ITALSAT F2 and Its EMS Payload for Mobile Communications

Summary

ITALSAT is the Italian domestic communication satellite system designed to provide digital communication capacity over Italy.

The first ITALSAT spacecraft (F1) was successfully launched in January ’91. Its primary objective was the in orbit evaluation of the advanced technologies and the architecture suitable for a domestic digital communication system. The purpose of the second spacecraft (F2) is to make the communication system fully operational. The ITALSAT digital communication system for fixed services is based on an innovative Regenerative Multibeam payload and on a more conventional Transparent Payload. Both operate at Ka band (20/30 GHz). Fl has, also, a propagation package on-board which allows experiments at 20 GHz (mainly for correlation with the existing data) and at 40 and 50 GfIz which are the next frequency bands still to be explored for future communication systems.

F2 will be launched in the second quarter of ’96. Its initial orbital position will be at 10.2 °East. F2 will be commissioned in this orbital position. When Fl will reach the end of its operational lifetime, expected by the end of ’97, if inclined orbit control strategy will not be used, F2 will be moved to 13.2 °East to take over the Multibeam payload operations.

In addition to the Regenerative Multibeam and the Transparent 20/30 GHz payloads, ITALSAT F2 includes an L-band payload for mobile communications developed by Alenia Spazio under a contract with the European Space Agency (ESA).

The need for a regional European satellite service able to provide both voice and data services has been growing during the last few years and has been rapidly taken on a new dimension with the opening of the borders with Eastern Europe.

In the late eighties and early nineties ESA conducted studies with the purpose of defining the architecture of mobile communications payloads to be embarked on geostationary satellites. At the same time initial development for the technology to be used was carried out, and potential host spacecraft for an eventual flight demonstration payload were identified. These activities resulted in the definition of the European Mobile Services (EMS) payload which, under 53 an agreement between ESA and the Italian Space Agency (ASI), has been embarked on ITALSAT -F2

This paper presents the ITALSAT program including a brief description of the two satellite systems, the Ka band communication system architecture and services. Special emphasis is given to the development and implementation of the EMS payload including the main technological challenges that have been met during the design phase of the project.

EMS will be used to establish up to 500 voice and data communication links between Fixed Earth Stations (FES) and Mobile Earth Stations (MES) over Western and Eastern Europe, North Africa and Turkey. The link between FES and Satellite (Forward link) will be performed in Ku-band while the link between Satellite and MES will be performed et L-band frequencies.

The paper provides a description of the main Mission parameters. A review of the requirements that ESA specified for the EMS Payload, including the frequency plan and the Service areas is given.

A functional description of the payload architecture is presented together with the main tradeoffs that have lead to the specific design. The main aspects of the technology which warranted particular attention during the development phase of the system are addressed.