BOX 3.1

NPOESS, EOS, AND THE SEARCH FOR SUSTAINED ENVIRONMENTAL MEASUREMENTS

The NPOESS program was, at the outset, driven by a single imperative—convergence of weather measurements, which would eliminate duplication in observations in the early afternoon but maintain the same temporal robustness that characterized the combination of the Polar Operational Environmental Satellite and the Defense Meteorological Satellite Program. The cost savings from eliminating duplication could then be reallocated to improve weather observations and models.

By the mid-1990s, it was clear that NASA would not sustain a long-term, broad observation and informationprocessing program like the Earth Observing System (EOS); therefore, the community developed a new strategy for obtaining climate measurements from NPOESS. That led to a second NPOESS program imperative—operationalizing a climate observing system, which would enable sustained, long-term measurements for climate studies and other environmental issues. However, that was done after consideration of optical designs, orbits, and data systems needed for weather forecasts; additional requirements for climate were then added, and they invoked different objectives and thus requirements for optical designs, orbits, and other mission and instrument characteristics.

Attempting to satisfy the two imperatives simultaneously constituted a difficult challenge, both technically and programmatically. Part of the challenge arose from trying to balance the inherent mismatch of data requirements. Weather forecasts demand frequent observations and rapid data dissemination, but climate studies and research demand accurate and consistent long-term records. The added requirements of instrument stability and accuracy, driven by the more stringent climate requirements, placed additional challenges on the instruments. Moreover, the expanded mission’s requirements to address climate and other environmental issues established demands for additional observations, such as ocean altimetry, which were themselves not weather-related. That expanded the scope of the mission, increased its complexity, and added to the pressure for larger platforms. Finally, although the mission of one of the operational partners (the Department of Commerce’s NOAA) included climate and other broad environmental issues, the mission of the other (the Department of Defense’s Air Force) did not. That led to conflicting priorities between the two agencies, which by law were required to share program costs on a 50–50 basis.

for which the dominant satellite-sensed signal is from the atmosphere, monthly viewing of the Moon is essential to quantify changes in sensor response.

In its interim report (NRC, 2005), this committee recommended that NOAA embrace its new mandate to understand climate variability and change by asserting national leadership in applying new approaches to generate and manage satellite CDRs, developing new community relationships, and ensuring long-term accuracy of satellite data records.4 The committee also noted that NOAA had stated its intention to create CDRs from data gathered by NPOESS. However, as detailed elsewhere in this report (see, for example, Tables 2.4 and 2.5 and discussions in Chapter 9), the NPOESS program has been substantially descoped to a focus only on “core” missions related to weather. Despite obvious consequent limitations on the utility of NPOESS for climate studies, some of the remaining instruments are potentially capable of producing CDRs if the requisite programs and facilities are in place. Therefore, the committee reiterates its previous recommendation (NRC, 2005, p. 8):

4

See NRC (2004a); see also testimony before the House Subcommittee on Environment, Technology, and Standards, House Committee on Science, by Mark R. Abbott, Dean, College of Oceanic and Atmospheric Sciences, Oregon State University, on July 24, 2002, available at http://gop.science.house.gov/hearings/ets02/jul24/abbott.htm.



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