typical antenna pattern of LAPAN-A2 AIS Antenna (**a**) nadir satellite attitude mode; (**b**) 45\({}^{\circ}\)-maneuvered; (**c**) 90\({}^{\circ}\)-maneuvered. the satellite back to its default position, i.e., nadir. Therefore, if the satellite maneuver is performed, three different AIS datasets will be the result. These datasets are related to the data recorded right before the maneuvering, during the maneuvering, and right after the maneuvering process. In the rest of this paper, the term \"before\", \"maneuver\", and \"after\" are related to the data recorded before the maneuvering, during the maneuvering, and after the maneuvering process, respectively. Due to the power limitation to hold the satellite on its maneuver position, the duration of the maneuvering must be limited to 11 h only. Based on this limitation, a multi-maneuvering configuration cannot be executed sequentially to provide a continuous \(D_{90}\) dataset which is acquired right after the acquisition of \(D_{45}\). Therefore, since the comparison was only performed between the datasets acquired continuously, the comparison is only possible to be carried out between the \(D_{90}\) and \(D_{0}\) and between \(D_{45}\) and \(D_{0}\) datasets. The continuously acquired datasets are required since in this research, we also perform continuous ship tracking during the maneuvering period to observe the individual message reception performances of a particular ship. All of the datasets recorded under different antenna orientations will be compared to each other in order to study the impact of different antenna orientations to the message reception performance. In order to perform a fair comparison, the \"before\" and \"after\" datasets have been cut so that the acquisition time range of these datasets also equals to 11 h, similar to the duration of acquisition of \"maneuver\" datasets. Finally, a complete procedure performed to provide the necessary datasets on this research is shown in Figure 6. The term \(t\) in Figure 6 refers to the current satellite system time while \(t_{start}\) and \(t_{end}\) refer to the desired start and stop time of satellite maneuvering. Figure 6: A complete step for providing the necessary dataset used to assess the impact of satellite maneuvering to message reception performance. It should be noted that the procedure presented in Figure 6 above was used to provide the necessary datasets recorded under the 45\({}^{\circ}\)-maneuvered or 90\({}^{\circ}\)-maneuvered conditions only. Therefore, different \(t_{start}\) and \(t_{end}\) have been chosen and applied in order to provide all necessary datasets. The complete \(t_{start}\) and \(t_{end}\) values set to provide the necessary datasets used in this paper have been provided in Table 1. From Table 1, two sets of observations for each of the 45\({}^{\circ}\)-maneuvered and 90\({}^{\circ}\)-maneuvered configuration have been performed. For convenience, the 45\({}^{\circ}\)-maneuvered were labeled as \"Run-3\" and \"Run-4\" as stated under the \"Task Name\" column, while the 90\({}^{\circ}\)-maneuvered were labeled as \"Run-1\" and \"Run-2\". We have found that one single set of observations consisted of 11 h of maneuvering, which is enough to provide representative datasets.