Climatological average daily high (blue) and low (brown) relative humidity for Albuquerque, New M... more Climatological average daily high (blue) and low (brown) relative humidity for Albuquerque, New Mexico (Top) and Dayton, Ohio (Bottom). Shaded regions indicate 25 th to 75 th percentile (inner band) and 10 th to 90 th percentile (outer band).
A new method for measuring the intensity of turbulence in the planetary boundary layer was invest... more A new method for measuring the intensity of turbulence in the planetary boundary layer was investigated, and showed high correlation with measurements from weather radar. This method takes measurements of cell phone signal strength and uses scintillation in the signal to estimate the strength of local turbulence. Using cell phone signals provides unique measurement advantages: it is a passive measurement method, it is not strongly affected by precipitation, and one device can potentially measure several paths at once. The measurements were taken using an Android cell phone running a custom built application. Turbulence was quantified using the index of refraction structure constant, C 2 n , which is related to the amount of energy in the turbulence. The goal of the investigation was to determine if C 2 n values calculated from the cell phone signal power show a relationship to C 2 n measurements taken over the communication path. Based on the strength of the agreement between measurements made by the new method and those done with an established method, it is concluded that turbulence changes can be measured using cell phone signals. The correlation of C 2 n values measured using the two methods was calculated for 42 periods of about 12 hours each. Correlation varied over the 42 periods, but was high and statistically significant in most measurements. The mean absolute value of peak Pearson correlation was 0.5865 with a mean p-value of 0.0251. Standard deviations of these values are 0.2311 and 0.0264, respectively. The standard deviations are relatively high due to two outliers where the correlation was particularly low. This thesis presents the experimental work that was done, the results of the work, the author's interpretation of the results, and suggestions for continued research.
Paper describes NEXRAD observations of vertical Cn2 profiles which are used to derive vertical gr... more Paper describes NEXRAD observations of vertical Cn2 profiles which are used to derive vertical gradients of passive additives potential temperature and potential vapor pressure. These gradients can be used to estimate Cn2 for optical systems.
Paper describes a novel method for measuring smaller-scale atmospheric turbulence on an arbitrary... more Paper describes a novel method for measuring smaller-scale atmospheric turbulence on an arbitrary path. This method permits ability to remotely measure and range the intensity of turbulence and associated refractive structure constant at any wavelength.
Paper links dynamics of near-surface aerosol particles with meteorological observations as well a... more Paper links dynamics of near-surface aerosol particles with meteorological observations as well as derived optical turbulence during a solar eclipse while suggesting causes for the unanticipated direct correlation of turbulence fluctuations and aerosol particle counts.
ABSTRACT A novel method for measuring the structure constant of the atmospheric turbulence on an ... more ABSTRACT A novel method for measuring the structure constant of the atmospheric turbulence on an arbitrary path has recently been demonstrated by the Air Force Institute of Technology (AFIT). This method provides a unique ability to remotely measure the intensity of turbulence, which is important for predicting beam spread, wander, and scintillation effects on High Energy Laser (HEL) propagation. Because this is a new technique, estimating C-n(2) using radar is a complicated and time consuming process. This paper presents a new software program which is being developed to automate the calculation of C-n(2) over an arbitrary path. The program takes regional National Weather Service NEXRAD radar reflectivity measurements and extracts data for the path of interest. These reflectivity measurements are then used to estimate C-n(2) over the path. The program uses the Radar Software Library (RSL) produced by the Tropical Rainfall Measuring Mission (TRMM) at the NASA/Goddard Flight Center. RSL provides support for nearly all formats of weather radar data. The particular challenge to extracting data is in determining which data bins the path passes through. Due to variations in radar systems and measurement conditions, the RSL produces data grids that are not consistent in geometry or completeness. The C-n(2) program adapts to the varying geometries of each radar image. Automation of the process allows for fast estimation of C-n(2) and supports a goal of real-time remote turbulence measurement. Recently, this software was used to create comparison data for RF scintillation measurements. In this task it performed well, extracting thousands of measurements in only a few minutes.
