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

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    © ASTRON

    Note from the editor: This submission is part of our AJDI reftrofit project, in which we endeavour to collect historic pictures and place them at roughly the correct date, often many years ago. You may view them by clicking the Archive button above. Please send us your old pictures, if you stumble across them. Preferably with some information as to time, place, subject and visible people.Thank you. Enjoy.

    In order to test and use the 5 GHz MASER in the Dwingeloo telescope, a 4 K closed cycle refrigerator was built in Dwingeloo, based on a similar NRAO design, using a CTI 1020 cooling system for precooling and a Joule-Thomson expansion to cool the He-gas to a 4 K working temperature for the MASER. The pictures show the 4 K cryostat with the heat exchangers between the 20 K cooler stations and the 4 K station, also showing the measured temperature of the 4 K station as a function of heat dissipation. The pictures also show the MASER mounted on top of the 4 K plateau, as well as other electronics at the 20 K station (e.g. an L-band Up-converter) and the 70 K station (with one of the first cryogenic FET-amplifiers).

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  • 12/31/59--16:00: Green Flash
  • © ?

    The Earth atmosphere is dispersive, i.e. light of different colors is refracted by different angles. The effect is most pronounced when the light travels a long distance through the atmosphere, e.g. the light of the Sun at sunrise or sunset. When only a thin sliver of the Sun is visible, it acts like the narrow slit of a spectrograph, so its rainbow colors are well-separated from each other. Thus it can happen, for a brief moment as the Sun rapidly sinks lower, that the light of the dying Sun appears green: The Green Flash.

    NB: This phenomenon should not be confused with the fact that the rising/setting Sun appears red (and the sky is blue), which is caused by Rayleigh scattering.

    Editors note: This picture appeared mysteriously, and for many years made little sense in the context of ASTRON or JIVE, especially since neither organization existed at the time. Until it was referred to by an AJDI in 2013, which is probably why you are now reading this. Since, after elimination of the impossible, whatever remains, however improbable, must be the truth, we can only conclude that it was dropped through a time-warp by a hyper-intelligent pan-dimensional being.

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    © Elizabeth Mahony

    Until recently, the radio sky above 5 GHz was relatively unexplored. This has changed with the completion of the Australia Telescope 20 GHz survey (AT20G; Murphy et al., 2010); a blind survey of the southern sky down to a limiting flux density of 40 mJy. The AT20G survey provides by far the largest and most complete sample of high-frequency radio sources yet obtained, offering new insights into the nature of the high-frequency active galaxy population.

    Whilst the radio data provides a unique sample of objects, these data alone are insufficient to completely constrain models of radio source properties and the evolution of radio galaxies. Complementary multiwavelength data is vital in understanding the physical properties of the central core.

    In this talk I will provide a brief overview of the AT20G survey, followed by a discussion of the multiwavelength properties of the high-frequency source population. In particular, I will focus on the optical properties of AT20G sources, which are very different to those of a low-frequency selected sample, along with the gamma-ray properties where we find a correlation between high-frequency radio flux density and gamma-ray flux density. By studying the multiwavelength properties of a large sample of high-frequency radio sources we gain a unique perspective on the inner dynamics of some of the most active AGN.

    The image above shows the Australia Telescope Compact Array (ATCA) on the left and the AT20G source distribution on the top right. The AT20G survey was only possible due to the custom-built wide band correlator (shown on the bottom right) which allowed us to scan the entire southern sky at high frequencies.

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    © Picture credit: European Space Agency

    On 21 February 2013, ESA has announced the outcome of a lengthy selection process for the science composition of its flagship JUpiter ICy moons Explorer mission, JUICE ( ). Among the lucky eleven winners� is the Planetary Radio Interferometry and Doppler Experiment (PRIDE) led by JIVE. The JUICE mission, the first Large-class mission in ESA's Cosmic Vision 2015-2025 programme is scheduled to blast-off toward Jovian system in 2022 and reach the destination around 2030. At the vicinity of Jupiter the mission will conduct detailed studies of the physical environment of the largest planet of the Solar System and investigations of the three Galilean moons, Ganymede, Europa and Calisto. One of the most intriguing parts of the mission is an attempt to find large undersurface bodies of water in Ganymede and Europa. Water means life. It is not unthinkable that if liquid water is present on the Jovian moons, traces of life, past or present, could be detected too.

