A rapidly changing Earth environment will stress a wide range of social and economic components of our nation and the rest of the world. Addressing the urgent need to provide timely, relevant data to policymakers faced with the challenges brought about by climate change is one of the science community’s highest priorities. NASA and the National Oceanic and Atmospheric Administration (NOAA) have defined plans to start a new set of climate observations, partly to replace aging missions and to provide more pertinent and more accurate climate measurements. A mixed portfolio of mission sizes is vital for Earth science in order to accomplish its broad scope of objectives. We are concerned that the trend toward larger Earth science missions is reducing the opportunities for small satellite missions that can provide nimble and lower-cost solutions for some of the required climate measurements. An immediate reversal of this trend is necessary to ensure the vitality of programs that are presently experiencing cost and schedule growth. We recommend that Principal Investigator-Mode Mission options such as the NASA Venture-class be competed and implemented now in order to meet the mounting challenges presented by global climate change.

There has never been a time when the human impact on the environment has received as much attention, both as a driver of climate change and other deleterious environmental effects and in the depletion of critical resources. Yet this also marks a transitional period in Earth remote-sensing and observing capabilities, between the current NASA Earth Observing System and the future decadal survey missions and the National Polar-orbiting Operational Environmental Satellite System (NPOESS). How well this transition occurs may impact our ability to assess the state of the Earth system and mitigate and react to global change. Small satellites will aid in bridging the current and future global observing systems by addressing focused science questions, adding flexibility, shortening development periods and reducing costs. They serve both to ensure continuity and provide new opportunities of discovery and exploration.

The urgency of the nation’s commitment to Earth observations from space has been a focus of others. Nancy Colleton, executive director of the Alliance for Earth Observations and president of the Institute for Global Environmental Strategies, noted a prior opinion piece [“Climate: Not Business as Usual,” Space News, March 9, page 19] that the environmental challenges that the global community faces due to climate change will require increasingly greater attention and public response to adapt to and mitigate those changes. Our ability to assess the state of the present climate and to predict future climate change must rely on a comprehensive observing system that makes the appropriate measurements and does so in a timely manner that allows for the appropriate response of decision makers.

The top-level science questions for Earth and environmental observations, and the requisite measurement variables and their prioritization, were addressed in detail in the National Research Council (NRC) report “National Imperatives for the Next Decade and Beyond.” This decadal survey was the culmination of two years of studies by several panels organized along discipline lines. It provided the roadmap to NASA and NOAA for 17 missions between 2010 and 2020. It is our understanding that implementing this vision in an orderly and efficient manner is being challenged by cost growth and expansion of mission elements. In light of this, and considering the urgency for which these observations are required for meeting societal objectives, a sensible range of mission sizes and broad community support must be considered as key options that NASA and NOAA should be considering.

The nation’s future of climate observations from space now is proceeding with the rather tentative start of the implementation of the decadal survey missions. It also is clouded by the long-delayed, over-budget and broadly de-scoped NPOESS program. The urgency is heightened when considering that ongoing NASA Earth Observing System measurements are already extended several years beyond their design life, increasing the risk of gaps in critical data records.

Our reflections on the above concerns reinforce the recommendations made by the 2000 NRC report, “Assessment of Mission Size Trade-offs for Earth and Space Science Missions.” Several advantages of smaller missions were addressed and found to be relevant for the urgency of addressing the current demands of a climate observing system. A primary finding by this earlier NRC committee, and one that appears to be universally applicable and accepted, is that a mixed portfolio of mission sizes is vital for Earth sciences in order to accomplish its broad scope of objectives.

While seemingly common sense advice, at the present time the national strategy appears to be diverging from this tenet as evidenced by the expanding decadal survey missions and by the tri-agency NPOESS program. NASA Earth science Pathfinder and Venture-class missions can make key contributions to the nation’s strategic climate objectives. However, funding for these small satellite programs is quite limited. The community must reverse the current trend toward increasingly larger missions and a narrowing of the overall portfolio of mission sizes, in line with recommendations in the 2000 NRC report. A viable path in this direction within the present decadal survey program is by expanding the size and frequency of the Venture-class opportunities. Principal investigator-led missions such as these help to maintain cost and schedule while targeting well-focused science goals.

The cost and schedule benefits that smaller missions bring may help to accelerate the critical set of climate observations from space and free up resources for other essential and synergistic elements of the observing system, such as aircraft missions and modeling programs. Small missions typically shorten the time between mission inception and science results, from decades to years in some cases. They provide added flexibility and responsiveness to new scientific opportunities and can address some of the more-focused questions that emerge from larger-scale research activities. The shorter development periods and cost reduction may relieve budgetary burdens to the benefit of other program elements. Finally, but potentially quite significantly, small missions add vitality and broad community involvement, including student opportunities, through focused high-quality science programs over shorter periods.

In summary, we endorse strongly the scientific and programmatic goals laid out in the Earth science decadal survey. However, we urge that small spacecraft approaches be fully considered in implementing these important missions. Principal investigator-led missions deploying smaller spacecraft, with their attendant leaner management approaches, could attain a large fraction of the decadal survey goals with a substantial reduction in the proposed costs. Moreover, quick implementation along this pathway will ensure that space-based Earth observations are much more relevant for key policy decisions.

Daniel N. Baker, Ph.D., is the director of the Laboratory for Atmospheric and Space Physics (LASP) and a professor of astrophysical and planetary sciences in the department of physics at the University of Colorado, Boulder. Thomas N. Woods, Ph.D., is the associate director of LASP at the CU Boulder.