The Soil Moisture and Ocean Salinity (SMOS) 卫星是欧洲空间局发射的一颗以探测地球土壤水含量以及海表盐度为目标的卫星，卫星所搭载的唯一载荷为Microwave Imaging Radiometerusing Aperture Synthesis (MIRAS微波成像综合孔径辐射计)。

It operates in L-band (1400-1427 MHz) and exploits theinterferometry principle, which by way of 69 small receivers will measure thephase difference of incident radiation. The technique is based on cross-correlationof observations from all possible combinations of receiver pairs. A two-dimensional'measurement image' is taken every 1.2 seconds. As the satellite moves alongits orbital path each observed area is seen under various viewing angles. Froman altitude of 763 km, the antenna will view an area of almost 3000 km in diameter.However, due to the interferometry principle and the Y-shaped antenna, the fieldof view is limited to a hexagon-like shape about 1000 km across called the'alias-free zone'. This area corresponds to observations where there is noambiguity in the phase-difference.

http://www.smos.zmaw.de/fileadmin/smos/Texte_PDFs/esa_Daten_AO.pdf

        一级数据包括传感器遥测获得的元数据产品、定标后的产品、科学产品以及辅助数据。

These products are obtained by processing the Level 1A calibratedvisibility function measured by the MIRAS Instrument. The main processing stepsare the correction for external sources (Sun, Moon, Galactic noise) and theimage reconstruction. The scientific content of the L1B data are the FourierComponents of the reconstructed image of the Brightness Temperature on theantenna plane. The product is organized as a series of “snapshots” ordered bytime stamp. Depending on the MIRAS operational mode this product is availableas:

- Dual (one snapshot containing Fourier componentsfor H or V polarization) or

- Full (one snapshot containing Fourier componentsfor H or V or HV polarization). These products are arranged on a pole-to-poletime interval such that ascending and descending passes appear as separateproducts.

These products are obtained by processing the Level 1Bproducts described above. The main processing steps are the inverse FourierTransformation of the Brightness Temperature components, the apodisation andthe geo-location. The scientific content of the Level 1C data is organized as aswath-based Brightness Temperature maps where the geo-localization of eachpixel is on a fixed ISEA 4-9 grid.

- For Dual products each pixel contains theBrightness Temperature at different incidence angle for H and V polarization.

- For the Full product is also added the HVBrightness Temperature (real and imaginary). Rotation of the BrightnessTemperature due to the acquisition geometry(采集方式) and geophysical correction are included in the productbut not applied therefore the Brightness Temperature is provided at the top ofthe atmosphere (TOA). Products (Dual and Full) are provided intwo different types:

- Land (MIR_SCLD1C, MIR_SCLF1C) and

- Sea (MIR_SCSD1C, MIR_SCSF1C).

A filter mask is used in the ground processing to selectwhich pixels will appear in each of the Land and the Sea productswith many pixels expected to appear in both. Sea and Land productscan be processed with different apodisation windows although the currentbaseline is that they will use the same. As for Level 1B, these products arearranged on a pole-to-pole time interval such that ascending and descendingpasses appear as separate products.

These products are obtained by interpolating theBrightness Temperature (ToA) of the Level 1C products at an incidence angle of42.5°. The Browse products are organised as per the Level 1C Science productsdescribed above.

二级数据包括数据分析产品、定标后的产品、科学产品以及辅助数据。

This product is still in the definition phase. Theseproducts are obtained by transforming the Brightness Temperature (TOA) of theLevel 1C products to the surface and applying the necessary geometry andgeophysical corrections. Products are expected to be organised as per the Level1C products described above.

This product is obtained by processing the Level 1C Landproduct described above. The algorithm used is based on an iterativeapproach(迭代接近法), whose aim is tofind the best vegetation characteristics and soil moisture parameters byminimizing the differences between the modelled direct and the measuredBrightness Temperature data. As for Level 1C, these products are arranged on apole-to-pole basis such that ascending and descending passes appear as separateproducts. The main parameters stored for each pixel are Soil Moisture(土壤水分), the Nadir Optical Thickness estimate for the vegetationlayer(植被的最小光学厚度估值), the SurfaceEquivalent Temperature(地表温度当量), the Dielectric Constant(介电常数), and the Scattering Albedo(散射率). These parameters appear in the product with theirassociated a posteriori variance(验后方差).

This product is obtained by processing the Level 1C Seaproduct described above. The algorithm used is based on an iterativeapproach, whose aim is to find the best atmospheric and sea surface parametersby minimizing the differences between the modelled direct and the measured BrightnessTemperature data. As for Level 1C, these products are arranged on apole-to-pole basis such that ascending and descending passes appear as separateproducts. The main parameters stored for each pixel are Sea Surface Salinityand Equivalent Neutral Wind Speed. These parameters appear in the product withtheir associated a posteriori variance.

The SMOS Near Real Time (NRT) service is still in thedefinition phase. Two products are expected to be available from this service.The first product is expected to very similar to the Level 1C products in termsof scientific content and format except that all non-essential information willbe removed. The second product will be a transformation of the first productinto BUFR (Binary Universal Form for the Representation of Meteorological Data)format and remove non-usable pixels. These products are to be obtained byfollowing an algorithm expected to be little changed versus that used to derivethe Level 1C products. Unlike Level 1C, these products will be provided on atime interval corresponding to the acquisition of the data by the groundstations.

SMOS数据的获取可以先参考这个文档：

http://www.inidep.edu.ar/oceanografia/SMOS-L3/SMOS_How_to_get_data_v5.pdf

文档中给出的数据获取途径中利用欧空局(ESA)提供的EOLisa软件进行下载数据，软件可以从网上获取：http://earth.esa.int/EOLi/EOLi.html

      给出EOLi sa软件的使用指南：

http://wenku.baidu.com/link?url=-ufOVZ-9uOCIfaQyPiE0pdeRNFGfX4MBN9SH24cCqdpZcPnuDVrLbG4ZFNzZ0OkxjD4tbILnLWcxWmNHKN6MpjjbVFA7XHVk5WjpA-iKubm

http://earth.esa.int/EOLIResources/Manual/EOLISA-UserGuide.pdf

https://earth.esa.int/download/EOLI-SA/EoliSA-Manual.pdf

      数据下载时选择其中downloadable的数据，这样可以直接通过数据列表前面的get键直接在线下载。

      选择其他数据(currentbaseline或者previousbaseline)的话需要预定，一般最多第二天就可以通过邮箱收到回复，进行数据下载。