Browsing by Author "Vierinen, Juha"
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Item Open Access On statistical theory of radar measurements(Aalto University School of Science, 2012) Vierinen, Juha; Lehtinen, MarkkuStatistical treatment of radar measurements is important as most radar measurements are corrupted by random receiver noise. In addition to this, many radar targets themselves have to be modeled as random processes. It is therefore not a coincidence that this thesis uses the framework of statistical inverse problems for modeling radar measurements. The introductory part of this thesis first goes through some important mathematical and numerical methods that can be used model radar measurements and to apply these models in practice. We then describe several different types of radar measurements, with emphasis on high power large aperture radars. After this, we go through several useful radar measurement models. Finally, with the help of these models, we discuss optimal experiment design which tupically amounts to radar transmission waveform optimization. The publications included in this thesis contain practical applications of the topics described in the introduction, incluiding amplitude domain estimation of incoherent scatter signals, radar transmission code optimization, inverse synthetic aperture radar, and measurements of space debris.Item Restricted Radar images of the Moon at 6-meter wavelength(Elsevier, 2017-11) Vierinen, Juha; Tveito, Torbjørn; Gustavsson, Björn; Kesaraju, Saiveena; Milla, MarcoWe present new range-Doppler images of the Moon using 6-mwavelength. The radar images were obtained using the Jicamarca Radio Observatory 49.92 MHz radar. The observations were performed using circular polarization on transmit and two orthogonal linear polarizations on receive, allowing scattering images to be obtained with the polarization matched to the transmitted wave (polarized), and at a polarization orthogonal to the transmitted wave (depolarized). Due to the long wavelength that penetrates efficiently into the subsurface of the Moon, the radar images are especially useful for studies of subsurface composition. Two antenna interferometry on receive was used to remove the Doppler north-south ambiguity. The images have approximately 10 km resolution in range 20 km resolution in Doppler, allowing many large scale features, including maria, terrae, and impact craters to be identified. Strong depolarized return is observed from relatively new larger impact craters with large breccia and shallow regolith. Terrae regions with less lossy surface material also appear brighter in both depolarized and polarized images. A large region in the area near the Mare Orientale impact basin has overall higher than mean radar backscatter in both polarized and depolaried returns, indicating higher than average presence of relatively newly formed large breccia in this region. Mare regions are characterized by lower polarized and depolarized return, indicating that there is higher loss of the radio wave in the subsurface, reducing the echo. We also report unexpected low polarized and depolarized backscatter from an old impact basin in the Schiller–Schickard region, as well as from the region poleward from Mare Imbrium.