Pub Date : 2005-05-09DOI: 10.1109/RADAR.2005.1435853
I. Gladkova, D. Chebanov
For uniform frequency stepped pulse trains, there can be undesirable peaks of the autocorrelation function, known as "grating lobes". In this paper we address this issue, using an approach, which allows us to suppress grating lobes below a desired threshold level in the case of appropriately chosen, stepped frequency waveforms, i.e., sequences of narrowband pulses that span the desired bandwidth. We discuss in detail how to choose relevant parameters in order to produce such waveforms with small grating lobes, and give examples of waveforms with small overlap ratio. We also discuss the issue of high sidelobes in the vicinity of the main lobe, which are inevitable in a train of LFM waveforms, and show that it is possible to suppress these, as well as the grating lobes, by means of phase modulation.
{"title":"Suppression of grating lobes in stepped-frequency train","authors":"I. Gladkova, D. Chebanov","doi":"10.1109/RADAR.2005.1435853","DOIUrl":"https://doi.org/10.1109/RADAR.2005.1435853","url":null,"abstract":"For uniform frequency stepped pulse trains, there can be undesirable peaks of the autocorrelation function, known as \"grating lobes\". In this paper we address this issue, using an approach, which allows us to suppress grating lobes below a desired threshold level in the case of appropriately chosen, stepped frequency waveforms, i.e., sequences of narrowband pulses that span the desired bandwidth. We discuss in detail how to choose relevant parameters in order to produce such waveforms with small grating lobes, and give examples of waveforms with small overlap ratio. We also discuss the issue of high sidelobes in the vicinity of the main lobe, which are inevitable in a train of LFM waveforms, and show that it is possible to suppress these, as well as the grating lobes, by means of phase modulation.","PeriodicalId":444253,"journal":{"name":"IEEE International Radar Conference, 2005.","volume":"119 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127606182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-05-09DOI: 10.1109/RADAR.2005.1435866
R.M. Cooper
In an airborne radar, clutter returns from stationary objects undergo a phase shift due to the relative motion of the airborne platform. For a low PRF radar, this phase shift can place the main beam clutter return at virtually any frequency within the clutter Doppler spectrum. Typically, a phase shift or frequency shift is applied to these returns in order to place them in the 0 Hz Doppler filter within the radar signal processor. This phase or frequency shift can be applied either on transmit or receive, and is commonly called the TACCAR shift. The term TACCAR is an acronym for time averaged clutter coherent airborne radar, and the implication of this term is that an average of pulse-to-pulse clutter phase in a coherent radar results in a measure of the main lobe Doppler frequency. In a PRI staggered STAP radar, this TACCAR shift may no longer be necessary, since the STAP solution places the null in the Doppler passband as appropriate to optimize clutter cancellation. However, given that an airborne radar usually has size and weight constraints that can result in limited on-board processing resources, a TACCAR shift may result in fewer processing operations needed to converge on a STAP solution. If this potential processing savings applies, then a TACCAR shift would still be desirable.
{"title":"The impact of TACCAR on STAP algorithm convergence","authors":"R.M. Cooper","doi":"10.1109/RADAR.2005.1435866","DOIUrl":"https://doi.org/10.1109/RADAR.2005.1435866","url":null,"abstract":"In an airborne radar, clutter returns from stationary objects undergo a phase shift due to the relative motion of the airborne platform. For a low PRF radar, this phase shift can place the main beam clutter return at virtually any frequency within the clutter Doppler spectrum. Typically, a phase shift or frequency shift is applied to these returns in order to place them in the 0 Hz Doppler filter within the radar signal processor. This phase or frequency shift can be applied either on transmit or receive, and is commonly called the TACCAR shift. The term TACCAR is an acronym for time averaged clutter coherent airborne radar, and the implication of this term is that an average of pulse-to-pulse clutter phase in a coherent radar results in a measure of the main lobe Doppler frequency. In a PRI staggered STAP radar, this TACCAR shift may no longer be necessary, since the STAP solution places the null in the Doppler passband as appropriate to optimize clutter cancellation. However, given that an airborne radar usually has size and weight constraints that can result in limited on-board processing resources, a TACCAR shift may result in fewer processing operations needed to converge on a STAP solution. If this potential processing savings applies, then a TACCAR shift would still be desirable.","PeriodicalId":444253,"journal":{"name":"IEEE International Radar Conference, 2005.","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121454938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-05-09DOI: 10.1109/RADAR.2005.1435852
J. Gray
In order to understand the problems intractable problems nature presents us, we are forced to make simplifications till we arrive at simple analytical models that we are capable of understanding. Such canonical models are rare, but useful as tools for constructing more realistic models that we can use analyze nature. The class of analytical models for clutter analysis limited to those that consist of various amplitude models with the phase noise assumed to have a probability density function that is uniformly distributed. These analytical models can be extended by relaxing the assumption of uniform phase noise to phase noise with non-uniform distributions. It is shown how to determine the probability density function for these non-uniform distributions in general and then the method is illustrated with such distributions as Gaussian, Laplacian, and Chi-squared. This enables one to determine the probability density functions of the individual components of clutter model such as x/sub t/ = v/sub t/ cos(/spl Phi//sub c/). Using the rule for determining the products of distributions, we show that the functional form for x/sub t/ is reduced to evaluating integrals that reduce to elliptical functions. Once the functional form has been determined, it is easy to determine the moments of the PDF and hence completely characterize its statistics.
