Space Probe

A space probe is any uncrewed, instrument-carrying spacecraft designed to travel to an extraterrestrial environment beyond Earth orbit. The first recorded mention of a possibility of a true space probe dates to 1919, when United States physicist and rocketry pioneer Robert Goddard (1882–1945) suggested that a flash from an explosion produced by a rocket on the Moon's surface could be observed from Earth with a telescope. The slight scientific value of such an experiment, along with the absence of the technology for its realization, made Goddard's idea premature. However, in coming years it was to reappear in more mature forms, first on paper and then in reality. In 1952, the term "interplanetary probe" was introduced in a paper by two members of the British Interplanetary Society (a private group of space enthusiasts); by the end of that decade, the dream had at last begun to materialize in hardware projects.

Space probes are used to enrich our scientific knowledge of conditions and bodies in space (asteroids, comets, stars, planets, the solar wind, etc.). Every probe is constructed to fulfill the goals of a particular mission, and thus represents a unique and sophisticated creation of engineering art. Nevertheless, there are some common basic problems underlying any space mission, whether Earth satellite, crewed flight, or automated probe: how to get to the destination, how to collect information, and how to return information to Earth. Successful resolution of these issues is impossible without a highly developed network of Earth-based facilities for assembling and testing the spacecraft-and-launcher system, for launching the spacecraft onto a desired trajectory, for remote control of devices in flight, and for receiving information transmitted back to Earth.

In general, a space probe may thus be considered a combination of interacting systems: on-ground facilities, the launch vehicle, and the spacecraft itself, all communicating with each other through numerous mechanical, electronic, and human interfaces. Each system, in turn, can be split into a set of subsystems interacting through interfaces of their own. A successful space probe therefore requires the fusion of cutting-edge knowledge from many fields. Celestial mechanics, rocketry, precision instrumentation, and telecommunications are only a few of the fields involved.

Automated space missions are, in general, far less costly than crewed missions; a camera or radiation detector, unlike an astronaut, does not require a massive life-support system. Uncrewed spacecraft are still, however, expensive. Today, for example, a probe to Mars is considered relatively inexpensive exploration.

Crewed or not, space missions are an expensive business. For over three decades the United States and the Soviet Union were the only powers technologically and economically capable of sustaining major space-exploration programs. Beginning in the late 1950s, when the Soviet Union's simple Sputnik became the first manufactured object to orbit the Earth, both superpowers spent many billions of dollars on space flight—especially crewed space flight, with its obvious power to impress the world. The prestige motive largely faded, however, after the U.S. won the space race, as it was popularly called, by landing on the Moon in 1969. After the collapse of the Soviet Union in 1991, Russia inherited its space program and continued it in a much reduced form, with emphasis on the Mir space station rather than on solar-system exploration via instrumented probes. In the U.S., the space shuttle and the International Space Station have continued to absorb most of the space budget. However, some funding has always remained available in the U.S. (and to a much smaller extent in Europe and Japan) for small, uncrewed, remote-controlled space vehicles capable of exploring the solar system.

The scientific returns from these missions have been of incalculable value. Scientific probes have been landed on the Moon, Venus, and Mars, and have orbited or flown by every major body in the solar system.