STELLA

Aerial view of the OTS satellite antenna installed in the courtyard of CNUCE, Pisa.

STELLA (1978–1983)

Europe's First Satellite Computer Network

In the late 1970s, while computer networking was still in its infancy, Europe embarked on an ambitious project that would pioneer the use of satellite communications for scientific collaboration. The project was called STELLA (Satellite Transmission Experiment Linking Laboratories) and became the first European satellite computer network.

The initiative originated within the high-energy physics community centered around CERN in Geneva. Physicists conducting experiments on elementary particles faced an increasingly difficult challenge: the enormous quantities of data generated by CERN's accelerators had to be processed by research groups scattered across Europe. Yet no efficient mechanism existed for transferring this information between laboratories.

My involvement in the project began in 1978, when Professor Italo Mannelli—who had supervised my degree thesis in Physics and later became Director of Research at CERN—telephoned me to propose that I participate in the design and implementation of the STELLA network. I immediately accepted, and within a few weeks CNUCE had become an official partner of the project.

The Challenge of Scientific Collaboration

The success of CERN has always depended on close collaboration among scientists working in different countries. Experiments performed at the particle accelerator generate vast amounts of data that must be analyzed by teams distributed throughout Europe.

Before STELLA, however, data exchange relied on surprisingly traditional methods. Experimental results were recorded on magnetic tapes—often hundreds of them—and physically transported to national laboratories by car, train, or airplane.

This approach was costly, inefficient, and increasingly unsustainable. Data sets and software versions multiplied across institutions, making management difficult. Researchers outside CERN could not follow the progress of experiments in real time and often received information only after significant delays. As a result, many scientists were effectively excluded from the most dynamic and intellectually stimulating phase of experimental work.

Recognizing these limitations, CERN enthusiastically welcomed a proposal from the European Space Agency (ESA): to exploit the newly available Orbital Test Satellite (OTS) as the foundation of a high-speed data network linking CERN with major European research laboratories.

For the first time, satellite communications would be used to support large-scale scientific collaboration across Europe.

Building the STELLA Network

The STELLA project officially began in 1978 through a partnership involving CERN, ESA, the Italian National Institute for Nuclear Physics (INFN), CNUCE, the Rutherford Laboratory in the United Kingdom, DESY in West Germany, University College Dublin, and the Technical University of Graz in Austria.

The participating institutions contributed according to their areas of expertise. ESA, University College Dublin, and the Technical University of Graz focused on satellite communications, antenna technology, and radio-frequency systems. CERN, CNUCE, and the Rutherford Laboratory concentrated on the design of the network architecture, protocols, and supporting hardware. The high-energy physics community served as both the driving force behind the project and its primary user base.

For Italy, participation in STELLA was formally endorsed by Professor Antonino Zichichi, then President of INFN.

The network was designed to provide a high-speed data service—2 Mbps, a remarkable rate for the period—between CERN and a number of major European research centers. Through satellite links, physicists could transfer large experimental data sets far more rapidly and efficiently than had previously been possible.

For CNUCE, STELLA represented a natural continuation of the networking experience gained through RPCNET. Since INFN had limited expertise in computer networking, CNUCE was entrusted with a leading role in the design and implementation of the networking components of the project.

Each participating laboratory was equipped with a PDP-11 minicomputer known as the Link Data Computer (LDC). This system interfaced with a Communications Interface Module (CIM), responsible for implementing the satellite access protocol, a modem, and a five-meter satellite antenna. In Pisa, the antenna was installed in the courtyard of CNUCE.

The MAC protocol governing access to the satellite channel was designed at CNUCE, while CERN developed the CIM hardware. The modem technology was supplied by Marconi and GTE according to ESA specifications. Together, these components formed one of the most advanced scientific communication infrastructures in Europe.

From Satellite Networking to the Internetworking Era

The first phase of the project, known as STELLA I (1978–1981), focused on high-speed file transfer between CERN and participating laboratories. During this period, CNUCE also carried out extensive testing using the Italian SIRIO satellite while waiting for ESA's OTS satellite to become fully operational.

The second phase, STELLA II (1981–1983), significantly expanded the project's ambitions.

One objective was the development of the Remote-Control Room, an innovative application that enabled scientists throughout Europe to follow CERN experiments in real time. Researchers located hundreds or even thousands of kilometers away could observe the same data and graphical displays seen by their colleagues at CERN, creating a new model of distributed scientific collaboration.

A second objective was equally visionary. STELLA II sought to interconnect local area networks with wide-area networks, making network services available even to institutions located far from satellite ground stations.

To achieve this goal, the CNUCE team designed and implemented an interconnection protocol functionally equivalent to the Internet Protocol (IP), which at that time was still undergoing experimental evaluation in the United States and Europe.

In retrospect, this was perhaps the most forward-looking aspect of the entire project. STELLA was no longer simply a satellite network; it had become an experiment in internetworking—the ability to connect heterogeneous networks into a unified communication system.

The Pisa Demonstration

On 19 October 1983, the results of the project were demonstrated at the Domus Galileiana in Pisa. Physicists from across Europe attended the event and were able to observe, in real time, the evolution of an experiment being conducted at CERN.

The participants could view exactly the same graphs and experimental data being observed by researchers at CERN. For many of those present, it was the first tangible demonstration that advanced scientific collaboration could take place across national borders through digital communications.

I still remember one unexpected moment before the demonstration began. While presenting the project to the audience, I noticed increasingly frantic gestures from a colleague at the back of the room. The system had stalled. We were experiencing what engineers often call the "demo effect": everything works perfectly until the public demonstration begins.

Realizing the situation, I deliberately prolonged my introduction while the development team worked to identify and solve the problem. Fortunately, the issue was resolved quickly. My colleague eventually re-entered the room and signaled that the system was operational again. The demonstration proceeded exactly as planned, and everything worked perfectly.

Historical Significance

Before the Internet connected people via social network platforms, STELLA connected European science.

At a time when digital communications were still in their infancy, STELLA demonstrated that geographically distributed research communities could collaborate effectively through high-speed computer networks. It transformed the way physicists interacted with CERN, allowing them to exchange large volumes of experimental data, access remote resources, and, for the first time, participate in scientific experiments almost as if they were physically present at the laboratory.

The Remote-Control Room application represented a remarkable innovation. Long before video conferencing, collaborative platforms, and remote scientific dashboards became commonplace, STELLA enabled researchers across Europe to observe experiments at CERN in real time and to share the same scientific information simultaneously.

Today, STELLA stands as a pioneering milestone in the history of European networking. Beyond addressing the immediate needs of the high-energy physics community, it anticipated the transition from isolated communication systems to interconnected networks and helped establish the foundations for a new model of scientific collaboration in the Internet era.