NSF-sponsored research projects continued to contribute new knowledge about the origins, composition, and dynamics of the universe. Astronomers at the University of Oklahoma and the University of Texas recently arrived at a new estimate of the age of the Milky Way galaxy that is independent of both stellar evolutionary or cosmological models. By measuring the abundance of thorium in emissions from an extremely old star, these scientists have estimated the age of the galaxy as 17, plus or minus 4 billion years.
Scientists at the National Radio Astronomy Observatory in New Mexico, at the California Institute of Technology, and in Italy made the first measurements of the size and expansion of the mysterious, intense "fireball" resulting from a particular cosmic gamma-ray burst. The radio observations have revealed a size of the fireball, unobtainable by any other technique, thereby enabling astronomers to learn about inner workings of such objects.
NSF-supported scientists used the Very Large Baseline Array telescope to image a light-year-sized radio jet in a relatively nearby spiral galaxy called NGC 4151, located approximately 43 million light-years from Earth. This galaxy is believed to contain a black hole with a mass that is millions of times greater than the mass of the Sun.
In response to the intriguing but controversial announcement that a team of scientists had discovered evidence of ancient life in a meteorite from Mars discovered in Antarctica in 1984, NSF and NASA developed a cooperative research program to investigate and shed light on this interpretation. NSF, NASA, and the Smithsonian Institution continued to manage Antarctic meteorites cooperatively.
NSF-sponsored studies also contributed to new understandings of the Earth. Researchers at the University of Illinois used a high-power lidar instrument in conjunction with the large, steerable optical telescope at Kirtland Air Force Base in New Mexico to make more sensitive measurements in the middle atmosphere of vertical heat fluxes, cooling rates, and particle movements associated with the dissipation of pressure waves that originated in the lower atmosphere. In the past year, the spectra of wave-induced perturbations in temperature, winds, and density have been measured simultaneously and compared with the predictions of the leading wave-dissipation paradigms. In addition to examining relationships between horizontal winds and pressure waves in new ways, the researchers are analyzing in unprecedented detail the characteristics of distinctive wave perturbations in temperature, winds, and density in the middle atmosphere, which is very sensitive to global change effects.
Arctic noctilucent clouds over Sondre Stromfjord, Greenland, have been studied using simultaneous backscatter lidar and ultraviolet spectrograph measurements. The combined measurements provide unique information about the sizes and density of the particles that make up these high-altitude clouds and also about the processes that disperse them.
Images from the first radar survey of Antarctica, using the Canadian Space Agency's Radarsat satellite, provided exciting new images of NSF's South Pole Station and of several segments of the Antarctic coastline. These images show some of the large glaciers that drain the vast ice sheet over Antarctica. In addition, NASA and NSF established a ground station at McMurdo Sound to acquire ozone data from the Total Ozone Mapping Spectrometer Earth Probe.
NSF researchers successfully completed the GPS-Meteorological (GPS-MET) proof-of-concept experiment. GPS-MET used a low-Earth-orbiting satellite that measured the way signals from GPS satellites bent as they passed at oblique angles through various layers of Earth's atmosphere. By analyzing these signals, scientists improved their capabilities for estimating ionospheric electron density, atmospheric density, pressure, temperature, and moisture profiles in the atmosphere to support weather research and prediction, climate research and climate-change detection, and ionospheric physics research.
This schematic diagram of GPS meteorology shows GPS signals passing from GPS satellites, orbiting at heights of ~20,000 km, through the intervening Earth's atmosphere to ground-based receivers and to a low-Earth orbit satellite.
NSF also continued to upgrade its facilities for space research. Most notably, in June 1997, a 5-year, $27 million upgrade to the world's most sensitive radio/radar telescope at Arecibo Observatory in Puerto Rico was completed with joint support from NSF and NASA.