Proceedings with Extended Abstracts (single PDF file) - Radio ...

Figure 1: Left: Principle of nested volume measurements with two radar beams characterizedby different beam widths. Right: Slice along the NW-SE axis through the the3D radiation pattern of the Saura MF radar antenna for a narrow (solid line) and wide(dashed line) beam tilted to 17.2 ◦ .System and experiment descriptionIn April 2003 experiments were carried out at the Saura MF radar to test the dual beamwidths method in the mesosphere. This new narrow beam MF radar has been installed atSaura on the Andøya island close to the Andøya Rocket Range as part of the ALOMARobservatory to improve the ground based capabilities for studies of the dynamical structureespecially small scale features and turbulence of the upper mesosphere (Singer et al.,2003). The main feature of the new radar is the transmitting/receiving antenna whichis formed by 29 crossed half-wave dipoles arranged as a Mills-cross. The spacing of thecrossed dipoles is 0.7 wave lengths resulting in a minimum beam width θ =6.6 ◦ (Half-Power-Full-Width, one way). Each dipole is fed by its own phase controlled transceiverunit with a peak power of 2 kW what provides a high flexibility in beam forming andpointing. The wide antenna beam with a half-power beam width θ w =13.8 ◦ was formedby feeding only half of the crossed dipoles of the Mills-cross. The wider antenna beamhas nearly twice the beam width of the narrow antenna beam and a reduced antennagain due to the less number of used antennas (Figure 1).A sequence of narrow beam and wide beam experiments each pointing interleavedwith 17.2 ◦ off-zenith towards NW and SE was run on April 24, 2003 to test the dualbeam method. Additionally 4 Doppler beam steering (DBS) experiments with narrowbeams at 7.3 ◦ off-zenith provided the horizontal wind information.ResultsDual-beams were formed at 17.2 ◦ zenith angle with a minimum of the antenna radiationpattern in vertical direction to reduce possible contaminations by specular reflections.Since the narrow and wide beam experiments used opposite azimuth angels alternatingin the NE-SW plane, the corresponding radial velocities must have opposite signs andcan be used as a quality criterion for the radar meassurements. We chose 3 hours between10:45 UT and 13:55 UT where the radial velocities had opposite signs in the altitude rangebetween 65 and 84 km (Figure 2) for the comparison of both the single beamwidth anddual beamwidth methods.246