# The Impact of Space-Based AIS Antenna Orientation on In-Orbit AIS Detection Performance
###### Abstract  
In this paper, a study on the impact of changing the space-based Automatic Identification System (AIS) monopole antenna orientation on its message reception performance in orbit has been conducted. The study has been carried out by maneuvering the attitude of LAPAN-A2, an equatorial orbiting microsatellite with AIS antenna fixedly mounted on the satellite's body, into the desired orientation. Based on the analysis of the datasets collected during the maneuver, the orientation of AIS monopole antenna 45\({}^{\circ}\) toward its flight direction increases the overall detection performance of the AIS message, including class A ship to 208.80% and also class B ships to 175.93%. This orientation also increases the detection of AIS messages in ocean areas having low detection probability due to AIS signal collision. The result of this research could become a reference in order to specify AIS antenna position and orientation in a small satellite carrying a space-based AIS system for maritime surveillance & monitoring purposes. automatic identification system (AIS); maneuver; antenna; satellite; LAPAN-A2 2009/09/11/00000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-  
In 2007, the U.S. tested space-based AIS tracking using TacSat-2 microsatellite. However, due to the simultaneous receipt of many signals from the satellite footprint, the received signal was corrupted [8]. Two years after this unsuccessful mission, in July 2009, the U.S launched AprizeSat-3 and AprizeSat-4 with AIS receivers which are capable of receiving U.S. Coast Guard's test beacons off of Hawaii in 2010 [9]. The demonstration of space-based AIS technology was continued by the Norwegians, which successfully launched a nanosatellite (AISSat-1) into polar orbit on July 2010. AISSat-1 was developed in order to improve the surveillance of maritime activities in the High North. On April 2011, Indian Space Research Organization also launched Resourcesat-2 bringing a Satellite-AIS (S-AIS) payload to provide the monitoring of maritime traffic in the Indian Ocean Search & Rescue (SAR) zone [10; 11]. Specifically, in Indonesia, the space-based AIS has been installed on LAPAN-A2 microsatellite and was launched successfully in September 2015 [12]. This satellite has been developed and operated by National Institute of Aeronautics and Space of Indonesia (LAPAN) until the present day. This satellite was equipped with a space-based AIS module capable of collecting vessel messages from about 650 km altitude with a 6-degree inclination. The LAPAN-A2 microsatellite is a unique satellite since it was placed in equatorial orbit; hence, it is capable of monitoring Indonesian maritime territory and other equatorial countries 14 times a day. This condition is in line with the purpose of installing the AIS system that is to monitor vessel activity crossing Indonesian waters. Therefore, for Indonesia, which consists of 5.8 million square kilometers of marine territory, the existence of this satellite is beneficial, especially in terms of maintaining maritime surveillance. Besides space-based AIS payload, Automatic Package Reporting System (APRS), Voice Repeater (VR), and multispectral camera were also installed to this satellite in order to support amateur communication and remote sensing purpose [13]. The illustration of the LAPAN-A2 microsatellite and its mounted payloads is provided in Figure 1 below. Since LAPAN-A2 is the first satellite designed by LAPAN that has brought AIS payload, advanced in-orbit research is needed in order to study the performance of the AIS payload. Various researches and experiments related to the performance of the AIS payload are carried out in order to design a better generation of space-based AIS systems in the future. The performance of a space-based AIS system represents its ability to collect vessel messages which can be observed from quantitative and qualitative aspects.