But it is very expensive to build one - if you want satellite to provide some satellite imagery, you'll have to put up some sensors, power source, computing power, some means to transport data back to earth (computer to store the data and send them once satellite passes over ground control center, or multiple satellites, once to make imagery, anothers to help relaying the data) and of course some ground control centre Plus, you won't get probably much higher resolution than landsat. Hi-res aerial imagery is usually done from airplanes from about 1 km height. Imagery satellites like landsat orbit around 700 km. Actually launching the satellite to orbit is only fraction of whole costs. A small fraction. Martin