The index of refraction structure constant, C 2 n indicates how strongly the index of refraction ... more The index of refraction structure constant, C 2 n indicates how strongly the index of refraction varies in a region of the atmosphere. These variations usually arise through turbulent motions, creating an inhomogeneous distribution of species, density, temperature and pressure. Because the index of refraction also depends on wavelength, the measured value of C 2 n will depend on wavelength. This C 2 n difference generally becomes more pronounced as the difference in wavelength increases. This paper describes a technique for converting between measurements of C 2 n at different wavelengths, and gives an example for converting from centimeter to visible and near IR wavelengths.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Jul 1, 2015
Recently, satellite-based systems have been introduced that utilize angle-of-arrival (AOA) measur... more Recently, satellite-based systems have been introduced that utilize angle-of-arrival (AOA) measurements to geo-locate objects of interest. In the previous work, we considered the application of nonlinear optimization to AoA-based geolocation to these systems. This previous work, however, assumed that all noise sources were independent. In the case of fast-moving objects, however, there is a significant source of error due to the propagation time inherent in satellite-based observation of objects due to the difference between the location of the object when it is observed by a satellite, and the location of the object when it emitted the signal that is being measured. This introduces a systematic error into the system that cannot be resolved by the system proposed by Burchett et al. In this paper, we extend our prior work to account for the time-delay inherent in satellite-based geolocation systems, making this system accurate for fast-movers as well as fixed or slow-moving objects. Results demonstrating significant improvement in geolocation performance both in terms of accuracy and estimated error bounds are presented.
This paper addresses the problem of object localization using only angle-of-arrival (AoA) data fr... more This paper addresses the problem of object localization using only angle-of-arrival (AoA) data from satellites. Traditionally, this is performed by a triangulation algorithm (TA) that minimizes the distances between the estimated object location to all lines-of-sight representing measurements of the object. However, when observing objects from satellites, the differences in distance from each satellite to the object can be significant. The error this induces in measurements from farther-distant satellites results in an inordinate impact on the geo-location error. To overcome this problem, we introduce a non-linear optimization (NLO) approach that models the measurement error at each satellites as a probability density function. By finding the most-probable geo-location of the object, this systematic error is eliminated. We found that the NLO provides a more accurate estimate of the object's location than the TA in 93% of instances. In addition, we analyze the uncertainty estimates generated by both the TA and NLO approaches. The NLO estimates of uncertainty are also considerably more accurate than the TA estimates in all cases.
Three approaches are applied to reconstruction of an object image from radar data collected in an... more Three approaches are applied to reconstruction of an object image from radar data collected in an Inverse-SAR (moving object, fixed radar location) geometry. These approaches attempt to reconstruct the object motion from the radar data alone. While all three approaches work with simulated data, application to this real-world data did not produce a recognizable image. Presented is a short description and comparison of the three methods, and what difficulties were found when applying these motion estimation algorithms to the real data set. The data that were used had been pre-processed into a time series of brightness-vs-range profiles. These range profiles were provided without any further information about the object or radar, providing a truly `blind' test.
In this paper, we describe the current stage of our design for a large-scale aerostat communicati... more In this paper, we describe the current stage of our design for a large-scale aerostat communication system and the future developments we anticipate. Aerostats provide many benefits that are not offered by other means. To take full advantage of these benefits, data must be streamed to a ground station at a very high rate. We have proposed a Multiple-Input Multiple-Output (MIMO) system with a phased array at the receiving end to fulfill this requirement. The phased array uses beam-forming to allow for individual transmitting elements to be resolved. Our current design and results are given, along with an analysis. In addition, we describe a scaled test-bed we have planned using Wireless Open-Access Research Platforms (WARP) from Rice University.
This paper describes the design and analysis of a 24-element dipole array which serves as an opti... more This paper describes the design and analysis of a 24-element dipole array which serves as an optimized feed structure for a 150-meter cruciform reflector antenna for satellite communications in the 1–2 GHz range. The radiation pattern for this structure was calculated using a Method of Moments based computational electromagnetics code yielding an overall 47 dBi reflector gain. The effect of incorporating this optimized feed is an overall performance improvement on an initial cruciform reflector antenna design by minimizing spillover and undesirable side lobes. Performance versus size-and-weight tradeoffs are discussed as is a detailed description of the cruciform antenna's mechanical design and its resultant RF characteristics.
Optical Turbulence estimates made from Numerical Weather Prediction using a modified approach bas... more Optical Turbulence estimates made from Numerical Weather Prediction using a modified approach based on Ciddor’s refractivity parametrization with temperature and hydrometer contributions is shown to predict measured 880nm scintillation better than a standard approach.
