Man-made satellites are important pieces of technology. They are built and launched with a specific purpose in mind. This purpose may be to take photographs of various things on Earth and in space while others send and receive a variety of signals for televisions, cell phones and GPS devices. Satellites do have disadvantages, however.
Satellites are expensive. In addition to the cost of building one of these devices, there is also the cost of launching the satellite into space. In 2008, "The Sunday Times" reported that the cost of launching a satellite using a new French rocket would be $120 million. This cost may rise as satellites grow and become more complex to handle different purposes.
Another problem with satellites is their somewhat unreliable signal. There are different factors that affect the strength and reception of a satellite signal. Errors might be made by the satellite or anyone working on it. This can cause a variable level of interference to the signal. There are also circumstances, such as weather which may be impossible to alter, that affect the satellite's signal. All these things can cause interference and make proper operation of the satellite very difficult.
Propagation delay is the term used to describe the length of time it takes for the satellite to communicate with Earth. This delay can vary greatly. More than anything else, this is caused by the huge distance over which the satellite must send the signal. The time can vary between 270 milliseconds to reach the satellite from Earth and return again to 320 milliseconds. This delay can cause an echo over telephone connections.
Satellites used to be impossible to maintain or repair in any way. Only with the successful repair of the Hubble Telescope did that change and it is still extremely difficult to repair a satellite. In February 2010, NASA announced it was in the process of designing robots whose sole purpose would be to repair satellites. The operation is being handled by a new department at NASA called the Satellite Servicing Development Office.