Astronomie radar et radioastronomie à l'aide du radar transhorizon Nostradamus
Résumé
The Nostradamus radar system is a set of 288 antenna elements distributed over the arms of a threebranchstar. It is operating in High Frequency waves (6 to 28 MHz) that bounce on the ionosphere,reaching areas far beyond the horizon. As an early warning radar system, its primary purpose was the detectionof aircraft at long ranges from 700 to 3 000 km. Whereas over-the-horizon (OTH) radars are usually bistatic andrequire huge linear antenna networks to beam the signals, the special surface distribution of Nostradamus makes itpossible to control the electronic beams both in azimuth and elevation. This original conception of the system allowsits use in many scientific fields.In the past years, research have been carried out on the ionosphere, on oceanography and on seismology. Morerecently, the radar has been used at trans-ionospheric frequencies to do radar astronomy by detecting meteoritesand the Moon, and radio astronomy by observing Jovian and Solar radio emissions. Few large instruments operateat decameter wave mainly because of man made radio frequency interference and because of the poor signal tonoise ratio of cosmic sources. However, interest for this frequency domain have recently been making something ofa comeback, as new giant telescopes are being built. After a quick presentation of the OTH radar, we present somespace observations that have been made. These radio observations are compared to data coming from a decameterradio telescope, the Nancay Decameter Array located in France. Finally, we will discuss about possible other experimentsthat could be carried out in the future.
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