Centro Astronomico Of Yebes

Yebes, Mexico

Centro Astronomico Of Yebes

Yebes, Mexico
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Ossenkopf V.,University of Cologne | Ossenkopf V.,SRON Netherlands Institute for Space Research | Rollig M.,University of Cologne | Simon R.,University of Cologne | And 39 more authors.
Astronomy and Astrophysics | Year: 2010

Context. The molecular gas in the DR21 massive star formation region is known to be affected by the strong UV field from the central star cluster and by a fast outflow creating a bright shock. The relative contribution of both heating mechanisms is the matter of a long debate. Aims. By better sampling the excitation ladder of various tracers we provide a quantitative distinction between the different heating mechanisms. Methods. HIFI observations of mid-J transitions of CO and HCO+ isotopes allow us to bridge the gap in excitation energies between observations from the ground, characterizing the cooler gas, and existing ISO LWS spectra, constraining the properties of the hot gas. Comparing the detailed line profiles allows to identify the physical structure of the different components. Results. In spite of the known shock-excitation of H2 and the clearly visible strong outflow, we find that the emission of all lines up to ≳2 THz can be explained by purely radiative heating of the material. However, the new Herschel/HIFI observations reveal two types of excitation conditions. We find hot and dense clumps close to the central cluster, probably dynamically affected by the outflow, and a more widespread distribution of cooler, but nevertheless dense, molecular clumps. © 2010 ESO.

Decin L.,Catholic University of Leuven | Decin L.,University of Amsterdam | Justtanont K.,Chalmers University of Technology | De Beck E.,Catholic University of Leuven | And 30 more authors.
Astronomy and Astrophysics | Year: 2010

During their asymptotic giant branch evolution, low-mass stars lose a significant fraction of their mass through an intense wind, enriching the interstellar medium with products of nucleosynthesis. We observed the nearby oxygen-rich asymptotic giant branch star IK Tau using the high-resolution HIFI spectrometer onboard Herschel. We report on the first detection of H 216O and the rarer isotopologues H2 17O and H218O in both the ortho and para states. We deduce a total water content (relative to molecular hydrogen) of 6.6 × 10-5, and an ortho-to-para ratio of 3:1. These results are consistent with the formation of H2O in thermodynamical chemical equilibrium at photospheric temperatures, and does not require pulsationally induced non-equilibrium chemistry, vaporization of icy bodies or grain surface reactions. High-excitation lines of 12CO, 13CO, 28SiO, 29SiO, 30SiO, HCN, and SO have also been detected. From the observed line widths, the acceleration region in the inner wind zone can be characterized, and we show that the wind acceleration is slower than hitherto anticipated. © 2010 ESO.

Bujarrabal V.,Observatorio Astronomico Nacional IGN | Alcolea J.,Observatorio Astronomico Nacional IGN | Soria-Ruiz R.,Observatorio Astronomico Nacional IGN | Planesas P.,Observatorio Astronomico Nacional IGN | And 30 more authors.
Astronomy and Astrophysics | Year: 2010

Aims. We aim to study the physical conditions, particularly the excitation state, of the intermediate-temperature gas components in the protoplanetary nebula CRL 618. These components are particularly important for understanding the evolution of the nebula. Methods. We performed Herschel/HIFI observations of several CO lines in the far-infrared/sub-mm in the protoplanetary nebula CRL 618. The high spectral resolution provided by HIFI allows measurement of the line profiles. Since the dynamics and structure of the nebula is well known from mm-wave interferometric maps, it is possible to identify the contributions of the different nebular components (fast bipolar outflows, double shells, compact slow shell) to the line profiles. The observation of these relatively high-energy transitions allows an accurate study of the excitation conditions in these components, particularly in the warm ones, which cannot be properly studied from the low-energy lines. Results. The 12CO J = 16-15, 10-9, and 6-5 lines are easily detected in this source. Both 13CO J = 10-9 and 6-5 are also detected. Wide profiles showing spectacular line wings have been found, particularly in 12CO J = 16-15. Other lines observed simultaneously with CO are also shown. Our analysis of the CO high-J transitions, when compared with the existing models, confirms the very low expansion velocity of the central, dense component, which probably indicates that the shells ejected during the last AGB phases were driven by radiation pressure under a regime of maximum transfer of momentum. No contribution of the diffuse halo found from mm-wave data is identified in our spectra, because of its low temperature. We find that the fast bipolar outflow is quite hot, much hotter than previously estimated; for instance, gas flowing at 100 km s -1 must have a temperature higher than ∼200 K. Probably, this very fast outflow, with a kinematic age <100 yr, has been accelerated by a shock and has not yet cooled down. The double empty shell found from mm-wave mapping must also be relatively hot, in agreement with the previous estimate. © 2010 ESO.

