Rooting for David over Goliath may make for good storytelling, but it is not necessarily good science policy. Unfortunately, there has been a long history of contrasting the value of smaller grant programs with NASA’s flagship science missions. While the smaller missions may appear to be more cost-effective, scientific metrics show us that the flagship missions actually have been the major contributors to science return — accounting for more than 42 percent of all NASA’s discoveries in the last three decades.

In the mid-1980s, I served at NASA during a time when the NASA Advisory Council issued a report titled “The Crisis in Space and Earth Science” to document the value of placing our resources in big missions. This led to a critical debate over the role of flagship missions, which typically cost more than $1 billion each. The Hubble Space Telescope is probably the most notable NASA flagship mission. In fact, after the discovery of Hubble’s flawed mirrors, Hubble was often cited as the kind of program NASA should not fly. As a result of these perceptions, the early 1990s saw a relative shift in investment from flagship to smaller science missions.

As the same debate of 15 to 20 years ago re-emerges, we need to look at what has happened subsequently in order to make better informed decisions about the future.

With the plethora of policy debates over flagship versus small missions in the early 1970 s, NASA headquarters employees grew frustrated with the lack of associated metrics. Therefore, we explored the use of metrics to benchmark scientific performance that would help illuminate our choices for the best path forward. No single metric is perfect, but the Science News metric stood out for its independence from NASA, ease of calculation, ease of comparison (over time and with non-NASA science), and its ability to be correlated with other metrics. Science News has identified approximately 200 of the most important discoveries in science each year. With a little research on our part, it was possible through the use of these metrics to identify trends in NASA scientific return. For example, NASA’s contributions to world science have varied from a low of 2.7 percent in 1986 to a high of 10.4 percent in 1994.

To elicit relevance to today’s debate, Luke Sollitt, a scientist at Northrop Grumman, recently analyzed the Science News database to find the key drivers for NASA scientific performance, and the results were surprising. Since 1973, flagship missions have been the major contributors to science return, accounting for 42 percent of NASA’s discoveries. Since its launch in 1990, Hubble has produced 25 percent of NASA’s science return. Despite the mirror problem, and cost growth higher than originally estimated , Hubble has delivered world-class scientific performance.

The NASA science community faces hard choices in an era of constrained resources and unusually rich space assets. Space shuttle delays in the 1980 s slid missions to launch manifests late in that decade or early into the 1990 s — such as Galileo, Magellan, Hubble, the Compton Gamma Ray Observatory and the Cosmic Background Explorer . The net result was a scientific windfall in the 1990 s from a combination of deferred missions, flagship new starts and new smaller missions developed on rapid schedules. But the last flagship to launch was EOS Terra in 1999. Only Cassini, launched in 1997, is still in its prime mission, thanks to six years of cruise time out to Saturn. There are no flagship missions officially approved for implementation; the next in the queue, the James Webb Space Telescope, will be ready for launch no earlier than 2013. From a historical perspective, the scientific risk is not from too many flagship missions, but from the 14-year gap in flagship prime missions .

Another surprising insight from Sollitt’s analysis concerns NASA’s smallest programs. The science productivity from innovative non-flight efforts has grown dramatically, outscoring any single flight program (including Hubble) by the Science News metric in two of the last three years. Typically, non-flight science includes individual researchers at NASA centers, grants to university researchers, observing time on NASA-administered telescopes and other traditionally small programs. Recent examples include a Goddard Space Flight Center researcher who drove a specially instrumented pickup truck through dust devils and found that they were electrostatically charged, the discovery of microbes in Yellowstone National Park that derived energy from hydrogen, not sulfur, and the discovery of microbes that use light from hydrothermal vents. Innovative work in NASA’s smallest programs has had a growing contribution to the productivity of NASA science. Everyone in the community hopes that increased funding can be added to NASA’s budget to help its science program, but sometimes that is not possible and choices must be made. However, by framing the debate as a choice between flagship missions and research grants, two of the most powerful engines for NASA science productivity are targeted.

Extrapolating NASA’s $5.3 billion annual science budget over the next 10 years provides $53 billion for science investments. If the budget for flagships was $10 billion of this total, that would provide the $3 billion needed to complete the James Webb Space Telescope and leave adequate funding for the Space Interferometry Mission, the Mars Science Lander and two to three more flagships, while leaving $43 billion for everything else. None of this makes trade-offs easy for leaders at NASA headquarters, because there are so many excellent opportunities within the science portfolio, but it does show that there is more than David and Goliath to consider.

Greg Davidson worked for 12 years at NASA and has been working for the last nine years on civil space programs at Northrop Grumman in Redondo Beach, Calif.