C- and Ku-band, dual-frequency, multi-polarization, combined scatterometer-radiometer system for sea, land, and atmospheric remote sensing

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1 C- Ku-b dual-frequency multi-polarization combined scatterometer-radiometer system for sea l atmospheric remote sensing Artashes K. Arakelyan* Astghik K. Hambaryan Vanik V. Karyan Melanya L. Grigoryan Gagik G. Hovhannisyan Arsen A. Arakelyan Marine G. Simonyan Tigran N. Poghosyan a Nubar G. Poghosyan a ECOSERV Remote Observation Centre Co. Ltd. G. Njdeh Str. # Yerevan Armenia 000 a Institute of Radiophysics & Electronics of ANAS Alikhanyan Br. Ashtarak Armenia 003 ABSTRACT In this paper a dual frequency (at C- K u -b) multi-polarization combined short pulse scatterometer-radiometer system is described. The developed system is applicable for simultaneous spatially coincident dual-frequency multi-polarization measurements of soil snow water surface microwave reflective emissive characteristics from a range beginning of m. Keywords: Radar radiometer antenna combined radar-radiometer scatterometer Doppler-radar.. INTRODUCTION Radio-physical methods means of remote sensing (radars radiometers combined radar-radiometers) have wide application for soil snow water surface mapping parameters retrieval. They are used for estimating Earth surface (sea l) atmospheric principal parameters such as sea salinity sea water near sea surface air temperatures wind speed direction sea wave force soil snow moistures temperatures snow cover thickness melting time soil vegetation biomass bounded water quantity maturity dryness precipitation quantity (clouds water content) snowfall rainfall parameters etc. They are used as well for - real-time detection of surface subsurface signatures (anomalous formations) targets; - identification of the origins of detected formations such as for instance hazardous waste sites oil spills spills of other surface active substances; - lmines mine-like targets detection; - classification of surface signatures of natural man-made origin e.g. volcanoes vegetation snow ice covers etc.; - detection of clouds clear-air turbulences in atmospheric boundary layer temperature distributions other. Detected formations are classified over the backgrounds of the observed surfaces for example the oil spill over waved unpolluted sea surface etc. For assessment of observed surfaces media parameters one uses - their radar backscattering coefficients or radar cross sections or equivalently their backscattered radar signal dispersions where indices i = "v " or "h " j = "v " or " "h indicate the polarization ( v for vertical h for horizontal polarization) of the transmitted reflected radar signals as well as - their brightness temperatures T Bi or equivalently their proper radiothermal signal dispersions i were the indices i = "v " or "h " again indicate polarization respectively. *arakelyanak@yahoo.com; phone/fax: (37 0) -877;

2 Principal attributes for description of surface signatures targets are the changes of dispersions vv hv v h relative to the background. hh vh Since the absolute values the changes of radar backscattering coefficients brightness temperatures T Bi of observed media are complicated functions of many parameters (variables) for precise solution of the Earth atmospheric remote sensing inverse problems it is necessary to provide unambiguity of solution. Really it is known for instance that the sea surface radar backscattering coefficients brightness temperatures T Bi are complicated functions of incidence ϑ azimuth ϕ angles of observation radio wavelength λ water dielectric constant ε water temperature t w salinity s w near sear surface air temperature t a wind speed V direction ϕ sea-surface short S (ω ) long S (ω ) waves spectrums long wave propagation direction V ϕ L relative area of surface foam formation S Σ etc: T Bi s L ( ϑ ϕ λ ε V ϕ S ( ω ) S ( ω ) ϕ t t s ) = f S V S L L w a w Σ ( ϕ λ ε V ϕ S ( ω ) S ( ω ) ϕ t t s ) = f ϑ S : i V S L L w a w Σ Some of these variables may be a priory known such as ϑ ϕ λ. The others however have direct measurable influence on T Bi. So for precise retrieval of certain parameters for example wind speed or direction water temperature or salinity long waves spectrum others it is necessary to provide estimation unambiguity. This is possible only by synergy data from multiple parallel independent measurements for instance by simultaneous measurements of vv hh vh hv T Bv T Bh. These problems exist in particular for snow bare vegetated soils remote sensing since radar cross sections brightness temperatures of the mentioned surfaces are complicated functions of: snow soil moistures temperatures soil type composition structure surface roughness soil surface vegetation type thickness bounded water quantity snow density structure melting time etc. For solving the problems occurring in snow soil vegetation remote sensing (parameters retrieval signatures detection) it is thus necessary to achieve independent measurements which are then jointly processed analyzed. It shall be noted that the co- ( vv hh ) cross- ( vh hv ) polarized components of the radar signals are often correlated. Therefore the set of independent usable parameters for retrieval of observed surface parameters detection of surface signatures is reduced to the set of values or. These variables are thus often insufficient for estimating certain parameters unambiguously for classifying of detected signatures for certain. It means that sometimes the utilization even of a single frequency dual-polarization combined radar-radiometer system may not provide required accuracy reliability of information. To overcome this problem it is necessary to carry out multi-polarization spatio-temporally collocated active passive remote sensing at least at two different frequencies from two different frequency bs. Using dual-frequency multi-polarization radarradiometer sensing the following measurement value sets are available for parameter estimation surface classification: { ω vv hh vh ω hv Bω v Bω h TBω v TBω h } or equivalently { ωvv ω hh ω ω T T ω hv ω v ω h ω v ω h } where indices ω ω show the frequency. But to make that it is necessary to have a dual-frequency multi-polarization combined radar-radiometer system. For the first time the idea to develop a dual-frequency multi-polarization combined radar-radiometer system was embodied patented fully described in [-3]. In this paper an embodiment of C- (5.GHz) K u -b (3.GHz) vv vh v h hh hí v h ω hv

