John HunterHi, my name is John Hunter and I’m a first year graduate student at Purdue University, USA. This summer I worked with Dr. Dhanya Nair on generating polarization maps of compact extragalactic radio sources at 83 GHz and 43 GHz with the Global mm-VLBI Array (GMVA).

The focus of my project was to use high-frequency radio vlbi data to image the vicinity of cosmic black holes, probing the finest structures and allowing for the extrapolation of the magnetic field structures in the jets associated with these objects. With this project, we hoped to address two questions. Does the production of high-energy gamma rays spatially coincide with the 86 GHz emission, thought to be where the jet is first collimating and accelerating? And, is there an ordered large scale magnetic field driving the flow of the jet at these scales or is the magnetic field already random, which is crucial for understanding the launching mechanisms of these jets?

In addition to my research I was available to explore much of the Netherlands and Germany on my weekends. It was easy to get around the country due to the Netherlands’ comprehensive public transportation system, so almost every weekend I would travel to a new city or region. Near the end of the summer I was able to take two trips to Germany, one for leisure and one for work. My first trip was to Berlin to meet a friend and my second trip was to Bonn to meet some of the collaborators on my project at the Max Planck Institute for Radio Astronomy (MPIfR). On top of these memorable trips, we also got to visit the ESA headquarters in Leiden, partake in a wadloping adventure, and gather for daily foosball tournaments in the canteen followed by seminars at least once a week.

Overall, this summer is one of the best that I’ve ever had. There was a great balance between progressing in my research and being able to explore a new place I may never have visited otherwise. I felt welcomed right when I arrived at JIVE and afterwards it felt very natural to meet people outside of my research group. This made for some great relationships to be formed and fond memories to be made over the course of the summer. I would highly recommend this program to anyone interested in radio astronomy and hope to be able to visit again soon.


AriannaHi everyone! My name is Arianna, I am from Italy and this summer I joined ASTRON just after having completed my Masters in Astrophysics at Royal Holloway, University of London.  Under the supervision of Maaijke and with the help of Andrè, Aleksandar and many other researchers I was investigating the suitability of AARTFAAC, an instrument based on the low frequencies of LOFAR, to monitor the ionosphere. This layer of our atmosphere is mainly constituted of electrons and ions and it is a very turbulent and chaotic medium, meaning that the particles concentration changes unpredictably in space and time. Therefore, the ionosphere is often a problem for radio astronomers, because it changes the apparent position and induces flux variations of the radio sources in the sky and only allows for short radio waves to penetrate and reach the detectors on the surface of the Earth. On the other hand, without the ionosphere all the radio signals that we constantly send and receive with modern days technology would just be lost into space. In fact, it is the ionosphere that allows the propagation of such signals around the globe. However, in occasion of strong ionospheric storms and highly turbulent conditions of the medium, telecommunications are affected as well. If we only could predict or at least monitor in real time the ionospheric changes, we would be prepared to modify our telecommunications systems accordingly

By investigating the position shifts of radio sources across the whole sky I was able to reconstruct ionospheric waves for simulated data, proving that AARTFAAC can indeed be implemented to monitor the ionosphere in real time. My project involved a lot of calibration and imaging with existing pipelines and programming in Python and bash. During this experience I massively improved my researching and programming skills and learned a lot about radio astronomy and interferometry, which I had never studied before. I particularly enjoyed the wide range of talks given to us summer students and the presentations during astrolunch.

I highly recommend this experience more than anything else, I got to explore the Netherlands from North to South, sightseeing many cities and tiny towns, cycling around the Dwingelderveld at sunset, detecting pulsars with the Dwingeloo telescope and visiting the LOFAR core, WSRT and ESA ESTEC. This was definitely an opportunity of a lifetime and I cannot thank enough all the people that made it such a memorable experience, in particular my supervisor and all the summer students.


Sophia(TL;DR) It was an amazing experience!

Hi, my name is Sophia and I am just about to start my final year of an integrated Master of Physics at Oxford University, UK. For my project at ASTRON/JIVE I worked with Huib at JIVE on ‘A pipeline for spectral line VLBI astrometry’.

