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

As we show below, Jicamarca offers unique observations to the world-wide effort ofimproving the understanding of meteors. It has the lowest frequency of all the high-powerlarge-aperture radars (50 Mhz), it is located under the magnetic equator and it is able tomeasure the three dimensional vector of head echoes by operating in the interferometricmode [Woodman, 1971]. The MU radar [Sato et al., 2000] and the ALTAIR radar [Close etal., 2002] are also able to determine the three dimensional vector velocity.2. Experimental SetupMeteor-head observations have been made using the large Jicamarca array(~300mx300m) for transmission and all four quarter sections for reception (~75mx75m), inboth cases using the same linear polarization. The antennas were phased to point on-axis, i.e.,-1.46 o off-vertical in the y direction (see Figure 2).Figure 2. (a) Antenna configuration for interferometric observations of meteors, note that the East-Westbaseline is rotated ~51.06 o respect to the x axes. Simplified geometry of a meteor trajectory respect to theilluminated beam: (b) altitudinal and (c) angular views.Although complex voltages (raw data) from four quarters were recorded, we onlyneed the information of three non-collinear antennas in order to locate the meteors inside thetransmitting beam. For the results we present in this work, we have used quarters A, C, and Dto get the direction cosines of meteors respect to the x and y axis. Note that the East-Westbaseline is rotated ~51.06 o respect to the x axes. Figures 2b and 2c show a simplified diagramof a meteor trajectory inside the illuminated beam as a function of altitude and for an angularview, respectively. The actual transmitting half-power beam width is ~1 o . Although thetransmitting beam width is very narrow for most observations at Jicamarca, it is wide enoughto detect meteors coming from a wide range of elevation angles.As it was mentioned in the introduction meteor-head echoes come from altitudeswhere strong geophysical ``clutter'' due to EEJ and meteor trail echoes occur. Therefore aspecial observing mode is needed to try to overcome this clutter. The main parameters of thisobserving mode are IPP of 200 kms, pulse width of 9.75 kms (using 13-bit Barker code),sampling range of 0.75 kms, initial sampling range at 70 kms, and transmitter peak power of2 MW.3. Technique DescriptionOnce the raw data has been recorded, we proceed to obtain the parameters of meteorheadechoes. We have divided our processing technique in three different stages: (a) raw datadecoding, (b) signal statistics and meteor detection, and (c) meteor characterization. In thecase of meteor-head echo observations the decoding is not only use for improving the rangeresolution but also for estimating the meteor radial velocities. In order to accomplish properdecoding, for each raw-data profile at time t, we have iteratively searched for the Dopplervelocity that optimizes the decoded power profile. Furthermore, we have used a second filter135