# The Impact of Space-Based AIS Antenna Orientation on In-Orbit AIS Detection Performance
## 3 Results and Discussion
### Class A and B Composition  
Besides analyzing the total number of received messages and other AIS data categories, in this work, an analysis to observe the impact of satellite maneuvering to the message reception of certain AIS classes has also been conducted. Because LAPAN-A2 receiver is capable of receiving both class A and class B types, in this case, we divide AIS message composition based on those two classes. Since the AIS message transmitted from a class A transponder will always be prioritized, the AIS message transmitted from a class B transponder will not be received until a slot on the AIS channel is available. Due to this schema, only a small portion of class B messages are recorded by the LAPAN-A2 space-based AIS receiver. This phenomenon can be used to study the effect of satellite maneuvering on AIS receiver sensitivity level on a small portion of AIS messages, i.e., class B AIS messages.  
Practically, class B AIS messages can be recognized by their message identity (message ID) assigned by \"18\" and \"19\" values while the others can be classified into class A AIS. The total number of class A and class B messages received during the observation are provided in Figure 13.  
Figure 13 shows that by using Run-1 and Run-2 datasets, the averaged message reception of class A AIS during the 90\({}^{\circ}\)-maneuvered is increasing by 17.17%, while for class B, the average message reception increases by 18.34% compared to before the maneuvering. It is also shown that Run3 & Run4 (45\({}^{\circ}\)-maneuvered) are capable of increasing the number of received class A & B messages. It is also confirmed that the averaged message reception is increasing by 208.80% and 175.93% for class A and B, respectively, compared to before the maneuvering. This condition indicates that by applying the 45\({}^{\circ}\)-maneuvered flight configuration, the LAPAN-A2 AIS receiver is capable of receiving more class A and class B AIS messages than the nadir flight configuration.  
In this work, a filtering process was also performed in order to observe only unique MMSI detected during each maneuvering period. As shown in Figure 14, during the 45\({}^{\circ}\)-maneuvered, the averaged detection performance of unique MMSI is consistently increasing by a factor of 33.34% compared to before the maneuver. Whereas the 90\({}^{\circ}\)-maneuvered is capable of increasing the averaged detection performance of unique MMSI by a factor of 13.43% compared to before the maneuver. By comparing 45\({}^{\circ}\)-maneuvered and 90\({}^{\circ}\)-maneuvered, it can also be seen that 45\({}^{\circ}\)-maneuvered are better in overall AIS receiver performance.  
Figure 13: Comparison of the number of received class A & B messages for each observation.  
We also notice that in all trials under 45\({}^{\circ}\)-maneuvered and 90\({}^{\circ}\)-maneuvered flight configurations, the detection performance after the maneuver gives a significant increase of AIS message detection compared to before the maneuver. However, 45\({}^{\circ}\)-maneuvered shows an overall increasing of MMSI number detection.