In order to determine the structure and type of the Milky Way, the distances and velocities of many stars need to be known very accurately and precisely. This information can then be used to reconstruct the properties of the Galaxy. The difficultly with this largely comes from very accurately determining an objects position on the sky. This is needed in order to get a good measure of the object's parallax distance and its velocity component in the plane of the sky. There are certain types of object that make this task easier though, one of these types of object is known as a MASER, for which we can do VLBI astrometry. The process of turning the raw data into an accurate measurement of the MASERs position has previously been done in the Astronomical Image Processing System (AIPS). The goal of this project, however, was to test whether the same analysis could be done with the current release of the Common Astronomy Software Applications (CASA) package. In the end, I was able to successfully demonstrate that CASA could measure the position of a MASER, with its results agreeing with that of AIPS, only with larger errors.

It wasn’t all work though, I had a wonderful summer exploring the Dutch country side. I loved cycling around the park and visiting the cute tea house in the forest. Every week we would have a trip to the Bospub for the best Dutch pancakes in the world! A few times I got to see the radio telescope in operation which was awesome. I also got the chance to travel further afield with some of the other summer students; visiting beautiful cities such as Leiden, Den Haag and Utrecht. There was also a group trip to go wadlooping. That was an amazing experience and I would thoroughly recommend everyone to go. I also recommend the sea grass, it tastes good.

I would like to thank everyone at ASTRON/JIVE for making this summer marvellous!


PeijinHey, my name is Peijin. I am a first year PhD student at the University of science and technology of China. This summer, I worked with Pietro and Sarrvesh on the LOFAR observation of solar radio bursts. The solar radio burst can help us understand the activities of the high energy electrons in the corona and the interplanetary space. Although the solar radio emission has been studied since 1950s, the process of the particle transport wave generation and propagation is not well understood due to the observational limits. With LOFAR, we can achieve unprecedented time, frequency and imaging resolution, which can advance the solar radio physics research in a big step. I mainly worked on two projects during my stay at ASTRON with the help of Pietro and Sarrvesh, the first is to study the fine structure of the Solar S-burst in HBA, it is the first time that the fine structure of S-Burst is observed in the frequency range of HBA, and we also proposed a scenario to interpret the fine structures in S-Burst based on the wave propagation effect, the result has been submitted to ApJ. The second project is on the interferometry of the sun, using remote LBA stations of recently upgraded LOFAR-2.0, we can image the Type IIIb radio burst with high spatial resolution, and found some interesting behavior of the visual source, another paper is under preparation regarding this work. Thanks to Pietro, Sarrvesh, Richard, Andre, Golam and Michiel, I’ve learned a lot new about radio astronomy and data processing methods.

I also had lots of fun during my stay in ASTRON, the foosball game was such fun! Always a match after lunch. The guesthouse is cozy and comfortable, I cooked for the first time in my life in the guesthouse kitchen. The night is really quiet here, and dark, the Milky way is visible to the naked eye. We summer students had small trips to the cities around, Giethoorn is beautiful. ASTRON arranged a group visit to LOFAR and WSRT, we touched the LBA antenna which produces the data we use.

I would say, this summer is the best summer ever.

Latest tweets

How does a radio wave become a picture? Part II: Compact receivers. A radio wave that has travelled light years is picked up by a receiver on a telescope through an antenna. The (very weak) signal is then amplified and digitized. Read part 2 here:

How does a radio wave become a picture? Planets, stars and nebula’s all emit radio waves, which are a form of invisible light waves. Read here the first part on what happens to those radio waves when they are received by a radio telescope! 📡🌠

What's it like to work at ASTRON?
Project manager @PieterBenthem tells about his job, among which his work on the AAVS1 for the @SKA_telescope, of which LOFAR is a pathfinder project.

What's it like to work at ASTRON?
Project manager @PieterBenthem tells about his job, among which his work on the AAVS1 for the @SKA_telescope.