Prof. George Goussetis and Dr. Carolina Mateo-Segura together with Thales Alenia Space (France), the European leader for satellite systems, and University of Rennes, have lead the participation on the Science in the City Festival which took place in Toulouse (9th-14th July 2018) as part of the 8th edition of the EuroScience Open Forum (ESOF). REVOLVE fellows together with volunteers from the three institutions showcased their latest innovations and proposed scientific challenges to visitors in a friendly and interactive Fun Family Day. The presented open session named ‘REVOLVE – Waves: Radio and Space’ allowed attendees of all ages to take part in a series of applied engineering experiments ranging from making your own speaker, setting up your own radio link and making music with the wave of a hand through interference of electromagnetic fields. All public actively engaged with the team and had alos the opportunity to see real satellite components. Being the largest interdisciplinary science meeting in Europe, the event offered a unique framework for interaction between engineers and the general public.
REVOLVE fellows participated in Edinburgh’s Explorathon 2018 in collaboration with Leith Labs! The venue this year was the popular Shopping Centre located in Ocean Terminal. One of the activities carried out at the event showed how researchers at the Microwave and Antenna Engineering Group at Heriot-Watt University are working to use traditional electromagnetic concepts to wirelessly transmit power that can recharge electronic devices. This will enable us to charge our devices on the move, become more environmentally friendly reducing the number of batteries in the waste strem, stored power and re-use it. Other activities presented introduced the concept of sound and light waves, which raised a great interest among the kids and, of course, the big ones!
The REVOLVE team will be taking part in the 8th edition of the ESOF 2018 which takes place in Toulouse from 9th to 14th July 2018. Our REVOLVE fellows are busy selecting scientific experiments to showcase at Toulouse.
ESOF (EuroScience Open Forum) is the largest interdisciplinary science meeting in Europe. It is dedicated to scientific research and innovation and offers a unique framework for interaction and debate for scientists, innovators, policy makers, business people and the general public – ESOF 2018
Space for Kids will post further details when they become available and don’t forget to keep a look out for more details on how to enter our 1st Annual School Competition!
by Holly, age 11 (Edinburgh)
If I was an Engineer I would build a landing gear station and send satellites to the moon!
Part of the Space for Kids project is to invite school-aged children to submit their own space videos and this is the first submission! Holly (age 11) has drawn her own animated storyboard with space rockets, satellites and even a space dog! Read her space story:
‘This video is for ‘Space for Kids!’ The animation is about a girl who is thinking about what she would do as a Space Engineer….she goes on a special journey to the moon and designs her own space station so that she can fly her own rockets. The girl dreams about Space and about being an engineer so that life is better for people. She is a dreamer and a princess. She has many ideas and wants to share them.’
Thank you to Holly for sharing her fantastic animation about Space for Kids!
One of the most difficult things when we are in high school is to know what we want to do. For my part, I have always been impressed by passionate people who knew exactly what they wanted to be in the future : Biologist, Actor, Doctor, Policeman…
In primary school I wanted to be President, in College a Biologist and in high school, I didn’t know what I wanted to be…..perhaps an Archaeologist or an Engineer. During my first year of Engineering my Human Resources colleague asked me, “What is your professional project?” The only answer I could give her was, “My dream is to have an interesting job, in an interesting company and to be involved in a project which will allow me to dream!”
During my Scholarship I met a number of passionate and interesting people and enjoyed a variety of useful experiences (internships, travels) which, step by step, have helped me to find my way and determine what I wanted to do.
I used the context of the REVOLVE project and the initiative of Mrs. Richard, my Teacher in Physics and Chemistry at the Lycée Condorcet, Paris when speaking with her final year students where I presented my scholarship, my experience and my research. It was really interesting for the students as they could relate to the different experiences of the various panel members.
I hope that my talk inspired the students and that they were touched by the concept of Space Engineering!
Post by Claire Benteyn, PhD Fellow
Being already in 2018 there is no doubt that satellite communications are an integral part of our life. Although not visible from earth, their importance can be met in a wide range of services. Just imagine the two most common facts: Using a positioning system to track yourself in an isolated place and using your smartphone to communicate with other people or have access to multimedia. Obviously, the satellites can provide these kind of services in an excellent way, whereas there is a great variety of further applications where their use is vital as well, such as weather prediction and space exploration to name a few.
