Soil Moisture Information and Thermal - Semantic Scholar

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. GE-20, NO. 3, JULY 1982

275

Soil Moisture Information and Thermal M icrowave Emission RICHARD W. NEWTON, MEMBER, IEEE, QUENTIN ROBERT BLACK, SHAHAB MAKANVAND, ANDREW J. BLANCHARD, MEMBER, IEEE, AND BUFORD RANDALL JEAN, MEMBER, IEEE

Abstract-This paper presents theoretical and experimental results that demonstrate the depth to which soil moisture can be directly measured using microwave radiometers. The experimental results also document the effect of uniform surface roughness on the response of thermal microwave emission to soil moisture. Experimental measurements were executed in July 1980 at the Texas A&M University Research Farm near College Station, TX. Thermal microwave emission measurements were made at 1.4, 4.9, and 10.7 GHz at both vertical and horizontal polarization at off nadir angles from 0 to 500. It has been demonstrated that passive microwave measurements at frequencies down to 1.4 GHz can only measure soil moisture directly to very shallow soil depths, approximately 2 cm. This is due to the fact that the soil moisture dependence of the transmission coefficient across the air-soil interface predominates over the soil moisture dependence of the total energy originating within the soil volume. It also has been demonstrated that the combination of low incident angle and measurement frequency in the C-band range does not minimize the effect of surface roughness for passive microwave measurements. This result is significant in view of the fact that this combination of frequency and incident angle has been described as the optimum combination for minimizing the effect of surface roughness on the response of radar-backscatter measurements to soil moisture.

I. INTRODUCTION URING THE PAST decade there has been significant interest in investigating the potential for using microwave remote-sensing systems to estimate soil moisture information. Significant progress has been made in developing an understanding of the interaction phenomena between microwave backscatter and thermal microwave emission with soil volumes. Three areas have been of most concern in investigating this phenomena: the effect of water on the permittivity of soil and the definition of the soil moisture to which the microwave sensors actually respond, the effect of soil surface roughness on the microwave remote-sensor response, and the effect of a vegetation cover in masking the response to the underlying soil. The purpose of this paper is to address two points. The first is to present the most recent theoretical and experimental results that demonstrate the depth to which soil moisture can be directly measured using microwave radiometers and second, to present the latest experimental results that document the effect of uniform surface roughness on the response of thermal

microwave emission to soil moisture. The experimental measurements presented in this document were acquired at 1.4, 4.9, and 10.7 GHz during July 1980 at the Texas A&M University Research Farm near College Station, TX. II. BACKGROUND

There has been much discussion and some disagreement during the last few years concerning the depth to which soil moisture can be directly measured using microwave remote sensors. The natural thermal microwave emission measured by a microwave radiometer consists of energy originating within a surface layer of soil volume. The amount of energy arriving at the antenna from any given soil depth is dependent upon the soil moisture profile and soil temperature profile. Since components of the energy measured by the radiometer originate within different regions of some soil volume within which the soil moisture and soil temperature are not uniform, it becomes difficult to identify what soil moisture value the microwave radiometer is actually responding to. Numerous investigators have used various techniques to try to identify this soil moisture value. Two techniques were used for doing this; one relies directly on experimental measurement while the other relies on theoretical computations based on measured soil moisture and soil temperature profiles. Due to the fact that the soil moisture at any given depth is correlated to the soil moisture at other depths, it is difficult to identify experimentally the soil layer to which the radiometer is responding by simply correlating measured brightness temperature to the average soil moisture within distinct soil layers. As a result, theoretical models have been used to predict the weighting of how much energy is emitted by individual soil layers to determine weighting functions. These weighting functions may be applied to soil moisture profiles to determine depth of penetration and "average" soil moisture over this

depth. Several investigators have attempted to identify soil moisture parameters defined for surface soil layers corresponding to the same surface soil layers for which the thermal microwave emis-

sion originates. Among the investigators pursuing this procedure were Lee [1], Batlivala and Ulaby [2], Wilheit [3], Schmugge et al. [4], and Newton [5]. Manuscript received August 17, 1981; revised February 17, 1982. The soil moisture parameters investigated by these authors R. W. Newton, A. J. Blanchard, and B. R. Jean are with the Remote are typically dynamic in depth. In other words, as the soil Sensing Center and the Electrical Engineering Department, Texas A&M goes from moist to dry, the depths over which the soil moisUniversity, College Station, TX 77843. Q. R. Black and S. Makanvand were with the Remote Sensing Center, ture parameters correspond increase, since the depth over Texas A&M University, College Station, TX 77843. Q. R. Black is now which measurable microwave emission originates increases. with the Southwest Research Institute, San Antonio, TX. S. Makanvand Newton [51 identified a parameter termed equivalent soil is now with Eaton Electronics, Los Angeles, CA.

