Editing Radar astronomy (section)

== Disadvantages ==

The maximum range of astronomy by radar is very limited, and is confined to the [[Solar System]]. This is because the signal strength [[Inverse-square law|drops off very steeply with distance]] to the target, the small fraction of incident flux that is reflected by the target, and the limited strength of transmitters.<ref name="Hey">{{Cite book  | last = Hey  | first = J. S.   | title = The Evolution of Radio Astronomy  | publisher = [[Paul Elek]] (Scientific Books)  | series = Histories of Science Series  | volume = 1  | date = 1973  }}</ref> The distance to which the radar can detect an object is proportional to the square root of the object's size, due to the one-over-distance-to-the-fourth dependence of echo strength. Radar could detect something ~1&nbsp;km across a large fraction of an AU away, but at 8-10 AU, the distance to Saturn, we need targets at least hundreds of kilometers wide. It is also necessary to have a relatively good [[ephemeris]] of the target before observing it.