The paper describes a project to determine and model a performance baseline for a satellite commu... more The paper describes a project to determine and model a performance baseline for a satellite communication system concept. It is expected to improve communication capabilities while maintaining low operational cost using a newly proposed antenna system. The system will consist of a large, stationary spherical reflector fed by multiple, steerable feeds. The size of the reflector will improve signal gain and resolvability of individual signals. This paper will use a derivation of far field solutions for spherical shaped current sources. These solutions will be used to look at the interaction between current distributions on the reflector and the resulting EM field distributions. This will allow for estimation of the beam quality of the system as a function of the reflector geometry, and feed illumination. Other methods may be applied as needed to determine the feed systems. This may include ray-tracing code for reflector based systems, and numerical simulations for phased array systems.
2016 IEEE National Aerospace and Electronics Conference (NAECON) and Ohio Innovation Summit (OIS), 2016
Vision-based automated aerial refueling requires a relative positioning solution capable of real ... more Vision-based automated aerial refueling requires a relative positioning solution capable of real time updates between the tanker and receiver. The processing time required for modern approaches are dominated by an iterative point alignment phase. This work presents an accelerated alignment variant which utilizes parallelization and Delaunay Triangulation to achieve real time estimates.
Paper links dynamics of near-surface aerosol particles with meteorological observations as well a... more Paper links dynamics of near-surface aerosol particles with meteorological observations as well as derived optical turbulence during a solar eclipse while suggesting causes for the unanticipated direct correlation of turbulence fluctuations and aerosol particle counts.
This paper describes the design and analysis of a 24-element dipole array which serves as an opti... more This paper describes the design and analysis of a 24-element dipole array which serves as an optimized feed structure for a 150-meter cruciform reflector antenna for satellite communications in the 1–2 GHz range. The radiation pattern for this structure was calculated using a Method of Moments based computational electromagnetics code yielding an overall 47 dBi reflector gain. The effect of incorporating this optimized feed is an overall performance improvement on an initial cruciform reflector antenna design by minimizing spillover and undesirable side lobes. Performance versus size-and-weight tradeoffs are discussed as is a detailed description of the cruciform antenna's mechanical design and its resultant RF characteristics.
Optical Turbulence estimates made from Numerical Weather Prediction using a modified approach bas... more Optical Turbulence estimates made from Numerical Weather Prediction using a modified approach based on Ciddor’s refractivity parametrization with temperature and hydrometer contributions is shown to predict measured 880nm scintillation better than a standard approach.
Climatological average daily high (blue) and low (brown) relative humidity for Albuquerque, New M... more Climatological average daily high (blue) and low (brown) relative humidity for Albuquerque, New Mexico (Top) and Dayton, Ohio (Bottom). Shaded regions indicate 25 th to 75 th percentile (inner band) and 10 th to 90 th percentile (outer band).
A new method for measuring the intensity of turbulence in the planetary boundary layer was invest... more A new method for measuring the intensity of turbulence in the planetary boundary layer was investigated, and showed high correlation with measurements from weather radar. This method takes measurements of cell phone signal strength and uses scintillation in the signal to estimate the strength of local turbulence. Using cell phone signals provides unique measurement advantages: it is a passive measurement method, it is not strongly affected by precipitation, and one device can potentially measure several paths at once. The measurements were taken using an Android cell phone running a custom built application. Turbulence was quantified using the index of refraction structure constant, C 2 n , which is related to the amount of energy in the turbulence. The goal of the investigation was to determine if C 2 n values calculated from the cell phone signal power show a relationship to C 2 n measurements taken over the communication path. Based on the strength of the agreement between measurements made by the new method and those done with an established method, it is concluded that turbulence changes can be measured using cell phone signals. The correlation of C 2 n values measured using the two methods was calculated for 42 periods of about 12 hours each. Correlation varied over the 42 periods, but was high and statistically significant in most measurements. The mean absolute value of peak Pearson correlation was 0.5865 with a mean p-value of 0.0251. Standard deviations of these values are 0.2311 and 0.0264, respectively. The standard deviations are relatively high due to two outliers where the correlation was particularly low. This thesis presents the experimental work that was done, the results of the work, the author's interpretation of the results, and suggestions for continued research.
Paper describes NEXRAD observations of vertical Cn2 profiles which are used to derive vertical gr... more Paper describes NEXRAD observations of vertical Cn2 profiles which are used to derive vertical gradients of passive additives potential temperature and potential vapor pressure. These gradients can be used to estimate Cn2 for optical systems.
Paper describes a novel method for measuring smaller-scale atmospheric turbulence on an arbitrary... more Paper describes a novel method for measuring smaller-scale atmospheric turbulence on an arbitrary path. This method permits ability to remotely measure and range the intensity of turbulence and associated refractive structure constant at any wavelength.
