遥感第三章海洋卫星与陆地卫星

第三章海洋卫星与陆地卫星

§装载有微波传感器的海洋卫星（Ocean-Looking Satellite with Microwave Sensors）因为微波能够穿透云层，特别是有较大功率的主动微波雷达能够穿透较厚的云层，故带有微波传感器的海洋卫星经常被誉为全天候遥感卫星。表3-1列出了装载有微波传感器的海洋卫星信息。

表3-1: 装载有微波雷达的海洋卫星

装载有微波传感器的海洋卫星属于海洋环境监测卫星，它的特点是扫描范围大，便于探测大面积海洋环境要素，例如海面风、海平面高度和海表面温度等。装载有可见光和红外波段传感器的陆地卫星属于陆地包括海岸带资源观测卫星，它的特点是扫描范围较小，但分辨率特别高，便于精确观测小面积土地资源极其变化。装载有合成孔径雷达的卫星既可以用于探测海洋环境要素，例如油污染和生物膜等生化要素、以及海洋内波、海面巨浪和海浪谱等动力要素，也可以用于探测陆地环境要素，例如水火灾害等，还可以用于探测陆地资源要素，例如地下水和矿产资源等。因此，装载有合成孔径雷达的卫星是多用途卫星。微波传感器包括高度计、散射计、合成孔径雷达和微波辐射计。高度计是一个垂直探测的主动雷达，可以测量卫星与地球之间距离、海面地形和粗糙度，并由此估计风速、表面海流和平均波高。散射计是一个宽刈幅主动雷达，通过测量海表面粗糙度可以计算海面风速和风向。合成孔径雷达是一个具有高空间分辨率的主动雷达，它利用多卜勒效应获得高空间分辨率，可测量涌浪、内波、降雨、海流边界、海冰位置及性质、和大块浮冰的速度等。微波辐射计是一个被动微波雷达，它可以测量海面反射、散射和自发辐射的辐射度和微波亮温，并由此可估计风速、水蒸气、降水率、海表面温度、海表面盐度和冰覆盖量等

§欧洲遥感卫星ERS-1 和ERS-2

欧洲遥感卫星ERS-1 和ERS-2分别于1991年和1995年由欧空局发射。由于ERS-1/2采用了先进的微波遥感技术来获取全天候与全天时的图象，比起传统的光学遥感图象有着独特的优点。ERS-1/2采用椭圆形太阳同步轨道，卫星高度为780km，半长轴为，轨道倾角为°，节点周期为(分)，每天运行轨道数为14 -1/3，降交点的当地太阳时为10:30AM，空间分辨率的方位方向<30m，距离方向<，刈幅幅宽为100km。

欧空局的ERS1/2是一个被赋予多种遥感任务的卫星。它载有主动微波装置（AMI）、雷达高度计（RA）、沿轨迹扫描辐射计(ATSR)、全球臭氧监测实验（GOME）设备、精确测距设备(PRARE)和激光回反射装置(LRR)。其中主动微波装置（AMI）结合了合成孔径雷达（SAR）和散射计的功能。欧空局网页介绍了关于ERS1/2的详细信息。欧空局网页关于SAR 和AMI等传感器的介绍如下：The first SAR was launched into space by Europe Ariane-4 rocket in July 1991 as one of three main instruments on ESA - ERS-1 spacecraft. It was followed by a second on ERS-2 in 1995. ERS-1 completed its operation in 1999, overlapping with the new ERS-2 launched in 1995. These highly successful ESA satellites have collected a wealth of valuable data on the Earth, land surfaces, oceans, and polar caps.

Active Microwave Instrument (AMI)is the largest onboard system and combines the functions of a Synthetic Aperture Radar (SAR)and a wind scatterometer (SCATT). The AMI has three modes of operation: image mode and wave mode (performed by the SAR); and wind mode (by the SCATT). In image mode, the SAR produces highly detailed images of a 100 km wide strip of the Earth surface day and night and in all weather conditions. In its wind and wave modes, the instrument continuously measures global ocean surface wind speeds and directions, and provides information on the direction and shape of ocean wave patterns.

Radar Altimeter (RA)provides accurate measurements of sea surface elevation, significant wave heights, various ice parameters and an estimate of sea surface wind speed. This measures variations in the satellite height above sea level and ice with an accuracy of a few centimetres and helps provide data to know the satellite exact orbital position.

As well as contributing data on the position of ice flows below, the instrument produces ocean surface wave height and wind speed information for climatologists.

In the light of the increasing concern about atmospheric ozone levels, the Global Ozone Monitoring Experiment (GOME) instrument was added to the ERS-2 payload. This ultraviolet and visible light spectrometer provides information on ozone, CFCs and trace gas levels.

A more advanced version of GOME will be carried on the Metop spacecraft series, three polar orbiting satellites currently under development. These will produce high-resolution images, detailed vertical temperature and humidity profiles and temperatures of the land and ocean surface on a global basis.

Along Track Scanning Radiometer (ATSR)combining an infra-red radiometer and a microwave sounder for the measurement of sea surface temperature, cloud top temperature, cloud cover and atmospheric water vapour content.

Precise Range and Range-rate Equipment (PRARE)is included for the accurate determination of the satellite's position and orbit characteristics, and for precise position determination (geodetic fixing).

Laser Retro-reflectors (LRR) allow measurement of the satellite's position and orbit via the use of ground-based laser ranging stations.

作为欧洲遥感卫星ERS-1 和ERS-2的接替者，又一颗欧洲微波遥感卫星ENVISAT 卫星于2002年3月由欧空局发射升空，并于2003年5月正式投入运行。星上的高级合成孔径雷达ASAR具有双极化和多模式的新特点，其数据的地面分辨率最高达25m，覆盖范围最宽可达400km，可应用于水灾监测、作物估产、油污调查和海冰监测等方面。根据合同，中科院中国遥感卫星地面站可以接收日本JERS 卫星、加拿大RADARSAT卫星、欧空局ERS卫星和ENVISAT 卫星的合成孔径雷达遥感资料。

§高度计专用卫星TOPEX/POSEIDON和Jason-1

高度计专用卫星TOPEX/POSEIDON（托派克和波塞冬是希腊神化中的两个人物）和Jason-1是法国国家空间研究中心和美国航空航天局合作项目，卫星载有高度计，按照特别为高度计设计的轨道运