0196-2892/82/0700-0275$00.75 © 1982 IEEE

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. GE-20, NO. 3, JULY 1982

moisture (EQSM) and demonstrated that this parameter correlates well with experimental microwave measurements. The EQSM parameter was defined as a weighted integral of the soil moisture profile times the thermal microwave emission profile. Newton demonstrated with this technique that the depths from which energy originates can extend to approximately 20 cm at 1.4 GHz for dry soil. For wet soil at 1.4 GHz the depth only extends to a couple of centimeters. Newton's [5] interpretation was in conflict with the results of Burke et a. [6] who predicted that the near surface layers (0-2 cm) had a dominant effect on the emission that could escape from the soil volume. In addition, Schmugge et al. [4] and Wilheit [3] agreed with the results of Burke et al. Since good correlation can be obtained between experimental measurements of thermal microwave emission and soil moisture parameters defined over dynamic depths, or depths defined over practically any surface soil layer shallower than 15 cm, the controversy concerning the depth to which soil moisture can be directly estimated from thermal microwave emission measurements has not been rectified. Another issue of great concern is the effect of surface roughness on the response of thermal microwave emission to soil moisture. Newton and Rouse [7] and Wang et al. [8] have reported experimental measurements of thermal microwave emission that describe the effect of uniform surface roughness and corrugated surface roughness at 1.4 and 10.7 GHz. The effect of uniform surface roughness was to decrease the sensitivity of the thermal microwave emission measurement to soil moisture. In addition, the magnitude of this sensitivity reduction for a given surface roughness is frequency dependent. The shorter the wavelength (or the higher the frequency) the rougher the surface appears. Newton [5] analyzed this phenomena in detail for 1.4 and 10.7 GHz. To date, the primary experimental work to determine the effect of surface roughness on microwave backscatter has been done at the University of Kansas, Lawrence. Ulaby et al. [9] and Ulaby and Batlivala [2] have analyzed experimental measurements to identify sensor parameters that would tend to minimize the effect of surface roughness on the sensitivity to soil moisture. They have concluded that low incident angles in the range of 10°-15° at frequencies near 5 GHz minimize the effect of surface roughness. Although there has been no theoretical evidence to explain these results, the significance of these results mandated that this frequency and incident angle range should be investigated with passive microwave remote sensors to determine if a similar effect occurred. At the time the results of Batlivala and Ulaby were presented, there had been no 5-GHz passive microwave data acquired. III. DEPTH OF PENETRATION An understanding of where the microwave radiation comes from in a soil profile is important when developing moisture estimation algorithms. Soil moisture parameters discussed by various investigators differ primarily in the soil depth over which they are defined. The principal differences and interpretation among various investigators are illustrated by the EQSM identified by Newton [5] and the thermal sampling depth and reflectivity sampling depth identified by Wilheit

[3]. The EQSM is defined in the following manner: EQSM =

N

SM(i) BT(i) t

i=1

Toa

(1)

where SM (i) is the soil moisture content for the ith layer, BT (i) is the contribution to surface brightness temperature from the ith layer, BTt,0ta is the total brightness temperature at the surface, N is the number of layers. It can be seen that the EQSM parameter is a function of both the moisture profile and radiative contribution profile. Newton defined an EQSM sampling depth as that depth where the average soil moisture (from the surface to that depth) is numerically equal to the EQSM. Thus the EQSM is interpreted as the average soil moisture over the EQSM sampling depth. The thermal sampling depth is defined by Wilheit [3] as follows: N =1

