A distributed and multi-mission capable ground segment software solution operating the nano satellite AISat

Abstract

The nano satellite AISat is designed for the reception of signals of the naval Automatic Identification System (AIS) in different ways to contribute to the understanding of how AIS signals are received in space and shall this process can be optimized. The satellite is equipped with multiple AIS receivers and two sets of antennas. One of these is a four-meter deployable helix antenna, which has a directional beam and thus concentrates the field of view on an area of 350 km in diameter. Another feature is the ability to amplify or attenuate the raw signal before it is demodulated. The satellite is scheduled for launch in 2013. In preparation for the launch the ground segment has been developed and implemented and is currently undergoing verification. The ground segment is divided into three major parts: the ground station network, the server-network and the user interface network. The ground station network contains every ground station which will send and receive packets to and from the satellite. Every one of these is using a special software application which decodes incoming packets of a custom protocol and converts them into CCSDS-conform structures or vice versa. These applications are directly connected to the Telemetry and Telecommand Server (TMTC Server) which is the heart of the server network. It distributes all kinds of packages, checks them and archives them. It will distinguish the different types of space packets and forward them accordingly (FTP-Server, MySQL-Database, or the TM/TC application). A PHP-webserver provides the user interface in the form of an easy accessible web application. Thereby each user inside the DLR network who has the necessary rights can send telecommands or monitor realtime telemetry via that web interface, although telecommand function is restricted to one operator at a time. The historical telemetry which has been archived by the TMTC Server can be accessed through other software applications.