21 May 1998
The Galaxy 4 communications satellite failed. The satellite, shaped like a nine-foot cube with a solar panel stretching 100 feet, remained in a stable orbit above the Equator, but the system that kept it pointed at the Earth malfunctioned, causing it to spin. A backup system also failed.
29 August 2000
The Spacecraft Control Processor aboard the Mexican Solidaridad 1 communications satellite malfunctioned, wiping out television, radio and pager services for Mexico.
21 November 2015
All communications with the Amos-5 satellite were lost. It provided coverage over the continent of Africa, as well as Europe and the Middle East.
As a society we have become dependent on satellite communications. But space is not a friendly place and satellites fail with alarming frequency. So if our satellite communications fail and we’re miles at sea, what do we do?
Before the advent of satellites, long distance communications were carried out with high frequency (HF) radio transmissions.
Some important communications still use HF radio, including NOAA Weather Fax transmissions.
Other communications continue to use low frequency (LF) transmissions, including time stations and some military communications.
In this lesson, we look at the factors that control long-distance radio communications, with an emphasis on refraction in the ionosphere, frequency selection, and solar radiation.