Third, NASA’s development of the light and relatively cheap ASRG plutonium-based power systems enables cheaper missions than were possible with the older, heavier power systems. Our only up close examinations of planets in this class were the flybys of Uranus and Neptune in the 1980s by the Voyager 2 spacecraft that carried 1970s vintage instruments. (Alas, new budget realities make any such mission look 20 years away or more now.) Second, the Uranus-sized worlds are proving to be common in other solar systems and may be the most common type of planet in the galaxy. Why the interest now? First, the 2011 Decadal Survey ranked a $2B Uranus orbiter and probe mission as a priority to launch in the coming decade.
I also read through the abstracts of mission concepts presented at the many planetary science and engineering conferences each year. Given my interest in future planetary missions, I regularly look through lists of missions submitted to space agency mission selection competitions.
