Planetary Science. Funding for planetary missions is \$1.631 billion, an increase of \$270 million above the request and \$193 million more than FY2015. It includes \$175 million for a mission to Jupiter's moon Europa, a priority of House Appropriations CJS subcommittee chairman Rep. John Culberson (R-TX). He added substantial funding for the mission in FY2013 (\$75 million) and FY2014 (\$80 million) although NASA did not request any. For FY2015, NASA requested \$15 million and Congress provided \$100 million. For this year, NASA requested \$30 million. Not only did Congress add \$145 million to that figure, but it directs NASA to build a lander as well as an orbiter. It reiterates that it wants the mission launched in 2022. NASA has been envisioning a later launch date to match the projected funding levels in the President's budget request.
Now, don't get me wrong, I'm all for an advanced Europa mission, but deciding so unilaterally, by a single congressman that happens to chair the House Committee on Appropriations Subcommittee on Commerce, Justice, Science, and Related Agencies, seems wrong to me. Countless advanced missions are proposed each year and compete for attention of the statesmen and budgetary support, and which ones succeed and which ones don't shouldn't be decided on by lone policymaker's wits.
It might backfire, and having watched the two day Exoplanets Program Analysis Group (ExoPAG) meeting that just ended today, it appears it already has. This unilateral budget increase for a single specific mission has been a subject of some ridicule, and Culberson's "vision" of focusing on Europa as one single world with highest likelihood of harboring life was corrected with the dioptric power of exoplanetology snark - that surely Earth-analog exoplanets have the highest likelihood of harboring life besides the Earth itself. I'm not going to comment if I agree or not (Enceladus! oops), that's not the point of my question, which is simply:
Is Culberson within his rights to unilaterally bypass all the mission prioritization and selection processes set in place so the scientific community and the society at large decide which ones to support, to what extent and when based on merit, feasibility, benefit, cost and other criteria that might apply? Can a single well-seated policymaker come up with and self-approve his own policy?
Please note that I'm not seeking an open discussion. I expect answers to be substantiated with verifiable sources of information, perhaps there's a precedent that I'm not aware of, but I also welcome some conjecture if you want to comment on this from your own perspective, as long as you first answer the question.