The scientists of the Department of Celestial Mechanics and Astrometry of the TSU Research Institute of Applied Mathematics and Mechanics has completed a project whose results are important for existing and planned space missions. In particular, the scientists have built a dynamic structure of the orbital space of the moon and identified a vast area in which the lifetime of the satellites is limited. In addition, the researchers obtained the data necessary for planning space missions to asteroids.

- Humanity is actively developing space. The number of missions sent to large and small objects of the solar system is increasing every year, - says Tatyana Bordovitsyna, head of the Department of Celestial Mechanics and Astrometry and professor in the Astronomy and Space Geodesy Department. - To increase the percentage of successful flights, we need fundamental data on dynamic processes in near-Earth and near-moon space.

Under the project, scientists built the dynamic structure of the near-moon space, examined the action of the main disturbing forces - compression of the moon, earth, and sun - and investigated the orbital evolution of 5180 near-moon objects over 10 years. As a result, it was possible to identify a large area where the lifetime of the satellites is very limited, no more than two years, and the lifetime of the circumpolar satellites is even less.

The scientists obtained clear data on where such systems should not be placed, and highlighted areas that are promising for further analysis on the placement of long-term satellite systems in them. The new data is also important for developing a strategy for disposing of spent spacecraft. The results are being discussed at conferences, also with representatives of structures related to the development of satellite systems.

Choosing the wrong location for a satellite can lead to disruptions in its operation or even the loss of the spacecraft. For example, the Luna-3 spacecraft, launched in 1959 to photograph the far side of the moon into orbit that covered the earth and the moon, made only 11 revolutions and fell to Earth due to the rapid growth of orbit eccentricity. Analysis showed that this happened because the orbit was strongly tilted to the orbits of the earth and the moon and had a large eccentricity.

One of the project objectives was to study the dynamics of asteroids with small perihelion distances (the minimum distance from the asteroid to the sun as it moves in orbit). This factor is relevant from the point of view of asteroid danger, since such objects can approach from the sun at high speeds.

- If an asteroid moves from the sun, but is not far from it in the sky, i.e. rapprochement or collision occurs during daylight, this makes ground-based observations impossible, - explains Tatyana Galushina, at the Department of Celestial Mechanics and Astrometry, associate professor at the Department of Astronomy and Space Geodesy. - A typical example is the Chelyabinsk event: the asteroid’s fall occurred at 9 a.m., and it was detected only at the moment of entering the atmosphere.

Another factor that reduces the ability to accurately predict the motion of asteroids is the Yarkovsky effect — the appearance of a weak reactive impulse due to thermal radiation from the surface of the asteroid heating during the day and cooling off at night. This effect is the reason that the number of asteroids that have reached the Earth is more than predicted in previous calculations.

The results of TSU studies helped to determine the parameters of the Yarkovsky effect and assess its impact on the movement of a whole class of objects. The obtained results can be applied for planning space missions to small celestial bodies, in particular, to work out the process of landing on an asteroid. In addition, the new data will help in the development of high-precision algorithmic and software of these missions.

Space missions to asteroids are a matter of the present. In particular, at present, the Japanese Aerospace Exploration Agency is carrying out the mission “Hayabusa-2” to asteroid (162173) Ryugu. In the future, the mission to the asteroid Phaeton is planned, which, among others, has been the subject of research by TSU scientists. Space missions help to obtain information about the surface and composition of asteroids, to work out the process of landing on the asteroid.

All the techniques and software used by the scientists in their research were developed by the staff of the department and institute either earlier or during projects scheduled for completion in 2019.