Satellites are in principle big and complex structures, where many components are assembled together so that the satellite can be launched from the earth to the space. One of the most significant part of a satellite is the antennas. If we could compare a satellite with a human, the antennas are “the eyes and the ears”. You can easily understand that without the antennas, a satellite cannot communicate with nobody and after all has not a reason to exist!
Here at REVOLVE we are doing research around antennas for satellites as you may already know. Every one of us studies different aspects and technologies. In a very fundamental analysis, the antennas implemented and used on satellites can be categorized into two principal domains: the so called Focal Array Fed Reflectors and the Direct Radiating Antenna Arrays. In the first category belong the typical parabolic structures fed by the so called feed-antennas (usually horn antennas) which are more or less widely known, whereas in the second single antennas are formed in an array and they radiate themselves.
My subject of research concerns the feed antennas. These antennas are almost always the typical horn antennas, which are used many years now because of their great performance. Although they are described as feed antennas this might be a bit confusing or misleading as the same antennas could be used as direct radiating arrays without the presence of a reflector. In any case, my 3 year journey at REVOLVE will go through the different existing technologies around the feed antennas and we will try to find out how we could make them function better and in a more compact shape as the current solutions have a bulky profile.
At last, somebody might wonder…so what is it so important about it? There may be many things important that neither myself could even recognize, but as I mentioned earlier the satellites are big and complex structures so imagine how important would be if we could provide something smaller and lighter. Furthermore, think about that this “something” are the antennas which constitute a very basic and important part of a satellite and after all we are moving ahead to the 5G era and the next years a great increase in the multimedia usage and communication services is about to take place, so we need to confine with these rules.
Lens antennas are a very attractive solution in space applications because they can provide high directivity beams. A specific type of Lense is called a ‘graded index lense’. This type of antenna is composed of periodic structures that have variable refractive indexes and can convert spherical waves into plane waves. Thus, we can focus the beam and steer it. As the aim is to integrate this antenna into the satellite we also need to make it more compact as well as provide multiple beams to cover multiple countries. In addition to the multiple beams that we need to provide we also need to achieve isoflux radiation pattern in the multibeam antenna. Practically, this type of pattern means that if we want to cover a country that is in the direct path of the satellite we need less gain than a country which is placed some angles from the satellite. Ideally, a 3D graded index Lens would be the best candidate for LEO and GEO satellites because we will be able to steer the beam in both E and H planes and thus cover multiple countries.
Well, I believe that some of these technical expressions might be tough to understand but when you begin to understand the meaning you can begin to be more interested in the space domain and the antennas. Talking to young students that are in high schools and in the universities, I would like to encourage them to become involved in space engineering and electromagnetics and my job will be to simplify the meanings. After that you will really the subject and be more passionate with it.
It is very likely to be that if you think about a space antenna, the image that appears in your mind is a parabola that sends electromagnetic waves toward the Earth or the deep space. An antenna, as it appears, is a metallic structure that captures and/or transmits radio electromagnetic waves. Antennas come in all shapes and sizes from little ones that can be found on your roof to watch TV to really big ones that capture signals from satellites millions of miles away (figure 1). The antennas that space satellites uses are a special bowl shaped antenna that focuses signals at a single point called a parabolic antenna. The bowl shape is what allows the antennas to both capture and transmit electromagnetic waves.
But what if this concept of capturing and/or transmitting electromagnetic waves would be performed in a slightly different way? Keeping in mind that a parabolic or shaped antennas exploits the geometric features of the reflecting surface to create a narrow and symmetric antenna beam, we can imagine to exploit another concept to perform this signal directivity.
The concept of a Reflect-Array is based on the fact that we want create this narrow and symmetric beam by using flat reflector, or we can say, flat antennas. This is the key point of the Reflect-Array technology. So, does not matter which kind of signal or for which application, a spacecraft would be equipped by a flat antenna. The simple geometric shape of this kind of antenna would allow to reduce the cost of manifacturing, would allow a more flexible allocation on the spacecraft, since it can be conceived foldable, it can be lighter (reduction of mass in Space satellite is very important) and, last but not the least, it can offer a very performing and smart technology for space application.
Another milestone concept of Reflect-Array is that it is constituted by a flat panel that is printed with several metallic patches. Electromagnetic waves can be reflected in different way if they imping of different surfaces, in this case on different patches. The way the signal is reflected by every single patch will determine an ensemble of small signals that interact, they sum up or erase each other. The result is a directive narrow signal as would be produced by a traditional shaped antenna.
