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History's greatest comet hunter nears major milestone NASA NEWS RELEASE Posted: July 6, 2005 The Solar and Heliospheric Observatory (SOHO) spacecraft is expected to discover its 1,000th comet this summer.
"Before SOHO was launched, only 16 sun grazing comets had been discovered by space observatories. Based on that experience, who could have predicted SOHO would discover more than 60 times that number, and in only nine years," said Dr. Chris St. Cyr. He is senior project scientist for NASA's Living With a Star program at the agency's Goddard Space Flight Center, Greenbelt, Md. "This is truly a remarkable achievement!" About 85 percent of the comets SOHO discovered belongs to the Kreutz group of sun grazing comets, so named because their orbits take them very close to Earth's star. The Kreutz sun grazers pass within 500,000 miles of the star's visible surface. Mercury, the planet closest to the sun, is about 36 million miles from the solar surface. SOHO has also been used to discover three other well-populated comet groups: the Meyer, with at least 55 members; Marsden, with at least 21 members; and the Kracht, with 24 members. These groups are named after the astronomers who suggested the comets are related, because they have similar orbits. Many comet discoveries were made by amateurs using SOHO images on the Internet. SOHO comet hunters come from all over the world. The United States, United Kingdom, China, Japan, Taiwan, Russia, Ukraine, France, Germany, and Lithuania are among the many countries whose citizens have used SOHO to chase comets. Almost all of SOHO's comets are discovered using images from its Large Angle and Spectrometric Coronagraph (LASCO) instrument. LASCO is used to observe the faint, multimillion-degree outer atmosphere of the sun, called the corona. A disk in the instrument is used to make an artificial eclipse, blocking direct light from the sun, so the much fainter corona can be seen. Sun grazing comets are discovered when they enter LASCO's field of view as they pass close by the star. "Building coronagraphs like LASCO is still more art than science, because the light we are trying to detect is very faint," said Dr. Joe Gurman, U.S. project scientist for SOHO at Goddard. "Any imperfections in the optics or dust in the instrument will scatter the light, making the images too noisy to be useful. Discovering almost 1,000 comets since SOHO's launch on December 2, 1995 is a testament to the skill of the LASCO team." SOHO successfully completed its primary mission in April 1998. It has enough fuel to remain on station to keep hunting comets for decades if the LASCO continues to function. |
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As excitement builds for the first space shuttle launch in over two years, this comprehensive video selection captures the major pre-flight events for Discovery and her seven astronauts.
Administrator Mike Griffin is the sole witness testifying before the House Science Committee in this hearing on the future of NASA. (2hr 01min 09sec file)
One day before beginning the space shuttle Flight Readiness Review, Administrator Mike Griffin gives a televised address to agency workers and answers questions. (26min 09sec file)
The Stafford-Covey Task Group holds a news conference from NASA Headquarters following the panel's final public hearing on the space shuttle program. (55min 58sec file)
The 18th Progress resupply ship launched to the International Space Station is guided to docking with the Zvezda service module's aft port via manual control from commander Sergei Krikalev. A problem thwarted plans for an automated linkup.
The House Science Committee, Subcommittee on Space and Aeronautics, begins its hearing on the International Space Station. (29min 59sec file)
House members question Expedition 11 crew member John Phillips living on the International Space Station. (16min 33sec file)
The hearing continues with questioning by House members of former station astronauts Peggy Whitson and Mike Fincke. (31min 33sec file)