This is the direction for our space program that two successive Congresses have endorsed, and that, according to a very recent Gallup Poll, three-quarters of our citizens "support", or "strongly support". This support is found roughly in equal proportions across the political spectrum, and between the genders. This is the kind of support that will fuel many of our space science initiatives in the future. And we are just at the beginning.
Having said this, I am aware that many in the science community have questioned NASA's commitment to science, and believe their own work to be gravely threatened by the Vision for Space Exploration. Let me speak directly to this point. I have frequently stated my belief that exploration will be a boon for science in the long-term. I have also said on many occasions that it is not our desire to sacrifice present-day scientific efforts for the sake of future benefits to be derived from exploration. We who run NASA today are doing our very best to preserve these efforts in the face of, frankly, some daunting fiscal realities. But we also must avoid setting unrealistic expectations. NASA's $5.4 billion investment in its Earth and space science portfolio is almost the size of the entire National Science Foundation, and this robust portfolio has grown at a rate significantly greater than has NASA's top line budget over the past decade. Such growth cannot logically be supported within an overall portfolio that is at best fixed in constant dollars.
But we must also acknowledge the plain fact that we cannot do everything that was on our plate when I assumed office. All of you know many reasons why this is so. NASA can only move forward on our fundamental missions of exploration, science and aeronautics at the pace that available resources will allow, so it is important to be as efficient as possible in allocating these resources. To this end, we have made several changes in recent months, and I would like to discuss some of these changes with you tonight.
First, we are reconstituting the organization the Science Mission Directorate into separate offices for Earth science, heliophysics, planetary science and physics and astronomy.
Second, Mary is defining an executable science program across each of these portfolios in Earth and space science. She is conducting a rigorous review of each flight project now in formulation and development, and establishing gates through which each program must pass in order to proceed from formulation to development. This process requires balancing technical performance against cost, evaluating the management team that is in place, and rigorously identifying risks and defining plans to mitigate them. We very much need better cost discipline in the large assignment missions, as cost growth inhibits the future of the smaller, but incredibly prolific, competed lines.