3 dual frequency multi-polarization combined short pulse scatterometer-radiometer system (ArtAr-C&K u ) is presented is described. The system ArtAr-C&Ku was developed in Armenia by ECOSERV Remote Observation Centre Co. Ltd. under the framework of the International Science Technology Center (ISTC) Project A-5. The developed system is applicable for simultaneous spatially coincident dual-frequency multi-polarization measurements of soil snow water surface microwave reflective emissive characteristics from low altitude stationary fixed or mobile measuring platforms vessels. Although the system may be used for a range up to 50m the minimum operational range of the system s scatterometers is m.. C- AND K u -BAND COMBINED SCATTEROMETER-RADIOMETER SYSTEM The principal requirements for a development of the system were: - Functional constructive combining both C- K u -b microwave combined active passive means of sensing as a single microwave device providing simultaneous operational peculiarities. - Coherent-pulse construction of system s scatterometers functional schemes provided high level of decoupling between transmitting receiving sections allowed realize short range operational potential for both scatterometers beginning from m. - Series (periodical) transmissions of the signals at two different frequencies at specified (vertical or horizontal) polarizations simultaneous receiving of both co- cross-polarized components of backscattered radar signals at two different frequencies. - Possibility for application of developed principles methods for signals forming processing for spaceaerial based prototype of the system. In comparison with earlier developed single-frequency combined scatterometer-radiometer systems of S (~3GHz) C (~5.GHz) K u (~5GHz) K (~0GHz) Ka (~37GHz) b of frequencies [-] the described system has two transmitting four receiving channels which allow simultaneously receipt co- cross polarized components of the backscattered signals at 5.GHz 3.GHz the signals of the observed surface proper radiothermal emissions at 5.GHz 3.GHhz at vertical horizontal polarizations. In Fig. a simplified block diagram of ArtAr-C&K u dual-frequency multi polarization combined scatterometerradiometer system is presented. A A A T T E B C F E B C F D S Multi-Channel Analog-To-Digital Converter Computer Fig. A simplified block diagram of ArtAr-C&K u dual-frequency combined scatterometer-radiometer system A Parabolic antenna (dish subdish) A A C- K u -b antenna feeds T T C- K u -b transmitter modules B B C- K u -b radar receivers for backscattered signals co-polarized components C C C- K u - b radar receivers for backscattered signals cross-polarized components E E C- K u -b radiometric receivers for radiothermal signals at vertical polarization E E C- K u -b radiometric receivers for radiothermal signals at horizontal polarization D Reference signal module S Synchronizer 3

4 Detailed block diagrams of C- K u -b modules of ArtAr-C&K u system are presented in Fig. Fig3 respectively. Time-division channeling of scatterometers radiometers functioning was used for the system functional scheme development. In Fig. a time diagram of operation of the system is presented. The work while of the system is divided by ms time periods in which 0% of the period is used for transmitting of 0 pulses receiving of 0 backscattered scatterometeric signals at co- cross polarizations. The remain of the time is used to receive proper radio thermal signals at vertical horizontal polarizations. The transmitted signal s polarization changes periodically (periodically changing operating mode) or stepwise by issuing the outside comm (polarization stability operating mode). A v-pol. 3 3 h-pol D S Multi-Channel Analog- 7 0 To-Digital Converter Fig. A block diagram of C-b module of ArtAr-C&K u dual-frequency combined scatterometer-radiometer system A C-b antenna feed Orthomode Polarization Splitter 3 Y-Circulator Antenna Switch Modulator 5 Directional Coupler Isolator 7 Power Divider 8 Attenuator 9 Double Power Divider 0 Noise Source Low Noise Amplifier Reference Oscillator 3 Pulse Modulator Mixer 5 IF Pre-Amplifier Radiometric IF Amplifier Controlled Square-Low Detector 7 Synchronous Detector Integrator 8 Quadrature Mixer (Phase Detectors Video Amplifiers) 9 Squarer Sample/Hold 0 C-B Microwave Oscillator (Heterodyne) Preliminary Power Amplifier Up-Converter 3 B Pass Filter Controlled Main Amplifier D Reference Signal Module S Synchronizer

