Question

What is the size of the smallest feature that could be distinguished on the surface of Venus (at closest approach) by the Arecibo radio telescope at an angular resolution of 1″?

Answer 1

`190" km"`.

Explanation:

At the average ckosest-approach distance of `4.0xx10^7" km"` (http://www.space.com/18529-distance-to-venus.html), one second of arc corresponds to the following object size:

`(4.0xx10^7" km")xx({1°}/{3600" sec"})xx({1" radian"}/{57.2958°})=190" km"`.