Doing quick math to determine the arc second radius of a 1m satellite at geostationary orbt, it turns out someone already published the maths and did the tests. 1.5m of aperture and some fancy CCD cameras and you can get size and shape detail. A square with a length of 36 inches at GEO distance will be roughly 1/10 of an arc second; at that resolution the atmosphere will limit your ability to get an image of the object. Something 20 feet wide would have an apparent diameter of .29" which, barely, is doable with a 2 meter class scope, and perfect seeing. Thierry Legault uses a 14 inch class SCT with great optics, a kick ass camera and a ton of patience to get images of satellites in low earth orbit. There are some images of his that track GEO stuff, but GEO is a lot farther away than the ISS and the other satellites in LEO. Now I kinda want to start tracking satellites and buy a better telescope.