| 1. |
- Elgered, Gunnar, 1955, et al.
(författare)
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The Onsala Twin Telescopes Project
- 2017
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Ingår i: The 23rd Working Meeting of the European VLBI Group for Geodesy and Astrometry (EVGA), Gothenburg, May 14–18, 2017.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Onsala Space Observatory is the European site in the International VLBI Service for Geodesy and Astrometry (IVS) that has the longest history in VLBI. First geodetic VLBI measurements were performed already in 1968 with the 25 m radio telescope. Onsala is today one of the sites with thelongest time series in the IVS data base. The observatory is one of the unique fundamental space geodetic sites that have a direct access to the coast line and co-locate VLBI, GNSS, gravimetry, and sea-level monitoring. Onsala is thus an important co-location site for the GlobalGeodetic Observing System (GGOS). Being well aware of the VGOS standard it was clear around 2010 that Onsala was in need for a telescope with significantly faster slew rates than the existing radome-enclosed 20 m telescope.
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| 2. |
- Elgered, Gunnar, 1955, et al.
(författare)
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The Onsala Twin Telescopes: the Status at the Time for the Inauguration
- 2017
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Ingår i: Proceedings of the 23rd European VLBI Group for Geodesy and Astrometry Working Meeting. - 9789188041098 ; , s. 136-139
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We summarise the activities related to the Onsala Twin Telescopes (OTT), from the time when the decision was taken to fund the proposal, to the inauguration on 18 May 2017.
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| 3. |
- Flygare, Jonas, 1988, et al.
(författare)
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Sensitivity and Antenna Noise Temperature Analysis of the Feed System for the Onsala Twin Telescopes
- 2017
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Ingår i: Proceedings of the 23rd European Very Long Baseline Interferometry Group for Geodesy and Astrometry Working Meeting, EVGA2017, Gothenburg, Sweden, 15-19 May 2017. - 9789188041104 ; , s. 10-14
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The demand for higher precision measurements in Very Long Baseline Interferometry (VLBI) continues to grow, which drives the technical development of next generation international VLBI stations called the VLBI Global Observing System (VGOS). The VGOS design includes the idea of twin telescopes, i.e. two identical telescopes that will be used for continuous observations to study geodynamical processes. Such a twin telescope system has recently been installed at the Onsala Space Observatory, Sweden. The Onsala twin telescopes (OTT) are 13.2 m diameter, dual-reflector systems with a ring-focus sub-reflector. In this paper we present the estimated performance, focusing on the achievable system equivalent flux density (SEFD), sky noise modeling, and antenna noise temperature. We evaluate the system for two different cryogenic wideband quad-ridge flared horn (QRFH) feed setups operating over 3-18 GHz and 4.6-24 GHz. Analysis based on measured feed data shows a low antenna noise temperature and that SEFD of 1000 Jy can be achieved for the system. The result from Y-factor test shows TREC = 10 K over most of the frequency band.
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| 4. |
- Flygare, Jonas, 1988, et al.
(författare)
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Sensitivity simulation and measurement of the SKA Band 1 wideband feed package on MeerKAT
- 2019
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Ingår i: 13th European Conference on Antennas and Propagation, EuCAP 2019. ; EuCAP 2019
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Konferensbidrag (refereegranskat)abstract
- Advances in wideband feed technology for radio telescopes enable high sensitivity observations over large bandwidths. The wideband quad-ridge flared horn (QRFH) feed package for Band 1 of the Square Kilometre Array (SKA) was optimized for high sensitivity. The 3:1 feed package covers 350-1050 MHz and is a complete room temperature system with low-noise amplifiers integrated inside the ridges of the horn. The QRFH is dual-linear polarized and designed with spline-defined profiles for the horn and ridge shape. Measured feed s-parameters show input reflection less than -11 dB across the band with good port isolation. In this paper we present the first measured sensitivity levels of the Band 1 feed package, which was tested on the SKA precursor reflector MeerKAT. We also present measured aperture efficiency and intrinsic cross-polarization (IXR). The measured results show good agreement with simulations.
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| 5. |
- Flygare, Jonas, 1988, et al.
(författare)
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Ultra-wideband feed systems for the EVN and SKA - evaluated for VGOS
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The design of the Square Kilometre Array (SKA) project for radio astronomy is now materializing at a rapid speed; the EU Horizon 2020 RadioNet project BRoad-bAND (BRAND) has the ambition to deliver a decade bandwidth receiver for EVN. The ultra-wideband quad-ridge flared horn (QRFH) feed systems developed for these projects show good performance within the geodetic VLBI Global Observing System (VGOS) frame due to the overlapping frequency bands and reflector geometries. We estimate, through simulation, system equivalent flux density (SEFD) of the two feed systems in the VGOS reflector and compare the it to the existing system installed on one of the 13.2 m diameter reflectors of the Onsala twin telescope (OTT). The two frequency bands analyzed cover 1.5−15.5 GHz and 4.6−24 GHz. Both systems show SEFD better than 1000 Jy over large parts of resp. frequency band - comparable to the 3−18 GHz feed systems. For the SKA QRFH over 4.6−24 GHz, the water vapor absorption line at 22 GHz is within the operational band, therefore we study the application of water-vapor radiometry in line-of-sight of the telescope.
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| 6. |
- Flygare, Jonas, 1988, et al.
(författare)
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Wideband single pixel feed system over 4.6-24 GHz for the Square Kilometre Array
- 2019
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Ingår i: Proceedings of the 2019 21st International Conference on Electromagnetics in Advanced Applications, ICEAA 2019. ; , s. 630-635
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Konferensbidrag (refereegranskat)abstract
- We present the Band B feed system over 4.6-24 GHz designed for the Square Kilometre Array (SKA) reflector for radio astronomy applications. The feed is a Quad-ridge Flared Horn (QRFH) with a customized shape based on spline-defined profiles to achieve improved wideband performance. The feed system shows high aperture efficiency and sensitivity on the SKA reflector in predictions based on measured feed beam patterns. We present the feed design overview, cryogenic dewar concept and measurement of receiver noise (10-20 K) with wideband low-noise amplifiers, and full system simulation of the performance.
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| 7. |
- Güsten, R., et al.
(författare)
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APEX - The Atacama Pathfinder Experiment
- 2006
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6267 I
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Konferensbidrag (refereegranskat)abstract
- 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 world's 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.
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| 8. |
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| 9. |
- Haas, Rüdiger, 1966, et al.
(författare)
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Status of the Onsala Twin Telescopes – One Year After the Inauguration
- 2019
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Ingår i: IVS 2018 General Meeting Proceedings "Global Geodesy and the Role of VGOS – Fundamental to Sustainable Development". ; NASA/CP-2019-219039, s. 17-19
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Konferensbidrag (refereegranskat)abstract
- We briefly describe the status of the Onsala twin telescopes and the experience gained since the official inauguration in May 2017.
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| 10. |
- Haas, Rüdiger, 1966, et al.
(författare)
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Status of the Onsala Twin Telescopes – Two Years After the Inauguration
- 2019
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Ingår i: Proceedings of the 24th European VLBI Group for Geodesy and Astrometry Working Meeting. - 9788441656345 ; , s. 5-9
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Konferensbidrag (refereegranskat)abstract
- We give a brief overview on the status of the Onsala twin telescopes (OTT), two years after their inauguration. The dierent components of the VGOS systems are briefly described, and the development towards routine operations.
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