    PRIDE, based to great extent on VLBI technologies, is a multidisciplinary component of the JUICE science suite. Its prime deliverable, a highly accurate determination of the spacecraft state vectors will be used for a variety of applications, ranging from gravimetry to geodynamics to fundamental physics. In particular, PRIDE measurements will be involved in the monitoring of Ganymede's and Europa's tidal deformations, a key technique for liquid water search. PRIDE-JUICE is a direct descendant of the Huygens VLBI tracking experiment conducted under the JIVE's leadership in 2005.

    At the current stage of the project, in addition to JIVE, the PRIDE-JUICE team includes scientists from Belgium, France, Germany, Hungary, the Netherlands (TU Delft), Romania and the USA. But the team is likely to grow, not least via very natural involvement of EVN institutes. An important role in triggering the PRIDE-JUICE activities was performed by the EC FP7 projects EuroPlaNet and ESPaCE.

    Is 17 years too a long waiting period for such an exciting endeavour as in-situ studies of the celestial bodies that have marked the beginning of modern astronomy some four centuries ago? There might be many answers on this rhetoric question. Readers are invited to find their own one.

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  • 03/15/13--17:00: Comet PanSTARRS C/2011 L4
  • ©

    At the moment a comet is visible in the western evening sky, although you might need binoculars to see it clearly. This picture was made on Thursday (March 14 around 8 in the evening) with a Canon 5D MKII DSLR and a 200mm F/2.8 tele-lens. The camera was set at 800 ISO, F/2.8, and the exposure was 4 seconds.

    The coming weeks the comet will climb higher in the evening sky, but it will also get fainter. On top of this, the Moon will grow brighter each day, so it will be a bit of a challenge. On April 3rd, it will be close to M31, the Andromeda galaxy.

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  • 03/28/13--17:00: Image processing of M51
  • ©

    Making pretty pictures of deep-sky objects is a lot of hard work. The good news is that, nowadays, it is within reach of the (hardworking) amateur astronomer. The flash animation gives an impression of the workflow.

  • First, 40 light frames are made of M51, with 180 second integration each. They were taken through a luminance (clear) filter with a 40cm F/4.5 telescope. In addition, 10 integrations each were made through red, green and blue filters.

  • Also 20 bias frames were made, with a minimal integration time and the telescope covered up to capture the offset voltages of all pixels.

  • Then 20 dark frames were made with the same integration time as the light frames, but with the telescope covered up.

  • Finally, using an evenly illuminated white screen, 20 flat frames were made for each filter, to capture the vignetting of the optics, dust donuts, and differences in sensitivity between the pixels.

    The dark frames are combined to a master darkframe, and subtracted from each light frame. The bias frames are combined, and then subtracted from the flat frames, which are then combined to a master flat frame (for each filter separately).

  • Next, the dark-subtracted light frames (for each filter separately) are divided by the master flats. The effect of this calibration is clearly visible in the animation.

  • Stacking images dramatically improves the signal to noise ratio: the improvement is equal to the square root of the total number of images. To this end, the calibrated light frames have to be registered perfectly to each other.
  • A non-linear stretch is used to make all information in the image clearly visible.

  • The RGB master lightframes are combined to an RGB image, which looks rather pale. Then, by using a process called L-RGB combination, this RGB image is used to add colour to the high-signal Luminance image.

  • The sharpness of the images comes solely from the lumination information. No noise is added by the RGB image, only the colour. The final image can usually be sharpened a bit using unsharp-masking.

