Planetary Invasion Options and Infrastucture

Several options are given for a ground invasion. Most of which will reduce the planet quality and destroy improvements. But how do I know the extent of improvements on a planet prior to invasion. I recently invaded a Dregin Planet and chose the traditional method, hoping to preserve the infrastructure. It turns out once I get the planet there was no improvements built. How come we cant see what is on an enemy planet. I had a high level of espionage on the Dregin at the time. I would think if I had ships in orbit I should at least know what the planets got besides the number of troops.

Another thing, how come when I am at war with another race I no longer can see the quantity of ships he has. When I am at peace I can see the ships on the trade screen. At war they disapper. I know one can argue "fog of war" or something but whats all the espionage and intellegence gathering for; so I know when its the Yors birthday?