Quantum radars allow to enhance performances of conventional systems by exploiting high order correlations between entangled states of light using quantum illumination protocols. Such systems can be used for short mid-range applications such as unmanned aerial system (UAS) detection or target detection in degraded visual environments (DVE).
In this work we present computational simulations of receiver operating characteristic (ROC) curves of a binary classifier system implementing quantum and classical resources for real case applications comparing benefits and drawbacks given current technological capabilities.
KEYWORDS: Meteorology, Satellites, Signal attenuation, Ka band, Data processing, Satellite communications, Data modeling, Microwave radiation, Antennas, Clouds
This work presents a real time method for rainfall estimation based on attenuation data acquired via Ka-band satellite link and discusses some results of its application. Data to be processed are recorded with a commercial kit for satellite web supplied by a European provider and operating above the urban area of Florence (Italy). Since the system automatically performs a continuous adjustment of the transmitted power in function of the intensity of the received signal, this information is being exploited to estimate the entity of the precipitation within the area. The adopted model for the attenuation of a microwave link due to hydrometeors is the one suggested by Olsen and Hodge and recommended by the ITU. The results are interpreted together with registered rain-rate measurements provided by three rain gauges dislocated within the area.
The exploitation of multifrequency differential attenuation measurements at microwaves made between two LEO
satellites in limb mode is the ground of the NDSA (Normalized Differential Spectral Attenuation) approach for
estimating integrated tropospheric water vapor profiles through multifrequency measurements at 17, 19, 21, 179 and 182
GHz, plus 32 GHz for liquid water detection and correction (whenever possible). Such measurements are affected by
two kinds of impairments, the first generated by thermal noise at the receiver, the second generated by the signals’
fluctuations due to the variations of the tropospheric refraction index and referred to as scintillation disturbance.
Characterizing scintillation for simulating its effects to evaluate NDSA performance is not easy in general: in particular,
it is quite hard (and also rather questionable so some extent) to relate the scintillation parameters to a given simulated
atmospheric situation. For this reason, in the past years we limited ourselves to evaluate the NDSA performance by
accounting for scintillation in a parametric way, independently of the atmospheric context in which simulations were
carried out. In this paper, instead, we show the first results of the NDSA performance analysis based on a completely
different approach, where the scintillation profiles and parameters are directly derived from the simulated atmospheric
context, based on a procedure that starts from high resolution radiosonde data. A brief critical analysis of such an
approach is proposed, evidencing some aspects related to the current knowledge of the scintillation spectra and
parameters. The NDSA performance analysis based on certain hypotheses for the scintillation characteristics is then
shown for some selected simulated atmospheric conditions.
The NDSA (Normalized Differential Spectral Attenuation) approach is based on the conversion of a spectral parameter (the spectral sensitivity S) derived from power measurements, into the total content of water vapor (IWV, Integrated Water Vapor) along the propagation path between the two LEO satellites, through pre-determined IWV-S relations. This paper shows how some problems concerning the relationships between IWV (Integrated Water Vapor) and S could be overcome. In fact, two basic problems affected the reliability of such empirical IWV-S relations found so far: the first was the fact that the accuracy of the radiosonde data used to derive them was not uniformly distributed in the northern and southern hemisphere; the second was the limited amount of radiosonde data available at the highest altitudes (above 10 km), and their scarce reliability. Furthermore, the problem of correcting for the presence of liquid water needed to be considered. Here we present the results of a global scale analysis of the IWV-S relations made utilizing the ECMWF global atmospheric model. S and IWV were simulated and computed at all altitudes from 0 to 20 km, obtaining IWV-S relations for 17, 19, 21, 179 and 182 GHz. Also, the correction of IWV estimates by the presence of liquid water is shown to be effective by using an additional frequency around 30 GHz.
As shown in the past years by researchers at the University of Florence, rainfall rate can be estimated in real time by
means of tomographic processing applied to power attenuation measurements made simultaneously along microwave
links. In this paper, we focus on the possibility to exploit the 'opportunity signals' provided by radio-base station
networks for mobile communication systems. We describe a new tomographic algorithm that has been specifically
developed for such kind of networks in urban areas, where a high number of microwave connections is typically
possible. We describe the performance of the algorithm after having tested it on a 2 hours simulated rainfall event based
on a sequence of real weather radar observations and on three kind of link networks, symmetric with lower link density
and asymmetric with lower and higher density. We considered 12 GHz for the test carrier frequency of the radio-base network.
