Satellite systems can be fruitfully utilized to provide connectivity to terrestrial sensor networks to exploit large-scale monitoring applications based on IP protocol. Sensor traffic patterns are very different from those occurring with current Internet applications, so that performance evaluation requires some specific investigation with the aim to draw the main requirements to achieve target Quality of Service (QoS). This paper addresses a preliminary study of the sensor data transmission over satellites highlighting the main key factors to take care in the system configuration: experienced delays, resource utilization and overall throughput. Analysis relies on a Ns-2 based simulator, which includes a sensor data generator and implements a DVB-RCS-compliant network.