Ground Testing Strategies for Verifying the Slew Rate Tolerance of Star Trackers

The performance of a star tracker is largely based on the availability of its attitude solution. Several methods exist to assess star tracker availability under both static and dynamic imaging conditions. However, these methods typically make various idealizations that can limit the accuracy of these results. This study aims to increase the fidelity of star tracker availability modeling by accounting for the effects of detection logic and pixel saturation on star detection. We achieve this by developing an analytical model for the focal plane intensity distribution of a star in the presence of sensor slew. Using the developed model, we examine the effects of slew rate on star detection using simulations and lab tests. The developed approach allows us to determine the maximum slew rate for which a star of a given stellar magnitude can still be detected. This information can then be used to describe the availability of a star tracker attitude solution as a function of slew rate, both spatially, across the entire celestial sphere, or locally, along a specified orientation track.

Ground Testing Strategies for Verifying the Slew Rate Tolerance of Star Trackers

The performance of a star tracker is largely based on the availability of its attitude solution. Several methods exist to assess star tracker availability under both static and dynamic imaging conditions. However, these methods typically make various idealizations that can limit the accuracy of these results. This study aims to increase the fidelity of star tracker availability modeling by accounting for the effects of detection logic and pixel saturation on star detection. We achieve this by developing an analytical model for the focal plane intensity distribution of a star in the presence of sensor slew. Using the developed model, we examine the effects of slew rate on star detection using simulations and lab tests. The developed approach allows us to determine the maximum slew rate for which a star of a given stellar magnitude can still be detected. This information can then be used to describe the availability of a star tracker attitude solution as a function of slew rate, both spatially, across the entire celestial sphere, or locally, along a specified orientation track.

Study of possible regularities of the metallic distribution of open cluster stars according to the LAMOST catalog

In this study were discussed the LAMOST catalog opportunities in the statistical studies of the spectra of stars in open star clusters (OSC). We considered the Pleiades and Praesepe clusters. We examined the absolute stellar magnitude — metallicity relationships for the members of these clusters. Contrary to expectations, a noticeable dependence of the metallicity on the absolute magnitude of the stars in the main sequences of the studied clusters was found, which may be associated with systematic errors in measuring the metallicities for visually faint stars.

Multi-Aperture Optical System of Photon Counting in the Image for Aberration-Free Space Debris Observations through a Turbulent Atmosphere (Part I)

The paper solves the problem of space debris monitoring to ensure the safety of space exploration. Space debris fragments are small-sized control objects with angular sizes up to 0.002 arcsecond. Therefore, optoelectronic systems of high resolution and permeability allowing one to measure the coordinates and recognize these weak control objects with a given accuracy and probability having integral brightness up to +18 stellar magnitude are necessary for the location (search, detection, measurement, and identification) of space debris fragments. To solve the optical location problems of space debris the Part I of the article proposes the concept of building a ground-based optoelectronic control system. The system consists of three consecutive and interrelated information channels: an image formation channel based on the matrix of individual telescopes and aperture synthesis technology; image detection channel based on scanning raster detectors and photon counting technology in the image; and image processing channel based on digital correlation compensation technology of atmospheric distortions. Advantages of a matrix of separate telescopes, photodetection and correlation processing are noted in the article. The proposed concept is protected by a patent of the Russian Federation, which is discussed in detail in Part II.

Long-term optical photometric monitoring of the FUor star V900 Mon

We present results from photometric monitoring of V900 Mon, one of the newly discovered and still under-studied object from the FU Orionis type. The FUor phenomenon is very rarely observed, but it is essential for stellar evolution. Since we only know about twenty stars of this type, the study of each new object is very important for our knowledge. Our data were obtained in optical spectral region with the BVRI Johnson-Cousins set of filters during the period from September 2011 to April 2021. In order to follow the photometric history of the object, we measured its stellar magnitudes on available plates from the Mikulski Archive for Space Telescopes. The collected archival data suggest that the rise in brightness of V900 Mon began after January 1989 and the outburst goes on so far. In November 2009, when the outburst was registered, the star had already reached the level of brightness close to the current one. Our observations indicate that during the period 2011-2017 the stellar magnitude increased gradually in each pass band. The observed amplitude of the outburst is about 4 magnitudes (R). During the last three years, the increase in brightness has stopped and there has even been a slight decline. The comparison of light curves of the known FUor objects shows that they are very diverse and are rarely repeated. However, the photometric data we have so far show that V900 Mon's light curve is somewhat similar to those of V1515 Cyg and V733 Cep.

Detection and cataloging of space debris’ small-sized fragment of the 20th stellar magnitude

На обсерватории Терскольского филиала ИНАСАН 24 сентября 2020 г. на комплексе телескопа Цейсс-2000 впервые был обнаружен и наблюдался в течение двух ночей фрагмент космического мусора 20-й звездной величины на геосинхронной орбите, что соответствует размерам менее 10 см. Объект был каталогизирован в динамической базе космических объектов ИПМ им. М.В. Келдыша под номером 71113. Топоцентрическое расстояние до фрагмента во время наблюдений менялось от 36862 км до 37224 км при фазовых углах от 53 ◦ до 68 ◦ , амплитуда изменения блеска объекта - от 19-й до 21-й звездной величины в интегральном свете. Приводятся параметры орбиты и диаграммы изменения блеска. On September 24, 2020, at the Terskol observatory of INASAN, a fragment of space debris’ of the 20th magnitude in geosynchronous orbit was first detected and observed for two nights using the Zeiss-2000 telescope, which corresponds to a size of less than 10 cm. The object was catalogued in the dynamic database of space objects of the Keldysh Institute of the RAS under the number 71113. The topocentric distance to the fragment during observations varied from 36862 km to 37224 km at phase angles from 53 ◦ to 68 ◦ . The object’s brightness ranged from the 19th to the 21st magnitude. The parameters of the orbit and the brightness change diagrams are given.