Nimbus-7 SMMR Antenna Temperatures, Version 1

The SMMR Antenna Temperatures (Nimbus-7) data set consists of antenna temperatures from passive microwave radiometers aboard NOAA's Nimbus-7 satellite. The instrument is the Scanning Multichannel Microwave Radiometer (SMMR). Each file consists of one days worth of data in swath format, i.e. the portion of the Earth's surface viewed by the scanning radiometer. Antenna temperature data are available from NSIDC from October 1978 to August 1987. SMMR was a ten channel passive microwave instrument using six conventional Dicke-type radiometers. It delivered orthogonally polarized antenna temperature data at five frequencies: 6.6, 10.69, 18.0 21.0 and 37.0 GHz. The two 37.0 GHz radiometers operated
continuously for each polarization. The other radiometers alternated polarizations on alternate scans. The size of each daily file is 35 MBytes. The data are distributed on FTP.

The scanner operated only on alternate days, due to spacecraft power limitations. There are typically at least 14 days of coverage per month, although major data gaps occur in August: in August, 1982, the 4th, 8th, and 16th are missing for both polar regions; in August, 1984, the 13th through the 23rd are missing for both polar regions.

SMMR天线温度（雨云7号）数据集由搭载于美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration，NOAA）雨云7号（Nimbus-7）卫星上的被动微波辐射计获取的天线温度数据组成。该仪器为扫描多通道微波辐射计（Scanning Multichannel Microwave Radiometer，SMMR）。每个文件包含单日的条带格式数据，即扫描辐射计所观测到的地球表面区域。天线温度数据可从国家冰雪数据中心（National Snow and Ice Data Center，NSIDC）获取，时间跨度为1978年10月至1987年8月。SMMR为10通道被动微波仪器，搭载6台传统迪克型（Dicke-type）辐射计。它可在5个频率下提供正交极化天线温度数据：6.6、10.69、18.0、21.0和37.0 GHz。其中两台37.0 GHz辐射计针对每个极化通道持续运行，其余辐射计则在交替扫描中切换极化方式。每个单日文件的大小为35兆字节（MBytes），数据通过文件传输协议（File Transfer Protocol，FTP）分发。
由于航天器电力限制，扫描仪器仅在隔日运行。通常每个月至少可获取14天的有效观测数据，但存在严重的数据缺失情况：1982年8月4日、8日及16日的南北极区域数据均缺失；1984年8月13日至23日的南北极区域数据均缺失。