ИСТИНА

UVS instrument onboard Voyager-1 has been performing measurements of the backscattered solar Lyman-alpha emissions for more than 35 years. Since 2003 when the scan platform movements were stopped, it measures Lyman-alpha radiation in one line of sight close to the upwind direction. The most interesting feature of these data is radial dependence of measured intensity. Namely, Voyager-1 data shows almost constant intensity (after correction for the solar flux variations) between 90 and 115 AU, while the numerical models of global heliosphere and radiative transfer predict decreasing intensity. Between 115 AU (beginning of 2011) and about 124 AU (beginning of 2013), the data show a decrease of the intensity again. This last period corresponds to motion of Voyager-1 in the transition region (Krimigis et al., 2011) before crossing the heliopause at 122 AU in August, 2012 (Stone et al., 2013). This behavior of the Lyman-alpha intensity observed by Voyager can be a tracer of complicated structure of the heliospheric boundary. Plasma instruments onboard Voyagers provide information about charged component of the solar and interstellar winds and energetic particles, while only the UVS data for the Lyman-alpha intensity reflect the distribution of the neutral hydrogen component. Therefore, interpretation of Voyager-1/UVS measurements is critical to understand the complete picture of the interaction between the solar wind and surrounding interstellar matter. In this work we will present preliminary results of analysis of Voyager-1/UVS data in the frame of the kinetic-MHD heliospheric model and radiative transfer code. Possible scenarios for hydrogen distribution consistent with Voyager-1 data will be proposed.