Optical system calibration for 3D measurements in a hydrodynamic tunnel

Для проведения бесконтактных трёхмерных измерений в гидродинамических трубах фотограмметрическими методами требуется уточнение стандартной модели формирования изображения в съёмочной камере, учитывающее эффект преломления лучей на границах оптических сред, а именно, на границе воздух–стекло и стекло–рабочая жидкость. В статье представлены модель формирования изображения для случая съёмки в рабочем пространстве, включающем различные оптические среды, и методика калибровки оптической системы для проведения трёхмерных измерений координат объектов сцены с учётом имеющихся границ оптических сред. Приведены результаты экспериментальных исследований по калибровке системы трёхмерных измерений для случая съёмки объекта через две границы оптических сред. For non-contact 3D measurements in hydrodynamic tunnels by photogrammetry methods, it is necessary to refine the standard model of image formation in the camera by taking into account an effect of refraction of rays at the boundaries of optical media, namely, at an air-glass boundary and glass-working fluid boundary. The article presents a model of image formation for shooting in a working environment that includes various optical media and methods for calibrating an optical system for 3D measurements of the coordinates of scene objects, while taking into account the real boundaries of the optical media. Experimental results on calibrating the system of three-dimensional measurements when an object image is formed by rays passing through two optical boundaries are discussed.Исследования были выполнены при поддержке Российского фонда фундаментальных исследований (РФФИ) в соответствии с проектом № 19-29-13040

RadioAstron as a target and as an instrument: Enhancing the Space VLBI mission’s scientific output

Context. The accuracy of orbit determination has a strong impact on the scientific output of the Space VLBI mission RadioAstron. Aims. The aim of this work is to improve the RadioAstron orbit reconstruction by means of sophisticated dynamical modelling of its motion in combination with multi-station Doppler tracking of the RadioAstron spacecraft. Methods. The improved orbital solution is demonstrated using Doppler measurements of the RadioAstron downlink signal and by correlating VLBI observations made by RadioAstron with ground-based telescopes using the enhanced orbit determination data. Results. Orbit determination accuracy has been significantly improved from ~600 m in 3D position and ~2 cm/s in 3D velocity to several tens of metres and mm/s, respectively.Department of Astrodynamics and Space MissionsAerospace Engineerin

New status of ISON - an open international project and database for space debris information exchange.

International Scientific Optical Network (ISON) was an open international scientific project specializing in observations of the near-Earth space objects. Started in Pulkovo observatory in 2004, ISON project then continued in Keldysh Institute of Applied Mathematics RAS (KIAM RAS), and is currently under dedicated company Small Innovation Enterprise "ISON Ballistics-Service" (SIE ISON-BS). With this goal SIE ISON-BS developed the observation scheduling centre and database. A new direction of project development was the arrangement of an international centre for the exchange of measurement and orbital information on space debris. SIE ISON-BS established an international exchange of data with a number of observatories, universities and scientific institutes. Therefore, although the number of observatories of the project has decreased to 22 (telescopes of SIE ISON-BS are now in 14 observation points and there are 8 partner observatories) the volume of measurements in the ISON database has grown few times. In 2022 ISON database received in average daily 120 thousand measurements and obtained to end of year over 45 mln. measurements in almost 5 mln. tracklets, and maintains the orbits of 10086 space objects (3122 GEO, 5267 HEO and 1697 MEO), from that 3226 are objects with high are to mass ratio (including 901 GEO, 1461 HEO and 864 MEO) on 01.09.2023. ISON carries out the scientific and commercial activities under grants and contracts with foreign organizations

RadioAstron gravitational redshift experiment: status update

A test of a cornerstone of general relativity, the gravitational redshift effect, is currently being conducted with the RadioAstron spacecraft, which is on a highly eccentric orbit around Earth. Using ground radio telescopes to record the spacecraft signal, synchronized to its ultra-stable on-board H-maser, we can probe the varying flow of time on board with unprecedented accuracy. The observations performed so far, currently being analyzed, have already allowed us to measure the effect with a relative accuracy of 4 × 10−4 . We expect to reach 2.5×10−5 with additional observations in 2016, an improvement of almost a magnitude over the 40-year old result of the GP-A mission.Astrodynamics & Space Mission

Probing the gravitational redshift with an Earth-orbiting satellite

International audienceWe present an approach to testing the gravitational redshift effect using the RadioAstron satellite. The experiment is based on a modification of the Gravity Probe A scheme of nonrelativistic Doppler compensation and benefits from the highly eccentric orbit and ultra-stable atomic hydrogen maser frequency standard of the RadioAstron satellite. Using the presented techniques we expect to reach an accuracy of the gravitational redshift test of order 10−5 , a magnitude better than that of Gravity Probe A. Data processing is ongoing, our preliminary results agree with the validity of the Einstein Equivalence Principle