{"title":"A common basis for analytical clutter representations","authors":"J. Gray","doi":"10.1109/RADAR.2005.1435852","DOIUrl":"https://doi.org/10.1109/RADAR.2005.1435852","url":null,"abstract":"In order to understand the problems intractable problems nature presents us, we are forced to make simplifications till we arrive at simple analytical models that we are capable of understanding. Such canonical models are rare, but useful as tools for constructing more realistic models that we can use analyze nature. The class of analytical models for clutter analysis limited to those that consist of various amplitude models with the phase noise assumed to have a probability density function that is uniformly distributed. These analytical models can be extended by relaxing the assumption of uniform phase noise to phase noise with non-uniform distributions. It is shown how to determine the probability density function for these non-uniform distributions in general and then the method is illustrated with such distributions as Gaussian, Laplacian, and Chi-squared. This enables one to determine the probability density functions of the individual components of clutter model such as x/sub t/ = v/sub t/ cos(/spl Phi//sub c/). Using the rule for determining the products of distributions, we show that the functional form for x/sub t/ is reduced to evaluating integrals that reduce to elliptical functions. Once the functional form has been determined, it is easy to determine the moments of the PDF and hence completely characterize its statistics.","PeriodicalId":444253,"journal":{"name":"IEEE International Radar Conference, 2005.","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128475598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-05-09DOI: 10.1109/RADAR.2005.1435958
A. Jaramillo, J. Portas, G. de Miguel Vela, J. Corredera
In this proposal, a real time bias estimation system for an airport surveillance data fusion system is presented. This bias estimation system is divided in two main parts. The first part estimates SMR bias terms, taking advantage of the knowledge of the airport map, which is useful because aircraft usually follow the axis of airport taxiways. The other part makes use of SMR corrected measures, which can be assumed to be unbiased. Using them, bias estimators for other important surface surveillance sensors are defined. These estimators are based on processing differences of measurement taken from each sensor and from the SMR. As simulation results show, if the sensor error models are precise enough, both estimations converge to the real bias values, and therefore unbiased measures may be obtained. These unbiased measurements should be provided to the fusion system, in order to enhance tracking performance. These estimation processes do not represent an important computer load increase for the data fusion system. The performance improvement in tracking is also presented.
{"title":"Airport based bias estimation of surface movement radars","authors":"A. Jaramillo, J. Portas, G. de Miguel Vela, J. Corredera","doi":"10.1109/RADAR.2005.1435958","DOIUrl":"https://doi.org/10.1109/RADAR.2005.1435958","url":null,"abstract":"In this proposal, a real time bias estimation system for an airport surveillance data fusion system is presented. This bias estimation system is divided in two main parts. The first part estimates SMR bias terms, taking advantage of the knowledge of the airport map, which is useful because aircraft usually follow the axis of airport taxiways. The other part makes use of SMR corrected measures, which can be assumed to be unbiased. Using them, bias estimators for other important surface surveillance sensors are defined. These estimators are based on processing differences of measurement taken from each sensor and from the SMR. As simulation results show, if the sensor error models are precise enough, both estimations converge to the real bias values, and therefore unbiased measures may be obtained. These unbiased measurements should be provided to the fusion system, in order to enhance tracking performance. These estimation processes do not represent an important computer load increase for the data fusion system. The performance improvement in tracking is also presented.","PeriodicalId":444253,"journal":{"name":"IEEE International Radar Conference, 2005.","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116658269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-05-09DOI: 10.1109/RADAR.2005.1435943
G. Kravaritis, B. Mulgrew
This paper studies the problem of ground tracking using a-priori information about the road structure. It presents an efficient variation of the variable structure multiple model particle filter, in which the number of active particles is allowed to vary. The proposed technique decreases the algorithmic computational intensity and can be generalized and used in various multi-model particle filters.