Paper links dynamics of near-surface aerosol particles with meteorological observations as well a... more Paper links dynamics of near-surface aerosol particles with meteorological observations as well as derived optical turbulence during a solar eclipse while suggesting causes for the unanticipated direct correlation of turbulence fluctuations and aerosol particle counts.
ABSTRACT A novel method for measuring the structure constant of the atmospheric turbulence on an ... more ABSTRACT A novel method for measuring the structure constant of the atmospheric turbulence on an arbitrary path has recently been demonstrated by the Air Force Institute of Technology (AFIT). This method provides a unique ability to remotely measure the intensity of turbulence, which is important for predicting beam spread, wander, and scintillation effects on High Energy Laser (HEL) propagation. Because this is a new technique, estimating C-n(2) using radar is a complicated and time consuming process. This paper presents a new software program which is being developed to automate the calculation of C-n(2) over an arbitrary path. The program takes regional National Weather Service NEXRAD radar reflectivity measurements and extracts data for the path of interest. These reflectivity measurements are then used to estimate C-n(2) over the path. The program uses the Radar Software Library (RSL) produced by the Tropical Rainfall Measuring Mission (TRMM) at the NASA/Goddard Flight Center. RSL provides support for nearly all formats of weather radar data. The particular challenge to extracting data is in determining which data bins the path passes through. Due to variations in radar systems and measurement conditions, the RSL produces data grids that are not consistent in geometry or completeness. The C-n(2) program adapts to the varying geometries of each radar image. Automation of the process allows for fast estimation of C-n(2) and supports a goal of real-time remote turbulence measurement. Recently, this software was used to create comparison data for RF scintillation measurements. In this task it performed well, extracting thousands of measurements in only a few minutes.
The index of refraction structure constant, C 2 n indicates how strongly the index of refraction ... more The index of refraction structure constant, C 2 n indicates how strongly the index of refraction varies in a region of the atmosphere. These variations usually arise through turbulent motions, creating an inhomogeneous distribution of species, density, temperature and pressure. Because the index of refraction also depends on wavelength, the measured value of C 2 n will depend on wavelength. This C 2 n difference generally becomes more pronounced as the difference in wavelength increases. This paper describes a technique for converting between measurements of C 2 n at different wavelengths, and gives an example for converting from centimeter to visible and near IR wavelengths.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Jul 1, 2015
Recently, satellite-based systems have been introduced that utilize angle-of-arrival (AOA) measur... more Recently, satellite-based systems have been introduced that utilize angle-of-arrival (AOA) measurements to geo-locate objects of interest. In the previous work, we considered the application of nonlinear optimization to AoA-based geolocation to these systems. This previous work, however, assumed that all noise sources were independent. In the case of fast-moving objects, however, there is a significant source of error due to the propagation time inherent in satellite-based observation of objects due to the difference between the location of the object when it is observed by a satellite, and the location of the object when it emitted the signal that is being measured. This introduces a systematic error into the system that cannot be resolved by the system proposed by Burchett et al. In this paper, we extend our prior work to account for the time-delay inherent in satellite-based geolocation systems, making this system accurate for fast-movers as well as fixed or slow-moving objects. Results demonstrating significant improvement in geolocation performance both in terms of accuracy and estimated error bounds are presented.
This paper addresses the problem of object localization using only angle-of-arrival (AoA) data fr... more This paper addresses the problem of object localization using only angle-of-arrival (AoA) data from satellites. Traditionally, this is performed by a triangulation algorithm (TA) that minimizes the distances between the estimated object location to all lines-of-sight representing measurements of the object. However, when observing objects from satellites, the differences in distance from each satellite to the object can be significant. The error this induces in measurements from farther-distant satellites results in an inordinate impact on the geo-location error. To overcome this problem, we introduce a non-linear optimization (NLO) approach that models the measurement error at each satellites as a probability density function. By finding the most-probable geo-location of the object, this systematic error is eliminated. We found that the NLO provides a more accurate estimate of the object's location than the TA in 93% of instances. In addition, we analyze the uncertainty estimates generated by both the TA and NLO approaches. The NLO estimates of uncertainty are also considerably more accurate than the TA estimates in all cases.
