An atmospheric correction algorithm is proposed for the reconstruction of the ground surface reflectance from the data of satellite measurements. A distinctive feature of the algorithm is that it ...takes into account the influence of the ground surface inhomogeneity on the adjacency effect and additional illumination of the ground surface by reflected radiation. These factors are important for the reconstruction of the reflectance of ground surface fragments with sharp reflectance changes and high atmospheric turbidity. The algorithm is based on Monte Carlo programs developed by the authors. To reduce the computing time, we have proposed some original criteria and approaches. To estimate the capabilities of the developed algorithm, its results have been validated by comparing with the results of the MOD09 algorithm for four MODIS bands and measurements for the Portugal surface fragment with coordinates 38.829 N, 8.791 W. Good agreement of the results obtained by the proposed algorithm with the surface measurements and the data obtained by the MOD09 algorithm demonstrates the efficiency of the proposed algorithm in the reconstruction of the ground surface reflectance.
We report Neutrino-4 experiment results of measurements of reactor antineutrinos flux and spectrum dependence on the distance in range 6–12 m from the center of the reactor core. The fit of ...experimental dependence with the law 1/
L
2
, where
L
is the distance from the reactor center, gave satisfactory result with goodness of fit 81%. However, we discovered that the experimental neutrino spectrum is different from the calculated one. Using experimental spectrum, we performed the model independent analysis of restrictions on oscillation parameters Δ
m
14
2
and sin
2
2θ
14
. The results of this analysis exclude area of reactor and gallium anomaly at CL more than 99.7% (>3σ) for values Δ
m
14
2
< 3 eV
2
and sin
2
2θ
14
> 0.1. However, we observed an oscillation effect at CL 2.8σ in vicinity of Δ
m
14
2
Δ
m
14
2
≈ 7.3 eV
2
and sin
2
2θ
14
≈ 0.39. The method of coherent addition of results of measurements, which allows us to directly observe the effect of oscillations, is proposed. The analysis of that effect is presented. In general, it seems that the effect predicted in gallium and reactor experiments is being confirmed but at sufficiently large value of Δ
m
14
2
. Future prospects of the experiment are discussed.
An opto-electronic system for non-line-of-sight (NLOS) communication using scattered laser radiation for unmanned aerial vehicle (UAV)–ground and ground–UAV schemes at a wavelength of λ = 450 nm and ...a ground–UAV scheme at a wavelength of λ = 510 nm are described. The symbol error rate (SER) and its standard deviation were analyzed for different schemes of the communication channel. The transceiver system included a laser source with a power supply, a modulator, a lens refractor, a bandpass filter, a photomultiplier tube (PMT), a demodulator, and a receiving computer. The experimental data obtained at nighttime showed that the NLOS atmospheric optical communication at a wavelength of λ = 450 nm was feasible for the UAV–ground scheme at a baseline distance of up to 150 m for a UAV with a transmitter at a height of 10 m and at a baseline distance of up to 125 m for a UAV at a height of 20 m. For the ground–UAV scheme, stable communication was observed at baseline distances of up to 50 m for a UAV with a receiver at a height up to 30 m. The NLOS atmospheric optical communication at a wavelength of 510 nm was obtained for the ground–UAV scheme at baseline distances of up to 100 m for a UAV with a receiver at a height up to 45 m, as well as at baseline distances of up to 385 m for UAV flying at a height up to 20 m.
The cloud adjacency effect on surface reflectance retrievals for the region of the Russian Federation with coordinates 51–54∘ N, 103–109∘ E including the southern part of Lake Baikal for the period ...of 1–23 July 2021 is assessed in this paper. The method is based on the computer program for statistical simulation of radiative transfer in the atmosphere with the stochastic cloud field including a deterministic gap of a given radius. The results of this program are then used in the interpolation formula. Masks of cloudless pixels, for which the cloud adjacency effect (CAE) changes the ground surface reflectance by more than 0.005, are constructed. The analysis of the resulting CAE radii shows that the average radius is 13.7 km for MODIS band 8, 11.2 km for band 3, 8.4 km for band 4, 7.2 km for band 1, and 7 km for band 2. For the considered MODIS images and bands, the pixels with strong CAE make up from 2.8 to 100% of the total number of cloudless pixels. The correlation coefficients between the initial data and the CAE radius suggest that the cloud optical depth, cloud cover index, and ground surface reflectance exert the major influence on the considered images. A simplified approximation equation for the CAE radius as a function of the cloud optical depth, cloud cover index, and surface reflectance is derived. The analysis of the approximation shows that for the considered images, the CAE radius decreases nearly linearly with wavelength for low reflective surfaces. However, for high reflective surfaces, its wavelength dependence is nonlinear.
