风云3号卫星微波湿度计的系统设计与研制

Design and Development of Microwave Humidity Sounder for FY-3 Meteorological Satellite

微波湿度计(MWHS)是风云3号卫星的主要有效载荷之一,其频率为150GHz(双极化)和183.31GHz(三通道),采用垂直于飞行方向的交轨扫描方式,科学目标是探测大气湿度的垂直分布。本文简要介绍微波大气湿度探测的基本原理,阐述了微波湿度计的系统构成及工作原理;描述了微波湿度计的性能指标要求。测试结果表明,微波湿度计性能指标满足设计要求。

FY-3 meteorological satellite is the 2nd generation of China's polar-orbit meteorological satellite,and the Microwave Humidity Sounder(MWHS) is one of its main payloads.The basic principle of atmospheric humidity sounding by microwave radiometer and the technical specifications of MWHS onboard FY-3 satellite are briefly introduced in this paper.The block diagram and operating modes of MWHS are presented.MWHS is a dual-frequency,five-channel millimeter wave radiometer which is a total power type microwave radiometer based on a heterodyne receiver,and performs cross-track scanning.The frequencies of MWHS include both the atmospheric transparent windows of 150GHz and water vapour absorption lines around 183.31GHz.The 150GHz radiometer has two polarizations of V and H,and the 183.31GHz radiometer has three channels of 183.31±1GHz,183.31±3GHz and 183.31±7GHz,respectively.The swath width of about 2700km is implemented by cross-track scanning of the antenna beams.Final testing verifies that the performance of MWHS satisfies technical requirements of specifications.MWHS consists of three units: antenna and receiver unit,electronic unit and power supply unit.Antenna and receiver unit collcets emission from the atmosphere. The received signal is focused to the horn-feed and the first element of the high frequency front end,and then down-converted by a double side band mixer to Intermediate Frequency;IF signal is been down-converted to Low Frequency(LF) by a detector,and then integrated.The electronic unit digitizes the LF signal, controls the scanning mechanism and measures physical temperature of the on-board hot target for calibration,and communicates with satellite through a 1553B data bus.The power supply unit performs DC/DC conversion,distributies the DC lines to the various sub assemblies and switches between the nominal and the redundant unit.One motor drives two separated reflectors for the 150GHz and the 183.31GHz channels,the scanning period is 2.667s.Main beams of the antenna scan over the observing swath(±53.35° from nadir) in the cross-track direction at a constant periodicity of 1.71s.During each period,two-point calibration are performed to calibrate the receiver gain and noise.The calibration is implemented by observing an onboard hot target and the background emission of the cold sky.