Smart Ice Cloud Sensing (SMICES) Sub-millimeterwave Combined Radar/Radiometer Instrument

Global observations of upper tropospheric water vapor and cloud ice particle size distribution and total ice water content are critically needed to improve weather and climate models [1]-[3]. Active/passive combined remote sensing of atmosphere from on-board radar and radiometer instruments is essential for obtaining high quality data products for advancing science. In addition, autonomous instrumentations embarked in space borne platforms can help in achieving improved accuracy, stability and spatio-temporal resolution of these measurements. The Smart Ice Cloud Sensing (SMICES) instrument is designed to provide high accuracy, enhanced resolution global measurements of cloud ice and tropospheric water vapor by utilizing synergic operation of radar and radiometer instrument through an on-board artificial intelligence (AI) processor. SMICES is collaborative effort between Northrop Grumman Aerospace Systems (NGAS) and NASA/Caltech Jet Propulsion Laboratory (JPL) supported by NASA ESTO under IIP-19. The SMICES receivers are based on 25-nm InP High Electron Mobility Transistor (HEMT)-based low-noise amplifiers (LNAs) designed collaboratively by NGAS and JPL and they are packaged in integrated receiver front-ends to provide low-noise and low-power operation in a small form factor at millimeter- and sub-millimeter-wave frequencies [4]. These include direct-detection receivers at 250 GHz, 310 GHz and 670 GHz, and heterodyne water-vapor sounding channels at 380 GHz. SMICES instrument has a 50 W Traveling Tube amplifier (TWTa) 239 GHz radar instrument autonomously controlled by the on-board real-time AI processor. SMICES receivers are designed to perform end-to-end calibration at each scan by viewing both an ambient calibration target near 290 Kelvin and the cosmic background noise of 2.73 Kelvin. The novel pseudo-correlation calibration is performed at 250 and 310 GHz radiometric channels using a 90° hybrid design. This novel calibration technique integrated with phase switches can provide high resolution measurements by allowing simultaneous acquisition of antenna and reference samples. Furthermore, the novel 1/f noise mitigation technique applied to all SMICES receiver channels for substantially reducing 1/f noise from acquired data samples [5]. SMICES instrument is being designed to fit into a SmallSat instrument but the technology demonstration will be performed from a Gulfstream II aircraft. The CAD model showing the airborne compatible design of the SMICES instrument is shown in Fig. 1 where the instrument is built for operating from the nose-cone of the aircraft.

为改进天气与气候模型，全球范围内对流层上层水汽、云冰粒子尺寸分布及总冰水量的观测至关重要[1]-[3]。利用星载雷达与辐射计仪器开展主动/被动联合大气遥感，是获取高质量数据产品以推动科学进步的核心手段。此外，搭载于星载平台的自主仪器系统有助于提升这些测量的精度、稳定性及时空分辨率。智能云冰传感（SMICES）仪器通过星载人工智能（AI）处理器实现雷达与辐射计的协同工作，旨在提供高精度、高分辨率的全球云冰及对流层水汽观测数据。SMICES是诺斯罗普·格鲁曼航空系统公司（NGAS）与美国国家航空航天局/加州理工学院喷气推进实验室（JPL）的合作项目，由NASA ESTO在IIP-19项目下提供支持。SMICES接收机基于25纳米磷化铟（InP）高电子迁移率晶体管（HEMT）低噪声放大器（LNAs），该放大器由NGAS与JPL联合设计，封装于集成接收前端中，可在毫米波及亚毫米波频段以小型化形态实现低噪声、低功耗运行[4]。这些接收机包括250 GHz、310 GHz及670 GHz的直接探测接收机，以及380 GHz的外差式水汽探测通道。SMICES仪器配备一台50瓦行波管放大器（TWTa）驱动的239 GHz雷达，由星载实时AI处理器自主控制。SMICES接收机设计为每次扫描时通过观测近290开尔文的环境校准目标与2.73开尔文的宇宙背景噪声，完成端到端校准。在250 GHz及310 GHz辐射通道中，采用90°混合设计实施新型伪相关校准技术。该校准技术与相位开关集成后，可通过同步采集天线与参考样本实现高分辨率测量。此外，所有SMICES接收通道均应用新型1/f噪声抑制技术，大幅降低采集数据样本中的1/f噪声[5]。SMICES仪器正按小型卫星（SmallSat）载荷规格设计，但其技术验证将通过湾流II型（Gulfstream II）飞机开展。图1展示了SMICES仪器的机载兼容设计CAD模型，该仪器可安装于飞机鼻锥部位运行。