In October 2017 I began my PhD and every time I answer the question, “What do you do?”, the next question would be, “What is your subject?”
The first time I answered whilst quoting the e-mail describing the job, “My PhD is part of the REVOLVE project which is a European initiative dealing with the study of the Smart Reflector Surfaces with processing capability based on actuated flexible thin organic large area surfaces.”
The second question, ‘What is your subject?’ took me by surprise and led me to create my PhD title: ‘Mechanically Reconfigurable Antennas.’ At this moment I was very proud of myself as I had finally found a way to explain what I will do using a title that people can understand. I looked at the eyes of my interlocutor and I understood that what I had described was not very clear. Describing or explaining something is much more difficult than trying to find a title, even more when you already have read a lot of papers about the subject area and when you try to interest people. It is my purpose on the blog to try and do this so do not hesitate to comment or to ask questions – I am still learning!
The first step to clarify a subject is to know more about the general context.
What is the context of the ESR5 ?
The REVOLVE project is a European initiative aimed at developing new solutions for future satellite systems. It will aim to investigate new technologies that will make the satellites easier to build and cheaper thus gaining time and reducing costs which is very important for industries. Moreover, the growth of the technical improvement is very fast and it is important to adapt in order to be competitive in the market.
The second is to understand a subject, and it is important to know the meaning of each word used :’ Smart Reflector Surfaces with processing capability based on actuated flexible thin organic large area surfaces’.
What is a Smart Reflector Surfaces for antenna?
In this PhD, the ‘Smart Reflector Surfaces’ will be a reflectarray. What is a reflectarray ? It combines some features of reflectors and of array antennas. A reflector antenna is a device that reflects electromagnetic waves while the array antennas is composed of groups of radiating elements which are distributed and oriented in a specific configuration. I have described two interesting experiments around Smart Reflector Surfaces for Antenna below:-
Take one curved mirror and a flashlight. Turn off every light. Illuminate the curved mirror with the flashlight, you will see on the wall in front of the mirror a circular lighted zone : it is the same process for the reflector antenna. The light rays are replaced by the electromagnetic waves which are directed on a precise zone on the Earth (see below)…
Take four plane mirrors and a flashlight. Turn off every light. Gather all the mirrors together but give them different orientation. Illuminate all the mirrors simultaneously with the same flashlight, you will see on the wall in front of the mirrors a lighted zone : it is the same process for the array antenna. Same as before, the light rays are replaced by the electromagnetic waves which are directed on a precise zone on the Earth. Nevertheless, it is important to note that the impact of the given incidence of the miror is equivalent of the array radiating elements geometry.
In conclusion, the reflectarray combines the simplicity of the reflector antenna with the performances of the array type. In fact, the reflectarray is a planar reflecting surface with a lot of radiating elements.
What is the meaning of processing capabilities?
As it is presented before, the technologies and the market change continuously and it is important to have an overview of all the possible applications a system could manage. For an antenna it could be : radio applications, space tracking or communications.
Furthermore, the main goal of this subject is to be able to reconfigure the antenna. We could say that for one mission, for exemple a satellite place at 500km of altitude which as to cover France, the antenna has one fixed shape and the satellite will be design and product during approximately 10 to 15 years. In conclusion what we ask now will be in-orbit in 2028-2033, it is too long as regard of the needs growth.
The figure below presents one cell phone of the year 2003:
What is TOLAE (Thin Organic Large Area Surface)?
It is an emerging technology and is the goal is to have a large area electronics that are thin, light weight, flexible and/or stretchable, suitable for large market sectors.
Why do we need TOLAE?
To reconfigure an antenna we could do it electromagnetically or mechanically. In my PhD we will try to do it with the second possibility in order to increase the fiability of the final system. If we take the hypothesis presented before : one shape of the antenna for one mission. So if we change the shape we change the mission and so the targeted zone on Earth, but it is quite more complicate.
To simplify the reflectarray is made of two layers separated by vacuum. On the upper layer you have the radiating elements which are illuminated by a feed (the flashlight). The electromagnetic waves will pass through this layer and be re-radiated by the second layer (the ground plane) in one direction.
Using the principle of the second experience presented before, if we modify the shape of the second layer, we will change the specification of the missions. To do it we could use some actuators which will push on this second layer at different zones and that is why we need a flexible surface.
