When the Voyager 2 spacecraft flew by Uranus back in January 1986, it saw an almost featureless planet. This was a disappointment after the spectacular images Voyager 1 and 2 obtained of Jupiter and Saturn. The only visible features on Uranus were very low-contrast cloud bands and a handful of very low-contrast, discrete cloud features. They were only clearly visible when image processing was used to greatly exaggerate the contrast of the Voyager 2 images.

In the years since the Voyager 2 flyby, Earth-based telescopes have been able to observe Uranus with steadily increasing clarity, thanks to both an increase in Uranus' atmospheric activity and better instruments (in particular, adaptive optics). A very important advantage over Voyager 2 is that these telescopes/instruments can observe Uranus in near-infrared light where Uranus' atmospheric features are more clearly visible. Voyager 2's problem was that it couldn't image Uranus at near-infrared wavelengths. The longest wavelength of light it could "see" was orange.

By far the most amazing Earth based images obtained of Uranus are the images described in this blog entry from 2012. I felt as if I was looking at a completely new planet when I saw these images. They are the result of sophisticated processing where a lot of images have been stacked and derotated to decrease noise and compensate for Uranus' rotation and east-west zonal winds over the long time required to obtain the images.