loops with temperatures up to 10,000,000°F are probably always present in the corona.The mission relayed its last data in 1989.
A joint project between NASA and the European Space Agency, the Ulysses spacecraft was launched on October 6,1990, and is now orbiting the Sun to study its north and south poles.The spacecraft went over the solar south pole for the first time in 1994 and the north pole for the first time in 1995. Ulysses had an unexpected encounter with the tail of comet Hyakutake, indicating that the comet's tail might be much longer than previously estimated. Its main mission is to measure and map the heliosphere in three dimensions. Ulysses made a second polar orbit around the Sun in 2001. In 2004, Ulysses was at the aphelion (the farthest distance from the Sun) of its huge orbit, near Jupiter.
Yohkoh, meaning "sunbeam" in Japanese, was a mission from the Institute of Space and Astronautical Science, launched on August 30, 1991. Yohkoh had the ability to image the entire Sun at once, with the highest-resolution X-ray instrument available at the time. In 1997, the solar minimum was reached, and the mission continued to gather X-ray data through the rise to the solar maximum in 2000. At times the missions Yohkoh, SOHO, and TRACE (see below) were all able to take images of the same solar structures at the same time, thus gathering invaluable data in several wavelengths simultaneously. The Yohkoh mission ended in December 2001, after 10 years of excellent data-gathering. The Yohkoh team has produced an excellent Web site for public outreach, filled with accessible information, at http:// solar.physics .montana.edu/YPOP.
Was this article helpful?