A real time approach for estimating the greenhouses gas emission flux by a surface-distributed source based on the use
of IR laser measurements over optical links has been recently proposed. An ad hoc arrangement of the laser optical links
allows to measure gas concentration over a closed surface corresponding to a volume that covers the emission area. The
closed volume is defined by 5 of the parallelepiped's surfaces, while the 6th is the emission surface. The emission flux is
obtained by applying the mass balance to the parallelepiped after having estimated the gas concentration over the five
sides. The gas concentration field over the five plane surfaces of the monitoring volume is obtained by ad hoc
tomographic processing of the laser measurements. Assuming realistic network topologies we simulate the whole
emitting and measurement scenario using a self-developed software tool based on Gaussian diffusion models for the
simulation of the gas concentration in atmosphere close to the emission area. Through a Monte Carlo approach we
compute specific error parameters that are then used as performance indices of the proposed flux estimation method, as a
function of the measurement topology network and the gas emitting conditions.
KEYWORDS: Scintillation, Signal attenuation, Error analysis, Signal to noise ratio, Satellites, Atmospheric propagation, Turbulence, Receivers, Absorption, Radio propagation
NDSA (Normalized Differential Spectral Absorption) was recently proposed as a differential attenuation measurement
method to estimate the total content of water vapor (IWV, Integrated Water Vapor) along a tropospheric propagation
path between two Low Earth Orbit (LEO) satellites during a relative set/rise (occultation) event. The NDSA approach is
based on the simultaneous estimate of the total attenuations at two relatively close frequencies and of a "spectral
sensitivity parameter" that can be directly converted into IWV through empirical relationships that can be previously
derived based on statistical regressions between spectral sensitivity and IWV simulated through real radiosonde data and
a propagation model. In this paper we present the error performance in the IWV profile retrievals in the troposphere (up
to 14 km) on the basis of an entire day of occultation events in a ECMWF-model simulated atmosphere. For the first
time, we present results of simulations of NDSA measurements made in the millimeter band (in addition to the Ku/K
bands analysed in previous works), specifically at 179 and 182 GHz.
KEYWORDS: Scintillation, Signal attenuation, Monte Carlo methods, Satellites, Atmospheric propagation, Receivers, Error analysis, Signal to noise ratio, Atmospheric sensing, Atmospheric modeling
NDSA (Normalized Differential Spectral Absorption) is a novel differential measurement method to estimate the total
content of water vapor (IWV, Integrated Water Vapor) along a tropospheric propagation path between two Low Earth
Orbit (LEO) satellites. A transmitter onboard the first LEO satellite and a receiver onboard the second one are required.
The NDSA approach is based on the simultaneous estimate of the total attenuations at two relatively close frequencies in
the Ku/K bands and of a "spectral sensitivity parameter" that can be directly converted into IWV. The spectral sensitivity
has the potential to emphasize the water vapor contribution, to cancel out all spectrally flat unwanted contributions and
to limit the impairments due to tropospheric scintillation. Based on a previous Monte Carlo simulation approach, through
which we analyzed the measurement accuracy of the spectral sensitivity parameter at three different and complementary
frequencies, in this work we examine such accuracy for a particularly critical atmospheric status as simulated through the
pressure, temperature and water vapor profiles measured by a high resolution radiosonde. We confirm the validity of an
approximate expression of the accuracy and discuss the problems that may arise when tropospheric water vapor
concentration is lower than expected.
A measurement approach for estimating the emission flux by a surface-distributed source, based on the use of IR laser
measurements over optical links and atmospheric diffusion models is presented. An ad hoc disposition of the optical
links close to the emission area allows to measure gas concentration over a closed surface corresponding to an air
volume that covers the whole emission area. The real time concentration measurements over this closed surface,
associated to suitable diffusion models, allow us to estimate the emission flux of the area under exam. The diffusion
model to be applied strictly depends on the current atmospheric conditions, therefore it requires the knowledge of the
main atmospheric parameters. In this paper we present some simulation results about a system for the surface flux
monitoring assuming the faces of a parallelepiped the surfaces interested by laser measurements. The closed surface is
therefore defined by 5 of its sides, while the 6th is the emission surface. We discuss some estimation results using
diffusion models where the air diffusion and transportation phenomena are due mainly to the wind strength.
A simple method for estimating the gas emission flux by spot source fields based on IR laser measurements and atmospheric diffusion models is presented. The method is based on a proper arrangement of the optical links around the emission area, over which the determination of the gas integral concentration is required. The first objective of such measurements is to tune the parameters of a basic diffusion model in order to estimate, as second objective, the gas emission flux by applying the tuned model to experimental measurements. After discussing the proposed model and method, experimental data obtained from some CO2-rich natural discharges in Tuscany (Central Italy) are presented
The NDSA (Normalized Differential Spectral Absorption) method has been proposed for estimating the total content of water vapor (IWV, Integrated Water Vapor) along a tropospheric propagation path between two Low Earth Orbit (LEO) satellites. This method requires a transmitter onboard the first LEO satellite and a receiver onboard the second one. It is based on the simultaneous measurement of the total attenuation at two relatively close frequencies in the Ku/K bands, and on the estimate of a parameter referred to as 'spectral sensitivity'. This approach is potentially able to emphasize the water vapor contribution, to cancel out all spectrally flat unwanted contributions and to limit the impairments due to tropospheric scintillation. The objective of this paper is to analyze the effects of liquid water presence along the propagation LEO-LEO link on the NDSA approach. Results are based on computer simulation and account for different frequency carriers in the 15-30 GHz range and for any value of liquid water content along the propagation path at 3 km tangent altitude.
