Satellite

In the context of spaceflight, satellites are objects which have been placed into orbit by human endeavor. They are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon. Depending on the application, they use different types of satellite orbits.

History

The first artificial satellite was Sputnik 1, launched by the Soviet Union on 4 October 1957. This triggered the Space Race between the Soviet Union and the United States of America.

Engineering challenges

Power

The most common means of providing electric power to satellites is a combination of photovoltaic cells and batteries.

Cooling

===Orbital drag and station-keeping===