X(i)f(i) (2)

f f(i)

i =1

where f (i) is the fraction of radiation incident on the air-soil interface that would be observed in the ith layer, and X(i) is the depth of ith layer. The reflectivity sampling depth determined by Wilheit is that depth at which the reflectivity from a soil volume containing a linearly varying soil moisture is equivalent to the reflectivity from a soil volume containing a uniform soil moisture numerically equal to the average of the linearly varying moisture to that depth. It should be noted that Wilheit used a coherent electromagnetic model while Newton used the incoherent model developed by Burke and Paris [10] . The penetration depths identified by Newton [5] varied from a few centimeters to 20 cm at 1.4 GHz. The penetration depths identified by Schmugge et al. [4] using Wilheit's model corresponds to approximately a tenth of a wavelength for the reflectivity sampling depth and greater than a wavelength for the thermal sampling depth. A study was done by Black and Newton [11] to determine which depth of penetration most reasonably defines the depth to which the measurement of thermal microwave emission from soil corresponds. Comparison of the depth of penetration computed for the above parameters using coherent and incoherent models shows that coherency never significantly affected computed contribution depth. The difference between coherent and incoherent percent contribution depth was never more than- a centimeter. Furthermore, surface incident angles did not appreciably affect penetration depth, confirming the results of Wilheit [3] and Newton [5]. It was determined that the EQSM sampling depth as defined by Newton [5] corresponds to the soil depth above which 90 percent of the thermal microwave emission originates. Since the EQSM represents the average moisture to the 90-percent

NEWTON et al.: SOIL MOISTURE AND MICROWAVE EMISSION

contribution depth, and the EQSM parameter does correlate to brightness temperature measurements, information about soil moisture at depths greater than a tenth of a wavelength is obviously contained in the microwave emission measurements. This does not necessarily mean, however, that the moisture information is related directly to the microwave measurement. It is possible that deep soil moisture information is available only because there is a strong correlation between near-surface soil moisture (approximately 0-2 cm) and deeper soil moisture. Microwave emissivity profiles were computed using both the Burke and Paris [6] model and the Wilheit [4] model and soil moisture and soil temperature profiles obtained by Jackson [12] in Tempe, AZ, in 1971. The computations demonstrated that the 0-1-cm soil moisture had a more direct correlation to microwave emissivity than did the EQSM parameter or average soil moisture within any other surface layer. This statement is made since the microwave emissivity versus the 0-1-cm soil moisture curve most closely resembles the variation of the transmission coefficient of an air-soil interface where the soil contains a uniform soil moisture. It was also determined that the EQSM parameter corresponded most closely to the 0-20cm soil moisture average. The results of Black and Newton [11] suggest that the brightness temperature generated by the model is dominated by the air-soil transmission coefficient. It can be seen in the equation for the EQSM parameter that the parameter is independent of the air-soil transmission coefficient due to the ratioing effect of the brightness temperature at each depth with the total brightness temperature. In addition, the thermal sampling depth as defined by Wilheit [31 is independent of the air-soil transmission coefficient although the reflectivity sampling depth is not. It should be noted that the EQSM sampling depths and the thermal sampling depths are very similar and much deeper than the reflectivity sampling depth. The effect of the air-soil transmission coefficient can be seen clearly in Fig. 1 where both the brightness temperature computed just above the soil surface (including the air-soil transmission coefficient) and the brightness temperature computed just below the surface are plotted as a function of EQSM. It can be seen that the brightness temperature just above the soil surface is strongly dependent on soil moisture while the brightness temperature just below the soil surface is only weakly dependent on soil moisture changes. This figure clearly shows the dominance of the air-soil interface transmission coefficient on overall soil emission. Since the EQSM parameter is not dependent on the air-soil transmission coefficient, microwave measurements directly correlate to it in a weak fashion. The strong correlation observed experimentally [5] is apparently due to the correlation of subsurface soil moisture to surface soil moisture. It is difficult to demonstrate the depths to which microwave radiometers can measure moisture directly. One method to experimentally demonstrate the penetration depth is by obtaining microwave emission measurements over bare soil acquired as a function of time during soil dry down from saturation to the dry state with no water input events during this dry-down period. The brightness temperature measurements can be converted to an estimated soil moisture and the dry-

