Kilpisjärvi Atmospheric Imaging Receiver Array

The Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) is an astronomical observatory operated by the Sodankylä Geophysical Observatory on behalf of Oulu University. It is located at Kilpisjärvi, Enontekiö near the border with Norway. It comprises two LOFAR-derived radio telescope systems and is capable of observing at HF and VHF radio frequencies. It is used for atmospheric, near-Earth space and astronomical research. KAIRA uses LOFAR phased-array antennas and digital signal-processing hardware. The phased array configuration has no moving parts and with digital control, allows KAIRA to quickly scan the sky, giving KAIRA a large field of view. KAIRA can produce a continuous all-sky image of the radio transparency of ionosphere, using cosmic radio noise for "illumination" (riometry). KAIRA can also obtain electron density profiles in the atmosphere. This allows the study of the interaction of the solar wind with the atmosphere, such as in aurora borealis and other space weather phenomena. In addition to near-space imaging, the use of KAIRA has been demonstrated for long-baseline interferometry observations of pulsars.

It operates as either a stand-alone passive receiver, as a receiver for the EISCAT VHF incoherent scatter radar (a conventional dish-type emitter) located at Ramfjordmoen, near Tromsø, Norway, or for use in conjunction with other regional VHF experiments. The site is also a pathfinder for the EISCAT_3D system, a planned network of KAIRA-like phased array systems for three-dimensional imaging.