5 A v-pol. 3 3 h-pol. 8 5 S D Multi-Channel Analog- 7 0 To-Digital Converter Fig. 3 A block diagram of K u -b module of ArtAr-C&K u dual-frequency combined scatterometer-radiometer system A K u -B Antenna Feed Orthomode Polarization Splitter 3 Y-Circulator Antenna Switch Modulator 5 Directional Coupler Isolator 7 Power Divider 8 Attenuator 9 Double Power Divider 0 Noise Source Low Noise Amplifier Reference Oscillator 3 Pulse Modulator Mixer 5 IF Pre-Amplifier Radiometric IF Amplifier Controlled Square-Low Detector 7 Synchronous Detector Integrator 8 Quadrature Mixer (Phase Detectors Video Amplifiers) 9 Squarer Sample/Hold 0 K u -B Microwave Oscillator (Heterodyne) Preliminary Power Amplifier Up-Converter 3 B Pass Filter Controlled Main Amplifier D Reference signal module S Synchronizer Such a construction allows improve relative accuracy of measurements by cross polarized signals simplify calibration procedure reduce complicity value of the system by using microwave intermediate frequency modules of the system as a common modules for both scatterometer radiometer channels. Of cause time-division channeling of scatterometer radiometer functioning has its shortage connected with a reduction of backscattered signals accumulation efficiency. However for stationary low speed platform application this fact is not sufficient if the main requirement for the system s operation its work stability accuracy of measured data. In Fig. a time diagram of the system operation is presented. The work while of the system is divided by T P time periods in which the while T R is equal to ~0% of the period T R =0.T P is used for radar channel operation the 5

6 rest of the period T B =T P -T R is used for radiometric channels operation. The while T S is used for transmission of a train of 0 probing pulses at both frequencies for reception of corresponding (vv or hh) cross (vh or hv) polarized components of the backscattered pulse signals at both frequencies. The reception of the backscattered pulse signals is implemented during the while T Re. The transmission is implemented during the while T T where T Pu is the pulse duration. The while T P r of the period is used for protection of the radiometer receivers inputs form the residual influence of both transmitters. The while T B is used for reception of proper radio thermal signals of the observed surface at both frequencies at vertical horizontal polarizations. C K u -b Heterodynes (microwave oscillators 0) generate continuous signals at baseb frequencies ω H ω H respectively. After amplifying these signals are used for forming probing signals by C K u -b upconverters. The signals at frequencies ω H ω H are used as well as local heterodyne signals for C K u - b mixers of the system. Therefore downstream of power dividers 9 the signals at ω H ω H are fed to the inputs of the up-converters to mixers of the system. Highly stable HF Reference Oscillator provides a continuous reference signal at reference frequency ω Re f. Downstream of the power divider 9 the signals at the reference frequency ω are fed to pulse modulator 3 to the phase detectors of the quadrature mixers 8. The Re f pulse modulator forms pulsed signals at frequency ω which are mixed with the heterodyne signals at ω ω in the up-converters. The resulting pulsed signals are filtrated by the bpass filters 3. H Re f H Transmission of pulses at v or h pol. at freq. ω at h or v pol. at freq. ω Radar reception at vv vh pol. at freq. ω at hh hv pol.. at freq. ω T T Time for receivers protection Radiometric reception at v h pol. at freq. ω at v h pol. at freq. ω T P u T Re T Pr T B t A train of 0 pulses T S T R T P Fig. A time diagram of the system operation

