WASHINGTON -- NASA has selected two science proposals to be the agency's next Explorer Program Mission of Opportunity investigations. One activity will study black holes and other extreme environments in the universe. The other will determine how the Earth's outer atmosphere responds to external forces.

The first investigation will provide a U.S. science instrument to the Japan Aerospace Exploration Agency's New exploration X-Ray Telescope, or NeXT. The telescope, currently planned for launch in 2013, will open a new observing window on X-rays and the study of astrophysical phenomena. NASA's proposed funding for the instrument and operations is $44 million.

The other investigation will fly an atmospheric remote sensing instrument package aboard a yet-to-be-determined future commercial satellite. The investigation initially will be funded at approximately $250,000 for a concept study to aid in a NASA decision on further development.

"These selections offer unique and cost-effective science opportunities," said Charles Gay, deputy associate administrator for NASA's Science Mission Directorate in Washington. "They expand NASA's science through partnerships with international and commercial organizations."

The two investigations were selected from among 17 proposals received by NASA earlier this year. They were evaluated by peer reviewers. The selected proposals are:

-- High-Resolution Soft X-Ray Spectrometer (SXS) for NEXT, Principal Investigator Richard L. Kelley, Goddard Space Flight Center, Greenbelt Md. The SXS will probe matter in extreme environments; investigate the nature of dark matter on large scales in the universe; and explore how galaxies and clusters of galaxies form and evolve.

-- Global-scale Observations of the Limb and Disk (GOLD), Principal Investigator Richard Eastes, University of Central Florida, Orlando, Fla. GOLD will increase our understanding of the temperature and composition in the ionosphere; and provide understanding of the global scale response of the Earth's thermosphere and ionosphere.

NASA's Explorer Program is designed to provide frequent, low-cost access to space for heliophysics and astrophysics missions with small to mid-sized spacecraft. The program is managed by NASA's Goddard Space Flight Center, Greenbelt, Md., for NASA's Science Mission Directorate.

For more information about the Explorer Program on the Internet, visit:

http://explorers.gsfc.nasa.gov