Yohkoh

1991

ate a better understanding of the composition of the solar wind. Genesis should have been pulled out of the air by helicopters on September 9, 2004, as it slowly descended to Earth, but its parachutes failed to deploy and the craft made a hard landing in the Dugway Proving Ground in Utah. The capsule broke open with the force of its landing and most of the solar wind sampling instruments were contaminated with terrestrial sand and mud. Some solar wind collectors are thought to remain uncontaminated, but results are in contention since the scientific community is not in agreement over the degree of contamination.

European and American

The SOHO satellite is a joint European-American effort, launched on December 2, 1995, that orbits 930,000 miles (1.5 million km) from the Earth. Among its many instruments is one called the Large Angle and Spectroscopic Coronagraph (LASCO), which, by blocking the Sun with an opaque disk, can take images of the corona in visible light. Shown in the lower color insert on page C-6, SOHO has successfully taken images of coronal mass ejections, dangerous and little understood phenomena. SOHO's primary scientific goals are to measure the structure and dynamics of the Sun's interior, to gain an understanding of the heating mechanisms of the corona, and to study the source and acceleration of the solar wind. SOHO has viewed amazing and unique events, including, on June 2, 1998, when two Sun-grazing comets following similar orbits entered the tenuous outer atmosphere of the Sun, and failing to reappear on the other side of the Sun, were melted and engulfed. Visit the SOHO Web site at http://sohowww.nascom.nasa.gov.

American

Stanford-Lockheed Institute for Space Research launched this satellite, called TRACE, into a polar orbit around the Earth on April 1, 1998.The mission's objectives are to follow the evolution of magnetic field structures from the solar interior to the corona, to investigate the mechanisms of the heating of the outer solar atmosphere, and to investigate the triggers and onset of solar flares and mass ejections. Its ultra high-resolution ultraviolet telescope has revealed many new aspects of thin coronal loops. As of early 2004, TRACE is still successfully orbiting, and movies of solar dynamics can be seen on its Web site, at http://vestige.lmsal.com/TRACE.

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