7 The so-obtained probing pulse signals at frequencies ω = ωh + ω Ref for C-b ω = ωh ω Re f for K u -b ten amplified by power amplifiers. The amplified probing pulse signals are then fed to the antenna via polarization switches circulators 3 orthomode polarization splitters antenna feeds A A. Antenna transmits the probing pulse signals as vertically or horizontally polarized electromagnetic pulsed waves at ω ω. Co-polarized (vv or hh) cross-polarized (vh or hv) components of reflected pulse signals at frequencies ω ω are received by antenna during the time interval T Re. The received signals are fed to the circulators 3 through orthomode antenna feeds A A the orthomode polarization splitters. The circulators forward the signals to the inputs of the antenna switches which operate during the time intervals T Re as transmission lines let the signals pass without changes. (During the time intervals T T the antenna switches are interrupted so as to protect the radar radiometric receivers inputs from the direct influence of the transmitters). From the outputs of the antenna switches the signals are fed to the mixers where they are mixed with the heterodyne signals at ω H ω H. The resulting outputs at the intermediate frequency ω Re f are passed through the power dividers 9 to quadrature mixers 8. The output signals of the quadrature mixers 8 are the I (in-phase) Q (quadrature) components of the signals which are fed to the inputs of squarers sample--holds 9. The outputs of sample--holds fed to the corresponding inputs of Multi-Channel Analog-To-Digital Converter of the system registered processed in PC Computer. During the time interval T B + T Pr the transmitters are turned off. During this time interval T B the antenna switches periodically switch the inputs of the low noise amplifiers to the antenna to the equivalent load (thermostable). Vertical horizontal polarized components of the observed surface proper radiotermal signals at frequencies ω received by the antenna passed through orthomode antenna feeds A A orthomode polarization splitters ω circulators 3 antenna switches low noise amplifiers are mixed with the heterodyne signals ω H ω H by mixers. The resulting intermediate frequency signals are fed to the controlled square-low detectors via power dividers 9. The keys of the controlled square-low detectors are turned off during the time interval T R are turned on during the time interval T B. The outputs are detected by synchronous detectors integrated by integrators 7. The outputs of integrators as so-obtained dispersions of the proper radiothermal signals fed to the corresponding inputs of Multi-Channel Analog-To-Digital Converter of the system then are registered processed in PC Computer. 3. REALIZED PARAMETERS In Fig.5 Fig. realized work prototype of ArtAr-C&K u dual frequency multi-polarization combined scatterometerradiometer system is presented. The system was built on the basis of in-house design modules. In Fig.5 a C-b part (module) of the system is presented. In Fig. a K u -b part of the system is presented. In Figs. 5 the system s antenna dual-frequency antenna feed are presented too. The main technical characteristics of the realized prototype are presented in the table below. C - B K u - B Radar Channel Radiometric Radiometric Radar Channel Channel Channel Central frequency 5.GHz 5.GHz 3.GHz 3.GHz Dual Frequency Parabolic Antenna Gain / Beamwidth / Sidelobes ~ db / 8 0 / -8dB ~ 3dB / 3 0 / -0dB Radar pulses type duration a train of 0 pulses 5ns each a train of 0 pulses 5ns each Pulse repetition frequency MHz MHz within the train Repetition frequency of the train KHz KHz Table 7

8 Pulse power 50-50mW 75-00mW Polarization: Transmission Reception: v or h vv vh or v h v or h vv vh or hv hh hv hh v h Pre-detection bwidth ~00MHz ~500MHz ~00MHz ~500MHz Receiver s sensitivity (at s) -30dB/W ~0.K -30dB/W ~0.5K Operational range - 50m Dimensions / weight 0 x 0 x 00mm 3 / 5kg Fig. 5 A C-b part of ArtAr-C&K u dual frequency multi-polarization combined scatterometer-radiometer system work prototype Fig. 5 A K u -b part of ArtAr-C&K u dual frequency multi-polarization combined scatterometer-radiometer system work prototype. CONCLUSION Thus C- K u -b dual frequency multi-polarization combined scatterometer-radiometer system is developed. The developed system allows investigate peculiarities of relationships between power (amplitude) phase characteristics of the backscattered radar signal between power characteristics of backscattered radar emitted proper radio thermal signals of the observed surface or object under test-control laboratory conditions at two different frequencies from two different frequency bs. The system may be used as a detector identifier will allow to detect to classify at least 5 types of anomalies originating on the background due to the changes of the observed surface geophysical biochemical parameters. The developed device is the first from the series of dual frequency multi- 8

