Endeavour’s Radar Surveys Volcanoes : Shuttle: Powerful unit gathers three-dimensional images. Astronauts take pictures, describe the scenes below.

KENNEDY SPACE CENTER, Fla. — Powerful radar waves from the space shuttle Endeavour sliced through clouds and sand Saturday to survey volcanoes and hunt for ancient river channels buried in the Sahara Desert.

Endeavour’s six astronauts described and photographed the scenes 138 miles below as the radar gathered three-dimensional images.

Late Saturday, ground controllers aimed the $366-million radar at the Klyuchevsky Volcano in Russia’s Far East.

The volcano erupted Friday, perfect timing for Endeavour. Previous eruptions were recorded only in 1737 and 1945. The latest blast began shortly after the shuttle took off on its 10-day mapping mission.

Video beamed down by the astronauts showed thick, gray smoke billowing eight miles high from the volcano, located on a sparsely populated part of the Kamchatka Peninsula.

“Quite a sight,” said astronaut Peter (Jeff) Wisoff.

By midday Saturday, the radar had scanned Hawaiian volcanoes and Washington state’s dormant Mt. Rainier. High school students from Seattle set up homemade radar reflectors on Mt. Rainier and photographed the area as Endeavour orbited overhead.

Later this week, the radar will focus on New Guinea volcanoes that began erupting two weeks ago and Mt. Pinatubo in the Philippines.

Pinatubo was among the volcanoes mapped by the shuttle radar during its orbital debut in April. There were no major eruptions then, however.

Scientists hope the radar images will shed light on the climatic effects of volcanic ash and gases spewing into the atmosphere. The findings may also provide clues for predicting volcanic eruptions and earthquakes, said NASA program scientist Miriam Baltuck.

Other radar researchers are more interested in the past. Archeologists hope to find traces of ancient river tributaries buried by the Sahara.

These old rivers are generally one-third of a mile wide and carved in bedrock, which is a strong radar reflector. The search for 2,000-year-old mud walls of towns along China’s Silk Road is expected to be much more difficult because of their small size and lack of bedrock.