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down curve of the estimated moisture compared to the drydown curves for the average soil moisture in various depth intervals. The penetration depth at any time can be obtained by observing the soil moisture average to which the estimated soil moisture corresponds at any point during the dry-down period. During the summer of 1980 field experiment at Texas A&M University, four bare fields were measured from saturation through dry down. These fields ranged in roughness from smooth to very rough. Since Texas experienced a severe drought condition during the experiment, no rainfall occurred during the dry down period. Fig. 2 shows the measured moisture in three depth increments, 0-2, 0-5, and 0-9 cm, as a function of time from soil saturation to soil dry-down. It can be seen that the soil moisture at the deeper depth intervals dries out much slower than at the shallower depth intervals. The microwave brightness temperature measurements for the smooth field were used to compute an estimated soil moisture by assuming a linear relationship between measured brightness temperature and measured soil moisture for the wettest and dryest soil conditions measured. These estimates were also plotted as a function of time in Fig. 3. The soil depths to which the microwave measurements correspond can be obtained by comparing the dry-down curve for the estimated soil moisture to the dry-down curve for the various depth intervals. It can be seen in Fig. 2 that these estimated soil moisture dry-down curves correspond very closely to the dry-down curves for the 0-2 cm or shallower soil moisture. This result supports the contention of Schmugge et al. [4] that only soil moisture in the very near surface can be measured directly. Fig. 3 also demonstrates that the depth of penetration is fre-

278

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. GE-20, NO. 3, JULY 1982

shorter the wavelength the rougher the surface appeared. At 1.4 GHz the microwave brightness temperature sensitivity to cm soil moisture decreased from -4.9 K/percent soil moisture (0- S cmn. 4 2 cm) for an rms surface height of 0.88 cm to - 1.9 K/percent 440 Sn ootI Fi eId soil moisture (0-2 cm) for an rms surface height of 4.2 cm. At Summer 1980 5H) 10.7 GHz the sensitivity decreases from -2.0 K/percent soil moisture (0-2 cm) for an rms surface height of 0.88 cm to 30 _ - 1.3 K/percent soil moisture (0-2 cm) for an rms surface .,-N~~~~~~~~ height of 4.2 cm. 0 Based on previous results of Newton [5], it was predicted A.~~~~~~~~~\ 20 _ that the effect of surface roughness on microwave brightness .4-E temperature measurements at 5 GHz would fall between the 1 effects seen at 1.4 and 10.7 GHz. However, the results re10 ported by Ulaby and Batlivala [2] for active microwave measurements on bare soil surfaces were that the effect of surface roughness was minimized at 5 GHz. Data were acquired at the OI_ Texas A&M University Research Farms during the summer of It 0 July 2 3 10 11 12 13 14 15 16 17 18 1 9 1980 for bare soil surfaces ranging from very smooth to very Fig. 2. Dry-down curves for three soil layers in the smooth field. rough. These measurements were acquired at 1.4, 5, and 10.7 GHz. To minimize soil temperature effects, the brightness temperature measurements were normalized by the average of P so the surface soil temperature and the 5-cm soil temperature. 1.4 GHz Figs. 4-6 demonstrate that surface roughness has a measureable effect at frequencies from 1.4 to 10.7 GHz. The results at _-_ 4.9 GHz 40 'lz ..... 1 ]. 1.4 and 10.7 GHz corroborate the results obtained by Newton Smooth Field [5] using microwave radiometer measurements acquired in sH Summer 1980 1974 at the Texas A&M University Research Farms. It is ap30 [ parent from comparing Figs. 4-6 that a given surface rough_ \\\ _~~~~~~ ness has a different effective roughness for each frequency. uz This statement is made since the measurements represented in these figures were all acquired over the same field conditions, \' 20 but the effect of the roughness on the measuremeent sensitivity 1. to soil moisture is frequency dependent. This is better illusE trated in Fig. 7 where measurements at 1.4, 5, and 10.7 GHz 10 are all plotted for the smooth field. It is apparent that even the smooth field appeared rougher at 10.7 GHz than at 5 GHz, and rougher at 5 GHz than at 1.4 GHz. This result confirms I I # uI 3 Julv 2 " 9 10 11 12 13 18 Newton's [5] expectation that 5-GHz measurements would Fig. 3. Percent soil moisture versus time estimated from 1.4-, 5.0-, and be affected by surface roughness in a similar fashion to 1.4-and 10.7-GHz measurements. Fig. 8 is a plot of the slope of the 10.7-GHz measurements of the smooth fi'eld. best fit lines contained in Figs. 4-6 for each frequency and each surface roughness. The slope corresponds to the sensitivquency dependent since the estimated soil moistures dry down of the microwave ratiometer response to soil moisture. ity slower as the wavelength gets longer. The data presented in Fig. 8 summarizes the results Figs. 4-6 again demonstrating Figs. 2 and 3 are the only data currently available from which the shorter the wavelength the rougher the surface appears, such analysis can be done. The results support the theoretical and that 5 GHz measurements do not minimize the roughness prediction of Wilheit concerning the effective reflectivity sameffect for passive microwave measurements. pling depths. Rn J)U