A method for estimating the cloud adjacency effect on the reflectance of ground surface areas reconstructed from passive satellite observations through gaps in cloud fields is proposed. The method ...allows one to estimate gaps of cloud fields in which the cloud adjacency effect can be considered small (the increment of the reflectance Δrsurf≤ 0.005). The algorithm is based on statistical simulation by the Monte Carlo method of radiation transfer in stochastic broken cloudiness with a deterministic cylindrical gap. An interpolation formula is obtained for the radius of the cloud adjacency effect that can be used for the reconstruction the ground surface reflectance in real time without calculations by the Monte Carlo method.
In this paper, we present investigations of non-line-of-sight (NLOS) communication carried out in Russia and in collaboration with researchers in Israel. The theories of radiative transfer and linear ...systems provide the theoretical basis for this joint research, and experimental results demonstrate that maximal ranges for NLOS communication through atmospheric channels can reach hundreds of kilometers in the visible range and tens of kilometers in the ultraviolet (UV) range of the spectrum. Finally, we predict the range of bistatic underwater communication systems can reach hundreds of meters.
We report Neutrino-4 experiment results of measurements of reactor antineutrinos flux and spectrum dependence on the distance in range 6-12 meters from the center of the reactor core. Using ...experimental spectrum, we performed the model independent analysis of restrictions on oscillation parameters Δm142 and sin2 2θ14. The results of this analysis exclude area of reactor and gallium anomaly at C.L more than 99.7% (> 3σ) for values Δm142<3eV2 and sin2 2θ14 > 0.1. However, we observed an oscillation effect at C.L 2.8σ in vicinity of Δm142≈7.3eV2 and sin2 2θ14 ≈ 0.39. The method of coherent addition of results of measurements, which allows us to directly observe the effect of oscillations, is proposed. The analysis of that effect is presented. In general, it seems that the effect predicted in gallium and reactor experiments is being confirmed but at sufficiently large value of Δm142. An additional analysis of the measurements was performed taking into account inhomogenei ty of the detector and background instability.
An experimental search for sterile neutrinos has been carried out at a neutrino facility based on the SM-3 nuclear reactor in Dimitrovgrad, Russia. The movable detector with passive shielding against ...the external radiation may be positioned at a distance varying between 6 and 12 m from the center of the reactor. The antineutrino flux has for the first time been measured using a movable detector placed close to the antineutrino source. The accuracy of the measurements is largely restricted by the cosmic background. The results of the measurements performed at small and large distances are analyzed in terms of the sterile-neutrino model parameters Δ
m
14
2
and sin
2
2θ
14
.
A laboratory for searching for oscillations of reactor antineutrinos has been created based on the SM-3 reactor in order to approach the problem of the possible existence of a sterile neutrino. The ...multisection detector prototype with a liquid scintillator volume of 350 L was installed in mid-2015. This detector can move inside the passive shield in a range of 6–11 m from the active core of the reactor. The antineutrino flux was measured for the first time at these short distances from the active core of the reactor by the movable detector. The measurements with the multisection detector prototype demonstrated that it is possible to measure the antineutrino flux from the reactor in the complicated conditions of cosmic background on the Earth’s surface.
Current Results of NEUTRINO-4 Experiment Serebrov, A; Ivochkin, V; Samoilov, R ...
Journal of physics. Conference series,
12/2017, Volume:
934, Issue:
1
Journal Article
Peer reviewed
Open access
The main goal of experiment "Neutrino-4" is to search for the oscillation of reactor antineutrino to a sterile state. Experiment is conducted on SM-3 research reactor (Dimitrovgrad, Russia). Data ...collection with full-scale detector with liquid scintillator volume of 3m3 was started in June 2016. We present the results of measurements of reactor antineutrino flux dependence on the distance in range 6- 12 meters from the center of the reactor. At that distance range, the fit of experimental dependence has good agreement with the law 1/L2. Which means, at achieved during the data collecting accuracy level oscillations to sterile state are not observed. In addition, the spectrum of prompt signals of neutrino-like events at different distances have been presented.
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