Space Radar Research Articles

A large-scale anomaly in Enceladus’ microwave emission

The Cassini spacecraft flew by Enceladus on 6 November 2011, configured to acquire synthetic aperture RADAR imaging of most of the surface with the RADAR instrument. The pass also recorded microwave thermal emission from most of the surface. We report on global patterns of thermal emission at 2.17cm based on this data set in the context of additional unresolved data both from the ground and from Cassini.The observed thermal emission is consistent with dielectric constants of pure water or methane ice, but cannot discriminate between the two. The emissivity is similar to those of other icy satellites (≈0.7), consistent with volume scattering. The most intriguing result, however, is an anomaly in the thermal emission of Enceladus’ leading hemisphere. Evidence presented here suggests the anomaly is buried at depths on the order of a few meters. This anomaly is located in similar geographic location to anomalies previously detected with the CIRS and ISS instruments on Mimas, Tethys, and Dione (Howett, C.J.A. et al. [2011]. Icarus 216, 221–226; Howett, C.J.A. et al. [2012]. Icarus 221, 1084–1088; Howett, C.J.A. et al. [2014]. Icarus 241, 239–247; Schenk, P. et al. [2011]. Icarus 211, 740–757), but also corresponds with a geological feature on Enceladus’ leading terrain (Crow-Willard, E., Pappalardo, R.T. [2011]. Global geological mapping of Enceladus. In: EPSC-DPS Joint Meeting 2011. p. 635). Simple models show that the Crow-Willard and Pappalardo (Crow-Willard, E., Pappalardo, R.T. [2011]. Global geological mapping of Enceladus. In: EPSC-DPS Joint Meeting 2011. p. 635) model is a better fit to the data. Our best-supported hypothesis is that the leading hemisphere smooth terrain is young enough (<75–200Myr old) that the micrometeorite impact gardening depth is shallower than the electromagnetic skin depth of the observations (≈3–5m), a picture consistent with ground and space radar measurements, which show no variation at 2cm, but an increase in albedo in the anomaly region at 13cm.

Using Ice Clouds for Mitigating the EarthCARE Doppler Radar Mispointing

The EarthCARE (EC) radar will be the first atmospheric cloud-profiling radar in space with Doppler capabilities. The mitigation of mispointing uncertainties related to thermal distortions and vibrations of the antenna structure, and/or attitude determination errors represents one of the several challenges to overcome for the reaching of high-quality Doppler velocity products. In addition to the possibility of adopting mispointing correction techniques based on the surface Doppler velocity in clear sky regions, we propose to use the presence of abundant natural targets (ice clouds) with climatologically very well characterized Doppler velocities as calibration points. This is demonstrated by showing that the ice clouds present on average in each EC orbit (emulated with CloudSat data) can be used to accurately retrieve the effect of an orbital harmonic, which represents the most relevant component in the modeling of the antenna mispointing error expected for the EC satellite. The residual errors associated to the orbital harmonic mispointing are negligible (<; 0.03 m/s) compared with the other errors typically involved in Doppler velocities observed from fast-moving platforms. On the other hand, high-frequency components of the torque spectrum cannot be mitigated and, according to the current thermal and mechanical models for the EC antenna, are estimated to contribute to an RMS error of 0.2 (0.3) m/s in the nominal (worst case) scenario.

Signal Processing in Synthestic-Aperture Radars During the Formation of the Earth-Surface Velocity Fields

We consider the signal-processing principles during the Earth-surface sounding by syntheticaperture radars (SARs) including the along-track interference radars. The aperture-synthesis features for solving two problems, namely the measurements of the local-reflector velocity and reconstruction of the velocity pattern of the rough surface, are discussed. The features of these problems and restrictions related to the aperture-synthesis process and other factors including the limited radiated power of a space radar are considered. Conclusions on the possibilities of the radar reconstruction of the surface velocity fields for both the local reflectors and the extended surface (sea currents) are drawn. Approximate calculations of the available parameters of the recorded fields in the SARs mounted onboard low-orbit spacecraft are performed.