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Two issues have been addressed in this paper, the depth A thorough analysis of experimental data was done by New- to which soil moisture can be directly measured with passive ton [51 to demonstrate the effect of uniform surface rough- microwave sensors, and demonstration that 5 GHz measureness on microwave brightness temperature measurements of ments do not minimize the effect of surface roughness on the bare soil. It was demonstrated that as roughness increases the passive microwave response to soil moisture. These points microwave brightness temperature also increases and the sensi- were addressed using passive microwave measurements activity of the brightness temperature to soil moisture decreases. quired at 1.4, 5, and 10.7 GHz at the Texas A&M University Newton reported only measurements at 1.4 and 10.7 GHz. At Research Farms during July 1980. These measurements were these two frequencies it was demonstrated that there was a acquired during a well-controlled experimental measurewavelength dependence on surface roughness whereby the ments program whereby bare fields varying in roughness from

NEWTON et al.: SOIL MOISTURE AND MICROWAVE EMISSION I

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smooth to very rough were irrigated to saturation and observed while they dried down to their original dry condition. Very extensive ground truth measurements were acquired during the microwave measurements program. It has been demonstrated that passive microwave measurement at frequencies down to 1.4 GHz can only measure soil moisture directly to very shallow soil depths, approximately

2 cm. This is due to the fact the soil moisture dependency of the transmission coefficient across the air-soil interface predominates over the soil moisture dependency of the total amount of energy originating within the soil volume below the air-soil interface. The energy originating within the soil volume can actually come from depths ranging up to 20 cm at 1.4 GHz for dry soil conditions. However, the air-soil trans-

280

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. GE-20, NO. 3, JULY 1982 -0.002

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mission coefficient is primarily dependent on the soil moisture within the upper couple of centimeters. The dependence of air-soil transmission coefficient on soil moisture predominates over emission variations due to changing soil moisture profiles at depths greater than 2 cm. It has also been demonstrated that the combination of low incident angle and frequencies in the C-band range do not minimize the effect of surface roughness for passive microwave measurements. It has been shown that the effect of increasing roughness at 5 GHz and at 200 incidence is to decrease the sensitivity to soil moisture. In addition, the measurements at 1.4 and 10.7 GHz verify the previous results reported by Newton [5] concerning the effect of surface roughness on soil moisture sensitivity.

ACKNOWLEDGMENT The field measurement program, from which the data reported in this paper were acquired, involved much hard work and many long hours by approximately twenty individuals. Although the names of these individuals are too numerous to list individually, two deserve special credit. They are Dr. J. Nieber and R. Lascano who spent many hours acquiring and processing ground-truth measurements.

mea-

[4] T. Schmugge, T. Wilheit, W. Webster, and P. Gloersen, "1976, remote sensing of soil moisture with microwave radiometers-II," NASA, Tech. Note TND-8321 (NTIS No. N76-32625), May 1976. [5] R. W. Newton, "Microwave remote sensing and its application to soil moisture detection," Remote Sensing Center, Texas A&M University, College Station, Tech. Rep. RSC 81, Jan. 1977. [6] W. J. Burke, T. Schmugge, and J. F. Paris; "Comparison of 2.8and 21-cm microwave radiometer observation over soils with emission model calculations," J. Geophys. Res., vol. 48, no. Cl, Jan. 20, 1979. [7] R. W. Newton and J. W. Rouse, Jr., "Microwave radiometer measurements of soil moisture content," IEEE 7rans. Antenna Propagat., vol. AP-28, Sept. 1980. [8] J. R. Wang, R. W. Newton, and J. W. Rouse, "Passive microwave remote sensing of soil moisture: The effect of tilled row structure," IEEE Trans. Geosci. Remote Sensing, vol. GE-18, Oct. 1980. [9] F. T. Ulaby, J. Cihlar, and R. K. Moore, "Active microwave measurements of soil water content," Remote Sensing of Environment, vol. 3, pp. 185-203, 1974. [10] W. J. Burke and J. F. Paris, "A radiative transfer model for microwave emissions from bare agricultural soils," NASA, Johnson Space Center, Houston, TX, TMX-58166, Aug. 1975. [11] Q. R. Black and R. W. Newton, "Airborne microwave remote sensing of soil moisture," Remote Sensing Center, Texas A&M University, College Station, RSC Tech. Rep. 108, Nov. 1980. [12] R. D. Jackson, "Diurnal changes in soil water content during drying," Field Soil Water Regions, R. R. Bruce, Ed. Madison, WI: Soil Science Society of America, 1973. *

