Aiming at the Sun with flying drones

Six weeks’ time, 12 PDEng trainees, and an ambitious project to be carried out with the European Space Agency (ESA), Europe’s gateway to space and dream workplace of many scientists, engineers and information technology specialists from all over the world.

Marcel Verhoef, Software Engineer at the Software Systems Division of the European Space Agency (ESA): “3 years ago, I was approached by Yanja Dajsuren, Program Director of the PDEng Software Technology (ST) program, with the request to set up a team challenge for the new classes of PDEng trainees to come. I immediately had to think of some of the relevant tasks of ESA, such as the dissemination of knowledge, the testing of our R&D results and the exposure of the new generations of engineers to the work of ESA.” With these prerequisites in mind, Verhoef and Dajsuren worked tightly to delineate a project based on quadcopters — drones with two pairs of propellers — flying together, in so called “formation flying”, which could have a huge range of applications for future and ongoing ESA’s missions.

To control this system, the multidisciplinary PDEng team could rely on TASTE, the ESA’s open source toolset for model-driven software engineering. Trupti Manik, PDEng ST trainee: “At the beginning we were not familiar with the software, so the initial part of the project was tough. However, we could always rely on the knowledge and experience of the ESA’s team, who gave us a big support throughout the entire project via personal meetings, Skype calls and emails. For the entire team, this experience turned out to be a real privilege.”

Project objectives and Business requirements

Konstantinos Smanis, ST trainee and project leader of this year’s assignment: “The project had two main objectives, to use the ESA’s TASTE platform and give feedback on it, and, secondly, to create a formation flying demonstration with quadcopters to showcase the importance of software in spacecrafts.” While doing so, the team had several business requirements to fulfil. “To start with” — explains Smanis — “we had to accurately measure the absolute position of the drones, including their altitude, by having several HD webcams observing the scene from above and at different angles. Also, we had to implement a lightweight physical enclosure for the drones, which was created via 3D printing.”

Quadcopters in flying formation: what for?

The PDEng team of 2017 worked at the control of three quadcopters operating in formation flying, with a control station positioned on the ground. This year, the new team was challenged by the introduction of an additional level of complexity. Verhoef: “We asked the team to get rid of the controller on the ground, and embed the motion control directly into the quadcopters.” This improvement might be beneficial for some of the ESA’s missions of the future. Verhoef: “Sentinel-2 and Sentinel-3 are two Earth observation missions using satellites pairs, both relying on ground control. The next challenge will be to have thousands of satellites working together. However, controlling them all directly from ground would be impossible due to visibility restrictions. And for deep space missions, the amount of data that can be sent is extremely limited, because of the long distance. The only way to optimize all these aspects is to include complex embedded control in the satellites. The use of multiple cameras by this year’s PDEng team represents a major progress, a nice benchmark that improves the demonstrator, as GPS does not work indoors”.

Preparing for the future: the Proba-3 mission

Proba-3 is ESA’s — and the world’s — first precision formation flying mission. “The project includes the development of two satellites” — explains Verhoef — “the first one carrying a camera pointing at the sun, and the second one hosting a shielding system which will create an artificial solar eclipse”. The paired satellites will form a 150-m long solar coronagraph to study the Sun’s faint corona, up to 60 000 km away from Earth, a seventh of the way to the Moon. Beside its scientific interest, the experiment will be a perfect instrument to measure the achievement of the precise positioning of the two spacecraft. Verhoef: “One of the biggest challenges will be to safely control the satellites and keep them correctly positioned relative to each other, which requires inter spacecraft collaboration and autonomy”. ESA’s double-satellite Proba-3 will rely on various new technologies, including formation-flying software, relative GPS information, intersatellite radio links, and optical visual sensors for close-up maneuvering. Verhoef: “Designing software is changing too — we believe that the use of model-based techniques, as we are developing at ESA, is needed to manage this level of complexity. The students experienced this first hand in the quadcopter formation flying demonstrator.”

The work of the PDEng trainees showcased at ESTEC Open Day 2018

ESA will showcase the flying quadcopters developed by the PDEng trainees during the ESTEC OpenDay on Sunday October 7th 2018. While the potential of the software used in this project is evident to the people in the field, “it can be extremely difficult to explain it to the general public”, Verhoef says. Verhoef: “This demonstrator will be used to disseminate knowledge, for instruction purposes, and to offer some tangible results of spacecraft flight on-board software to the visitors of the open day.”

The PDEng experience

The PDEng programs at TU/e are salaried two-year programs on a doctorate level for MSc graduates, with special focus on technological design for High Tech industry. Smanis: “We are technological designers, thinkers working on prototypes development. We have trainees from three different programs, ASD (Automotive Systems Design), MSD (Mechatronic System Designs) and ST (Software Technology).” The ST track focuses on systems architecting and designing software for software-intensive systems in multiple application domains for the High Tech Industry, as in the case of the project in collaboration with ESA.

Regardless of the chosen program, the emphasis of the PDEng program is to develop the capability of individuals to work within a professional context. It advocates a scientific research based approach to solving problems, and a critical and independent attitude in analysing and interpreting evidence. Bahareh Aboutalebian, PDEng trainee: “In my previous job, I was assigned to a supervisor I had to refer to. During this PDEng program, I have been learning how to proceed independently and take decisions on my own. Also, even though I personally had previous experience working with people with different backgrounds, other colleagues in this team did not. This experience has been advantageous for them in this respect too.” Mohamed Abdel-Alim Alosta, PDEng MSD trainee : “As a team, we all have different backgrounds. Some people might say that this is a disadvantage, but we always considered it as an added value. Also, by being aware of the knowledge and technical skills of the team members, we could split the tasks of this project based on our competences, and trust each other’s work and results.”

A video of the ESA-ESTEC project can be found at this link.