Zou, ZihaoHuang, PenghuiLin, XinXia, Xiang-GenXi, PeiliSun, YongyanLiu, Xingzhao2023-08-152023-08-152023-06-02Z. Zou et al., "Air Moving Target Indication in Nadir Region for Spaceborne Surveillance Radar Systems," in IEEE Geoscience and Remote Sensing Letters, vol. 20, pp. 1-5, 2023, Art no. 3504805, doi: 10.1109/LGRS.2023.3282411.1558-0571https://udspace.udel.edu/handle/19716/33073© 2023 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. This article was originally published in IEEE Geoscience and Remote Sensing Letters. The version of record is available at: https://doi.org/10.1109/LGRS.2023.3282411. This article will be embargoed until 06/02/2025.For air moving target indication (AMTI) in nadir region, due to the fact that a spaceborne radar beam can illuminate the top of fuselage, the target radar cross Section is usually high, which is beneficial for the detection of a low-observable target. However, due to the short slant range, specular reflection effect, and relatively low radar ground resolution, the power of clutter component from nadir region is comparatively high, leading to the insufficient clutter suppression and the degradation of target detection performance. Fortunately, when an air moving target is adequately high, the target echo can be separated from the main clutter echoes due to a shorter time delay, making it possible to be only mixed with low-power ambiguous clutter echoes. Based on these considerations, this letter analyzes the performance of AMTI in nadir region for a spaceborne surveillance radar system. It analyzes the target minimum detectable velocities with different target heights and beam center elevation angles. Also, an effective sample selection method based on adaptive range segmentation is proposed to solve the power heterogeneity issue between the main clutter area and the range ambiguous clutter area. As a conclusion, the larger the elevation angle of an air moving target is, the higher the minimum target detectable height is.en-USair moving target indication (AMTI)clutter suppressionnadir echospaceborne surveillance radarArticle