September 28, for the first time ever, SES, the Luxembourg-based satellite operator, has allowed an Ariane 5 rocket to transport a TV satellite into space, which is made by Astrium and runs entirely on latest generation software. Every single one of the programs used to operate the satellite was written in the new satellite language SPELL. The acronym stands for "Satellite Procedure Execution Language & Library."
What we are talking about here is a new standard, which will help the many different programming languages that were previously used to operate satellites and their subsystems to be unified under one roof. The University of Luxembourg's Interdisciplinary Centre for Security, Reliability and Trust (SnT) has contributed substantially to SPELL's being adopted in the operations of Astrium satellites. To this end, SnT scientists took an existing mathematical tool and refined it getting it ready for practical application, with whose help the procedures written in different native languages can now be translated into SPELL using a fully automated process.
SES is one of the world's biggest satellite operators with a vast fleet of satellites in orbit. The satellites and their technical components are produced by different manufacturers who each use their own programming language. "Because of the complete and utter lack of common standards up until now, we used to have to make a big production out of operation and maintenance of the machines," explains Martin Halliwell, Chief Technology Officer at SES. "Our operators were working with a number of different programming languages to help us control our SES fleet through space." Which is problematic as the machines don't easily forgive programming errors. Says Halliwell: "If a single error is made, it may result in our satellite getting lost in space. Which, for us, literally means incurring millions in losses."
Which is why SES decided a while ago now to develop the open-source software, SPELL. SPELL allows for the careful execution of every imaginable navigational procedure from any given ground control system for all potential satellites in the fleet. In other words, maximum flexibility with maximum security. "There is, however, a catch to the whole thing," concedes Dr. Frank Hermann, SnT scientist. "All the various control procedures that exist in different programming languages and that are being used must be converted over to SPELL. If that does not happen automatically and is one hundred percent error-free, it quickly turns into very resource-intensive and error-prone undertaking."
Together, SnT's Frank Hermann and his collegues, in close collaboration with SES automation specialists, have tackled the problem head-on using a methode known as triple graph transformation to automatically translate the programming languages employed by the new satellite's subsystems into the common language SPELL. According to Hermann, " triple graph transformation is a mathematical tool that has been the focus of active research since the 1990s. Along with other mathematical tools, it represents the ideal instrument for combining different programming languages under SPELL."
What's special about the new translation process is that it does not require any source code programming. "We are working with a visual development setting, which records translation rules in a graphic user interface," explains Hermann. These rules are automatically executed by specialized transformation tools. Quality assurance happens through consistency checks, which are automated as well. "Their efficacy has been documented through multiple formal mathematical proofs," says Hermann. If the translation runs smoothly, every piece of information from the original language is first converted into a graph. "This creates a network made up of many different nodes on the graphic interface," explains Hermann. The network is then read and translated into target graphs for the target language SPELL. "Every single bit of information in the original language has a corresponding SPELL counterpart."
The SES validation teams have confirmed that the translation is highly precise. "This was a prerequisite for being able to unanimously program our new satellite's systems using SPELL," says Martin Halliwell. SnT's Vice-Director, Prof. Thomas Engel, is very pleased with the SnT scientists' performance specifically and with the SES/SnT collaborative in general: "The new satellite and SPELL will now have to prove themselves in space. If everything runs smoothly -- which we are quite certain that it will -- our basic science research will have made an important contribution to increasing SES's performance and to making Luxembourg more competitive in this area."
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