SAN FRANCISCO — Seven years after an independent review board cited the importance of two ambitious Earth science missions, NASA officials are investigating ways to perform scaled-back versions of the original projects that fit within current budget projections.

NASA and the Indian Space Research Organisation (ISRO) are conducting a study to determine the feasibility of launching a spacecraft equipped with L-band and S-band synthetic aperture radars to observe a variety of phenomena, including changes in global vegetation, wetlands, coastlines and soil moisture. If the project proceeds, it would be the first satellite built jointly by NASA and ISRO, NASA spokesman Stephen Cole said.

The proposed NASA-ISRO mission would meet nearly all of the important scientific objectives of the radar portion of the Deformation, Ecosystem Structure and Dynamics of Ice (DESDynI) mission, which was cited in the National Research Council’s 2007 Earth science decadal survey as a top priority, Cole said by email. Unlike the proposed DESDynI mission, the NASA-ISRO satellite would not include a lidar to gather data on tree canopies, ground topography and global vegetation. Some of that information, however, may be provided by the lidar NASA plans to fly on its ICESat-2 mission scheduled for launch in 2016, NASA officials said.

“The NASA-ISRO synthetic aperture radar mission does not meet all the science objectives of DESDynI, but it goes a long way,” said Paul Rosen, Radar Science and Engineering Section manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “The radar was the mapping workhorse.”

The planned NASA-ISRO mission would include L-band and S-band synthetic aperture radars sharing a common reflector. The proposed DESDynI mission featured a single L-band radar. By gathering data in two wavelengths, researchers obtaining data from radars onboard the NASA-ISRO satellite would be able to more accurately observe and classify various types of vegetation and measure changes in the amount of carbon stored in vegetation, Rosen said.

In addition, the dual radars would help researchers identify movement of Earth’s surface as small as a fraction of a centimeter, which they could use to detect stress building near earthquake faults and dormant volcanoes. With that information, researchers would be able to improve the models designed to depict processes occurring deep underground before, during and after these events. That, in turn, would lead to improved forecasting of the risk of earthquakes and volcanoes, Rosen said.

Under preliminary plans, ISRO would supply the S-band radar, satellite bus and launch vehicle for the joint mission, while NASA would provide the L-band radar, said Mike Freilich, NASA Earth Science Division director. NASA hopes to move the joint mission into the first phase of planning, the mission formulation stage, in late February or early March, Freilich said Dec. 11 at the American Geophysical Union conference here.

Clarifying CLARREO

DESDynI is one of two high-priority missions identified by the decadal survey that have not proceeded into the mission formulation stage. The other is the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission, a joint NASA-U.S. National Oceanic and Atmospheric Administration (NOAA) campaign to improve the accuracy of climate models by collecting data on atmospheric, land and sea-surface temperatures; cloud properties; ocean color; solar irradiance; and aerosols. One unique aspect of that mission was its plan to include an on-board instrument calibration system.

NASA officials approved the CLARREO mission concept in November 2010, but halted work on the project in 2011 due to a lack of available funding. “The CLARREO group has done tremendous work getting their hands around that extremely ambitious mission and its cost but it is not likely to fly before 2023 at the very earliest,” Freilich said. “CLARREO remains a challenge.”

As a result, the CLARREO study team is exploring lower-cost options for the mission that maintain as much of the desired science return from the notional decadal survey mission as possible, Cole said.

Researchers currently obtain related observations from Northrop Grumman Corp.’s Clouds and the Earth’s Radiant Energy System (CERES) sensors flying on NASA’s Aqua and Terra spacecraft as well as the NASA-NOAA Suomi National Polar-orbiting Partnership satellite. To ensure data continuity without CLARREO, the science community will rely on observations made by CERES and its successor, the Radiation Budget Instrument (RBI), to measure changes in Earth’s outgoing radiation. NASA continues to place a high priority on obtaining those observations over the long term, Cole said.

NASA began soliciting RBI proposals from industry in June. The space agency plans to award a contract in the spring for the design, development, testing and delivery of RBI. RBI is scheduled to fly on the second NASA-NOAA Joint Polar Satellite System spacecraft, scheduled for launch in November 2021.

In spite of the challenges facing the DESDynI and CLARREO missions, NASA officials are quick to point out that the Earth Science Division has robust program plans, which include the launch of six research missions by the end of 2015. Three of those missions are slated to fly on their own spacecraft: the Global Precipitation Mission, Orbiting Carbon Observatory-2 and Soil Moisture Active Passive. The other three instruments will be installed on the international space station, Freilich said. The space station will play host to Rapidscat, Cloud Aerosol Transport System and Stratospheric Aerosol and Gas Experiment-3, Cole said.

When the National Research Council conducted a midterm assessment in 2012 of NASA’s Earth Science portfolio, the division won praise for the steps it had taken to implement the recommendations of the 2007 decadal survey in spite of receiving far less money in annual appropriations than the review panel anticipated. Those lower funding levels posed significant problems for the ambitious CLARREO and DESDynI missions, NASA officials said.

“Owing to the costs and technical challenges of the notional CLARREO and DESDynI missions, inclusion of those missions in the plan for launch before 2021 would have required exclusion or delay of many of the missions now being developed, substantially diminishing the overall scientific potential of the full portfolio,” Cole said.

Debra Werner is a correspondent for SpaceNews based in San Francisco. Debra earned a bachelor’s degree in communications from the University of California, Berkeley, and a master’s degree in Journalism from Northwestern University. She...