Miniature Synthetic Aperture Radar Research Articles

Identification of tectonic deformations on the south polar surface of the moon

Recent extensional and contractional tectonic features present globally over the lunar surface have been studied to infer lunar crustal tectonism. Investigation of indicators of recent crustal tectonics, such as fault lines, thrust fault scarps, and dislocation of debris along the identified fault planes, primarily using data from the miniature-synthetic aperture radar (mini-SAR) aboard CHANDRAYAAN-1 mission and Narrow angle camera (NAC) images, are the focus of this study. Spatial orientation of these tectonic features helps to elucidate the change in the interior geological dynamics of any planetary body with time. The ability of microwave sensors to penetrate the lunar regolith, along with application of m-χ decomposition method on Mini-SAR data has been used to reveal unique features indicative of hidden tectonics. The m-χ decomposition derived radar images expose hidden lineaments and lobate scarps present within shadowed crater floors as well as over the illuminated regions of the lunar surface. The area around and within Cabeus B crater in the South Polar Region contains lobate scarps, hidden lineaments and debris avalanches (associated with the identified lineaments) indicative of relatively recent crustal tectonism.

Application of m- <inline-formula> <tex-math notation="TeX">$\chi$</tex-math></inline-formula> Decomposition Technique on Mini-SAR Data to Understand Crater and Ejecta Morphology

Miniature Synthetic Aperture Radar (Mini-SAR) data conveniently reveals the unique morphological characteristics associated with crater ejecta blankets. Various surface and subsurface features in and around shadowed polar regions can be inferred using this data to explain the newly formed topography after impact events. A group of three craters lying north of Cabeus. A crater have unique ejecta morphology when m-χ decomposition technique is applied on mini-SAR data. The volume scattering observed for the region describes the relative slope of the terrain around and within crater walls. Alternately, Wapowski crater, which lies at the southern rim of Scott crater, has a different ejecta morphology indicative of it being relatively young. The high circular polarization ratio (CPR) calculated inside and outside Wapowski crater rim suggests that the presence of water ice within the shadowed portion of the crater is highly unlikely. The high CPR therefore is obtained due to the fresh blocky proximal ejecta blanket formed post impact. Volume scattering in m-χ decomposition image also corresponds to the region having high CPR. m-χ decomposition technique also shows that the proximal ejecta blanket is asymmetrically distributed around the crater rim. This technique therefore helps to study the process of impact cratering and the features generated thereafter.

Research Spotlight: Thick water ice observed in lunar craters

Water ice exists in large quantities in many small craters near the Moon's north pole, according to a new study. Spudis et al. present initial results from the miniature synthetic aperture radar (Mini‐SAR) experiment on board India's Chandrayaan 1 spacecraft, which mapped most of the area near the north pole of the Moon between February and April 2009. The Mini‐SAR instrument collected data on the polarization of radio waves reflected off the lunar surface. These data give the researchers insight into lunar surface features. For instance, high values of the circular polarization ratio (CPR) indicate either surface roughness or ice.

KOMSAR를 이용한 실제 항공기 ISAR 영상 제작

표적에 대한 레이더 영상 중의 하나인 ISAR(Inverse Synthetic Aperture Radar) 영상은 표적에 대한 전자파 산란 특성에 대한 2차원 공간 분포를 나타낸다. 이러한 ISAR 영상은 원거리에서 레이더를 이용한 표적 식별에 주로 사용된다. 본 논문에서는 움직이는 실제 항공기에 대한 ISAR 영상을 얻기 위하여, 국방과학연구소에서 제작 및 운용하고 있는 KOMSAR(Korea Miniature Synthetic Aperture Radar) 장비를 이용하여 측정을 수행하였다 이렇게 얻어진 측정된 데이터에 포함되어 있는 표적의 움직임에 의한 위상 오차를 제거하기 위하여, 엔트로피 기반 ISAR 자동 초점 기법(autofocusing technique)을 사용하였다. 실험 결과, 실제 움직이는 항공기에 대한 ISAR 영상을 성공적으로 얻을 수 있었으며, 이는 향후 레이더를 이용한 표적식별에 중요한 기술적 토대가 마련되었음을 의미한다. Inverse synthetic aperture radar(ISAR) images represent two-dimensional(2-D) spatial distribution of electromagnetic scattering phenomenology against a target. Hence, they are usually used in the areas of automatic target recognition (ATR) or non-cooperative target recognition(NCTR), identifying a target using radar in a long distance. This paper makes use of Korea Miniature Synthetic Aperture Radar(KOMSAR) to generate ISAR images of a real and maneuvering aircraft. The data obtained from KOMSAR are processed to eliminate phase errors due to motion of a target, with the use of entropy-based ISAR autofocusing technique. Results show that we can successfully obtain ISAR images of a real aircraft, and the success of experiments implies that a significant step toward ATR using radar has been established.