By funding most missions in flight and continuing development of missions already approved, the budget is largely status quo. The radical changes to NASA’s program would come for the missions that will follow these.

NASA’s mission strategy has been to fly a mixture of mission that fall into different cost classes. Some scientific priorities require expensive, highly capable spacecraft, such as the 2020 Mars rover in development. NASA refers to these missions as Flagships that would cost $1.5B to $2.5B (more expensive Flagship missions were flown in the past). Flagship missions would do the difficult, high priority studies that simply can’t be done more cheaply. The expectation has been that one or two Flagship missions would be developed per decade, with missions to Mars, Europa, and Uranus (in that order) having the highest priority.

NASA has a second mission class for high priority studies that can be done more cheaply ($700M to $1B), known as the New Frontiers program. In the past, this program was used to develop the New Horizons spacecraft on its way to Pluto, the Juno orbiter en route to study the interior of Jupiter, and the OSIRIS-REx asteroid sample return mission that is in development. For the future, the scientific community has prioritized a Venus lander, a Saturn atmospheric probe, a Trojan asteroid tour and rendezvous, a comet surface sample return, and a Lunar South Pole-Aitken Basin sample return for this program. The expectation had been that New Frontiers missions would be selected every five to seven years. As recently as last summer, NASA was planning to select the fourth mission in the series in the next year or two.

Discovery program missions cost approximately $450M and are competitively chosen from proposals submitted by scientific teams to study any solar system body except the sun and Earth (NASA has other programs to study those two bodies). NASA originally selected Discovery missions every two years, but that has been stretched to every five years recently.

The new budget proposal would radically shift the mixture of mission classes for the future. The budget for the Discovery program would be ramped up to a level that would again allow selection of missions every two and a half years (In a past meeting, Jim Green, head of NASA’s Planetary Science program, has said that a budget of ~$350M would support starting a Discovery mission every two years.) However, the budget states that after the launch of the OSIRIS-REx mission, funding for the New Frontiers program drops to near zero and no money is foreseen up to 2019 to develop future missions (it is silent about whether New Frontiers missions might be selected after that).

The proposed budget also doesn’t foresee any new outer planets Flagship missions to be started before 2019 and looks to see if the highest priority future Flagship mission could be descoped to the equivalent of a New Frontiers mission. The approach proposed in the budget is the second case where I am left scratching my head wondering what the thinking is. Thanks to generous funding added by Congress in the last two budgets, NASA has extensively studied a ~$2B proposed mission called the Europa Clipper. For the FY15 budget, NASA proposes to spend $15M (a substantial cut from last year’s $80M inserted into the budget by Congress for Europa mission studies) to assess the potential for a $1B Europa mission. Testing different cost points to learn what each could provide is a smart management move. What doesn’t make sense is that the budget proposes to spend $15M next year, and then nothing for a Europa mission until possibly sometime in the 2020s. The engineers who will study the descoped mission will have moved on to other projects or retired; technologies available today will be obsolete. So why bother?

While Congress has strongly supported doing a Europa mission earlier than the 2020s, it can’t force the formal start of development on a new mission. Congressional budgets expire every September 30th. To start development on a new mission, NASA needs both for its budget to show proposed budgets in future years to complete the development and for Congress to appropriate the funds for that development each year. Under the proposed budget, we would have one more year of studies and then nothing for perhaps another decade.

This budget proposal presents almost no vision for NASA’s planetary program following the completion of the missions currently in development. No money would be spent to prepare for a Flagship mission to launch in the 2020s. The Outer Planets program shrinks to near zero, and the same for the New Frontiers program. In the proposed budget, the only firm plan for the following decade appears to be a robust program of Discovery missions, but that alone isn’t enough for a robust planetary science program.

Unless the Planetary Science budget suffers a severe cut at the turn of the next decade, funds should be available to develop several missions for the 2020s. By my back-of-the-envelope calculations*, continuing the current funding levels (with inflation adjustments) would support development of the Europa Clipper, a New Frontiers mission, and five Discovery missions in the 2020s. Alternatively, NASA could fund three New Frontiers-class missions (including perhaps, a budget Europa mission) and five Discovery missions.

However, preparing to fly these missions requires funding in advance of mission selection to have robust programs ready, and the budget doesn't show funding to do this.

My take is that the new budget proposal is an interim document when it comes to preparing for the next decade’s missions. The President’s budget managers have placed a low priority on planetary science compared to other NASA programs, and the program’s budget has suffered substantial cuts as a result. This is the first budget proposal in several years that shows essentially flat spending into the future instead of new cuts. NASA’s managers likely are revamping their expectations for the planetary program given the new budget realities. We haven’t heard (and NASA may well not know) what mission portfolio it plans to support in the future within that reality.

Statements by Jim Green at last week's Lunar and Planetary Science Conference suggests that the the outyear budget projections are a placeholder. At the conference, he said that NASA wants to begin selection of a new New Frontiers mission (number 4 in the series) in 2016, which suggests that development would start in 2018 or 2019. He also said that he wants to increase the frequency of Discovery missions to three to four a decade from the current two a decade. And NASA has said that it expects to fly a Europa mission in the mid-2020s, suggesting that development would start between 2019 and 2021. Only the increased funding for Discovery missions is shown in the budget, suggesting that beyond the next two or three years, the budget numbers are placeholders.

For NASA's future planetary program, the top priorities are clear. First, NASA needs to complete the 2020 Mars rover mission with the capability to cache samples for a possible future return to Earth for analysis in terrestrial laboratories. The caching of samples was the highest priority Flagship mission identified by planetary scientists in their last roadmap assessment, the Decadal Survey. NASA also needs to complete the next New Frontiers and Discovery missions in development. The proposed budget would fund all these missions.

Beyond the three missions in development, we will need to wait to hear NASA's plan to continue to explore the solar system into the next decade. To meet the priorities laid out in the Decadal Survey, NASA's managers will need to select additional missions for the New Frontiers (number 4) and Discovery (number 14) programs toward the end of this decade and begin development of a mission to Europa. We will need to be patient as they develop their plans to do so.

*My back-of-the-envelope calculation assumes that the total costs to NASA for a Discovery mission is ~$700M, for a New Frontiers mission ~$1.3B, and for a Flagship mission ~$2.6B. These include costs such as launching missions that are in addition to the generally quoted costs for for the spacecraft, instruments, and operations. I also assume that funding to develop and fly new missions continues at the ~$775M per year shown for FY19.