House Science and Technology Committee Chairman Bart Gordon (D-Tenn.) applauded a new National Academy of Sciences report urging the U.S. government to fund 17 Earth-observing satellite missions between 2010 and 2020 in order to rebuild the nation's aging network of environmental spacecraft.

Without the reinvestment, the report warns, the number of U.S. satellites monitoring the Earth's climate could drop from 29 today to seven by 2017.

Gordon said the findings should come as no surprise to anyone who has paid attention to the budget cuts NASA's Earth science program has sustained since 2000 and the disruption on National Oceanic and Atmospheric Administration (NOAA) observation programs caused by cost overruns on the nation's next-generation weather satellite systems.

Gordon said his committee would be "watching closely" to see whether the 2008 budget request the White House puts forward in February is consistent with the recommendations in the report, "Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond," a 10-year-plan for U.S. Earth science missions known as a decadal survey, which can be found here. The first-of-its-kind assessment was released by the National Academy of Sciences Jan. 15 at the American Meteorological Society's annual meeting in San Antonio.

"The decadal survey recommends a path forward that restores U.S. leadership in Earth science and avoids potential collapse of our system of Earth science satellites," said Richard Anthes, co-chairman of the two-year-study and newly elected president of the American Meteorological Society.

Anthes told reporters Jan. 15 that NASA's investment in Earth science, measured in constant dollars, has dropped from $2 billion in 2002 to $1.5 billion today.

To fund the missions proposed in the report, NASA would have to go back to spending $2 billion a year on Earth science while NOAA would have to maintain a steady $1 billion annual investment in satellites and instruments that monitor Earth's climate.

Two of the proposed missions identified in the report would be undertaken by NOAA. The remaining 15 would be NASA's responsibility.

Half of the proposed missions, the report estimates, could be accomplished for $300 million or less with none costing more than $800 million in today's dollars.

The first of the new missions proposed that is not already in NASA's or NOAA's pipeline is DESDynI, which stands for Deformation, Ecosystem Structure and Dynamics of Ice. Anthes said DESDynI would cost an estimated $700 million and be designed to fly a Ka-band interferometric synthetic aperture radar instrument and laser altimeter in a sun-synchronous low Earth orbit.

Another early mission, the Climate Absolute Radiance and Refractivity Observatory, or Clarreo, would be a joint effort of NASA and NOAA, with NASA covering the bulk of the project's $265 million price tag.

The most expensive of the proposed missions is the ACE (Aerosol/Clouds/Ecosystem) mission. According to the National Academy of Sciences report, the satellite for that $800 million mission would be equipped with four instruments. The launch would take place between 2013 and 2016 to help reduce uncertainties in predictions about global climate change.

NASA made a robust investment in environmental satellites in the 1990s, building an Earth Observing System that was completed in 2004 with the launch of the multiple-instrument Aura satellite. The three satellites in the system were complemented by the launch of several smaller, more focused satellites, including Cloudsat and Calipso, which launched as a pair in early 2006.

Thanks to that robust investment -- as well as launch delays and satellites lasting longer than expected -- the United States has an unprecedented number of environmental spacecraft and instruments currently in orbit: 29 operating satellites and 122 instruments, according to the report.

But "a great fraction" of those Earth-observation capabilities are expected to go dark over the next few years, Anthes said. The report forecasts a 40 percent decline in the number of working sensors and instruments on orbit "given that most satellites in NASA's current fleet are well past their nominal lifetimes."

NASA has a small number of new missions in development, including the single-instrument Orbiting Carbon Observatory, the Ocean Surface Topography Mission, and a greenhouse gas-monitoring satellite dubbed Glory. All three are slated to launch in 2008, according to NASA Goddard Space Flight Center's Earth Observing System Web site.

NASA also has in development for a 2009 or 2010 launch a multi-instrument satellite designed to serve as a bridge between the first round of Earth Observing System missions and the launch of the National Polar-Orbiting Operational Environmental Satellite System (NPOESS) next decade. NASA Administrator Mike Griffin testified before the House Science and Technology Committee last June that the NPOESS Preparatory Mission would help ensure the continuous collection of certain Earth Observing Systems measurements and provide flight validation of some key NPOESS sensors, including the behind-schedule Visible/Infrared Imaging Radiometer Suite.

The NPOESS program was restructured in July when its projected cost soared from $6.8 billion to more than $11 billion. As part of the restructuring, several key climate, environmental and weather observation capabilities important to scientists were dropped from NPOESS. The sensors that are still part of the NPOESS plan, the report says, "are generally less capable than their Earth Observing System counterparts."

The report recommends adding capabilities back to NPOESS or finding a way to obtain them by other means. In addition to laying out a phased sequence of new missions from 2010 to 2020, the report urges NASA to take a number of more immediate steps, among them committing to launching a Landsat 7 no later than 2011 and launching the long-planned Global Precipitation Measurement mission not later than 2012.

The report also calls for NASA to complete the Geosynchronous Imaging Fourier Transform Spectrometer and find a ride for it. The instrument was being built for an experimental weather satellite called Earth Observer-3, a satellite that lost its U.S. Air Force-sponsored launch reservation amid budget uncertainties and subsequently was canceled.