Vol 56, No 4 (2018)

Seismo-ionospheric variations during the strong earthquake on February 27, 2010 in Chile have been considered. An analysis of the ionospheric state has been performed using measurements based on a GPS satellite navigation system. The results of processing have shown that the decrease in the electron concentration on February 24, 2010 relative to the preceding day was from 24 to 35%. It has also been noted that, 3 days prior to the seismic event, a substantial drop in the rate of change of in the total electron content was observed near the epicenter zone for 1.5 h. It has been shown that, directly before the earthquake, instantaneous variations in the rate of change in the electron content by an order of value that exceeds normal background behavior was observed.

The concept of the System for the Observation of Daytime Asteroids (SODA system) has been developed, the purpose of which is to detect at least 95% of hazardous celestial bodies larger than 10 m in size that fly towards Earth from the Sun side. Spacecraft, equipped with the optimum version, which has three wide-angle optical telescopes of small aperture (20–30 cm) will be placed in a halo orbit around the L₁ libration point of the Sun–Earth system. This will provide a warning on the hazardous object, approaching from the Sun side, and will allow one to determine the orbit and the point of body entering Earth atmosphere to a sufficient accuracy, at least a few hours before the body collides with Earth. The requirements to the system are considered, the results of a preliminary design of the set of instruments have been described, the areas of visibility are calculated, and the versions of data transmission modes have been proposed. It has been shown that, in cooperation with other (particularly ground-based) projects aimed to observing objects flying from the night sky side, it is possible to detect in advance all hazardous bodies in the near-Earth space larger than 10 m in size that approach Earth from almost any direction.

The precession of Saturn under the effect of the gravity of the Sun, Jupiter and planet’s satellites has been investigated. Saturn is considered to be an axisymmetric (A = B) solid body close to the dynamically spherical one. The orbits of Saturn and Jupiter are considered to be Keplerian ellipses in the inertial coordinate system. It has been shown that the entire set of small parameters of the problem can be reduced to two independent parameters. The averaged Hamiltonian function of the problem and the integrals of evolutionary equations are obtained disregarding the effect of satellites. Using the small parameter method, the expressions for the precession frequency and the nutation angle of the planet’s axis of rotation caused by the gravity of the Sun and Jupiter are obtained. Considering the planet with satellites as a whole preceding around the normal to the unmovable plane of Saturn’s orbit, the satellites effect on the Saturn rotation is taken into account via the corrections in the formula for the undisturbed precession frequency. The satellites are shown to have no effect on the nutation angle (in the framework of the accepted model), and the disturbances from Jupiter to make the main contribution to the nutation angle evolution. The effect of Jupiter on the nutation angle and the precession period is described with regard to the attraction of satellites.