Unmanned Solar Observatory Lifts Off

A solar observatory hurtled toward the sun Saturday after rocketing into space on a $1-billion mission.

An unmanned Atlas rocket carrying the Solar and Heliospheric Observatory, called Soho, blasted off at 12:08 a.m. PST from Cape Canaveral Air Station. Within a few hours, the spacecraft was boosted out of Earth’s orbit and heading toward the sun, with its power-generating solar panels and antennas fully extended.

Soho should reach its final destination in four months--a point nearly 1 million miles from Earth and 92 million miles from the sun. The gravitational pulls of Earth and the sun cancel each other out at this point.

There, Soho will peer continuously at the sun and send back data for two years, longer if the National Aeronautics and Space Administration and the European Space Agency can afford it.

It’s considered the most complex observatory ever built to study the sun’s deep interior as well as the corona, its outer atmosphere and the always-radiating solar wind.

Unlike the 5-year-old Ulysses spacecraft, which just completed a northern polar pass of the sun and now is headed to Jupiter’s orbit, Soho will remain between the sun and Earth, going around an imaginary point in a so-called halo orbit.

Fabrizio Felici, mission director for the European Space Agency, said Soho will provide a “special new look at the sun” from this unique vantage point. The 4,100-pound observatory has 12 telescopes and other science instruments--three from the United States and nine from Europe.

Scientists plan to probe the sun’s mysterious interior by sound waves, exhibited on the solar surface by oscillations and variations in brightness. This new method, called helioseismology, is analogous to using earthquakes to study the Earth’s interior.

“These experiments provide a new and really exciting, we believe, chance to journey from the center of the sun all the way out to the surface,” said Philip Scherrer, a Stanford University physicist in charge of one of the Soho instruments. “Soho will see the conditions out to the farthest limits of the heliosphere.”

Other scientists will use Soho to study charged particles streaming into space from the sun’s outer atmosphere. This solar wind, if strong enough, can disrupt radio communication and cause blackouts on Earth.

Saturday’s launch was originally scheduled for Thanksgiving Day but was delayed nine days so technicians could replace two fuel regulators in the rocket.

Workers used the wrong material when making those two regulators, a potentially catastrophic problem.