Oil Pollution in the Southeastern Baltic Sea in 2009-2011

Abstract From January 2009 to April 2012 a satellite survey of the central and southeastern parts of the Baltic Sea was carried out by the Space Radar Laboratory at the Space Research Institute of Russian Academy of Sciences (RAS). The main attention was focused on the detection of oil pollution as well as biogenic and anthropogenic surfactant films. The basic data are high resolution radar images obtained by advanced synthetic aperture radar (ASAR) on board of the Envisat satellite of the European Space Agency. Remotely sensed data in visual and infrared (IR) bands acquired by sensors MERIS Envisat, MODIS-Terra and -Aqua, and AVHRR NOAA nearly simultaneously with the ASAR images, were processed and analysed in order to facilitate the discrimination between different types of surface pollutants, to understand a comprehensive features of meteorological and hydrodynamic processes in the sea area of investigation, and to reveal factors determining pollutants spread and drift. The regions of the most intense oil pollution are outlined.

Polarization Diversity for Millimeter Spaceborne Doppler Radars: An Answer for Observing Deep Convection?

AbstractSpaceborne Doppler radars have the potential to provide key missing observations of convective vertical air motions especially over the tropical oceans. Such measurements can improve understanding of the role of tropical convection in vertical energy transport and its interaction with the environment. Several millimeter wavelength Doppler radar concepts have been proposed since the 1990s. The Earth Clouds, Aerosols, and Radiation Explorer (EarthCARE) Cloud Profiling Radar (CPR) will be the first Dopplerized atmospheric radar in space but has not been optimized for Doppler measurements in deep convective clouds.The key challenge that constrains the CPR performance in convective clouds is the range–Doppler dilemma. Polarization diversity (PD) offers a solution to this constraint by decoupling the coherency (Doppler) requirement from the unambiguous range requirement. Careful modeling of the radar signal depolarization and its impact on radar receiver channel cross talk is needed to accurately assess the performance of the PD approach.The end-to-end simulator presented in this work allows reproduction of the signal sensed by a Doppler radar equipped with polarization diversity when overpassing realistic three-dimensional convective cells, with all relevant cross-talk sources accounted for. The notional study highlights that multiple scattering is the primary source of cross talk, highly detrimental for millimeter Doppler velocity accuracy. The ambitious scientific requirement of 1 m s−1 accuracy at 500-m integration for reflectivities above −15 dBZ are within reach for a W-band radar with a 2.5-m antenna with optimal values of the pulse-pair interval between 20 and 30 μs but only once multiple scattering and ghost-contaminated regions are screened out. The identification of such areas is key for Doppler accuracies and can be achieved by employing an interlaced pulse-pair mode that measures the cross and the copolar reflectivities. To mitigate the impact of attenuation and multiple scattering, the Ka band has been considered as either alternative or additional to the W band. However, a Ka system produces worse Doppler performances than a W-band system with the same 2.5-m antenna size. Furthermore, in deep convection it results in similar levels of multiple scattering and therefore it does not increase significantly the depth of penetration. In addition, the larger footprint causes stronger nonuniform beam-filling effects. One advantage of the Ka-band option is the larger Nyquist velocity that tends to reduce the Doppler accuracies. More significant benefits are derived from the Ka band when observing precipitation not as intense as the deep convection is considered here.This study demonstrates that polarization diversity indeed represents a very promising methodology capable of significantly reducing aliasing and Doppler moment estimate errors, two main error sources for Doppler velocity estimates in deep convective systems and a key step to achieving typical mission requirements for convection-oriented millimeter radar-based spaceborne missions.

Simulation of radar with a knife-like antenna beam using precipitation radar data

The concept of radar using a knife-like antenna beam is discussed and compared with precipitation radar (PR). An example of PR data processing is given. Two approaches are used to retrieve variance of slope: point-to-point algorithms and a linear angular algorithm. The algorithm for the PR data transformation into data of radar with a knife-like antenna beam has been developed. Transformation of real satellite data into data of radar with a knife-like antenna beam enables one for the first time to simulate measurements of future space radar qualitatively. Transformed data are used to validate the retrieval algorithms developed for radar with a knife-like antenna beam. Numerical simulation is also used to test the retrieval algorithms. The noise effect on the precision of slope variance retrieval for the PR and radar with a knife-like antenna beam is considered. Data processing confirms that the precision of radar with a knife-like antenna beam is significantly higher than the precision of PR. Numerical simulation is also used to explore the possibility of sea-surface slope imaging. The obtained results confirm that only radar with a knife-like antenna beam can be employed to retrieve real images of the processes occurring on sea-surface slopes.

