CIESIN Reproduced, with permission, from: National Aeronautics and Space Administration (NASA). 1993. Earth Observing System (EOS) Reference Handbook, ed. G. Asrar and D. J. Dokken. Washington, D. C.: National Aeronautics and Space Administration, Earth Science Support Office, Document Resource Facility.



Planning for the EOS mission began in the early 1980s, and an Announcement of Opportunity (AO) for the selection of instruments and science teams was issued in 1988. 458 proposals were received in response to the AO. Early in 1990, NASA announced the selection of 30 instruments to be developed for EOS, along with their science teams; 29 Interdisciplinary Science Investigation teams were also selected at this time.

EOS was recognized as part of the Presidential initiative Mission to Planet Earth in 1990, receiving its "new start" from Congress in October. The EOS Program was funded under a continuing resolution, and ramped up to its full funding with the approval of the FY91 budget in January 1991. At that time, plans called for the instruments to be divided into three groups--the EOS-A and EOS-B series spacecraft, and for flight as attached payloads on Space Station Freedom. Instrument selection were also made for the proposed Japanese and European polar-orbiting satellites, then referred to as the Japanese Polar-Orbiting Platform (JPOP) and the European Polar-Orbiting Platform (EPOP). Table 4 provides the major milestones of the EOS Program to date.


In 1991, as directed by the U.S. Congressional Committee on Appropriations, the original plans for EOS were restructured for three principal reasons:

To meet these constraints, NASA restructured the EOS Program via a thorough review by an external engineering committee, evaluation by the scientists who will use the EOS data, and systematic engineering studies of spacecraft configurations and launch options. The basic guiding principles for restructuring follow:

In July 1991, an EOS External Engineering Review (EER) Committee was convened in La Jolla, California. NASA and selected Interdisciplinary Science Investigation PIs briefed the EER Committee on the Congressional constraints, their opinions regarding reconfiguration, and options that they should consider. The EER Committee endorsed the presented options in its report as a "proof-of-concept" for an EOS that contains a "favorable measure of resiliency." In August 1991, NASA discussed payload options at the Seattle EOS IWG meeting; in October, a formal review was conducted by the EOS Payload Advisory Panel in Easton, Maryland. This latter body is composed of the EOS Interdisciplinary Science Investigation PIs, and is formally charged with examining and recommending EOS payloads to NASA based on the scientific requirements and priorities established by the Earth science community at large. Concurrently, extensive engineering studies were conducted at Goddard Spate Flight Center (GSFC) to determine the most effective spacecraft configurations so that the instruments could be accommodated on smaller platforms. In December 1991, the NASA Administrator conducted a thorough review and approved the restructured EOS Program.

On March 9, 1992, NASA submitted a report on the restructuring of EOS to the Committees on Appropriations of the House of Representatives and Senate. Congress endorsed its contents as both comprehensive and fiscally responsible, with the final payload configurations for the restructured EOS satisfying all Congressional constraints. EOS focused on climate change; the observatories originally slated for launch aboard Titan IV expendable launch vehicles (ELVs) were to be launched on multiple smaller platforms via smaller ELVs; and the program was to have a total cost of $11 billion through FY2000. The final payloads were very similar to those endorsed by the EER Committee and wholly consistent with its recommendations. See Figure 4 for the payloads and launch dates of the restructured EOS. These payloads satisfied the recommendations of the EOS Payload Advisory Panel, with the caveat that some of the instruments would fly later than recommended due to budgetary constraints. Refer to the EOS Science Objectives sections for the rationale leading to these payload configurations.


The recommendations mode by the EER Committee and the consequent restructuring of the EOS Program were based on integrated 1992-2000 budget of $11 billion, down from the $17 billion projected in 1990. In October 1992, the FY93 appropriations bill passed by the U.S. Congress reduced the decadal budget to $8 billion; thus, in 2 years, the budget was essentially cut in half. Each cut has reduced the scope and resilience of the EOS Program. Obviously, lower funding requires that NASA pursue only the highest priority science and policy issues, significantly reducing the breadth of observations that were to be collected under the baseline plan of 1990.

Rescoping studies had begun soon after the restructured EOS Program was endorsed by Congress. As part of an internal examination of all major programs, the NASA Administrator established "Red" and "Blue" Teams in May 1992, to review content, schedule, and cost. The Blue Team consisted of NASA employees (Headquarters and GSFC) who "own" the program and budget resources; the Red Team was composed of NASA employees [augmented by Jet Propulsion Laboratory (JPL) personnel] with project management experience outside of the program in question. The Red Team was charged with challenging the current approach and suggesting innovations to help NASA streamline its programs--that is, make them faster, better, and cheaper. The Administrator had also set a 30 percent reduction in budget as a target (i.e., from $11 to $8 billion), which was to act as a stimulus for the teams to reassess EOS content and configurations. Red and Blue Team recommendations focused on the budget for the later years, not the FY93 request which had already been pared back consistent with the above-mentioned Congressional directive. NASA Headquarters carefully considered the input of both the Red and Blue Teams and the EOS Payload Advisory Panel to arrive at the rescoped payloads listed in Table 5. As can be seen, most changes were confined to the EOS-AlT and -CHEM series payloads. Refer to the EOS Science Objectives sections for more detail about instrument configurations and the impact that the rescoped program has on the science return.

