In 1995, NASA and the European Space Agency (ESA) launched the Solar and Heliospheric Observatory (SOHO) to study the Sun. The spacecraft’s handlers hoped the mission would last two years. To paraphrase Timex’s slogan, SOHO has taken a beating but keeps on ticking.
Today marks SOHO’s 10th anniversary in space. The spacecraft has advanced our understanding of the Sun, especially how solar activity causes space weather.
“It’s impossible to overstate the importance of SOHO to the worldwide solar science community,” explains Joe Gurman, a NASA project scientist for SOHO. “In the last 10 years, SOHO has revolutionized our ideas about the solar interior and atmosphere and the acceleration of the solar wind.”
“I tip my hat to SOHO’s engineering and operations teams, whose skills and dedication have overcome multiple technical challenges over the last decade,” says Bernhard Fleck, an ESA project scientist for the mission.
In addition its solar and space-weather observations, SOHO is a prolific comet-hunter. In August 2005, researchers discovered the 1,000th comet in spacecraft data. Amateur astronomers combing images over the Internet have detected many of SOHO’s comets. The observatory is responsible for discovering nearly half of the known comets orbiting the Sun. While the SOHO team knew the spacecraft would find sungrazing comets, 1,000 comets in a decade is beyond all expectations.
“We didn’t realize how good the scattered light characteristics of the LASCO coronagraphs would be, nor the dynamic range of the CCD detectors,” Gurman told Astronomy. “Before launch, people probably would have estimated about 100 comets in 10 years.”
How long will SOHO last? Gurman believes the spacecraft could operate for decades, but budget cuts will hamper this. Funding from NASA slowly declines until 2008 and then drops sharply following the 2008 launch of the space agency’s Solar Dynamics Observatory.