Three approaches are applied to reconstruction of an object image from radar data collected in an... more Three approaches are applied to reconstruction of an object image from radar data collected in an Inverse-SAR (moving object, fixed radar location) geometry. These approaches attempt to reconstruct the object motion from the radar data alone. While all three approaches work with simulated data, application to this real-world data did not produce a recognizable image. Presented is a short description and comparison of the three methods, and what difficulties were found when applying these motion estimation algorithms to the real data set. The data that were used had been pre-processed into a time series of brightness-vs-range profiles. These range profiles were provided without any further information about the object or radar, providing a truly `blind' test.
In this paper, we describe the current stage of our design for a large-scale aerostat communicati... more In this paper, we describe the current stage of our design for a large-scale aerostat communication system and the future developments we anticipate. Aerostats provide many benefits that are not offered by other means. To take full advantage of these benefits, data must be streamed to a ground station at a very high rate. We have proposed a Multiple-Input Multiple-Output (MIMO) system with a phased array at the receiving end to fulfill this requirement. The phased array uses beam-forming to allow for individual transmitting elements to be resolved. Our current design and results are given, along with an analysis. In addition, we describe a scaled test-bed we have planned using Wireless Open-Access Research Platforms (WARP) from Rice University.
This paper describes the design and analysis of a 24-element dipole array which serves as an opti... more This paper describes the design and analysis of a 24-element dipole array which serves as an optimized feed structure for a 150-meter cruciform reflector antenna for satellite communications in the 1–2 GHz range. The radiation pattern for this structure was calculated using a Method of Moments based computational electromagnetics code yielding an overall 47 dBi reflector gain. The effect of incorporating this optimized feed is an overall performance improvement on an initial cruciform reflector antenna design by minimizing spillover and undesirable side lobes. Performance versus size-and-weight tradeoffs are discussed as is a detailed description of the cruciform antenna's mechanical design and its resultant RF characteristics.
Optical Turbulence estimates made from Numerical Weather Prediction using a modified approach bas... more Optical Turbulence estimates made from Numerical Weather Prediction using a modified approach based on Ciddor’s refractivity parametrization with temperature and hydrometer contributions is shown to predict measured 880nm scintillation better than a standard approach.
The paper describes a project to determine and model a performance baseline for a satellite commu... more The paper describes a project to determine and model a performance baseline for a satellite communication system concept. It is expected to improve communication capabilities while maintaining low operational cost using a newly proposed antenna system. The system will consist of a large, stationary spherical reflector fed by multiple, steerable feeds. The size of the reflector will improve signal gain and resolvability of individual signals. This paper will use a derivation of far field solutions for spherical shaped current sources. These solutions will be used to look at the interaction between current distributions on the reflector and the resulting EM field distributions. This will allow for estimation of the beam quality of the system as a function of the reflector geometry, and feed illumination. Other methods may be applied as needed to determine the feed systems. This may include ray-tracing code for reflector based systems, and numerical simulations for phased array systems.
2016 IEEE National Aerospace and Electronics Conference (NAECON) and Ohio Innovation Summit (OIS), 2016
Vision-based automated aerial refueling requires a relative positioning solution capable of real ... more Vision-based automated aerial refueling requires a relative positioning solution capable of real time updates between the tanker and receiver. The processing time required for modern approaches are dominated by an iterative point alignment phase. This work presents an accelerated alignment variant which utilizes parallelization and Delaunay Triangulation to achieve real time estimates.
Paper links dynamics of near-surface aerosol particles with meteorological observations as well a... more Paper links dynamics of near-surface aerosol particles with meteorological observations as well as derived optical turbulence during a solar eclipse while suggesting causes for the unanticipated direct correlation of turbulence fluctuations and aerosol particle counts.
This paper describes the design and analysis of a 24-element dipole array which serves as an opti... more This paper describes the design and analysis of a 24-element dipole array which serves as an optimized feed structure for a 150-meter cruciform reflector antenna for satellite communications in the 1–2 GHz range. The radiation pattern for this structure was calculated using a Method of Moments based computational electromagnetics code yielding an overall 47 dBi reflector gain. The effect of incorporating this optimized feed is an overall performance improvement on an initial cruciform reflector antenna design by minimizing spillover and undesirable side lobes. Performance versus size-and-weight tradeoffs are discussed as is a detailed description of the cruciform antenna's mechanical design and its resultant RF characteristics.
Optical Turbulence estimates made from Numerical Weather Prediction using a modified approach bas... more Optical Turbulence estimates made from Numerical Weather Prediction using a modified approach based on Ciddor’s refractivity parametrization with temperature and hydrometer contributions is shown to predict measured 880nm scintillation better than a standard approach.
Uploads
Papers by Lee Burchett