Location Method of Near Space Radar Network Based on Regularized Constrained Total Least Square

摘要: 该文研究了一种基于归一化约束最小二乘的近空间雷达网定位算法。首先将距离与角度信息的非线性方程转换为线性方程，通过一阶Taylor展开分析了噪声对线性方程的影响，然后将定位问题转化为归一化约束总体最小二乘问题，并通过Lagrange函数将其转换为无约束的优化问题，根据定位均方误差最小原则选取加权因子得到定位解，最后进行了定位误差分析，仿真结果表明了该算法的有效性。 关键词: 雷达网 / 归一化约束最小二乘 / 定位精度

V/UHF space radars: Spatial phase decorrelation of transionospheric signals in the equatorial region

[1] The spatial decorrelation of V/UHF signals by equatorial ionospheric turbulence is studied using 150 and 400 MHz signals transmitted from low-earth-orbiting beacon satellites. The signals are monitored on a linear array of spaced antennas located on Ascension Island, and processed coherently to determine the cross-correlations of the phases of the received signals. Analyzing signals from the low-inclination satellite C/NOFS has provided an opportunity to investigate the correlation variations in and out of scintillating structures. As a necessary step, the geometrical component of the phase difference between antennas has been accurately removed by adjusting the satellite orbital information using the measured phases. In order to unambiguously measure the spatial phase correlation without any temporal effects, the phase cross-correlation was calculated as the cross-correlation function of time-synchronized signals. As expected, the VHF signals were more affected by scintillation than the UHF signals. When the signal propagated through patches of strong scintillation, the VHF signal became completely uncorrelated over an ionospheric distance of 130 m, while over the same distance the UHF phase correlation decreased to 0.55. The time-synchronized technique limited the spatial variations assessed to east-west distances of ∼300 m. To extend this range, a novel ‘phase reconstruction’ technique was developed to link arrays of samples together. In the absence of scintillation the measured decorrelation distance is ∼10 km at both frequencies, but with increasing scintillation, the decorrelation distance falls to ∼100 m at VHF and 300 m at UHF. A clear relation between the decorrelation distance of the measured phase and S4 is observed and a simple empirical model has been derived.

Matching Space Antenna Deformation Electronic Compensation Strategies to Support Structure Architectures

Radar systems are engineered to achieve a complex, yet functional, balance between diverse subsystems and competing requirements. One important trade for large deployable space radar antennas is between antenna dimensional stability and electronic signal processing for deformation compensation. This trade is first investigated for several different electronic compensation methods, and compensation capabilities are mapped into structural requirements. Second the structural requirements are translated into appropriate structural architectures. The scope of this study is limited to space radar systems, where loads causing antenna deformations differ significantly from terrestrial systems. Compensation strategies that allow structural requirements to be reduced by several orders of magnitude are identified. When considered early in the systems engineering process, the methods presented herein can be used to form a rationale for the selection and the development of a complementary combination of compensation electronics and structural architectures.

Discrimination of Mixed- versus Ice-Phase Clouds Using Dual-Polarization Radar with Application to Detection of Aircraft Icing Regions*

AbstractDual-polarization radar measurements and in situ measurements of supercooled liquid water and ice particles within orographic cloud systems are used to develop probabilistic criteria for identifying mixed-phase versus ice-phase regions of sub-0°C clouds. The motivation for this study is the development of quantitative criteria for identification of potential aircraft icing conditions in clouds using polarization radar. The measurements were obtained during the Mesoscale Alpine Programme (MAP) with the National Center for Atmospheric Research S-band dual-polarization Doppler radar (S-Pol) and Electra aircraft. The comparison of the radar and aircraft measurements required the development of an automated algorithm to match radar and aircraft observations in time and space. This algorithm is described, and evaluations are presented to verify its accuracy. Three polarization radar parameters, the radar reflectivity factor at horizontal polarization (ZH), the differential reflectivity (ZDR), and the specific differential phase (KDP), are first separately shown to be statistically distinguishable between conditions in mixed- and ice-phase clouds, even when an estimate of measurement uncertainty is included. Probability distributions for discrimination of mixed-phase versus ice-phase clouds are then developed using the matched radar and aircraft measurements. The probability distributions correspond well to a basic physical understanding of ice particle growth by riming and vapor deposition, both of which may occur in mixed-phase conditions. To the extent that the probability distributions derived for the MAP orographic clouds can be applied to other cloud systems, they provide a simple tool for warning aircraft of the likelihood that supercooled water may be encountered in regions of clouds.

