The Universe and Galaxies: Exploring The Solar System

Discovery Space: Exploring The Solar System

Space probes travel through space for months or years, journeying millions or even billions of miles to their destinations. Along the way, they help expand our knowledge of unexplored regions.

Space probes are unmanned spacecraft designed to gather information about the sun, planets, moons, asteroids, comets, and the space between them. Basic types include flyby, lander, and orbiter missions. Unlike a terrestrial satellite, which remains in the Earth’s orbit, a space probe leaves the vicinity of the Earth to explore its target on location. Probes are generally launched from Earth on a path toward the target.

On arrival, a braking maneuver must be carried out to place the probe in orbit around the faraway object. To save fuel or allow more cargo to be carried, a probe may not take the most direct path to its destination. Instead, it takes a “swing- by,” circling another planet to gain a gravity boost. If the target object has an atmosphere—such as Mars—fuel can also be saved in the deceleration process: the probe enters the atmosphere at an angle, using the resistance for aerobraking.

Space probe navigation must be extremely precise; due to the vast distances within the solar system. Large antennas are used to track probes from Earth. Depending on the distance, navigational commands may take several minutes or more to reach the probe. However, modern computer technology, probes enables probes to undertake some actions independently, especially in critical situations.


Space probes exploring the moon and inner planets usually produce their own electricity by using solar cells to convert the light energy from the sun. Yet, very little sunlight is available beyond Mars. Probes traveling further than this use energy supplied by a radioisotope generator. The emissions of a radioactive substance produce heat that is then converted into electrical energy.

Depending on their mission, space probes may be equipped with cameras sensitive to various wavelengths, or with sensors that measure radiation or magnetic fields. Many orbiter probes use radars that can penetrate deep into the surface of an object in space, revealing its inner structure. Some space probes carry landing units for placement on the object’s surface.

Remotely controlled rovers or robots can survey a larger area than fixed landing units. Impactors or penetrators are probes that collide forcefully with an object, burrowing into it and collecting information about its constituent parts.


The human eye can differentiate be tween a significantly larger number of colors than it can distinguish degrees of light intensity Thus, the details of a picture can be made clearer by using a visual trick: replacing the various brightness levels with different colors.

This technique has proved especially useful in space science, medicine, and the evaluation of satellite images.


THE FIRST SPACE PROBE to leave Earth’s orbit was the Soviet Union’s Luna 1 mission. In 1959 it successfully traveled past the moon and began collecting data about magnetic fields, radiation, and the density of inter- planetary gases.