Miroslav Pantaleev

A Swedish heterodyne facility instrument for the APEX telescope

Aims. In March 2008, the APEX facility instrument was installed on the telescope at the site of Lliano Chajnantor in northern Chile. The main objective of the paper is to introduce the new instrument to the radio astronomical community. It describes the hardware configuration and presents some initial results from the on-sky commissioning. Methods. The heterodyne instrument covers frequencies between 211 GHz and 1390 GHz divided into four bands. The first three bands are sideband-separating mixers operating in a single sideband mode and based on superconductor-insulator-superconductor (SIS) tunnel junctions. The fourth band is a hot-electron bolometer, waveguide balanced mixer. All bands are integrated in a closedcycle temperature-stabilized cryostat and are cooled to 4 K. Results. We present results from noise temperature, sideband separation ratios, beam, and stability measurements performed on the telescope as a part of the receiver technical commissioning. Examples of broad extragalactic lines are also included.

Cryogenic 2–13 GHz Eleven Feed for Reflector Antennas in Future Wideband Radio Telescopes

The system design of a cryogenic 2-13 GHz feed is considered with emphasis on its application in future wideband radio telescope systems. The feed is based on the so-called Eleven antenna and the design requires careful integration of various sub-designs in order to realize cryogenic operation. The various sub-designs include the electrical design of the Eleven antenna, design of the critical center puck, alternative solutions for integrating the Eleven antenna with low-noise amplifiers (LNAs), mechanical and cryogenic design and tests, and system noise temperature estimation and measurements. A great deal of simulated and measured results are presented throughout this paper, including the electrical, mechanical and cryogenic performance, and an assessment of the system noise temperature. The objective of this work is to present a good feed candidate that is well-suited for VLBI2010 and SKA radio telescopes. Further developments needed to completely fulfill the requirements for these future wideband radio telescopes are also discussed.

A 1.3-THz Balanced Waveguide HEB Mixer for the APEX Telescope

In this paper, we report about the development, fabrication, and characterization of a balanced waveguide hot electron bolometer (HEB) receiver for the Atacama Pathfinder EXperiment telescope covering the frequency band of 1.25-1.39 THz. The receiver uses a quadrature balanced scheme and two HEB mixers, fabricated from 4- to 5-nm-thick NbN film deposited on crystalline quartz substrate with an MgO buffer layer in between. We employed a novel micromachining method to produce all-metal waveguide parts at submicrometer accuracy (the main-mode waveguide dimensions are 90 times 180 mum ). We present details on the mixer design and measurement results, including receiver noise performance, stability and ldquofirst-lightrdquo at the telescope site. The receiver yields a double-sideband noise temperature averaged over the RF band below 1200 K, and outstanding stability with a spectroscopic Allan time more than 200 s.

APEX: the Atacama Pathfinder EXperiment

APEX, the Atacama Pathfinder Experiment, has been successfully commissioned and is in operation now. This novel submillimeter telescope is located at 5107 m altitude on Llano de Chajnantor in the Chilean High Andes, on what is considered one of the worlds outstanding sites for submillimeter astronomy. The primary reflector with 12 m diameter has been carefully adjusted by means of holography. Its surface smoothness of 17-18 μm makes APEX suitable for observations up to 200 μm, through all atmospheric submm windows accessible from the ground.

Micromachining Approach in Fabricating of THz Waveguide Components

In this paper, we describe our progress in micromachining of submillimeter waveguide structures such as a quadrature waveguide coupler which is a part of a THz balanced heterodyne receiver. We have set up and developed pilot testing of the micromachining process with required high quality of structure.

Design of Compact Dual-Polarized 1.2–10 GHz Eleven Feed for Decade Bandwidth Radio Telescopes

The Eleven antenna is a log-periodic folded-dipole-pair array with two unique radiation characteristics: a constant beamwidth and a fixed phase center location over a decade bandwidth. This paper presents a new compact design of a 1.2-10 GHz Eleven antenna, as a feed for reflector antennas by re-arranging the geometry of the outermost elements of the antenna. Due to the compact size, it is possible to put the whole feed system inside a compact cryostat and cool it down to cryogenic temperatures, in order to reduce the system noise temperature in radio telescope applications. The new compact Eleven feed has only a 40% volume of the original standard Eleven feed with a very similar performance. This reduces the capacity requirement for the cryogenic cooling system significantly and therefore the power consumption for future radio telescopes, such as the square kilometer array (SKA). The concept behind this compact design is analyzed in the paper. Simulations and measurements presented here have verified the design.

MMIC-Based Components for MM-Wave Instrumentation

In this letter, we present results of fully integrated 90-130 GHz receiver based on 100 nm mHEMT technology. The receiver contains a low noise amplifier (LNA), mixer and LO multiplier chain integrated into a single monolithic microwave integrated circuit (MMIC). The circuit is packaged into a waveguide block, characterized and compared to on-wafer measurements. Waveguide to microstrip transitions are used to interface the MMIC to the waveguide. A breakout LNA circuit is also packaged, and its performance is compared to the receiver. The LNA noise was characterized on a wafer and after packaging. The packaged module is measured at both room and cryogenic temperatures, NF of 3.7 dB is measured at 300 K and 0.9 dB at 20 K.