Mitigation and exploitation of the ionosphere: A military perspective

The ionosphere is a critical element in the design and operation of many military RF systems. While judicious engineering choices, such as transmission frequency, can mitigate many ionospheric effects, the research scientist and engineer are being asked to meet ever more demanding operational requirements. These, in turn, require ever more sophisticated situational awareness, mitigation, and exploitation techniques, which are being variously realized against a backdrop of evolving ground‐ and space‐based instrumentation. The latter, in combination with improved modeling and assimilative techniques, promises a new generation of more capable real‐time ionospheric models. Through examples this paper describes the benefits and problems associated with the ionospheric medium. HF communications and space radar systems are discussed as exemplars, and an emphasis is placed on the need to understand the engineering details of those systems if ionospheric research and development is to provide its full benefit.

Changes in the TRMM Version-5 and Version-6 Precipitation Radar Products Due to Orbit Boost

The performance of the version-5 and version-6 Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) products before and after the satellite orbit boost is assessed through a series of comparisons with Weather Surveillance Radar (WSR)-88D ground-based radar in Melbourne, Florida. Analysis of the comparisons of radar reflectivity near the storm top from the ground radar and both versions of the PR indicates that the PR bias relative to the WSR radar at Melbourne is on the order of 1 dB for both pre- and post-boost periods, indicating that the PR products maintain accurate calibration after the orbit boost. Comparisons with the WSR-88D near-surface reflectivity factors indicate that both versions of the PR products accurately correct for attenuation in stratiform rain. However, in convective rain, both versions exhibit negative biases in the near-surface radar reflectivity with version-6 products having larger negative biases than version-5. Rain rate comparisons between the ground and space radars show similar characteristics.

Tracking Chinese Strategic Mobile Missiles

This paper analyzes the maneuverability, capabilities, and survivability of Chinese DF-31 mobile missiles and the ability of a proposed U.S. Space Radar system to persistently track them. The author posits possible defense strategies for the Chinese military and concludes that the survivability of the mobile DF-31′s is not guaranteed during a nuclear attack given the huge U.S. strategic arsenal, but also questions the ability of the proposed U.S. Space Radar system to persistently track the DF-31′s if the Chinese military engages in relatively simple countermeasures. Neither China nor the United States can be completely confident of a strategic advantage. The two countries need strategic dialogues to improve relations on this topic.

Evaluation of Ice Water Content Retrievals from Cloud Radar Reflectivity and Temperature Using a Large Airborne In Situ Microphysical Database

Abstract The objective of this paper is to assess the performances of the proposed ice water content (IWC)–radar reflectivity Z and IWC–Z–temperature T relationships for accurate retrievals of IWC from radar in space or at ground-based sites, in the framework of the forthcoming CloudSat spaceborne radar, and of the European CloudNET and U.S. Atmospheric Radiation Measurement Program projects. For this purpose, a large airborne in situ microphysical database is used to perform a detailed error analysis of the IWC–Z and IWC–Z–T methods. This error analysis does not include the error resulting from the mass–dimension relationship assumed in these methods, although the expected magnitude of this error is bounded in the paper. First, this study reveals that the use of a single IWC–Z relationship to estimate IWC at global scale would be feasible up to −15 dBZ, but for larger reflectivities (and therefore larger IWCs) different sets of relationships would have to be used for midlatitude and tropical ice clouds. New IWC–Z and IWC–Z–T relationships are then developed from the large aircraft database and by splitting this database into midlatitude and tropical subsets, and an error analysis is performed. For the IWC–Z relationships, errors decrease roughly linearly from +210%/−70% for IWC = 10−4 g m−3 to +75%/−45% for IWC = 10−2 g m−3, are nearly constant (+50%/−33%) for the intermediate IWCs (0.03–1 g m−3), and then linearly increase up to +210%/−70% for the largest IWCs. The error curves have the same shape for the IWC–Z–T relationships, with a general reduction of errors with respect to the IWC–Z relationships. Comparisons with radar–lidar retrievals confirm these findings. The main improvement brought by the use of temperature as an additional constraint to the IWC retrieval is to reduce both the systematic overestimation and rms differences of the small IWCs (IWC &amp;lt; 0.01 g m−3). For the large IWCs, the use of temperature also results in a slight reduction of the rms differences but in a substantial reduction (by a factor of 2) of the systematic underestimation of the large IWCs, probably owing to a better account of the Mie effect when IWC–Z relationships are stratified by temperature.