REFERENCES [1] S. L. Lee, "Dual frequency microwave radiometer measurements of soil moisture for bare and vegetated rough surfaces," Remote Sensing Center, Texas A&M University, College Station, Tech. Rep. RSC 56, Aug. 1974. [2] F. T. Ulaby and P. P. Batlivala, "Optimum parameters for mapping soil moisture," IEEE Trans. Geosci. Electron., vol. GE-14, pp. 81-93, Apr. 1976. [3] T. Wilheit, "Radioactive transfer in a plan stratified dielectric," IEEE Trans. Geosci. Electron., vol. GE-16, pp. 138-143, Apr. 1978.

Richard W.

Newton

(S'76-M'77)

was

born in

Baytown, TX, on August 26, 1948. He received the B.S., M.S., and Ph.D. degrees from Texas A&M University, College Station, in 1970, 1971, and 1977, respectively, all in electrical engineering. From 1971 to 1973, he was employed by Lockheed Electronics Company, Inc. at the NASA Johnson Space Center, Houston, TX. He joined the Remote Sensing Center at Texas A&M University, College Station, in 1973,

NEWTON et aL: SOIL MOISTURE AND MICROWAVE EMISSION

working in the area of microwave remote sensing technique development, sensor-system development, and signal processing. He is currently Director of the Remote Sensing Center, a Division of the Texas Engineering Experiment Station and Associate Professor in the Electrical Engineering Department at Texas A&M University. DL Newton is a Registered Professional Engineer in the State of Texas and a member of Eta Kappa Nu, Tau Beta Pi, and Sigma Xi.

*

Quentin Robert Black was born on May 10, 1956, in Sacramento, CA. He received the B.S. degree in electrical engineering from Texas A&M University, Colege Station, in 1978. He also received the M.S. degree from the same University. He was employed as a Research Assistant by the Remote Sensing Center at Texas A&M University, College Station. He is presently employed by Southwest Research in San Antonio, Texas. Mr. Black is a member of Eta Kappa Nu.

Shahab Makanvand was born on April 5, 1958, in Tehran, Iran. He received the B.S. degree in electrical engineering at Rolla, in 1979. He received the M.S. degree in electrical engineering from Texas A&M University, College Station. While at Texas A&M, he worked as a Research Assistant. He is presently working for Eaton Electronics, Los Angeles, CA.

281

Andrew1. Blanchrd (S'70-M'77) received the B.S. degree from the University of Southwestern Louisiana, Lafayette, LA, in 1972, the M.S. degree from Colorado State University, Fort Collins, in 1973, and the Ph.D. degree in 1977 from Texas A&M University, College Station, alin electrical engineering. He is presently an Assistant PrOfessor with the Department of Electrical Engineering and an Associate Research Engineer with the Remote Sensing Center, Texas A&M University, College Station. From 1977 to 1979 he was group supervisor of the Remote Sensing Group in the Exploration Research Division, Conoco Inc., Ponca City, OK. He has been associated with the Remote Sensing Centex and the Electrical Engineering Department since 1979. His research interests include microwave remote sensing, petroleum instrumentation involving microwave techniques, and radar systems. Dr. Blanchard is a member of AGU, Phi Kappa Phi, Eta Kappa Nu, and Tau Beta Pi. He is a Registered Professional Engineer in the State of Texas. _MOP......... 01 l ,

*

*

~~~~Buford Randall Jean (S'67-M'71) was born in Hilsboro, TX, on May 14, 1948. He received

the B.S., M.S., and Ph.D. degrees all in electrical engineering from Texas A&M University, CoDlege Station, in 1970, 1971, and 1978,

g 1.respectively. From 1971 to 1974, he worked at the Bendix Research Labs in Southfield, MI, where he was an engineer in the Electromagnetic Systems and Technology Department. In 1974 he returned to Texas A&M University, College Station, as an Engineering Research Associate at the Remote Sensing Center. He currently holds a joint appointment between the Remote Sensing Center and the Department of Electrical Engineering. His current interests include microwave sensor development and signal processing. Dr. Jean is a member of Phi Eta Sigma, Phi Kappa, Tau Beta Pi, and Eta Kappa Nu. He is a Registered Professional Engineer in the State of Texas.