    The final result can be viewed at:

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    © Copyright Roy Smits + Neeraj Gupta

    On a sunny yet windy Sunday a group of ASTRON astronomers (plus family) made a trip to Franeker to visit the oldest operational planetarium in the world: The Royal Eise Eisinga Planetarium

    This unique planetarium was constructed from 1774 to 1781 by Eise Eisinga, making it 232 years old! It was built into the roof of his living-room. Located on the floor above is the remarkable clockwork that drives this orrery. Along with the planets, this device also shows the time and date, phases of the moon and other astronomical phenomena. Even today it runs without any electricity. All that is required, is to pull up the weights once in a while, and to adjust for the leap-day once every four years, and to replace the year numbers every decade.

    Eise Eisinga was a Dutch amateur astronomer. All the mathematics and astronomy that allowed him to produce his real-time model of the Solar-system was acquired by self-study.

    Franeker also happens to be the birthplace of the famous Dutch astronomer Jan Hendrik Oort, one of the most important pioneers in the field of radio astronomy. A commemorative plaque marks the house in which he was born.

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  • 04/02/13--17:00: Green Science
  • © MCC

    Three score years ago, during the fundamental fifties, a certain kind of people complained that the new 25m Dwingeloo dish was an eyesore that polluted the pristine landscape(*). Ever sensitive to public opinion, the SRZM management hired some expensive consultants who recommended that, in order to blend in with the surroundings, the upper half of the telescope should be painted sky-blue, and the lower half a leafy green. They somehow overlooked that the Dutch sky is not always blue (see the picture), and that the woods reflect at least fifty shades of green.

    Today, the unnatural color of the newly reconstituted astronomy wing demonstrates that effective mimicry is not so easy (although it at least hides the new management wing behind it). But inside the green walls, because of green-body radiation, ASTRON astronomers will naturally develop green thoughts. For instance, they may contemplate the vexing question why the objects in the Universe are red or yellow or ultraviolet (or simply dark), but almost never green. Rare exceptions are Hanny's Voorwerp, and the Green Flash. The former is sponsored by the Director of ASTRON, while the latter may only be sighted once in a blue moon.

    Research continues. Just watch our green scientific output increase exponentially, leaving other institutes green with mixed emotions.

    (*) 50 years later, the same kind of people argued that the telescope is an inalienable feature of the Dwingeloo horizon, and should be preserved for ever. This time, we followed their suggestion.

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    © Francesco Massaro

    About one third of the gamma-ray sources detected by Fermi have still no firmly established counterpart at lower energies. Here I present a new approach to find candidate counterparts for the unidentified gamma-ray sources (UGSs) based on the 325 MHz radio survey performed with Westerbork Synthesis Radio Telescope (WSRT) in the northern hemisphere.

    First we investigate the low-frequency radio properties of blazars, the largest known population of gamma-ray sources; then we search for sources with similar radio properties combining the information derived from the Westerbork Northern Sky Survey (WENSS) with those of the NRAO VLA Sky survey (NVSS). We present a list of candidate counterparts for 32 UGSs with at least one counterpart in the WENSS.

    We also performed an extensive research in literature to look for infrared and optical counterparts of the gamma-ray blazar candidates selected with the low-frequency radio observations to confirm their nature. On the basis of our multifrequency research we identify 23 new gamma-ray blazar candidates out of 32 UGSs investigated.

    I will also present the first analysis of very low frequency radio emission of blazars based on the recent Very Large Array Low-Frequency Sky Survey (VLSS) at 74 MHz. I show that blazars present radio flat spectra when evaluated at 74 MHz, about an order of magnitude in frequency lower than previous investigations. The implications of these findings in the contest of the blazars - radio galaxies connection will be discussed.

    Image: This artist's concept shows a "feeding," or active, supermassive black hole with a jet streaming outward at nearly the speed of light. Such active black holes are often found at the hearts of elliptical galaxies. Not all black holes have jets, but when they do, the jets can be pointed in any direction. If a jet happens to shine at Earth, the object is called a blazar. Image credit: NASA/JPL-Caltech

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    © ASTRON

    In recent years, the interest in the potential of greening� Science has taken off (see e.g. AJDI 25 Sep 2012). Some thought went into this matter much earlier, at the conception stages of LOFAR in 2001, but this proved to be a bit ahead of its time.

