The Onsala radio observatory (OSO), the Swedish National Facility for Radio Astronomy, provides scientists with equipment to study the Earth and the rest of the Universe. In Onsala, 45 km south of Göteborg, several radio telescopes for astronomy and geodesy are in operation. OSO takes part in international radio astronomical projects, e.g., Atacama Pathfinder Experiment (APEX), European VLBI Network (EVN), Global mm-VLBI Array (GMVA), International VLBI Service (IVS), Atacama Large Millimeter/submillimeter Array (ALMA) and Square Kilometre Array (SKA). The observatory is a geodetic fundamental station.

Telescope 1:

geographic longitude:	11° 55′ 04″
geographic latitude:	57° 23′ 35″
altitude above sea level:	18 m
diameter telescope 1:	25.6 m
minimum elevation:	7°

Telescope 2:

The 20 m diameter, radome enclosed, millimetre wave telescope in Onsala is equipped with receivers for frequencies up to 116 GHz. It is used for observations of millimetre wave emission from molecules in comets, circumstellar envelopes, and the interstellar medium in the Galaxy and in extragalactic objects. It is also used for astronomical VLBI observations of star forming regions, radio stars, and active galactic nuclei, and for geodetic VLBI observations to study e.g. crustal dynamics and polar motion. The telescope itself was built in 1975-76 and upgraded in 1992. The radome was replaced in 2014. Front-ends and back-ends are updated regularly.

geographic longitude:	11° 55′ 35″
geographic latitude:	57° 23′ 45″
altitude above sea level:	23 m
diameter telescope 2:	20 m
minimum elevation:	6o

Available observing mode: single dish, Very Long Baseline Interferometry (VLBI).

Telescope 3:

Two VLBI Global Observing System (VGOS) radio telescopes, Onsala Twin Telescope (OTT), will be operational in 2017. The telescopes will be equipped with broad-band dual-polarized receivers covering the band 2–15 GHz. OTT will mainly be used for geodetic and astrometric VLBI. The technique can e.g. be used to measure very accurately geodynamical phenomena such as the distances between continents as well as the Earth’s rotation rate, polar motion and nutation.

OTT1:

geographic longitude:	11° 55′ 11″
geographic latitude:	57° 23′ 37″
altitude above sea level:	16 m
diameter of telescope:	13.2 m
minimum elevation:	0°

OTT2:

geographic longitude:	11° 55′ 08″
geographic latitude:	57° 23′ 35″
altitude above sea level:	16 m
diameter of telescope:	13.2 m
minimum elevation:	0°

LOFAR: 

The Swedish LOFAR (Low Frequency Array) station is located at Onsala Space Observatory. It is one of eight LOFAR stations being planned and built in Europe. The LOFAR station consists of 192 simple antennas for frequencies below 250 MHz, distributed over an area about 100 m x 200 m. The antennas are of two types: the Low Band Antenna (LBA) elements for 10–80 MHz, and the High Band Antenna (HBA) tiles for 120–240 MHz. The antennas are connected together to form an array which can be used as a single radio telescope. But most of the time, signals from the Onsala station are transferred by fibre link to a central processor, where they are digitally combined with signals from the other LOFAR stations in Europe.

geographic longitude:	11° 55′ 47″
geographic latitude:	57°23′ 56″
altitude above sea level:	23 m

Frequencies used currently:

Frequency band	Observing mode
10 – 80 MHz	LOFAR
120 – 240 MHz	LOFAR
0.8 – 1.2 GHz	25m single dish, VLBI
1.2 – 1.8 GHz	25m single dish, VLBI
2 – 15 GHz	OTT, single dish, VLBI
2.2 – 2.5 GHz	20m single dish, VLBI
4.5 – 5.3 GHz	25m single dish, VLBI
6.0 – 6.7 GHz	25m single dish, VLBI
8.2 – 9.0 GHz	20m single dish, VLBI
18 – 26 GHz	20m single dish, VLBI
26 – 36 GHz	20m single dish, VLBI
36.0 – 49.8 GHz	20m single dish, VLBI
67 – 87 GHz	20m single dish, VLBI
85 – 116 GHz	20m single dish, VLBI

Research programs: galactic and extra-galactic molecular line radio astronomy, Very Long Baseline Interferometry.