Ballistics, navigation, and motion control for a spacecraft during its landing on the surface of Phobos

Basic concepts and algorithms laid as foundations of the scheme of landing on the Martian moon Phobos (developed for the Phobos-Grunt project) are presented. The conditions ensuring the landing are discussed. Algorithms of onboard navigation and control are described. The equations of spacecraft motion with respect to Phobos are considered, as well as their use for correction of the spacecraft motion. The algorithm of estimation of the spacecraft’s state vector using measurements with a laser altimeter and Doppler meter of velocity and distance is presented. A system for modeling the landing with a firmware complex including a prototype of the onboard computer is described.     

Approximate Calculation of Required and Available Lateral Range Achieved in a Spacecraft Descent to a Preset Point on the Earth's Surface

The results of calculation of the required lateral range are presented for the orbital reentry of a spacecraft having a preset inclination and preset ascending node longitude to land at a preset point on the Earth's surface. The suboptimum laws of roll angle variation in velocity are determined, which allows one to reach the maximum available lateral range for a given value of constant lift-to-drag ratio taking into account constraints imposed on the maximum equilibrium temperature.     

Trajectory Control for a Spacecraft with an Inflatable Braking Device in the Martian Atmosphere

The possibility of using an inflatable braking device for controlled descent in the Martian atmosphere of large-capacity cargoes is analyzed. The most complicated version of the trajectory control problem is considered, namely, the injection of a spacecraft at hyperbolic velocity into a parking orbit after braking in the atmosphere.