Planetary Missions of the 20th Century*

Among of the highlights of the 20^th century were flights of spacecraft to other bodies of the Solar System. This paper describes briefly the missions attempted, their goals, and fate. Information is presented in five tables on the missions launched, their goals, mission designations, dates, discoveries when successful, and what happened if they failed. More detailed explanations are given in the accompanying text. It is shown how this enterprise developed and evolved step by step from a politically driven competition to intense scientific investigations and international cooperation. Initially, only the USA and USSR sent missions to the Moon and planets. Europe and Japan joined later. The USSR carried out significant research in Solar System exploration until the end of the 1980s. The Russian Federation no longer supports robotic planetary exploration for economic reasons, and it remains to be seen whether the invaluable Russian experience in planetary space flight will be lost. Collaboration between Russian and other national space agencies may be a solution.     

Nonlinear Localized Electrostatic Structures and Their Experimental Diagnostics in the Magnetosphere Plasma

The theoretical models of the formation of the three-dimensional quasi-stationary structures of variations of density and electrostatic potential in a multicomponent magnetosphere plasma are considered. On the basis of the perturbation method, we have studied the domains of the parametric space, where the occurrence of nonlinear quasi-stationary ion-acoustic and electron-acoustic structures are possible. For these structures, the velocities of motion along the direction of the magnetic field are estimated, together with the longitudinal and transverse scales with respect to the direction of the Earth's magnetic field. The calculated dependences of the scales l and l _|| of the structures on the plasma parameters in the three-component plasma allow one to compare the results of the considered theoretical models with new experimental data of measuring the form of soliton structures onboard the FAST, POLAR, and GEOTAIL satellites.     

Local Radiation Belts of the Sun (Quasi-Stationary Coronal and Heliospheric Giant Traps for Solar Cosmic Rays)

The local radiation belts of the Sun are defined as giant quasi-stationary coronal and heliospheric traps for solar cosmic rays. These traps are formed by loop magnetic fields, both solar and interplanetary. Using observational data, some experimental examples of the local radiation belts of the Sun are considered. The hypotheses on the origin of energetic particles in the outer heliosphere and on the local radiation belts of the Sun are discussed.     

Families of Periodic Solutions to the Beletsky Equation

A review of achievements in the investigation of the planar periodic oscillations and rotations of a satellite around its center of mass, which moves along an elliptic orbit in the central gravitational field, is presented. These oscillations and rotations of the satellite are described by an ordinary differential equation (Beletsky equation) of the second order with periodic coefficients and two parameters. The equation is equivalent to a periodic Hamiltonian system with a single degree of freedom and has a singularity. It turned out that two-parameter families of the generalized periodic solutions to this simple equation form complicated structures of a new type. A comparison of numerous separate results made it possible to outline a sufficiently unified and complete picture of the location and structure of the families of generalized 2-periodic solutions with an integer number of rotation. These families are compared with known data related to the resonance rotations of the natural satellites in the solar system.     

The Fine Structure of the AKR Electromagnetic Field as Measured by the Interball-2 Satellite

The fine structure of the Auroral Kilometric Radiation (AKR) is studied using multicomponent measurements of the electric component of the electromagnetic field in the frequency band 4 kHz–1 MHz (the POLRAD experiment onboard the INTERBALL-2 satellite). Special attention is paid to the measurements near the source of the AKR: under conditions when the lower boundary of the emission range descended sufficiently low, down to the local gyrofrequency of electrons. From the analysis of the electric field structure the conclusion is drawn that the bulk of the AKR power is carried by the signal component fast variable in time and frequency (flickering component). The power of a constant component (continuum) is lower by at least an order of magnitude. During strong bursts of the AKR, the relative contribution of the flickering component increases. The spatial structure of the zone of generation has at least three characteristic scales along and across the magnetic field.     

Modeling of Plasma Density in the Earth's Dayside Inner Magnetosphere

The results of comparison of the model profiles of density, obtained by means of the CDPDM model, with the experimental data of the ISEE-1 satellite for the years 1977–1983 are presented. The hypothesis on the validity of the mirror mapping of the convection boundary relative to the dawn–dusk direction is verified. An attempt to improve the CDPDM model for the dayside is made.     

One hundred US EVAs: a perspective on spacewalks

In the 36 years between June 1965 and February 2001, the US human space flight program has conducted 100 spacewalks, or extravehicular activities (EVAs), as NASA officially calls them. EVA occurs when astronauts wearing spacesuits travel outside their protective spacecraft to perform tasks in the space vacuum environment. US EVA started with pioneering feasibility tests during the Gemini Program. The Apollo Program required sending astronauts to the moon and performing EVA to explore the lunar surface. EVA supported scientific mission objectives of the Skylab program, but may be best remembered for repairing launch damage to the vehicle and thus saving the program. EVA capability on Shuttle was initially planned to be a kit that could be flown at will, and was primarily intended for coping with vehicle return emergencies. The Skylab emergency and the pivotal role of EVA in salvaging that program quickly promoted Shuttle EVA to an essential element for achieving mission objectives, including retrieving satellites and developing techniques to assemble and maintain the International Space Station (ISS). Now, EVA is supporting assembly of ISS. This paper highlights development of US EVA capability within the context of the overarching mission objectives of the US human space flight program.     

The importance of space policy teaching in communicating space activities to society

The governments’ priority and budgets for space activities are steadily decreasing and the importance of space activities is not any longer reaching the front pages of the newspaper, as in the 1960s. On the other hand in Europe the people, at large, have shown an important interest and support for space activities. A contribution to bridge the gap between decreasing funding and important support of citizen can come from teaching space policy in universities as well as in special workshops for government, industrial and military circles. The paper will outline a course that fulfils this goal.     

Conditions of the Maximum Principle in the Problem of Optimal Control over an Aggregate of Dynamic Systems and Their Application to Solution of the Problems of Optimal Control of Spacecraft Motion

The necessary first-order conditions of strong local optimality (conditions of maximum principle) are considered for the problems of optimal control over a set of dynamic systems. To derive them a method is suggested based on the Lagrange principle of removing constraints in the problems on a conditional extremum in a functional space. An algorithm of conversion from the problem of optimal control of an aggregate of dynamic systems to a multipoint boundary value problem is suggested for a set of systems of ordinary differential equations with the complete set of conditions necessary for its solution. An example of application of the methods and algorithm proposed is considered: the solution of the problem of constructing the trajectories of a spacecraft flight at a constant altitude above a preset area (or above a preset point) of a planet's surface in a vacuum (for a planet with atmosphere beyond the atmosphere). The spacecraft is launched from a certain circular orbit of a planet's satellite. This orbit is to be determined (optimized). Then the satellite is injected to the desired trajectory segment (or desired point) of a flyby above the planet's surface at a specified altitude. After the flyby the satellite is returned to the initial circular orbit. A method is proposed of correct accounting for constraints imposed on overload (mixed restrictions of inequality type) and on the distance from the planet center: extended (nonpointlike) intermediate (phase) restrictions of the equality type.