Intersatellite link for Earth Observation Satellites constellation

This paper is devoted to investigate the possibility to implement a data Intersatellite Link between satellites of an Earth Observation constellation and a dedicated TLC GEO satellite. An EO system is mainly composed of two segments (space and ground) connected by a complex network of communications that permits to manage the operations of the constellation. Due to the high performances in terms of imaging capabilities of the radar/optical payloads a corresponding high capacity to download data to ground is needed. To guarantee that the system is able to download to the ground station, in a proper time, all the images taken from the radar during the mission, external ground stations, located in a polar zone, have to be foreseen. Polar stations offer a service needed to provide the requested images to the users in a near real-time manner. In this paper an alternative approach, using an Intersatellite link system (ISLs) instead of polar stations, is presented. The most relevant trade-offs from technical point of view have been addressed. The purposes of this activities is to demonstrate the capability of a high speed two way optical link, between LEO and GEO terminals, with a bit rate in the order to 2.5 Gbps in the frame of satellites constellation. This implementation should permit to avoid the use of polar stations ensuring in the same time the achievement of high system time performances, in an operational cost-saving approach