I think that the most interesting planet to visit would be Mars. I would sink in the giant plants and their satellites are too cold. Yes three of the gyroscopes on Hubble are still working of the six origianlly on the satellite. However, it they lost one of these, they could not continue to point the telescope at the stars and would have to stop work. I am not sure exactly what has gone wrong.
Gyroscopes are quite delicate electronic instruments and various things can happen.
I have not kept up with the number of satellites orbiting the earth for research. It must be in the dozens, in addtion to the commercial and military satellites. Japan and Europe both have very active programs and Russia still has a few. I think there will be a telescope on the moon some day. It will probably be a thin mirror mounted much like our newest earth-based telescopes.