Editing Satellite Data System (section)

== Orbital characteristics ==
SDS satellites have a [[highly elliptical orbit]], going from about 300 kilometers at [[Apsis|perigee]] to roughly 39,000&nbsp;km at [[Apsis|apogee]] in order to allow communications with [[Geographical pole|polar]] stations that cannot contact [[geosynchronous]] satellites. The high apogee meant that the polar regions were visible for long amounts of time, and only two satellites were required in order to achieve constant communications ability. In addition, two geostationary satellites appear to be part of the system. The SDS satellites were constructed by [[Hughes Aircraft Company]].