The goal of Onsala Space Observatory, as the Swedish National Facility for Radio Astronomy, is to provide world class observing facilities for the national and international communities in astronomy and Earth sciences. In Onsala the observatory operates therefore two radio telescopes (with 20 m and 25 m diameter), and equipment for geodesy, and a LOFAR station (for low frequency radio astronomy). Further, the observatory is a partner in APEX (Atacama Pathfinder Experiment, a submillimetre telescope in Chile), is involved in the ALMA project (a radioastronomical observatory in Chile), and operates laboratories for the development of new receivers.

The telescopes and other facilities are used by several research groups at the Department of Earth and Space Sciences (Advanced receiver development, Radio astronomy and astrophysics, Space geodesy and geodynamics, and Global environmental measurements and modelling); their research activities are described elsewhere.
 

The telescopes in Onsala are used for astronomical research by both Swedish and international scientists. As a single dish, the 20 m telescope 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. The 20 m telescope is also used together with radio telescopes in Europe and in other parts of the world for high-resolution very long baseline interferometry (VLBI) observations of star forming regioins, evolved stars and active galactic nuclei. The 25 m telescope, for decimetre waves, is also used for astronomical VLBI observations, and is occasionally operated as a single dish for, e.g., studies of molecular clouds in the Galaxy.

The observatory's LOFAR station is to be opened in September 2011. LOFAR (Low Frequency Array) is a large array of simple antennas for frequencies below 250 MHz, led by ASTRON in the Netherlands. The station in Onsala will increase the resolution of the array.

The Onsala 20 m telescope is used in geodetic research for VLBI observations to investigate, e.g., the dynamics of the Earth's crust and the motion of the polar axis. At the observatory in Onsala, there is also equipment for space geodesy (e.g., GPS receivers), a superconducting gravimeter, and a radio aeronomy station monitoring gases in the Earth's atmosphere.

Onsala Space Observatory also maintains the data centre and coordinates the astronomy research with the Odin satellite (used also for studies of the Earth's atmosphere). Parts of the scientific equipment on Odin, which has orbited the Earth since 2001, were built by scientists and engineers at the observatory. The astronomical studies with Odin concerned mainly the physics and chemistry of interstellar gas. Odin is now used only for studies of Earth's atmosphere.

The National Facility operates development laboratories, both in Onsala and on the Chalmers campus (MC2).  The laboratories develop state-of-the-art receivers and equipment for the National Facility telescopes and for international projects, e.g. APEX, ALMA (the Atacama Large Millimetre/submillimetre Array, an array of radio telescopes under construction in Chile).