In conclusion, the main purpose of my PhD is to find a mechanical way to change in-orbit the mission’s specifications which has to be lightweight, cheap and simple.
The Winter 2018 edition of the REVOLVE Newsletter is now available!! You can read all about our 7 Revolvers and their research as well as listen to an interview about Women in Engineering by our PhD fellow Claire Benteyn,
What are beamformers good for? And why do they need to be reconfigurable when used on a satellite?
Once in orbit, the key task of every satellite is based on the transmission and reception of electromagnetic waves. These waves carry all the information that is necessary to provide for example a certain channel on your TV or to explore the Earth’s surface. Due to the spherical shape of our planet it is obvious that at a particular time, only certain parts of the Earth can be in contact with a satellite while other parts are out of reach. But that’s all right because many services are only needed in a certain area. In fact, it is often essential that a satellite reaches only users that are located within a specific region, for example to provide a TV channel that is only available in your country. But which part of the satellite takes care that information arrives only at relevant points on Earth?
Correct – it’s the beamformer! The beamformer is only one part of the satellite’s antenna system but as you’ll see, it packs quite a punch. We should have a look first on what would happen if a satellite was launched without beamformer. As shown on the left below (not to scale), the antenna of a satellite emits electromagnetic waves which spread as distance increases.
Since a satellite is very far away in space, only a smaller (and in this case random) portion of the transmitted waves will impinge somewhere on the Earth’s surface, while a major part will be lost. To avoid this, the satellite is equipped with a beamformer (below depicted as a crescent).
As shown in the figure, this allows us to direct or form the emission of waves so that as many as possible of them reach the Earth’s surface. But this is rather the very basic task of every satellite antenna. The beamformer itself makes sure that the transmitted information strikes the region on Earth where it is actually needed, that is within a certain footprint, such as a single country or a whole continent. In many cases it is also useful to have a beamformer that allows the satellite to communicate with two or more separate regions at the same time.
So far, so good – but there is an important point that we must not forget: everything goes round. More precisely, the Earth rotates around its axis and the satellite orbits around the Earth. This is no big deal for geosynchronous satellites which appear to be at a fixed point in the sky if you could spot them from ground. But to follow the Earth’s rotation, they need to be placed at a very large distance. This is not always unproblematic because the further a satellite is away from us, the longer it takes to transmit and receive information. A satellite at lower altitude, by contrast, is able to communicate much quicker with us but he does not remain at a fixed position relative to Earth. Here it gets tricky if we want to make sure that we don’t loose connection once the satellite has passed us. In fact, a stable connection is only possible if more than one satellite is used so that every time a satellite leaves our field of view, a following one on the same orbit takes over. It seems like things are getting costly at this point. Is the beamformer of any help here?
The answer is…yes, if it is reconfigurable! To make it more clear, “reconfigurable” means that the way the beamformer shapes and directs the emission of waves can be adjusted. This flexibility opens up a lot of possibilities and allows us to do fancy things with a beamformer. In the previously mentioned case with multiple satellites we can use the beamformer for example to track a target zone on Earth. In this way, a satellite can stay in connection with a certain point for a longer time during each orbital period. This has the great advantage that we get by with a lower number of satellites in space. But take a look at this video – it should give a bit more of insight into what is actually going here.
The reconfigurable beamformer helps us here every time the satellite orbits our planet, that means it works in a recurring manner and for the long term. But there are also sporadic scenarios where this flexibility is of great help. Imagine for example the Olympic games are just around the corner. In this case, reams of information need to be transmitted from and received within a relatively small area on Earth, but all that only for a couple of weeks. Satellites that are equipped with such beamformer can then be used to focus all capacity, for a certain amount of time, on the region where the event takes place. That’s all very well, but what is it that I am actually working on?
Well, obviously we are able to control a beamformer remotely from ground every time we want to reconfigure it. But resources are limited on a satellite and we can’t afford moving the whole bulky antenna system whenever we wish to sweep the satellite’s footprint on Earth. Instead, it would be much better if only a tiny part within the beamformer was adjustable – and this is what I am looking for. In fact, it might be even possible to do that without any mechanical movement at all, but more on that very soon.
So yes, what am I doing exactly? “Deployable structures for antennas” – what is it? And why does it have to be “deployable”?
REVOLVE Fellow, Louis Dufour, has updated his blog and added a new post discussing telecommunication satellites and antennas……
An exciting research project promoting Engineering for Space