Rivera-Lavado A.,Charles III University of Madrid | Llorente-Romano S.,Charles III University of Madrid | Herraiz-Martinez F.-J.,Charles III University of Madrid | Garcia-Munoz L.-E.,Charles III University of Madrid | And 4 more authors.
8th European Conference on Antennas and Propagation, EuCAP 2014 | Year: 2014

A new topology that potentially can open new solutions for covering the new VLBI2010 configuration and its frequency bands associated is presented in this manuscript. In this approach a single band from 2 to 14 GHz is considered. A log-spiral antenna is printed on a conic surface. The whole structure is adjusted in order to obtain a pure circular polarization at broadside direction. An array of four elements is proposed for obtaining a dual-polarization feeder. © 2014 European Association on Antennas and Propagation.

Cano J.L.,University of Cantabria | Wadefalk N.,Chalmers University of Technology | Gallego-Puyol J.D.,Centro Astronomico Of Yebes
IEEE Transactions on Microwave Theory and Techniques | Year: 2010

A 20-dB chip attenuator designed for cryogenic noise measurements from dc up to 40 GHz is presented. The chip is based on the use of temperature-stable tantalumnitride thin-film resistors, a high thermal conductivity substrate such as crystal quartz (z-cut), and a suitable design that avoids inner conductor thermal heating, which is an important limiting factor for the precision of cryogenic noise measurements. A high-accuracy temperature sensor installed inside the attenuator module provides precise temperature characterization close to the chip location. The high thermal conductivity of the chip substrate in the designed attenuator assures a negligible temperature gradient between the resistive elements in the chip and the sensor, thus improving the measurement accuracy. The attenuator also shows an excellent electrical performance with insertion losses of 19.9 dB ± 0.65 dB and return losses better than 20.6 dB in the whole frequency range at 296 K. The insertion loss change when cooled to 15 K is less than 0.25 dB, which demonstrates its temperature stability. © 2010 IEEE.

Serra G.,National institute for astrophysics | Bolli P.,National institute for astrophysics | Busonera G.,CRS4 | Pisanu T.,National institute for astrophysics | And 6 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Microwave holography is a well-established technique for mapping surface errors of large reflector antennas, particularly those designed to operate at high frequencies. We present here a holography system based on the interferometric method for mapping the primary reflector surface of the Sardinia Radio Telescope (SRT). SRT is a new 64-m-diameter antenna located in Sardinia, Italy, equipped with an active surface and designed to operate up to 115 GHz. The system consists mainly of two radio frequency low-noise coherent channels, designed to receive Ku-band digital TV signals from geostationary satellites. Two commercial prime focus low-noise block converters are installed on the radio telescope under test and on a small reference antenna, respectively. Then the signals are amplified, filtered and down-converted to base-band. An innovative digital back-end based on FPGA technology has been implemented to digitize two 5 MHz-band signals and calculate their cross-correlation in real-time. This is carried out by using a 16-bit resolution ADCs and a FPGA reaching very large amplitude dynamic range and reducing post-processing time. The final holography data analysis is performed by CLIC data reduction software developed within the Institut de Radioastronomie Millimétrique (IRAM, Grenoble, France). The system was successfully tested during several holography measurement campaigns, recently performed at the Medicina 32-m radio telescope. Two 65-by-65 maps, using an on-the-fly raster scan with on-source phase calibration, were performed pointing the radio telescope at 38 degrees elevation towards EUTELSAT 7A satellite. The high SNR (greater than 60 dB) and the good phase stability led to get an accuracy on the surface error maps better than 150 μm RMS. © 2012 SPIE.

