海水盐度是研究大洋环流和全球气候变化的重要参数,L波段(1400-1427MHz)微波辐射计是进行海水盐度遥感的最有效工具.在该频段内,微波辐射亮度温度对海水盐度变化的灵敏度为0.5K/psu,而用于海洋研究的盐度分辨率为0.1-0.2psu,要求微波辐射计的灵敏度优于0.1K.高灵敏度机载L波段微波辐射计,应用数字增益波动自动补偿和温度补偿技术,保证了系统的稳定性,并采用高效的滤波技术有效地抑制了全球定位信号(GPS)对接收机的干扰,灵敏度达到0.08K.进行了多次航空和海上对比遥感试验,获得了分辨率优于0.2psu、误差精度0.42psu的测量结果.

Sea surface salinity(SSS) is a very mi portantparameter of ocean s circulation and globalmeteorological and clmi atic predictions. Salinity data will permit estmi ates of sea surface density, or buoyancy, which drives the ocean s three-dmi ensional circulation.L-band(1400—1427MHz) microwave radiometer is themosteffective remote sensing toolof SSS measurement. In L-band, the sensitivity of radiometer brightness temperature variations associated with salinity is 0.5K/psu. Since a salinity change of0.2psu results in a brightness temperature change of0.1K, it isnecessary to have a microwave radiometer with sensitivity of better than 0. 1K.Highsensitivity airborne L-band microwave radiometer uses digital auto-compensationmethods for gain-fluctuations and environment temperature variations, and 6-th Chebyshev high effect filter to reduceGPS interferencewhich helps its sensitivity surpass0.08K.The antennawith dmi ensions of1m×1m belongs tomicrostrip type, antenna3dB beamwidth is15°, nadir incidence angle is35°, and itsweight is about15kg. The antenna gain is 20 dB and side lobe level is lower then -17dB. In September2005, the aircraft remote sensingmeasure-mentswere carried out. The L-band horizontl and vertical polarization signalswere recived smi ultaneously.The cross-po-larization isolation is≥30 dB.Themicrowave radiometerwas fixed onCMS3807 (Y12mode) aircraftover flatsea surface conditions at122°50′E,39°30′N—39°6′N. During the expermi ent, sea surface salinitywere detected on a shipwhen air-craftwas flying in same area of the sea at the same tmi e.The expermi entswere comparedwith site teston the sea.The re-sults of these measurements are presented in this paper,with the resolution of better than 0. 2psu and the accuracy of 0.42psu.