GPM SSMI on F08 Common Calibrated Brightness Temperatures L1C 1.5 hours 13 km V08 (GPM_1CF08SSMI) at GES DISC

All 1C products have a common L1C data structure, simple and generic. Each L1C swath includes scan time, latitude and longitude, scan status, quality, incidence angle, Sun glint angle, and the intercalibrated brightness temperature (Tc). One or more swaths are included in a product. The radiometer data are recalibrated to a common basis so that precipitation products derived from them are consistent. 1CSSMIS contains common calibrated brightness temperature from the SSMIS passive microwave instruments flown on the DMSP satellites. Swath S1 has 3 low frequency channels (19V 19H 22V). Swath S2 has 2 low frequency channels (37V 37H). Swath S3 has 4 high frequency channels (150H 183+/-1H 183+/-3H 183+/-7H). S4 has 2 high frequency channels (91V 91H). All the above frequencies are in GHz. Earth observations for all four swaths are taken during a 144o segment of the instrument rotation when SSMIS scans in the direction of foreward satellite motion. We define the spacecraft vector (v) at the center of this segment.
SSMI geometric footprints are: 69 x 43 km (19.35 GHz), 50 x 40 km (22.235 GHz), 37 x 28 km (37 GHz), 15 x 13 (85.5 GHz). GPM Project cross-calibrates channels at spatial sampling: 19.35-37 GHZ at (25x25 km) and channel 85 GHz at (12x12 km).

所有1C级产品均采用统一的L1C数据结构，设计简洁且具备通用性。每条L1C条带（swath）均包含扫描时刻、经纬度、扫描状态、质量标识、入射角、太阳耀斑角（Sun glint angle）以及经过交叉定标的亮温（brightness temperature, Tc）。单个产品可包含一条或多条条带。辐射计数据已被重新定标至统一基准，使得基于其反演的降水产品具备一致性。1CSSMIS数据集包含搭载于国防气象卫星计划（DMSP）卫星的SSMIS无源微波辐射计（passive microwave instrument）所获取的统一定标亮温数据。条带S1包含3个低频通道：19V、19H、22V。条带S2包含2个低频通道：37V、37H。条带S3包含4个高频通道：150H、183+/-1H、183+/-3H、183+/-7H。条带S4包含2个高频通道：91V、91H。上述所有频率的单位均为吉赫兹（GHz）。当SSMIS沿卫星前进方向开展扫描时，仪器旋转过程中的144°弧段内会完成上述四条条带的对地观测。我们将该弧段中心点处的航天器矢量（spacecraft vector）定义为v。SSMI的几何观测足迹（footprint）参数如下：69×43 km（19.35 GHz）、50×40 km（22.235 GHz）、37×28 km（37 GHz）、15×13 km（85.5 GHz）。全球降水测量（GPM）项目针对各通道开展空间采样交叉定标：19.35~37 GHz通道的采样分辨率为25×25 km，85 GHz通道的采样分辨率为12×12 km。