Structurally topological algorithm for star recognition and near-Earth space’ object detection

When solving a variety of celestial navigation tasks there is a problem of determining parameters of spacecraft motion and onboard primary payload orientation based on the coordinates of registered star images. Furthermore, unwanted objects, like active satellites, natural and artificial space debris, that reduce the probability of correct recognition may get into the field of view of a satellite sensor. This prompts the necessity to filter out such interference from the star field images. However, if the objects under recognition are bodies located in near-Earth space, in this case, the star images themselves will act as interferences. In addition, since the detection and cataloging of these objects from the Earth’s surface is complicated by their small size, the atmospheric effects, as well as other technical difficulties, it is worthwhile to use the existing equipment onboard spacecrafts to solve this task. The existing recognition algorithms for star groups, as well as their classification, are presented in this paper. Moreover, a structurally topological approach for identifying groups of stars based on the properties of enveloping polygons used in constructing topological star patterns is proposed. Specific features in the construction of topological configurations on the analyzed set of points, as well as the principles of dynamic space object detection within their limits are described. Results of the numerical experiments performed using the developed algorithm on the star field maps and model scenes are presented.

Relationship between Faithfulness and Preference of Stars in a Planetarium

A planetarium imitates a starry sky with physical and technical limitations using a dome, projector, and light source. It is widely used for entertainment, and astronomy and physics educations. In our previous study, we investigated the evaluation for faithful reproduction of a star field in a planetarium by performing psychometric experiments with 20 observers for plural projection patterns with different reproduction factors (color, luminance, and size of projected stars). In this study, we investigate the relationship between faithfulness and preference of a star field in a planetarium through a psychometric experiment with 47 observers. The experimental procedure followed the previous study. The rating of faithfulness improved for the projection pattern with a smaller star size. For the preference evaluation, the projection pattern with low luminance significantly lowered the preference rating. The results of the experiment indicate that the preferable star reproduction was different between male and female observers, whereas the faithful star reproduction was not significantly different in the evaluations between male and female observers. The male observers sought a faithful star reproduction as the preferred reproduction. In contrast, the female observers did not feel the faithful star reproduction preferable, and evaluated the more brilliant star reproduction as the preferred reproduction. These results were not dependent on the experience in astronomical observations.

Automatic georeferencing of astronaut auroral photography

Astronauts on board the International Space Station (ISS) have taken thousands of high-resolution colour photographs of the aurora, which could be made useful for research if their pointing information could be reconstructed. We describe a method to do this using the star field in the images, and how the reconstructed pointing can then be used to georeference the images to a similar level of accuracy in existing all-sky camera images. We have used this method to make georeferenced auroral images taken from the ISS available and here describe the resulting data set, processing software, and how to access them.

Real-Time Hardware-in-the-Loop Tests of Star Tracker Algorithms

This paper deals with star tracker algorithms validation based on star field scene simulation and hardware-in-the-loop test configuration. A laboratory facility for indoor tests, based on the simulation of star field scenes, is presented. Attainable performance is analyzed theoretically for both static and dynamic simulations. Also, a test campaign is presented, in which a star sensor prototype with real-time, fully autonomous capability is exploited. Results that assess star field scene simulation performance and show the achievable validation for the sensor algorithms and performance in different operating modes (autonomous attitude acquisition, attitude tracking, and angular rate-only) and different aspects (coverage, reliability, and measurement performance) are discussed.

NGC 2587: a sparse open cluster projected onto a populous star field

We present CCD BVIKC photometry in the field of the open cluster NGC 2587. We developed a new method to clean statistically the colour–magnitude diagrams. NGC 2587 is found to be slightly younger than the Hyades and probably of solar metallicity. From 18 probable members with measured proper motions, we derived the following mean cluster values: μα = −4.3 ± 3.6 mas yr−1 and μδ = −2.5 ± 3.4 mas yr−1. Colour excesses, E(B − V) = 0.10 and E(V − I) = 0.15 mag, and a heliocentric distance of 3.7 ± 0.7 kpc are obtained. The interstellar extinction in the cluster direction is found to follow the normal reddening law.