| 1. |
- Elgered, Gunnar, 1955, et al.
(författare)
-
The Onsala Tide Gauge Station: Experiences from the first four years of operation
- 2019
-
Ingår i: Proceedings of the 24th European VLBI Group for Geodesy and Astrometry Working Meeting. ; , s. 75-79
-
Konferensbidrag (refereegranskat)abstract
- A tide gauge station was installed at the Onsala Space Observatory in 2015. The official tide gauge station includes several independent senors: one radar and three pneumatic sensors (also referred to as bubblers). The radar and two bubblers are mounted in a well and one bubbler outside the well. Additional sensors such as one laser sensor and three radar sensors have been used during dierent time periods in order to further assess the quality of the acquired sea level data. Here we compare the four ocial sensors and the laser sensor which was installed in April 2016. The expected accuracy (one standard deviation) for all of these sensors is approximately 3 mm, according to the datasheet specifications. Results from the first four years of operations are used to assess and estimate the actual accuracies by means of comparisons between the sensors. We observe typical biases over time scales of months of up to 10 mm. Biases are caused by uncertainties of the reference level of the sensor, the density of the water for the bubblers, multipath eects for the radar, and nonlinearities with temperature for the laser. The observed monthly standard deviation between the sensors in the well vary between 2 mm and 6 mm, which is roughly consistent with the data sheet specifications.
|
|
| 2. |
|
|
| 3. |
- Haas, Rüdiger, 1966, et al.
(författare)
-
Status of the Onsala Twin Telescopes – Two Years After the Inauguration
- 2019
-
Ingår i: Proceedings of the 24th European VLBI Group for Geodesy and Astrometry Working Meeting. - 9788441656345 ; , s. 5-9
-
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.
|
|
| 4. |
- Flygare, Jonas, 1988, et al.
(författare)
-
Sensitivity simulation and measurement of the SKA Band 1 wideband feed package on MeerKAT
- 2019
-
Ingår i: 13th European Conference on Antennas and Propagation, EuCAP 2019. ; EuCAP 2019
-
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.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Haas, Rüdiger, 1966, et al.
(författare)
-
Status of the Onsala Twin Telescopes – One Year After the Inauguration
- 2019
-
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
-
Konferensbidrag (refereegranskat)abstract
- We briefly describe the status of the Onsala twin telescopes and the experience gained since the official inauguration in May 2017.
|
|
| 8. |
|
|
| 9. |
- Pantaleev, Miroslav, 1970, et al.
(författare)
-
Onsala Space Observatory – IVS Technology Development Center
- 2011
-
Ingår i: International VLBI Service for Geodesy and Astrometry 2010 Annual Report, edited by D. Behrend and K.Baver. ; :NASA/TP-2011-215880, s. 280-283
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This report briefly describes the technical development relevant for geodetic/astrometric VLBI done during 2010 at the Onsala Space Observatory.
|
|
| 10. |
- Belitsky, Victor, 1955, et al.
(författare)
-
A new 3 mm band receiver for the Onsala 20 m antenna
- 2015
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 580
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
