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R. Lulli et al.
polarization but used only the LCP polarization because the spectrometers were set to
work on a single channel. In this polarization, opposite to that transmitted, we had the
maximum power of the signal reflected by the asteroid surface. During our observations, the frequency of the transmitted signal was continuously tuned to compensate
for the expected Doppler shift between the Goldstone DSS-14 antenna and the SRT
64-m radio telescope.
For these observations, we used the first pilot project and the first final project
for the echo radar detection. We also used the second pilot project but only for
comparative tests because of its too low spectra rate. The signal bandwidth received
from the Medicina RT-32 was filtered to 781.250 kHz and the spectrometers were set
up at a frequency resolution of 6.25 Hz useful for maintaining the residual Doppler
signal smearing inside a single frequency channel.
A preliminary test was performed on December 11 by injecting a signal similar to
the expected radar echo into the spectrometer. The NEO observations were carried
out on December 17, 20, and 22. The last day observation was the most important
since it was the time of the close approach of the asteroid to Earth.
The first two observations were made controlling the spectrometers from the
receiver room, while the last observation was made controlling the spectrometers by
remote. The spectrometer data were stored in binary files with a dedicated format
(named NEO) and analyzed by post-processing software developed specifically in
MATLAB. Although the spectra appear to be contaminated by a high noise level,
which is still under investigation, the radar echoes from the asteroid were successfully
detected at the expected frequency. Figure 7.15 shows the observed radar echo,
integrated for about 10 s, acquired on December 22 at 14:47:23 UT.
Fig. 7.15 The asteroid 2003 SD220 radar echo detected in LCP polarization on December 22nd at
14:47:23 UT. It was produced integrating 54 single spectra obtained at 6.25 Hz frequency resolution
R. Lulli et al.
polarization but used only the LCP polarization because the spectrometers were set to
work on a single channel. In this polarization, opposite to that transmitted, we had the
maximum power of the signal reflected by the asteroid surface. During our observations, the frequency of the transmitted signal was continuously tuned to compensate
for the expected Doppler shift between the Goldstone DSS-14 antenna and the SRT
64-m radio telescope.
For these observations, we used the first pilot project and the first final project
for the echo radar detection. We also used the second pilot project but only for
comparative tests because of its too low spectra rate. The signal bandwidth received
from the Medicina RT-32 was filtered to 781.250 kHz and the spectrometers were set
up at a frequency resolution of 6.25 Hz useful for maintaining the residual Doppler
signal smearing inside a single frequency channel.
A preliminary test was performed on December 11 by injecting a signal similar to
the expected radar echo into the spectrometer. The NEO observations were carried
out on December 17, 20, and 22. The last day observation was the most important
since it was the time of the close approach of the asteroid to Earth.
The first two observations were made controlling the spectrometers from the
receiver room, while the last observation was made controlling the spectrometers by
remote. The spectrometer data were stored in binary files with a dedicated format
(named NEO) and analyzed by post-processing software developed specifically in
MATLAB. Although the spectra appear to be contaminated by a high noise level,
which is still under investigation, the radar echoes from the asteroid were successfully
detected at the expected frequency. Figure 7.15 shows the observed radar echo,
integrated for about 10 s, acquired on December 22 at 14:47:23 UT.
Fig. 7.15 The asteroid 2003 SD220 radar echo detected in LCP polarization on December 22nd at
14:47:23 UT. It was produced integrating 54 single spectra obtained at 6.25 Hz frequency resolution