    Now the time may have come, so a greener LOFAR was on the table in a recent Charrette� held in Dwingeloo. It assembled all the energy-related parties in the Northern Netherlands, a region that is famous for slowly sinking due to natural gas extraction, accompanied by deep rumbles on the lower Richter scales. Serious thought was expended by the various panels, which consisted of a stimulating mixture of experts and energy laypeople, the latter mostly from ASTRON.

    The picture shows a fair cross-section of the participants, as some had already left, given the dynamics of the field of renewable energies.

    In the end, plans were drawn up for further steps. It is encouraging that, after a winter in which the Sun has not often been seen in the Netherlands, people continue to believe in solutions involving Solar energy. In fact, a small team was formed to look into the possibilities of greening the core of LOFAR with non-obstructing Solar PV installations around the SuperTerp. Of course this will only go ahead if and when absolute certainty has been obtained that this new neighbour of the super-sensitive radio telescope is RFI-friendly. At the same time, the arguments against unfriendly� windmills near the LOFAR core might be strengthened.

    We are looking forward to a future update of these activities!

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    The 32-meter Irbene radio telescope is located near Ventspils, Latvia, close to the Baltic Sea. It is a fully steerable parabolic antenna, operated by the Ventspils International Radio Astronomy Center (VIRAC). The main purpose of VIRAC is to take part in observations of cosmic sources of natural and artificial radiation in order to accumulate observational data for fundamental and applied research programs such as radio astronomy and astrophysics, cosmology, geophysics, geodynamics, geodesy, and coordinate-time service. Currently one of the main VIRAC goals is to become a member of the European VLBI Network (EVN).

    A great milestone was achieved on 2013 March 19, when the Irbene telescope took part in real-time e-VLBI observations with the rest of the e-EVN. Fringes with good signal-to-noise ratio were produced. A total data-rate of 512 Mbit/s was sent from the telescope to JIVE in real-time. The image in the upper right corner shows the test source (0234+285) image, made from the e-EVN+Irbene data.

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    © Ivy Wong

    The Local Universe provides an excellent high-resolution laboratory for studying the detailed processes of star formation and galaxy evolution. In this seminar, I will present some highlights from multiwavelength star formation studies of nearby HI-selected galaxies as well as our latest results on galaxies in transition. I will show that: (i) selecting galaxies via their HI content is a good way of selecting a large variety of star-forming galaxies regardless of size/stellar luminosity; (ii) the upper mass end of the stellar IMF may not be uniform; (iii) nearby post-starburst galaxies occupy the low-mass end of the green valley and represent a population of galaxies that are quickly going from the blue cloud to the red sequence; and (iv) unlike strong gravitational interactions, ram pressure does not strongly induce star formation. In addition, I will describe the current progress of the ASKAP project.

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    © Astron

    The digital beamformer for Apertif is taking shape. It consists of eight ADUs (Analog to Digital converter Units), four UniBoard digital processing units, a PAC (Power And Clock distribution) and an AUB (ADU-to-UniBoard Backplane).

    For this demonstration, three kinds of test signals simulate the signals from 64 antennas: wide-band (WB) and band-limited (BL) noise, and a CW signal of 719 MHz. The sequence of images shows what happens at the various monitoring points in the processing chain. Note that, as each image is shown, the relevant monitoring point is emphasized in the block diagram above it.

  • For the data-capture and DDR3 figures, raw samples are used. A Hanning taper is applied (in Python), prior to a 1024-point FFT. The output is plotted in a different color for each antenna input.

  • The subband statistics plot shows the power of the individual subbands at the output of the filterbank, integrated over one second. The integration is done on the UniBoard.

  • The beamformer weights are set in such a way that 42 beams are formed, with a bandwidth of 300MHz, with each beam containing one unique antenna input. The powers of the beamlets (i.e. beam-frequency combinations) are integrated for one second, and plotted in the beamlet statistics figure.

  • In total, 20 beams of a single subband are transferred to the control PC (LCU) via an Ethernet control link. On these raw beamlet outputs, a 256 point FFT is performed in Python. Subsequently, 128 of these spectra are averaged for each beamlet.