EOS retains its emphasis on collecting observations over a 15-year period, but many important measurements have been cancelled or deferred due to the fact that it is now a "cost-driven" program. As can be seen in Table 5, several instrument changes are anticipated for the later launches in the EOS-AM and -PM series. Some instruments must now be provided by international partners, as will the spacecraft for the EOS-AERO series.

The descope to an $8 billion threshold required difficult tradeoffs to minimize the adverse impact on EOS science objectives. One key choice involved reducing the amount of contingency funds held to handle unexpected problems in instrument development due to engineering and design challenges, and/or to accommodate changes in science requirements that drive specifications for the instruments and data system. This contingency had to be balanced against savings that would result from complete elimination of instruments and their associated scientific information. The Red and Blue Teams and the EOS Payload Advisory Panel recommended that NASA reduce program contingency funds in favor of a loss in future EOS design flexibility.

The Payload Advisory Panel, which represents the EOS investigators, believes that a properly structured $8 billion funding profile through the rest of this decade is enough to design and put in place the initial components of EOS. The increased risk associated with a reduction in contingency is implicitly mitigated, because EOS is a long-term measurement program with instruments flown on 5-year intervals. As such, instrument development problems or changes in science specifications could be handled in the next versions of the instruments. Obviously, some level of resilience and flexibility must be maintained to guarantee that a fully functional EOS be carried out regardless of ever-changing budgets, and to allow for the necessary technology developments that benefit U.S. competitiveness. Figure 5 shows the overlapping coverage that the phased launches will provide, and projects the total number of instruments in orbit at any given time over the first 12 years of the EOS Program.

The funding profile developed under the restructured program already reduced EOS to a minimum set of instruments to pursue the focused objective of global climate change. The measurement capabilities of the remaining instruments have been optimized to the maximum level possible, and further reductions prove unfeasible. At $8 billion, EOS must depend increasingly on the international partners. Failure to accomplish planned international cooperation on the Advanced Earth Observing System (ADEOS), Polar-Orbit Earth Observation Mission (POEM), Tropical Rainfall Measuring Mission (TRMM), and their follow-on missions will leave gaping holes in IEOS. Undoubtedly, further budget cuts would require wholesale elimination of instruments, thus information critical to understanding global climate change.


The National Spate Council (NSpC), chaired by the Vice President, issued National Space Policy Directive 7 (NSPD 7) in June 1992, covering the space-based elements of USGCRP. This document directed NASA to implement the restructured EOS Program as part of an overall space-based global change observation system. Specifically, the policy directive formalized the following:

NSPD 7 established a focused national effort to improve multiagency collaboration in developing, collecting, analyzing, and archiving space-based observations of the Earth, with the ultimate goal of improving the world's ability to detect and document changes in global climate.

NSPD 7 directed NASA to coordinate production of an interagency program plan entitled "The Space-Based Global change Observation System (S-GCOS) Program Plan: An Assessment of current Status and Interagency cooperation," which was first released in October 1992. In addition, NSPD 7 stipulated that the working group preparing this document identify an integrated plan for the development of new Earth remote-sensing instruments, missions, and associated technologies that involve NASA, DOE, and DoD. To meet their joint responsibilities, the participating agencies agreed on the following guidelines:

In March of each year, the annual program plan will be submitted to CEES through the Federal Coordinating Council for Science, Engineering, and Technology (FCCSET) to NSpC, the National Security council (NSC), the Office of Science and Technology Policy (OSTP), and the Office of Management and Budget (OMB). The annual report will address the S-GCOS architecture, existing and planned S-GCOS satellite systems, technology development activities, sensor suites, launch systems, supporting agency contributions, and data and information systems. Specifically, the plan will identify innovative flight alternatives (e.g., small satellites, or piggybacks on commercial or military launches) and sensor options that might provide the earliest possible availability of high-priority observations or that fill critical gaps in the existing observation plan.

At present, the S-GCOS Program Plan Working Group has identified three primary Earth remote-sensing areas where joint-use requirements and/or associated research and technology development prove suitable for collaboration between NASA, DOE, and DoD: Laser remote sensing of atmospheric winds, high resolution multispectral imaging of the Earth's surface, and synthetic aperture radar (SAR) imaging of the Earth's surface. In December 1992, working groups were established to review coordination among agency programs and schedules, science matters, data management matters, and technology improvement needs--all of which will be addressed in the first S-GCOS Annual Report slated for release in March 1993.

As can be seen in the above discussion, the EOS Program has helped decisionmakers recognize the value of space-based global climate observations. Over the past decade, politicians--both at the national and international level--have become increasingly more aware of the urgency of collecting such information on a global scale. NASA and its interagency/international partners have undertaken an exciting challenge to provide the necessary data and knowledge required to establish sound polity decisions on human activities, which have a direct effect on the global environment. Informed and timely decisions are needed to guide the stewardship of planet Earth and ensure its habitability for future generations.