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A daily view of all the goings-on at ASTRON and JIVE.
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    © M. Mevius

    Calibration of LOFAR low band data is particularly difficult due to the ionosphere, which effects become increasingly important towards lower frequencies. The low signal-to-noise regime of these data is a furthercomplication in removing the ionospheric effects. In a recent paper by F. de Gasperin et al. the effects of ionospheric induced systematic errors on LOFAR LBA data are characterized and quantified, thereby providing guidelines for data reduction of current and future low frequency radio telescopes such as SKA.

    The most prominent effect of the ionosphere is a frequency dependent phase delay, due to propagation effects of the electromagnetic signal through the ionized plasma. To first order this effects goes with 1/frequency although for the lowest frequencies higher order terms (1/frequency^3) become important. Combined with the Earth magnetic field the propagation through the ionosphere causes a splitting of right and left handed signal phases, effectively causing a frequency dependent rotation of the linear polarization, an effect well known as Faraday rotation. The signals at two arms of an interferometer experience a slightly different ionospheric Faraday rotation, resulting in a net polarization in the cross correlation of the signal, even for unpolarized sources. Finally, amplitude scintillation due to small scale structures in the ionosphere is a non negligible effect at LBA frequencies.

    Here we show one of the highlights of this paper. From the phase solutions of a calibrator observation we were able to detect 3 different ionospheric effects. Using the different frequency behavior over the wide frequency band

    we were able to separate from the diagonal phases the clock errors (top left), the first order differential ionospheric TEC (top right) and also the third order ionospheric effect (lower right) versus time. Where the ionospheric TEC gives the integrated electron density along the line of sight, the third order effect is related to the vertical distribution of the electrons in the ionosphere. The plot on the lower left shows the differential Faraday rotation. Each line represent a single station. The different ionospheric effects are clearly correlated.

    https://arxiv.org/abs/1804.07947


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    © A.J. Boonstra / ASTRON

    In the middle of the night, after half an hour bus ride, we arrive at the Xichang Space Center. Apart from soft music and staccato speaker-messages from the launch site it is quiet. In a few hours the sun will rise. Our CNSA hosts invite us to join them at the platform. We are at 3 km distance from the rocket position, and I can see the launch facilities in the valley below, completely lit. We're talking a little and take some pictures to test the camera settings, knowing this is a one-shot event.

    After a while the tension starts building up, and then a roar comes from the valley below. With loud noise and fumes the rocket lifts and starts penetrating the dark sky. Very slowly at first, and after several seconds it seemed not to speed up and it even seemed to bend its course a little towards us.

    But then it gained strength and pursued its course towards the moon. The sky was clear and many stars were visible, and I saw Mars shining bright. The torch bended towards the planet, but then passed it and continued. I realized that at this early time of day there were no airplanes in the sky, and then I saw a bright dot, most likely a satellite, coming towards the rocket. Fortunately, the two crossed without colliding. A stripe of exhaust fume was clearly visible, and with a visible puff the first stage appeared to be ejected. All this with a lot of noise of course, and I thought of our radio instrument being subjected to all this vibration, but it had survived vibration tests on Earth, right?

    Then it soared higher and higher till it disappeared, following its route towards the moon. It left a patch of exhaust fume colouring blue-purple high in the skies.

    The moon, of course, will never again be the same for us. And as honoured guests we were given the front row to watch the spectacle, which left me speechless.

    The first phase of the NCLE project is now finished, the ASTRON - Radboud University - ISIS - NAOC receiver is on its way towards the moon. Big thanks to CNSA, ESA/PRODEX, NSO and our other scientific partners. Now it's time to prepare for the next phase, commissioning and science, unravelling cosmic mysteries.


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    © Jesper Spraakman, Koos Kegel, Jeroen Herrewijnen, Sjouke Kuindersma, Gijs Schoonderbeek, Paula Fusiara; BrainBricks from SunIdee

    Do you want a huge number of creative ideas in a short amount of time but you do not know how to trigger your team or how to go about it?

    Ask the Mechanical Group!

    We can facilitate your innovation process with a very simple, but effective approach towards concepts creation (it is suitable for team building as well!). Here is the recipe:

    You will need the following ingredients:

    (contents of P.'s brainstorm Magic Box, no it is not a pancake baking kit according to some:))

    - 3 decks of BrainBricks

    - Set of colorful hexagonal post-its

    - Stationary

    - Fuel for the mind

    - 10 sheets of A3

    - Set of uninhibited & open minds (obviously these are not included in the Magic Box, you have to seek & arrange those minds yourself, challenging enough?)

    - Multidisciplinary team (make sure NOT to invite those who reveal any signs of features leaning towards strong or narrow-minded conservatisms)

    - 1 small furnished office

    Rules of the game

    You lock up 1 Digital &Embedded Signal Processing Engineer in a small furnished office together with 1 System Engineer, 2 Mechanical Engineers, 1 Research Instrument maker and a Mechanical Engineering Graduate;

    Give them a set of BrainBricks (a facilitator is needed, otherwise chaos is guaranteed)

    Tell them that they are free to say anything (I mean really anything, a free opinion zone); no idea is bad, freaky ideas are more than welcome, criticism is forbidden!