    These images demonstrate that the Apertif beamformer is getting in shape to be tested in full detail. All blocks are lined up, data is flowing as expected, and the Python scripts to control the boards are working. We look forward to an exciting period of further lab-tests, integrated with the other analog boards. This should then lead to the ultimate trials at the WRST telescope, with real celestial data!

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    © ASTRON

    Dutch companies and knowledge organisations in the top sector of HTSM (High Tech Systems and Materials) set themselves apart by their technological excellence, and are part of the world top in their market segments. High Tech Systems and Materials' ambition for growth is to double the export of 32 billion euros in 2009 to 77 billion euros in 2020, which is why the Holland High Tech House presented itself at the Hannover Messe this whole week. The Hannover Messe is the largest industrial trade fair in the world, and took place from 8 through 12 April. The Holland High Tech House was present in both Hall 2 with Research & Technology and Hall 4 with the Dutch supply industry. This is a clear platform on which to present the entire Dutch high-tech sector, with representatives from companies and knowledge organisations, and with that, the Netherlands as an important high-tech country.

    NWO institute ASTRON was part of the Holland High Tech House at the Hannover Messe. The knowledge and expertise gained by research and development in radio astronomy allows ASTRON to design and build extremely sensitive antenna systems, sensor technology, embedded computing, smart software, nano photonics, low noise amplifiers, low-power micro electronics and precision technology. At the Hannover Messe, ASTRON showed, among other things, the technology involved in the International LOFAR Telescope and the SKA, the watercooled Uniboard currently being the ultimate high performance embedded processing platform ASTRON has to offer, and a photonic smart antenna demonstrator.

    The picture shows the VIP-meeting at the Holland High Tech House held on Wednesday 10 April. We see Mr Bertholt Leeftink, Director-General of Industries and Innovation from the Ministry of Economic Affairs making a statement to Mrs Ineke Dezentje-Hamming (General director of FME) about the open communication in Dutch industries internally and their will to collaborate with other companies giving Dutch industries a tremendous advantage on finding high-tech solutions for the global challenges we are facing.

    NWO Director General Hans de Groene (left of the far table) with his presence emphasized that the Advanced Instrumentation programmes of the NWO institutes firmly contribute to the Dutch High Tech Systems and Materials programme.

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    © monique ankone

    On the 1st of March, the elementary school in Beilen, the Harm Smeengeschool, visited Westerbork. Thanks to pupil Douwe Westerdijk, his whole class won a trip to the famous WSRT radiotelescope.

    The 5th grader thought of a new name for the experiments along the "Milky Way" path, where visitors can experience the weight of the same object on different planets. After all, an object has an intrinsic mass (expressed in kg), but its weight is a force (expressed in Newtons) that depends on the mass of the planet, and the distance to its center.

    The new name "Overbrug de zwaartekracht" ("bridge over gravity") was found with a little help from his father...

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    © Lars Venema

    The second phase of the FP7 OPTICON program started on January 1st. On March 26 and 27, the kickoff meeting for Workpackage 5 took place in Budapest, Hungary. The subject of this Workpackage is "Smart Instrument Technologies - Development on active freeform mirrors".

    The scale and requirements of future (optical) astronomical instruments, like those for the giant 42m E-ELT, drive the scale and complexity of the optics. Instruments based on current technology tend to get bigger and more complex, leading to increasingly tight requirements on the overall performance.

    In order to reduce the systems complexity, and thus the overall instrument weight, size and cost, without compromising on performance, new technology is needed. One way forward is the introduction of extremely freeform mirrors. These allow a reduction of the total number of mirrors in the optical train, facilitating larger spectral bandwidth, wider fields of view, and increased reliability and operational availability, while minimizing the loss of photons.

    The goal of Workpackage 5 is to combine two innovative technologies (freeform mirrors and active optics) to produce Active Freeform Mirrors (AFMs). The meeting reviewed the activities and tasks that will be needed for the research and development of a demonstrator for the Freeform Active Mirror Experiment (FAME).

