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spacecraft designed to carry out physical studies of near-earth space and the heavenly bodies of the solar system. In contrast to high-altitude sounding rockets, space probes make measurements at distances from the earth’s surface that exceed its radius. The term “space probe” is not used for satellites inserted into orbits with low or medium eccentricity.
Space probes are spacecraft launched to the moon and the planets.
The first space probe, Luna 1, was launched by the USSR on Jan. 2, 1959. It was inserted into a hyperbolic orbit relative to the earth. On Jan. 4, 1959, it flew by the moon, left the earth’s sphere of gravitational influence, and became the solar system’s first artificial planet. Spacecraft inserted into heliocentric orbits are often called deep-space probes. In Soviet usage, space probes designed to study the moon, Mars, and Venus are often called unmanned interplanetary probes, lunar probes, and so on. In the USA such spacecraft are called lunar probes, Mars probes, and so on. Probes designed to study the outer regions of near-earth and interplanetary space are often called space stations (for example, the American IMP satellites and Soviet space probes of the Elektron series). Examples of typical space probes are the Zond spacecraft (USSR) and the Pioneer spacecraft (USA). They were designed to study near-earth and interplanetary space. Beginning with Zond 3, spacecraft of the Zond series provided a great deal of valuable information for the study of the moon and its environs.
Scientific measurements on space probes are made by onboard equipment (measurements of particle streams, the magnetic field, and so on) or by photographic studies and telemetry measurements. The results of an experiment are usually transmitted on telemetry or television channels (in the case of Luna 3 and spacecraft of the Venera series) or are returned to earth in a reentry capsule (some craft of the Zond series; Luna 16).
Space probes are usually inserted into interplanetary trajectories from an intermediate earth parking orbit. They also normally land on other heavenly bodies from an intermediate satellite orbit. During return to earth, space probes usually enter the atmosphere at orbital escape velocity. The parameters of a probe’s trajectory are determined by means of a radio tracking system. Photographic observations of artificial comets are sometimes used for this purpose (for example, on Luna 1 and Luna 2).
Space probes provided the first experimental data on the fringe regions of near-earth space. The earth’s magnetosphere was discovered and studied in detail. The solar wind (the continuous stream of particles emitted by the sun under normal conditions) and the ejection of particles that occurs during intensified solar activity were discovered by Luna 1 and Luna 2, and the magnetic fields “frozen into” the particle streams were studied. The interaction of the solar wind with the earth’s magnetosphere, which is of great importance for the study of the dynamics of magnetic storms, the origin of the polar aurora, and other geophysical phenomena resulting from sun-earth interaction, was also studied.
Space probes launched to Venus and Mars have made it possible to obtain experimental data on the immediate vicinity of those planets, and also on their atmospheres. Space probes have been used to photograph the lunar and Martian surfaces and for the study of the physical properties of the lunar soil. The latter studies were conducted both on the lunar surface and through analysis of lunar soil samples returned to earth.
An international system exists for registering and designating space probes. In addition, the various national space programs often have their own designations, such as the Luna, Zond, and Mariner series.
REFERENCEDictionary of Technical Terms for Aerospace Use. Washington, D.C., 1965.
M. G. KROSHKIN