Variation of weather radar sensitivity at ground level and from space: case studies and possible causes

Firstly, this paper summarizes the procedure for correcting the variation of sensitivity of radars at ground level, using a radar in space for reference, as already described in the literature. Around 10dB have to be added to the measured radar reflectivity Z (in mm 6 /m 3 ), when increasing the range from 10 km to 100 km. In other words, instead of an r -2 -dependence (where r is the range, i.e. the distance between the radar and the meteorological target), we find an apparent reduction proportional to r -3 . A similar procedure is used to analyze the dependence of the TRMM radar, using the adjusted data of the radar at ground level for reference. We have to add around 3dB to the measured reflectivity, when increasing the distance from close to Nadir (10 km) to the edge of the swath (100 km). In other words, instead of a constant sensitivity over the swath of the satellite, we find a reduction of sensitivity with the range, proportional to r -0.3 . Secondly, the paper illustrates possible causes of the systematic range dependence of both radars. The old, dominant cause - overshooting of precipitation - is already vastly discussed in literature. We describe the variability of the precipitation with three case studies. The variability of the precipitation is difficult to quantify. It is concluded to be responsible for the variable range dependence and for many disillusions with radar.

Subsidence monitoring within the Athens Basin (Greece) using space radar interferometric techniques

Abstract The application of conventional SAR Interferometry (InSAR) together with the two techniques of subcentimeter accuracy, the Stacking and the Permanent Scatterers (PS) Interferometry, were used to study the ground deformation in the broader area of Athens for the period 1992 to 2002. Using the Stacking interferometric method, 55 ERS-1&amp;2 SAR scenes, between 1992 and 2002, were acquired producing 264 differential interferograms. Among these only 60 were finally selected as fulfilling certain criteria. The co-seismic deformation associated with the Athens Earthquake (Mw = 5.9, September 7, 1999) was excluded from the analytical procedure in an attempt to present results of only aseismic character. In total ground subsidence results of about 12 mm in the southern suburbs of Athens, but higher value of about 40 mm in the northern ones for the period 1992–2002. Based on the PS technique, a precise average annual deformation rate-map was generated for the period 1992–1999, ending just before the Athens earthquake event. Both circular and elongated-shape areas of subsidence are recognizable especially in the northern part of the Athens Basin (3–4 mm/yr), as well as at its southern part (1–3 mm/yr). In addition, a rate of 2–3 mm/yr is also yielded for some part of the Athens city center. Subsidence rates of 1–2 mm/yr are measured at the western part of the basin over an area of old mining activities, and around the newly built Syntagma Metro Station. The correlation of the observed deformation patterns with respect to the spatial distribution of water pumping, older mining activities, metro line tunneling and other local geological parameters is examined and discussed.

Independent Evaluation of the Ability of Spaceborne Radar and Lidar to Retrieve the Microphysical and Radiative Properties of Ice Clouds

Abstract The combination of radar and lidar in space offers the unique potential to retrieve vertical profiles of ice water content and particle size globally, and two algorithms developed recently claim to have overcome the principal difficulty with this approach—that of correcting the lidar signal for extinction. In this paper “blind tests” of these algorithms are carried out, using realistic 94-GHz radar and 355-nm lidar backscatter profiles simulated from aircraft-measured size spectra, and including the effects of molecular scattering, multiple scattering, and instrument noise. Radiation calculations are performed on the true and retrieved microphysical profiles to estimate the accuracy with which radiative flux profiles could be inferred remotely. It is found that the visible extinction profile can be retrieved independent of assumptions on the nature of the size distribution, the habit of the particles, the mean extinction-to-backscatter ratio, or errors in instrument calibration. Local errors in retrieved extinction can occur in proportion to local fluctuations in the extinction-to-backscatter ratio, but down to 400 m above the height of the lowest lidar return, optical depth is typically retrieved to better than 0.2. Retrieval uncertainties are greater at the far end of the profile, and errors in total optical depth can exceed 1, which changes the shortwave radiative effect of the cloud by around 20%. Longwave fluxes are much less sensitive to errors in total optical depth, and may generally be calculated to better than 2 W m−2 throughout the profile. It is important for retrieval algorithms to account for the effects of lidar multiple scattering, because if this is neglected, then optical depth is underestimated by approximately 35%, resulting in cloud radiative effects being underestimated by around 30% in the shortwave and 15% in the longwave. Unlike the extinction coefficient, the inferred ice water content and particle size can vary by 30%, depending on the assumed mass–size relationship (a problem common to all remote retrieval algorithms). However, radiative fluxes are almost completely determined by the extinction profile, and if this is correct, then errors in these other parameters have only a small effect in the shortwave (around 6%, compared to that of clear sky) and a negligible effect in the longwave.

