STUDY OF STELLITE-BORNE PASSIVE MICROWAVE RADIOMETERS FOR REMOTE SENSING OF SOILS

THE CENTRAL PROBLEMS IN STUDYING THE EARTH'S SURFACE USING MICROWAVE RADIOMETRY ARE RESOLUTION AT LOW FREQUENCIES AND INTERPRETATION OF RESULTS. IT IS CONSIDERED GENERALLY DESIRABLE TO USE A TWO-DIMENSIONAL SCANNING RADIOMETER WHICH PRODUCES A RASTER-SCAN IMAGE OF THE APPARENT TEMPERATURE OF THE LAND SURFACE. FURTHERMORE, THE FREQUENCY WOULD LIKELY BE LESS THAN 8 GHZ IN ORDER TO AVOID OBSCURATION BY ATMOSPHERIC WATER. IN ORDER FOR THE PENETRATION DEPTH TO BE 20 CM OR MORE (I.E., PLANT ROOT DEPTHS), THE FREQUENCY MIGHT BE AS LOW AS 1.5 GHZ. THIS RAISES SERIOUS RESOLUTION PROBLEMS USING AVAILABLE SCANNING ANTENNA TECHNIQUES. FURTHERMORE, SINCE THE APPARENT TEMPERATURE MAY DEPEND CRITICALLY ON SURFACE ROUGHNESS, A GOOD MODEL OF THE SCATTERING CHARACTERISTICS OF LAND SURFACES IS NEEDED. IN SPITE OF THESE DIFFICULTIES, THE MICROWAVE RADIOMETER IS THE ONLY PASSIVE SENSOR THAT GIVES APPRECIABLE PENETRATION OF THE EARTH'S SURFACE. FOR SURFICIAL SOIL STUDIES, VEGETATIVE COMMUNITY ANALYSIS AND OTHER AREAS REQUIRING PENETRATION OF SEVERAL INCHES, THIS IS THE ONLY TECHNIQUE WHICH APPEARS TO BE CAPABLE OF PROVIDING SOIL MOISTURE DATA AT SOME DEPTH. THE BULK OF THE REPORT IS EMPLOYED TO DESCRIBE THE TECHNICAL CONSIDERATIONS RELATING TO THE DESIGN OF A MICROWAVE SCANNING ANTENNA FOR USE ON A SATELLITE IN THE PASSIVE RADIOMETRIC MEASUREMENT OF SEA STATE AND SOIL MOISTURE. THERE IS A GENERAL DISUCSSION OF THE RADIOMETER ANTENNA PROBLEM IN TERMS OF THE VARIOUS DESIGN REQUIREMENTS, AND AN ANALYSIS OF SEVERAL ANTENNA TYPES SUITABLE FOR USE AS SPACEBORNE RADIOMETRIC ANTENNAS. IN PARTICULAR, A COMPARISON IS MADE BETWEEN TWO MAJOR TYPES OF ANTENNAS, THE MECHANICALLY STEERED ANTENNA VERSUS THE ELECTRONICALLY SCANNED ARRAY. THE SPECIFIC PROPERTIES OF THE PARABOLOIDAL REFLECTOR, SPHERICAL REFLECTOR, AND MODIFIED REFLECTOR ANTENNAS ARE DISCUSSED AND COMPARED WITH THOSE OBTAINED WITH ELECTRONICALLY SCANNED ARRAYS. FINALLY, THE SPECULAR SURFACE MODEL AND THE PHYSICAL OPTICS MODEL ARE USED TO CALCULATE THE EMISSIVITY OF A BARE SOIL SURFACE AS A FUNCTION OF THE VIEWING ANGLE AND THE POLARIZATION OF THE EMITTED RADIATION.

  • Supplemental Notes:
    • Tr No 73, 107 PP, FIGS, TABS, 26 REF, 3 APP
  • Corporate Authors:

    New Mexico State University, Las Cruces

    Department of Electrical Engineering
    Las Cruces, NM  USA  88003
  • Authors:
    • Carver, K R
    • Potts, B
    • Widner, R
  • Publication Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 00230083
  • Record Type: Publication
  • Files: TRIS
  • Created Date: May 9 1972 12:00AM