A new differential measurement concept is presented for retrieving the total content of water vapor (Iwv, Integrated water vapor) along the propagation path between two Low Earth Orbiting (LEO) satellites, while such path is immersing in the atmosphere during a so called set occultation. This new approach, referred to as DSA (Differential Spectral Absorption) method, is based on the simultaneous measurement of the total attenuation at two relatively close frequencies in the K band, and on the estimate of a "spectral sensitivity parameter" that is highly correlated to the Iwv content of the LEO-LEO link in the low troposphere. The DSA approach has the potential to overcome all spectrally 'flat' and spectrally correlated phenomena, including atmospheric scintillation, but a very appealing aspect is the aforementioned correlation, on which we focus in this paper, taking into consideration signals at 17 and 20 GHz, and verifying how the correlation between Iwv and spectral sensitivity changes with season, latitude and inhomogeneity of the atmosphere.
The DSA (Differential Spectral Attenuation) approach, presented in a companion paper in this conference's proceedings, has the potential to provide the total content of water vapor (IWV, Integrated Water Vapor) along the propagation path between two Low Earth Orbiting (LEO) satellites. The interest towards the DSA, based on the ratio of simultaneous measurements of the total attenuation at two relatively close frequencies in the K-Ku bands, was moved by the need for limiting the effects of tropopheric scintillation and by the fact that DSA measurements are highly correlated to the IWV along the LEO-LEO link. However, the impact of tropospheric scintillation in a LEO-LEO radio occultation geometry using frequencies above 10 GHz still has to be thoroughly investigated. In this paper we focus on the analysis of such effects, taking into account the fact that the formulations presented in the literature have to be modified in order to fit the specific problem under consideration. Specifically, an expression is derived for the variances of the amplitude and phase fluctuations of the wave, their spectrum and the correlation between fluctuations at different frequencies. In particular, the latter is extremely useful to evaluate the potential of the DSA approach through simulations whose results are reported in the last part of the paper.
A new differential measurement concept is presented for retrieving the total content of water vapor (IWV, Integrated Water Vapor) along the propagation path between two Low Earth Orbiting (LEO) satellites, while such path is immersing in the atmosphere during a so called set occultation. The new approach, referred to as DSA (Differential Spectral Absorption) method, is based on the simultaneous measurement of the total attenuation at two relatively close frequencies in the K band, and on the estimate of a "spectral sensitivity parameter" that is highly correlated to the IWV content of the LEO-LEO link in the low troposphere. The DSA approach has the potential to overcome all spectrally 'flat' and spectrally correlated phenomena (atmospheric scintillation among these) and provides estimates that can then be usefully integrated with standard radio occultation data products. In the paper we describe the signaling structure chosen for DSA measurements and the transmit-receive system used to simulate an end-to-end transmission during a complete LEO-LEO set occultation. Simulations are based on atmospheric models and on real radiosonde data, which allows us to account for the natural variability of the atmospheric conditions. The effects on the IWV estimates of impairments such as thermal noise at the receiver, atmospheric scintillation, multipath and defocusing are evaluated.
Based on the evidence of the correlation between certain differential spectral parameters that can be estimated through attenuation measurements in the 18-22 GHz spectral range and the columnar content of atmospheric water vapor (IWV: Integrated Water Vapor), recently we pointed out that such correlation can be profitably exploited to provide direct estimates of the IWV along vertical Earth-satellite links, showing in particular that at 19 GHz a practically deterministic relationships holds between the IWV and such differential spectral parameters. In this paper we present some new simulation results to show that the parameters can be estimated by means of a 19 GHz CW-FM nadir pointing radar, providing in this way a continuous monitoring of the IWV along vertical atmospheric sections. Differential attenuation measurements are made by exploiting the backscatter from the Earth surface. Simulations, that are based on real vertical profiles of temperature, pressure and water vapor concentration as provided by a large radiosonde dataset, refer to a LEO satellite and to an airborne configuration, indicate the possibility to retrieve the IWV in both cases.
