The dotted line is the budget growth expected by the original decadal survey. The black line is the actual budget (far less than the proposed cuts). The dashed line is the projected White House funding for Planetary Science. I have (crudely) updated the chart to reflect congressional budget action in 2017 and 2019, and the updated proposal from the White house going forward with the new lunar exploration effort. The House is proposing upwards of $2.7 billion for planetary science in 2019, the Senate maintains the proposal at $2.2 billion.

Given the generous congressional and public support, the program is now making real progress in addressing the top priorities and recommendations made in the original decadal survey.

Key to this was reducing the costs of two major flagship missions: the Mars 2020 rover and the Europa Clipper. The original decadal survey recommended starting a sample return campaign from Mars only if the first mission could be done for less than $2.5 billion, down from an early estimate of $3.5 billion. The sample-caching Mars 2020 rover project has a ~$2.4 billion budget. The Europa mission was similarly given a conditional recommendation if it could reduce its costs significantly below its original $4.7 billion estimate and if new money could be found to support it. Congress has certainly provided the funding, and though the Europa Clipper project has yet to receive an official budget estimate, the Government Accountability Office estimates its budget as between $3.1 billion and $4 billion, depending on the launch vehicle used.

NASA also received positive analysis from the new report regarding its funding for basic scientific research, which has increased; maintaining a healthy budget for technology development; and balancing the portfolio of scientific investigations and destinations.

However, the report does find that NASA, through both "budgetary and policy decisions," was unable to maintain the recommended cadence for its smaller planetary missions, and significantly delayed critical technology investment needed to return samples from Mars—the top scientific priority for all of planetary science. Basically, due to the limited budget, NASA chose its flagship missions over smaller missions. The new report recommends that NASA select three new small-class (Discovery) missions in between 2019 and 2021 in order to help make up for lost time. NASA selected two missions in the previous Discovery competition (Lucy and Psyche), so this is not inconceivable.

The Europa lander project, which was not considered in the realm of possibility in the decadal survey, but now is up for discussion based on Congressional mandate, received an icy response from the new report. Declaring multiple times that "a lander was not prioritized" in the decadal survey, and "given its cost and its potential impact on the rest of the planetary science program" the report recommends that "the mission should be vetted within the decadal survey process." In other words, NASA should wait until the next decadal survey, set to be released in 2021, to see if it should pursue a lander mission.

These efforts to meet the top scientific recommendations for exploring our solar system will require continued support and oversight in order to pay off. Most of the investment for planetary science happening now won't be realized until the next decade. But the direction is positive, and given the starting conditions for NASA's Planetary Science Division in this decadal period, this report is very encouraging. The outlook for planetary exploration is brighter than it has been in years (there is an exception—the Mars Exploration Program—which this report analyzes and I will discuss in a separate post).

Note: a previous version of this article incorrectly stated that the report called for six new Discovery missions in the next three years. The text has been corrected to reflect that the recommendation is for three new mission selections spread out between the next two selection opportunities.