Before revision: Fast E-sail Uranus entry probe mission In 2015, NASA announced it had begun a feasibility study into the possibility of orbital missions to Uranus and Neptune, within a budget of 2 billion in 2015 dollars.
After revision: In 2015, NASA announced it had begun a feasibility study into the possibility of orbital missions to Uranus and Neptune, within a budget of 2 billion in 2015 dollars.