The southern area of Italy is characterized by the presence of many active volcanic areas. In Pozzuoli (Napoli, Italy), an urban area characterized by high volcanic risk, a gaseous emitting site is present. CO2 is one of the emitted gases and the measurement of its atmospheric concentration is an important task in many environmental and scientific applications. A mobile IR laser system, able to measure the CO2 concentration along rectilinear atmospheric paths up to 1 km length, has been used in that area. The system computes the average concentration by processing the received IR laser radiation propagated along an open-air rectilinear link connecting the transmitter/receiver laser unit and a passive retroreflector device. The laser system scans a spectral range centered on 1580 nm wavelength. An isolated CO2 absorption line characterizes such range. A one-day measurement campaign has been made and more than 15 different atmospheric propagation links were considered moving the transmitter/receiver unit and some retroreflectors. The links were located over a gaseous emitting area whose extension is less than 100x100 square meters. A meteorological station was present and also temperature and wind measurements have been collected. CO2 measurements and meteorological data are presented and discussed. Moreover, the spatial configuration of the measurement links is such that ad-hoc tomographic data processing procedures are profitably usable. The two-dimensional time-averaged spatial distribution of the CO2 at about 1.5 meters over the monitored area is reported as retrieved by the tomographic procedures. Potential and perspectives of tomographic processing are also evidenced.
Recent studies pointed out the correlation existing between the differential attenuation measurements, made using frequencies falling around the 22.235 GHz absorption line of water vapor, and the shape of the water vapor profiles. Such evidence induced us to develop a deterministically based profile retrieval procedure that exploits several differential attenuation measurements made at several frequencies around 22.235 GHz. In this paper, after having described the aforementioned deterministic procedure, a transmission system is proposed to obtain the differential attenuation measurements for a quasi-vertical satellite- Earth multifrequency link. Such transmission system is based on a sinusoidal amplitude modulation and a feasibility study about the minimum exploitable signal-to-noise ratio was considered as well. Both the retrieval procedure and the results of the feasibility study on the transmission system are then tested through simulations of multifrequency attenuation measurements. Such simulations are based on an atmospheric propagation model (MPM: Millimeter-wave Propagation Model) and on real radiosonde data providing profiles of temperature, pressure, and water vapor concentration.
An algorithm for storm tracking through weather radar data is presented. It relies on the crosscorrelation principle as in TREC (Tracking Radar Echoes by Correlation) and derived algorithms. The basic idea is to subdivide the radar maps in Cartesian format in a grid of square boxes and to exploit the so called local translation hypothesis. The motion vector is estimated as the space shift such that corresponding boxes at different times exhibit the maximum correlation coefficient. The discussed technique adopts a multiscale, multiresolution, and partially overlapped box grid which adapts to the radar reflectivity pattern. Multiresolution decomposition is performed through 2D wavelet based filtering. Correlation coefficients are calculated taking into account unreliable data (e.g. due to ground clutter or beam shielding) in order to avoid strong undesired motion estimation biases due to the presence of such stationary features. Data are gathered through a C-band multipolarimetric doppler weather radar. Results show that the technique overcomes some problems highlighted by researchers in previous related studies. Comparison with radial velocity maps shows good correlation values; although they may vary depending on the specific event and on the orographic complexity of the considered area, estimated motion fields are consistent with the shift of the pattern determined through simple visual inspection.
In this paper we address the problem of estimating vertical profiles of atmospheric water vapor by means of attenuation measurements simultaneously made at different frequencies along a vertical satellite-ground link. The operating frequencies are those around the spectral absorption lines of water vapor at 22.235 GHz, the number of frequencies depending on the required vertical detail. A simulation is presented of such a system, based on a atmospheric propagation model and on radiosonde data providing true profiles of temperature, pressure and water vapor.
Most satellite measurements of atmosphere related quantities and parameters come from passive instrumentation, that provides huge amounts of data for global scale atmospheric analysis with quite limited spatial resolution. When higher resolution is desired, ground based systems are opportunely exploited. The increasing use of satellites pushes the research towards the realization of systems, based both on spaceborne and ground instrumentation, designed to exploit attenuation measurements at the infrared. The distribution of atmospheric molecular components can be retrieved from such measurements through ad-hoc tomographic processing. In this paper we describe a methodology that allows attenuation measurements at infrared to estimate mean concentrations of atmospheric molecular components along quasi-vertical rectilinear paths. A number of ground passive infrared stations is needed, distributed along a baseline in the area of interest, and spaceborne monochromatic infrared sources. Measurements made along all rectilinear paths defined by each satellite pass above the site, are processed following an ad hoc tomographic inversion technique to provide the 2D vertical distribution of the atmospheric molecular components of interest. Some simulation results are presented to demonstrate the applicability of the cited tomographic technique. Carbon Monoxide has been considered as the molecular test species in the simulations, based on standard atmospheric models.
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