标题： SHARAD 借助 MRO 航天器的巨大滚转提升了对火星更深次表层结构的探测能力 显示英文标题

标题： SHARAD Illuminates Deeper Martian Subsurface Structures with a Boost from Very Large Rolls of the MRO Spacecraft

摘要： 在整个任务期间，火星勘测轨道飞行器（MRO）经常沿其航迹轴滚动多达28{\deg }，以部分抵消浅层雷达（SHARAD）天线在航天器边缘的次优位置，该边缘与成像有效载荷甲板相对，从而提高从表面返回的回波信号的信噪比（S/N）。 最近的建模工作预测，更大的滚转角度可以将S/N相对于天底指向观测提高约10 dB后，MRO开始了一组有限的120{\deg }次滚转操作，以测试其对雷达探测的影响。 自2023年5月以来，已经获得了三次这样的SHARAD超大滚转（VLR）观测，并且显示了信号清晰度和穿透深度的显著改善，相比0{\deg }滚转角的几乎重叠的观测，S/N分别提高了9 dB、11 dB和14 dB。 在低介电常数的地貌区域，第一次和第二次VLR观测使基底检测达到了前所未有的深度，分别在美杜莎裂谷材料中达到800米，在乌利提斯裂谷冰层中达到1500米。 第二次VLR观测还增强了整个冰层堆栈的反射。 在亚马逊平原的高介电常数地形中，第三次VLR观测改善了倾斜地下界面的连续性，但并未揭示界面延伸到更深的深度或任何更深层的界面。 MRO任务计划对极地地形以及中纬度地区的冰川和地面冰、沉积物和火山岩获取更多的SHARAD VLR观测数据。 显示英文摘要

摘要： Throughout its mission, the Mars Reconnaissance Orbiter (MRO) has often rolled about its along-track axis by up to 28{\deg} to partially compensate for the suboptimal location of the Shallow Radar (SHARAD) antenna along an edge of the spacecraft that is opposite the imaging payload deck, thereby enhancing the signal-to-noise ratio (S/N) of echoes returned from the surface. After recent modeling work predicted that a much larger roll would improve the S/N by ~10 dB relative to nadir-pointed observing, MRO began a limited series of 120{\deg} roll maneuvers to test the effects on radar sounding. Three such SHARAD very-large-roll (VLR) observations have been acquired since May 2023, and they show dramatic improvements in signal clarity and depth of penetration, with S/N increasing by 9, 11, and 14 dB over that of nearly coincident observations at 0{\deg} roll angle. In low dielectric terrains, the first and second VLR observations enabled basal detections at depths previously unachievable, reaching depths of 800 m in Medusae Fossae materials and 1500 m through the ice of Ultimi Scopuli, respectively. The second VLR observation also obtained enhanced reflections throughout the ice stack. In the higher dielectric terrain of Amazonis Planitia, the third VLR observation improved continuity of a dipping subsurface interface, but it revealed neither an extension of the interface to greater depths nor any deeper interfaces. The MRO mission intends to obtain more SHARAD VLR observations of polar terrains and of midlatitude glacial and ground ices, sediments, and volcanics.