Variations in the radiothermal radiation of the ice cover of Lake Arakhley as a geo-indicator of deformation and cracking

In January-March, 2020-2021, radiophysical studies were conducted of radiothermal radiation intensity for the testing site for Lake Arakhley, Transbaikalia, Russia. The set of equipment consisting of four microwave radiometers for the wavelengths from 0.3 to 2 cm was placed on the shore of the lake mounted on a stationary platform. The temperature and deformation of ice were simultaneously measured at the depth of 0.4 meters in two orthogonal directions: west-east and north-south. The temperature was measured with heat gauges in a vertical profile at the depths of 5, 10, 15, 20 and 40 cm. In the process of contact measurements in the period of cracking, signal impulses were recorded in the channel of the deformation sensor placed in the direction of the lake center (west-east). The measurement results were used in monitoring of the condition of the water body. It turned out that in the periods of registering the deformation impulses, changes in the radio brightness temperature and decrease in the ice temperature were observed. The microwave characteristics correlate with the temperature and deformation of the ice cover and may serve as an indicator of the meteorological conditions of the region.

Synthesis of an optimal digital filter of a compensation radiometer for radiometric correlation-extreme navigation systems of unmanned aerial vehicles

The expediency of using a compensation radiometer (CR) with periodic absolute calibration as a sensor for preprocessing the information of correlation-extreme navigation systems (CENS) of unmanned aerial vehicles (UAV) was shown. This is determined by the possibility of obtaining and using the estimates of gain fluctuations obtained in previous frames which will provide an increase in the radiometer sensitivity. In addition, due to the accumulation of information, an increase in accuracy of measurement of the elements of the current image formed by the CENS will be provided. The algorithm of processing the obtained calibration estimates during linear processing corresponds to a certain digital filter (DF). By defining a set of the DF weight coefficients, it is possible to improve the CR fluctuation sensitivity by reducing the gain fluctuations. Up to 1.8-time gain in sensitivity can be reached for typical frequency and time parameters of the compensation radiometer of UAV CENS. The problem of synthesis of a digital filter was set. A solution to the problem of synthesizing an optimal digital filter was proposed. Its use in a CR will improve the fluctuation sensitivity. In its turn, this will make it possible to improve the quality of a current image generated by the system when siting by means of sighting surfaces with low-contrast objects taking into account fluctuations in radio-brightness temperature. It was found that the gain in sensitivity when using the optimal digital filter increases with an increase in the operating period of the radiometer and an increase in the digital filter order. Improvement of fluctuation sensitivity of the CENS data preprocessing system is important for UAV location in low-contrast areas

Electrodynamic model of relict radiation scattering by vegetation cover to improve the accuracy of soil moisture measurement by microwave radiometer

The possibilities of electrodynamic model of relict radiation scattering by vegetation cover to improve the accuracy of soil characteristics measurement by microwave radiometer are demonstrated. The dependence of the reflective characteristics of the soil-vegetation system on the type and parameters of vegetation cover is considered. The accuracy of measuring the radio brightness temperature of the soil is estimated depending on the type and characteristics of the vegetation cover.