Montero-De-Paz J.,Charles III University of Madrid | Garcia-Perez O.,Charles III University of Madrid | Garcia-Perez O.,Centro Astronomico Of Yebes | Rivera-Lavado A.,Charles III University of Madrid | And 8 more authors.
Proceedings of the 5th European Conference on Antennas and Propagation, EUCAP 2011 | Year: 2011

A focusing system for a 300 GHz radar with two target distances (5m and 10m) is proposed, having 1cm resolution in both cases. The focusing system is based on a gaussian telescope scheme and it has been designed using gaussian beam quasi-optical propagation theory with a homemade Matlab analysis tool. It has been translated into a real focusing system based on two elliptical mirrors and a plane mirror in order to have scanning capabilities and validated using the commercial antenna software GRASP. © 2011 EurAAP.

Munoz L.E.G.,Charles III University of Madrid | Lavado A.R.,Charles III University of Madrid | Aller M.M.,Charles III University of Madrid | Puente J.M.S.,Centro Astronomico Of Yebes | And 2 more authors.
2013 7th European Conference on Antennas and Propagation, EuCAP 2013 | Year: 2013

Two new topology that potentially can open new solutions for covering the new VLBI2010 configuration and its frequency bands associated are presented in this manuscript. In the first approach three bands are covered: 2.2-2.7 GHz, 7-9 GHz and 28-33 GHz. This new topology is based on an archimedean spiral on the top of two frequency selective surfaces (FSS's) and a ground plane. The architecture of the FSS's and their height to the antenna are optimized for covering the complete sub-bands. Second approach consider a single band from 2 to 14 GHz. A log-spiral printed on a semi-conic surface is place over a PEC ground plane. Whole structure is adjusted in order to obtain a pure circular polarization at broadside direction. © 2013 EurAAP.

Alt A.R.,Wave Group | Bolognesi C.R.,Wave Group | Gallego J.D.,Centro Astronomico Of Yebes | Diez C.,Centro Astronomico Of Yebes | And 2 more authors.
Conference Proceedings - International Conference on Indium Phosphide and Related Materials | Year: 2011

InP HEMTs provide the best available low-noise transistor performance. The availability of InP HEMTs for cryogenic front-ends is of paramount importance in ultra-low noise Deep-Space Network (DSN) and Radio-Astronomy (RA) applications. In DSN applications, cryo-cooled InP HEMT front-ends are at the heart of the ESA 34 m antennas used to detect data carrying signals and telemetry information from deep space probes, and excellent HEMT noise performances are key to reducing antenna size and cost, as well as to simplifying spacecraft payloads. In RA, very low noise temperatures are required because of the cold cosmic microwave background (∼2.73K). © VDE VERLAG GMBH.

Garcia E.,Charles III University of Madrid | Romano S.L.,Charles III University of Madrid | Lamperez A.G.,Charles III University of Madrid | Martinez F.J.H.,Charles III University of Madrid | And 7 more authors.
2015 Loughborough Antennas and Propagation Conference, LAPC 2015 | Year: 2015

VLBI2010 requires a feed that simultaneously has high efficiency over the full 2-14 GHz frequency range. The simultaneity requirement implies that the feed must operate at high efficiency over the full frequency range without the need to adjust its focal position to account for frequency dependent phase center variations. Two feeds meet this specification with some lacks to be fulfilled [1]: The Eleven Feed developed at Chalmers University and the Quadruple Ridged Flared Horn (QRFH) developed at the California Institute of Technology. In this frame, Universidad Carlos III de Madrid has developed a new topology for complete covering the requirements of the VLBI2010, including two new pretty attractive characteristics: dual circular polarization (versus the dual lineal solutions present in the state of the art) and constant input impedance of the antenna due to its self-complementary geometry, what is highly interesting for the LNA design. This manuscript is divided as follows: first, results of the complete system using an ideal Gaussian feed are summarized. Then, the new topology proposed is presented and analyzed both, isolated and integrated in the radiotelescope. Finally, a closed solution for covering all the requirements has been manufactured and results from full wave electromagnetic simulations together with measurements are presented. Conclusions and future lines are presented at the end of the present manuscript. © 2015 IEEE.

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