KAIRA (Kilpisjärvi Atmospheric Imaging Receiver Array) completed the first phase of the High Band Antenna (HBA) array verification with the first incoherent radar scatter echoes detected on the 17th August 2012. 224 MHz radar pulses were transmitted from the EISCAT (European Incoherent Scatter Scientific Association) VHF system at Ramsfjordmoen, near Tromsø, Norway. KAIRA was used to form multiple beams along the transmission path and receive independent bi-static measurements at 31 different altitudes simultaneously. More information is available on the KAIRA web page.
This mode of operation is a first for the EISCAT system and the data quality proved to be exceptionally good.
Incoherent Scatter is the physical phenomenon where radio waves “bounce off” (are scattered) by ions and electrons in the atmosphere. The scattered radio waves are referred to as incoherent because they do not all scatter from one point. With a hard object, like a metal plate, the radio waves would all bounce off the surface. But with the atmosphere, some are scattered back immediately, whereas others penetrate further before being returned.
If the strength and frequencies of the returned incoherent scatter signal is observed, scientists can work out what the atmosphere is doing. The strength will tell the level of ionisation, the width of frequencies will indicate the temperature and the shift in frequency will denote how it is moving; i.e. a Doppler shift. By using these, and many other features that can be derived from the returned radar echoes, scientists can characterise the atmosphere at extremely high altitudes.
Although incoherent measurements have been made before, the way that the KAIRA system works permits multiple measurements at varying angles and heights to be made. This allows a much larger part of the atmosphere and space to be studied simultaneously, giving scientists a big picture which has until now been unavailable.
KAIRA is a project of the Sodankylä Geophysical Observatory, Finland, with deployment and commissioning support from RAL Space. The facility has two antenna fields, utilising LOFAR technology. Early in August 2012 the construction of the Low-Band Antenna (LBA) array was completed, ahead of the first snow of the season. The KAIRA LBA system operates from approximately 20 to 80 MHz, initial bandpass tests show good sensitivity over a wide, largely RFI-free spectrum. Full commissioning of the LBA system will occur in September, with initial results expected shortly.
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For more information please contact: RAL Space Enquiries