First 230? GHz VLBI fringes on 3C 279 using the APEX Telescope (Research Note)

Aims. We report about a 230 GHz very long baseline interferometry (VLBI) fringe finder observation of blazar 3C 279 with the APEX telescope in Chile, the phased submillimeter array (SMA), and the SMT of the Arizona Radio Observatory (ARO). Methods. We installed VLBI equipment and measured the APEX station position to 1 cm accuracy (1σ). We then observed 3C 279 on 2012 May 7 in a 5 h 230 GHz VLBI track with baseline lengths of 2800 Mλ to 7200 Mλ and a finest fringe spacing of 28.6 μas. Results. Fringes were detected on all baselines with signal-to-noise ratios of 12 to 55 in 420 s. The correlated flux density on the longest baseline was ∼0.3 Jy beam−1, out of a total flux density of 19.8 Jy. Visibility data suggest an emission region .38 μas in size, and at least two components, possibly polarized. We find a lower limit of the brightness temperature of the inner jet region of about 1010 K. Lastly, we find an upper limit of 20% on the linear polarization fraction at a fringe spacing of ∼38 μas. Conclusions. With APEX the angular resolution of 230 GHz VLBI improves to 28.6 μas. This allows one to resolve the last-photon ring around the Galactic Center black hole event horizon, expected to be 40 μas in diameter, and probe radio jet launching at unprecedented resolution, down to a few gravitational radii in galaxies like M 87. To probe the structure in the inner parsecs of 3C 279 in detail, follow-up observations with APEX and five other mm-VLBI stations have been conducted (March 2013) and are being analyzed.

Heterodyne single-pixel facility instrumentation for the APEX Telescope

APEX, the Atacama Pathfinder Experiment, is collaboration between Max Planck Institut fur Radioastronomie (MPIfR) with Astronomisches Institut Ruhr Universitat Bochum, Onsala Space Observatory and the European Southern Observatory (ESO). The telescope was supplied by VERTEX Antennentechnik in Duisburg, Germany, and is a 12 m antenna with 15 μm rms surface accuracy operating at the Atacama Desert Llano Chajnantor, in the Chilean Andes at 5100 m altitude. APEX heterodyne single pixel facility receiver are placed in the telescope Nasmyth cabin A. The receivers are coupled to the antenna via relay optics providing possibility to operate either one of the two different PI-type instruments or a multi-channel facility heterodyne receiver to cover 211 - 1500 GHz frequency range. In this report, we present the optical design for APEX single-pixel facility heterodyne receiver providing frequency independent illumination of the secondary for all the receiver channels. We present design of the two-channel facility receiver APEX A, installed and operating since June 2005, and of the coming 6-channel APEX facility receiver. The report includes a brief review of the mixer technology development status for APEX Band 1, 211 - 270 GHz, using sideband separation technology (2SB), Band 2, 270 - 370 GHz, 2SB, Band 3, 385 - 500 GHz, 2SB, and Band T2, 1250 - 1390 GHz, HEB waveguide balanced mixer, those on the development at Onsala Space Observatory. We present description of the receiver control system and example observation of APEX 2a receiver.

A new 3 mm band receiver for the Onsala 20 m antenna

A new receiver for the Onsala 20 m antenna with the possibility of being equipped with 3 mm and 4 mm bands has been built and the 3 mm channel has been commissioned during the Spring 2014. For single-dish operation, the receiver uses an innovative on-source/off-source optical switch. In combination with additional optical components and within the same optical layout, the switch provides two calibration loads (for the 3 mm and 4 mm channels), sideband rejection measurement, and tuning possibilities. The optical layout of the receiver employs all cold (4 K) offset elliptical mirrors for both channels, whereas the on-off switch employs flat mirrors only. The 3 mm channel employs a sideband separation (2SB) dual polarization receiver with orthomode transducer (OMT), 4-8 GHz intermediate frequency (IF), x? 2pol x? upper and lower sidebands (USB? +? LSB). The cryostat has four optical windows made of high density polyethylene (HDPE) with anti-reflection corrugations, two for the signal and two for each frequency band cold load. The cryostat uses a two-stage cryocooler produced by Sumitomo HI? RDK? 408D2 with anti-vibration suspension of the cold-head to minimize impact of the vibrations on the receiver stability. The local oscillator (LO) system is based on a Gunn oscillator with aphase lock loop (PLL) and four mechanical tuners for broadband operation, providing independently tunable LO power for each polarization. This paper provides a technical description of the receiver and its technology and could be useful for instrumentation engineers and observers using the Onsala 20 m telescope.