The hub of the ICARUS system is the International Space Station (ISS). It travels in a virtually circular orbit. In this way, the ISS passes over more than 90 percent of the earth's surface every day. Due to its low orbital height of roughly 400 km, it is well accessible for low-power radio transmitters. This gave the ICARUS project partners the idea of using the ISS as a remote station for the animals to be observed.