<i>OK... active sensing makes sense. That's a lot of money on each probe just to map the surface of any planets though. I would think Hubble can do a lot if only face planets within the solar system. </i><br /><br />Not in the detail the current orbital probes can do it in. Contrary to popular thought the Hubble is not "all that and a bucket of chicken". It works very well for what it was designed to do in its cosmology role and it can image planets but it can only image them as well as its focal point will allow.