{"title":"Ground tracking using a variable structure multiple model particle filter with varying number of particles","authors":"G. Kravaritis, B. Mulgrew","doi":"10.1109/RADAR.2005.1435943","DOIUrl":"https://doi.org/10.1109/RADAR.2005.1435943","url":null,"abstract":"This paper studies the problem of ground tracking using a-priori information about the road structure. It presents an efficient variation of the variable structure multiple model particle filter, in which the number of active particles is allowed to vary. The proposed technique decreases the algorithmic computational intensity and can be generalized and used in various multi-model particle filters.","PeriodicalId":444253,"journal":{"name":"IEEE International Radar Conference, 2005.","volume":"131 S3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114100504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-05-09DOI: 10.1109/RADAR.2005.1435930
L. Yongxiang, L. Xiang, Zhu Zhaowen
Radar imaging is an important way to obtain the structural information of target. Based on the geometrical projection of scattering center on the line of radar sight, the principle of reconstructing scattering centers' 3-D distribution based on multi-aspect measures is provided in this paper. After analyzing the characteristic differences between true and false scattering centers, the multiple elastic modules (MEM) is introduced to perform scattering centers association and radar target imaging. The experiments are developed with simulated and experimental data, and experimental results show the feasibility and validity of proposed approach.
{"title":"Scattering centers association and radar imaging based on multi-aspect measures","authors":"L. Yongxiang, L. Xiang, Zhu Zhaowen","doi":"10.1109/RADAR.2005.1435930","DOIUrl":"https://doi.org/10.1109/RADAR.2005.1435930","url":null,"abstract":"Radar imaging is an important way to obtain the structural information of target. Based on the geometrical projection of scattering center on the line of radar sight, the principle of reconstructing scattering centers' 3-D distribution based on multi-aspect measures is provided in this paper. After analyzing the characteristic differences between true and false scattering centers, the multiple elastic modules (MEM) is introduced to perform scattering centers association and radar target imaging. The experiments are developed with simulated and experimental data, and experimental results show the feasibility and validity of proposed approach.","PeriodicalId":444253,"journal":{"name":"IEEE International Radar Conference, 2005.","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114430142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-05-09DOI: 10.1109/RADAR.2005.1435918
M. Khanpour-Ardestani, R. Adve, M. Wicks
Several space-time adaptive processing algorithms have been proposed to detect weak targets in the presence of strong interference, especially clutter and jamming. Except for displaced phase center array (DPCA) processing, radar signal processing algorithms ignore the fact that the location of the clutter ridge in angle-Doppler space is known, given the platform speed and direction. This paper introduces our attempt to exploit this a priori knowledge in conjunction with the joint domain localized processing algorithm. Using a two-dimensional filter, clutter is rejected in a first, non-adaptive stage, followed by adaptive processing in the angle-Doppler domain.
{"title":"Pre-filtering for clutter rejection in beamspace STAP","authors":"M. Khanpour-Ardestani, R. Adve, M. Wicks","doi":"10.1109/RADAR.2005.1435918","DOIUrl":"https://doi.org/10.1109/RADAR.2005.1435918","url":null,"abstract":"Several space-time adaptive processing algorithms have been proposed to detect weak targets in the presence of strong interference, especially clutter and jamming. Except for displaced phase center array (DPCA) processing, radar signal processing algorithms ignore the fact that the location of the clutter ridge in angle-Doppler space is known, given the platform speed and direction. This paper introduces our attempt to exploit this a priori knowledge in conjunction with the joint domain localized processing algorithm. Using a two-dimensional filter, clutter is rejected in a first, non-adaptive stage, followed by adaptive processing in the angle-Doppler domain.","PeriodicalId":444253,"journal":{"name":"IEEE International Radar Conference, 2005.","volume":"222 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127166342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-05-09DOI: 10.1109/RADAR.2005.1435793
P. Corbell, M. Temple, T. Hale, W. Baker, M. Rangaswamy
This work investigates the impact of interpulse (pulse-to-pulse) transmit pattern diversity on space-time adaptive processing (STAP) performance. It is shown that varying interpulse transmit characteristics within a coherent processing interval (CPI) can reshape the clutter power spectrum, resulting in an interference whitening effect. For conducting comparative analysis with non-adaptive transmit techniques, a commonly used clutter model is extended to effectively incorporate interpulse pattern diversity effects. The work shows promise for achieving better minimum discernable velocity (MDV) using phased array transmits weights derived from optimum STAP weights (known covariance). Pattern diversity effectively redistributes clutter energy away from the clutter ridge. For the unambiguous clutter case, the proposed adaptive transmit technique shows promise for improving MDV at the clutter ridge peak.