    Give them at least 2 hours (do not forget to FUEL* them)

    Example Goal:

    Come up with 10 creative ideas for generic cooling for Gemini Project.

    But first, DO the warm up:

    Show 1 card at a time, induce associations to each uncovered card; straightforward descriptions will not be rewarded, facilitator will only accept associations. A person with the tallest deck of cards ... gets a cookie*** (if there are any left).

    BrainBricks? What kind of cards are these, you may ask? A good mix of pictures of all kinds of animals (biomimicry is all around us, yay!! definitely!), landscapes, objects, people, events, buildings ... everything that can trigger the mind and generate associations.

    Shake & stir 'em up (the brains), have a good facilitator and give your team sufficient time to settle and you will be amazed with the result.

    Ideas are in all of you!

    We can help you unveil them.

    *Their motivation and quality of their input is strongly correlated** with fuel quality

    ** not really scientifically proven, just a bold assumption

    *** if your brainstorm team consists of mainly blue & green type of 'communication styles' forget telling them "the person who has the tallest deck wins!". Only do that when the red types are around. So better bribe (ooopss!!!... sorry, wrong expression) MOTIVATE them with a cookie/fruit/chocolate etc...


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  • 05/23/18--17:00: En route for NCLE
  • © Photos: ASTRON / RH

    Caught in action! Pictured here are ASTRON designers Mark Ruiter and Sieds Damstra fully committed to designing and routing the printed circuit board for NCLE's Low Noise Amplifier.

    Heavy pressure was felt in delivering in time the design for the NCLE system. Rockets do not wait for additional payload when a launch date is set! So Mark and Sieds returned to their office after sending off their families back home assuming the yearly ASTRON-JIVE BBQ (summer 2017) was about to finish. "The window of My Eyes" song still could be heard as played by our L-band (ASTRON-JIVE's house rock-band) while the after-party at the first floor went on.

    However, the window of the eyes of Mark and Sieds where oriented to the Mentor Graphics CAD tool which was applied to design this complex RF board for the NCLE system.

    The Netherlands Chinese Low-Frequency Explorer (NCLE) actually is a 3 monopole antenna system with receiver suitable for receiving frequencies from 80 kHz .. 80 MHz. Frequencies, which normally are blocked by Earth atmosphere.

    The LNA board conditions the (three) received antenna signals to be transported to the Analog Interface System board. It determines the frequency band, sets a large portion of the receiver noise figure and amplifies the signal to the required level.

    The NCLE instrument is developed and built by engineers from ASTRON, the Netherlands Institute for Radio Astronomy in Dwingeloo, the Radboud Radio Lab of Radboud University in Nijmegen, and the Delft-based company ISIS. NCLE greatly is supported by the Netherlands Space Organisation NSO. More about the NCLE mission can be found here.

    Apparently, the team met all deadlines as the Chinese Chang'e-4 relay satellite with on board the NCLE system, successfully lifted off atop a Long March 4C rocket from the Xichang Satellite Launch Centre at 23:28 CET on Sunday 20th (05:28 Beijing time, May 21) and is on a nine day journey to the second Earth-Moon Lagrange point (L2) some 60-80,000 kilometers beyond the Moon and nearly half a million kilometers from our planet Earth...


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    © Benito Marcote

    e-ASTROGAM is a breakthrough Observatory space mission dedicated to the study of the non-thermal Universe in the photon energy range from 0.3 MeV to 3 GeV. The mission is based on an advanced space-proven detector technology, with unprecedented sensitivity, angular and energy resolution, combined with polarimetric capability.

    Thanks to its performance in the MeV-GeV domain, substantially improving its predecessors and covering the energy gap between INTEGRAL and Fermi, e-ASTROGAM will open a new window on the non-thermal Universe, making pioneering observations of the most powerful Galactic and extragalactic sources, elucidating the nature of their relativistic outflows and their effects on the surroundings.

    e-ASTROGAM will exhibit unique polarization capabilities and a line sensitivity one to two orders of magnitude better than previous generation instruments. The mission will provide unique data of significant interest to a broad astronomical community, complementary to powerful observatories such as LIGO-Virgo-GEO600-KAGRA, SKA, ALMA, E-ELT, TMT, LSST, JWST, Athena, CTA, IceCube, KM3NeT, and LISA. e-ASTROGAM was submitted as a M5 mission to the recent ESA call for proposals to be launch in 2018. Unfortunately, it has not been selected for the short list published these weeks for further study in this call (the three chosen ones are SPICA, THESEUS, and EnVision). But this will not be the end of the project!

    For further information about e-ASTROGAM, see the White Book about the mission and the science cases in de Angelis et al. (2017, arXiv:1711.01265).