9 polarization combined radar-radiometers which are planned for development manufacturing in the framework of the ISTC (International Science Technology Center) Project A-5 applied to multi-frequency multi-polarization measurements of snow bare vegetated soil perturbed water surface microwave reflective emissive characteristics angular dependences under test-control quasi-field conditions by spatio-temporally combined activepassive systems. ACKNOWLEDGEMENT Authors express their gratitude to the International Science Technology Center of Moscow for its financial support maintenance provided through the ISTC Project A-5 allowed to patent to develop to built to realize to test dual-frequency multi-polarization combined scatterometer-radiometer system. REFERENCES. A.Arakelyan Dual-frequency multi-polarization combined radar-radiometer system by Artashes Arakelyan Armenian National Patent # 57À 009. (in Armenian).. A.Arakelyan Dual-frequency multi-polarization combined scatterometer-radiometer system Armenian National Patent # 33A 009. (in Armenian). 3. A.Arakelyan Multi-polarization combined radar-radiometer system International Patent Application (PCT Patent) PCT/IB009/ A.K.Arakelyan E.R.Alaverdyan A.A.Arakelyan S.A.Darbinyan A.K.Hambaryan V.K.Hambaryan V.V.Karyan G.G.Ogannisyan N.G.Poghosyan A.I. Smolin Polarimetric Ka-B Combined Short Pulse Scatterometer Radiometer System for Platform Application Radar Sensor Technology IX edited by Robert N.Trebits James L.Kurtz Proceedings of SPIE Vol (SPIE Bellingham WA 005) pp A.K.Arakelyan A.K.Hambaryan A.I.Smolin V.V.Karyan N.G.Poghosyan M.A.Sirunyan M.R.Manukyan A.A.Arakelyan Polarimetric Ka-B Combined Short Pulse Scatterometer Radiometer System Progress in Contemporary (Present-Day) Radio Electronics No pp (In Russian).. A.K.Arakelyan A.K.Hambaryan A.I.Smolin V.V.Karyan G.G.Hovhannisyan E.R.Alaverdyan A.A.Arakelyan V.K.Hambaryan Short Pulse C-B Doppler Scatterometer Radar Sensor Technology IX edited by Robert N.Trebits James L.Kurtz Proceedings of SPIE Vol (SPIE Bellingham WA 005) pp A.K.Arakelyan I.K.Hakobyan A.A.Arakelyan A.K.Hambaryan M.L Grigoryan E.A.Vardanyan V.V.Karyan M.R.Manukyan G.G.Hovhannisyan Short Pulse Polarimetric Scatterometer at 5.GHz Progress in Contemporary (Present-Day) Radio Electronics No. 00 pp. -9. (In Russian). 8. A.K.Arakelyan I.K.Hakobyan A.A.Arakelyan A.K.Hambaryan M.L Grigoryan E.A.Vardanyan V.V.Karyan M.R.Manukyan G.G.Hovhannisyan N.G.Poghosyan Short Pulse Polarimetric Combined Scatterometer- Radiometer at 0GHz Progress in Contemporary (Present-Day) Radio Electronics No pp.5-3. (In Russian). 9. A.K.Arakelyan A.A.Arakelyan S.A.Darbinyan M.L.Grigoryan I.K.Hakobyan A.K.Hambaryan V.V.Karyan M.R.Manukyan G.G.Hovhannisyan T.N.Poghosyan N.G.Poghosyan S.F.Clifford Polarimetric combined short pulse scatterometer-radiometer system at 5GHz for platform vessel application Proceedings of SPIE edited by Robert N.Trebits James L.Kurtz Radar Sensor Technology XI Vol pp 57OH- - 57OH A.K.Arakelyan I.K.Hakobyan. A.A.Arakelyan A.K.Hambaryan M.L.Grigoryan V.V.Karyan M.R.Manukyan G.G.Hovhannisyan N.G.Poghosyan S.F.Clifford Ku-B Short Pulse Dual-Polarization Combined Scatterometer-Radiometer Progress in Contemporary (Present-Day) Radio Electronics No. 007 pp (In Russian).. A.K.Arakelyan A.A.Arakelyan S.A.Darbinyan M.L.Grigoryan I.K.Hakobyan A.K.Hambaryan VK.Hambaryan V.V. Karyan G.G.Hovhannisyan N.G.Pogosyan E.A.Vardanyan S-b polarimetric combined short pulse scatterometer-radiometer for platform vessel application in Radar Sensor Technology X edited by Robert N. Trebits James L. Kurtz Proceedings of SPIE Vol (SPIE Bellingham WA 00) 00J.. A.K.Arakelyan I.K.Hakobyan A.A.Arakelyan A.K.Hambaryan M.L.Grigoryan V.V.Karyan M.R.Manukyan G.G.Hovhannisyan N.G.Pogosyan S-B Polarimetric Short Pulse Short Distance application Combined Scatterometer-Radiometer Electromagnetic Waves Electronic Systems Vol. No pp (In Russian). 9