    The team consists of people from the Astronomy Technology Centre in Edinburgh (UK), Laboratoire d'Astrophysique de Marseille in France, and NOVA and ASTRON in the Netherlands. The location was selected to visit the Konkoly institute in Budapest.

    The meeting was very successful and happened in very good spirit. All team members went home highly motivated to make this project a success.

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    © ASTRON

    Last week we were officially awarded an NWO-M grant to expand Apertif with a tied-array beamformer and a time-domain back end, thus turning these new receivers into high-speed and very high resolution cameras. Apertif's factor 30 increase in field-of-view already allows for all-sky surveys with unprecedented sensitivity and speed. We will extend this wide-field Apertif system to both high time and angular resolution, enabling precision neutron-star timing, unique searches for fast transients, and extremely sharp imaging through VLBI.

    ARTS, the Apertif Radio Transient System, is a hybrid FPGA-GPU machine, which will serve as a cutting-edge transient survey instrument, and as a pulsar-timing and VLBI backend for all WSRT users. The grant covers the extension of the firmware on the Apertif correlator Uniboards to produce up to 450 (!) simultaneous tied-array beams. These can fill out the entire Apertif field of view for transient searching. Through this same tied-array capability, Apertif can join VLBI observing; ARTS will even stream the individual Westerbork dishes to the expanded EVN correlator at JIVE, for VLBI over a field that is 10,000 times larger than currently possible with Westerbork. The beam-forming is also essential for Apertif-era pulsar timing studies. After this FPGA beamforming, signals for all these applications are further processed on a 500 TFLOP GPU cluster. This versatile back end covers the VLBI formatting, the coherent dedispersion for timing, or the full field fast-transient search.

    Thanks to the work by the engineers, administrators and astronomers involved, at both ASTROn and JIVE, ARTS ended top-ranked a in very competitive NWO-M round. In a few years, ARTS that will offer a combination that is unique in the world, of wide-field detection and high-precision characterization of both neutron stars and black holes, for unprecedented studies of the nature of matter, space and time.

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    © D. Smyth, CSIRO

    One of the biggest questions in galaxy formation is how gas from the inter-galactic medium is accreting onto galaxies to fuel star formation. Numerical simulations predict that there is a large reservoir of gas in filamentary structures surrounding the galaxies. Until today it has proven to be extremely challenging to observe this intergalactic gas as most of it is ionised. To detect the gas in neutral hydrogen non-trivial observations are required to reach a brightness sensitivity that probes the column densities of Lyman Limit systems. I will present recent observations with the Australia Telescope Compact Array that confirm very faint HI features outside of galaxies, which were tentatively detected in previous studies. Some of these objects do not have obvious optical counterparts and could be the denser components of an underlying Cosmic Web.

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  • 04/18/13--17:00: SKA - One View of the LFAA
  • © Swinburne Astronomy Productions/ICRAR/U.Camb./ASTRON

    This visualization shows U. Camb. SKALA log-periodic dipole antennas deployed at the Murchison Radioastronomy Observatory in Western Australia, the site of the low-frequency SKA. The view is through the central core "sea of elements" where 75% of the collecting area will be located. The computer-generated image is remarkably similar to some views of the small, recently-deployed AAVS 0.5 array, a joint project between ICRAR, U. Camb. and ASTRON.

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    © ASTRON

    In the second half of the late 90's, ASTRON cooperated with Catena electronics in Delft on the design of a quadrature mixer chip in Si-technology for application in the IVC, the IF to Video Converter system of the DZB. The quadrature mixer was used to build an image rejection mixer with 30-40 dB image suppression, converting 20 MHz sidebands from 200-220 MHz intermediate frequency to a 20 MHz baseband, for further processing by the correlator. The chip was successfully applied in the Converter Modules of the IVC, in use at the WSRT since the beginning of this century, with hardly any failure of the chips over almost 15 years of contineous operation.

    The pictures show the ASTRON 01 chip on a test and evaluation board, as well as close views of the interior of the chip at 20x and 100x zoom.

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