{"title":"Performance improvement using interpulse pattern diversity with space-time adaptive processing","authors":"P. Corbell, M. Temple, T. Hale, W. Baker, M. Rangaswamy","doi":"10.1109/RADAR.2005.1435793","DOIUrl":"https://doi.org/10.1109/RADAR.2005.1435793","url":null,"abstract":"This work investigates the impact of interpulse (pulse-to-pulse) transmit pattern diversity on space-time adaptive processing (STAP) performance. It is shown that varying interpulse transmit characteristics within a coherent processing interval (CPI) can reshape the clutter power spectrum, resulting in an interference whitening effect. For conducting comparative analysis with non-adaptive transmit techniques, a commonly used clutter model is extended to effectively incorporate interpulse pattern diversity effects. The work shows promise for achieving better minimum discernable velocity (MDV) using phased array transmits weights derived from optimum STAP weights (known covariance). Pattern diversity effectively redistributes clutter energy away from the clutter ridge. For the unambiguous clutter case, the proposed adaptive transmit technique shows promise for improving MDV at the clutter ridge peak.","PeriodicalId":444253,"journal":{"name":"IEEE International Radar Conference, 2005.","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121997342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-05-09DOI: 10.1109/RADAR.2005.1435820
A. Nelander, S. Bjorklund
Terrain scattered interference mitigation methods for airborne radar have been described in previous papers and deconvolution methods for interference suppression have been proposed. This paper describes a refined method for terrain scattered interference mitigation and investigates performance for different conditions and limitations. An important part of the method is a threshold function to enable least squares estimation of the multipath impulse response. Least squares estimation can be applied if the impulse response is time limited or if a limited number of impulse response coefficients are required for sufficient interference suppression. The impulse response estimation can be performed either before or within the coherent processing interval. It is assumed that the direct path signal can be accurately estimated without strong multipath errors. Small relative Doppler shift errors are required between the direct path and the terrain scattered paths. Several strong jamming signal sources cannot be resolved and suppressed. Receiver blocking gives errors in the impulse response estimate and jamming signal residues in the main beam signal. Clutter signals might have to be suppressed to get accurate impulse response estimates. Bandwidth effects must be considered to get numerical stability in the inverse filtering and deconvolution operations. The refined method can suppress interference down to the receiver noise level in simple terrain scattering scenarios.
{"title":"Refined method for terrain scattered interference mitigation","authors":"A. Nelander, S. Bjorklund","doi":"10.1109/RADAR.2005.1435820","DOIUrl":"https://doi.org/10.1109/RADAR.2005.1435820","url":null,"abstract":"Terrain scattered interference mitigation methods for airborne radar have been described in previous papers and deconvolution methods for interference suppression have been proposed. This paper describes a refined method for terrain scattered interference mitigation and investigates performance for different conditions and limitations. An important part of the method is a threshold function to enable least squares estimation of the multipath impulse response. Least squares estimation can be applied if the impulse response is time limited or if a limited number of impulse response coefficients are required for sufficient interference suppression. The impulse response estimation can be performed either before or within the coherent processing interval. It is assumed that the direct path signal can be accurately estimated without strong multipath errors. Small relative Doppler shift errors are required between the direct path and the terrain scattered paths. Several strong jamming signal sources cannot be resolved and suppressed. Receiver blocking gives errors in the impulse response estimate and jamming signal residues in the main beam signal. Clutter signals might have to be suppressed to get accurate impulse response estimates. Bandwidth effects must be considered to get numerical stability in the inverse filtering and deconvolution operations. The refined method can suppress interference down to the receiver noise level in simple terrain scattering scenarios.","PeriodicalId":444253,"journal":{"name":"IEEE International Radar Conference, 2005.","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126711691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-05-09DOI: 10.1109/RADAR.2005.1435871
Rubin G, T. Carney, J. Floyd, H. Henderson, J. Mitchell, A. Siegel, J. Vila
System Planning Corporation (SPC) fielded an airborne measurement system to observe the reentry of the Ariane 5 launch vehicle's main cryogenic stage (EPC). On March 2, 2004, the system acquired both optical images and 50-MHz radar data as the EPC reentered the atmosphere. This paper describes SPC's radar system, provides an overview of the radar data, and discusses some of the more interesting ionization-related phenomena observed as the EPC passed through the upper atmosphere.
{"title":"Airborne radar measurements of the reentry of the Ariane 5 EPC","authors":"Rubin G, T. Carney, J. Floyd, H. Henderson, J. Mitchell, A. Siegel, J. Vila","doi":"10.1109/RADAR.2005.1435871","DOIUrl":"https://doi.org/10.1109/RADAR.2005.1435871","url":null,"abstract":"System Planning Corporation (SPC) fielded an airborne measurement system to observe the reentry of the Ariane 5 launch vehicle's main cryogenic stage (EPC). On March 2, 2004, the system acquired both optical images and 50-MHz radar data as the EPC reentered the atmosphere. This paper describes SPC's radar system, provides an overview of the radar data, and discusses some of the more interesting ionization-related phenomena observed as the EPC passed through the upper atmosphere.","PeriodicalId":444253,"journal":{"name":"IEEE International Radar Conference, 2005.","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126816658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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