Quality control algorithms for rainfall measurements

One of the basic requirements for a scientific use of rain data from raingauges, ground and space radars is data quality control. Rain data could be used more intensively in many fields of activity (meteorology, hydrology, etc.), if the achievable data quality could be improved. This depends on the available data quality delivered by the measuring devices and the data quality enhancement procedures. To get an overview of the existing algorithms a literature review and literature pool have been produced. The diverse algorithms have been evaluated to meet VOLTAIRE objectives and sorted in different groups. To test the chosen algorithms an algorithm pool has been established, where the software is collected. A large part of this work presented here is implemented in the scope of the EU-project VOLTAIRE ( Validati on of mu ltisensors precipit ation fields and numerical modeling in Mediter ran ean test sites).

Global and Local Precipitation Measurements by Radar

The detection and measurement of precipitation by radar has been pursued since its introduction as a meteorological tool. The main advantage of using radar for precipitation estimation is that measurements can be made over large areas, with either fairly high temporal and spatial resolution or extensive spatial coverage (about 10 000 km2 for ground-based radars and an order of magnitude more for space-based radars). To sample the area covered by a typical ground-based radar, substituting each radar spatial sample with a rain gauge, would require about a quarter-million gauges. Using a similar analogy to space radars, nearly one-half-million gauges would be required per orbit. Since the radar transmitter and receiver normally use the same antenna (monostatic operation), the measurements are sent to a central location at the speed of light by “natural wireless networks.” In addition, radars can provide fairly rapid updates of the three-dimensional structure of precipitation. Because of these advantages, radar measurements of precipitation have enjoyed widespread use for meteorological applications, independent of the accuracy or the type of algorithm used to derive precipitation estimates.

Methodology for Aligning and Comparing Spaceborne Radar and Ground-Based Radar Observations

Direct intercomparisons between space- and ground-based radar measurements can be a challenging task. Differences in viewing aspects between space and earth observations, propagation paths, frequencies, resolution volume size, and time synchronization mismatch between space- and ground-based observations can contribute to direct point-by-point intercomparison errors. This problem is further complicated by geometric distortions induced upon the space-based observations caused by the movements and attitude perturbations of the spacecraft itself. A method to align measurements between these two systems is presented. The method makes use of variable resolution volume matching between the two systems and presents a technique to minimize the effects of potential geometric distortion in space radar observations relative to ground measurements. Applications of the method are shown that make a comparison between the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) reflectivity measurements and ground radar. A method has been developed that aligns space radar (SR) data with ground radar (GR) observations for the purpose of cross validation of the two systems. Accurate and precise alignment of observations requires meticulous attention to detail that is important in minimizing measurement uncertainties between the two systems so that quantitative analysis of bias, attenuation, and characterization of the microphysical properties of the atmospheric medium can be made along space radar beams via ground-based measurements. Reconciliation of the difference in resolution volumes between the two systems, due to size and orientation, and the need to align ground and space radar points have been previously investigated: Bolen and Chandrasekar (1999, 2000a) used a correlation-shift procedure and a momentbased technique, respectively, for final alignment of points. The work of Bolen and Chandrasekar was motivated by the need to evaluate attenuation correction in space radar echo returns. An independent procedure, motivated by the need to match reflectivity, was presented by Anagnastou et al. (2001), who provided a comprehensive study comparing space radar with ground radar reflectivity measurements. The method presented in this paper uses a variable volume matching scheme with a polynomial technique for alignment of SR and GR points. A theoretical modeling of potential