NASA to end three-year Deep Space 1 mission

By Andrew Bridges The Associated Press
Friday December 14, 2001

SAN FRANCISCO — NASA will cease communicating with its Deep Space 1 spacecraft on Tuesday, ending a three-year mission capped in September when the probe imaged what may be the darkest object in the solar system. 

The National Aeronautics and Space Administration will stop sending the robotic probe commands next week and let it drift, leaving it to silently orbit the sun, Robert Nelson, the mission’s project scientist, said Thursday. 

Members of the $164 million mission, based at NASA’s Jet Propulsion Laboratory in Pasadena, had hoped to extend the life of the spacecraft into next year and send it flying past an asteroid known as 1999 KK1 to capture images of the space rock at close range. The feat would have cost NASA several million dollars. 

“We did not get an enthusiastic response from NASA headquarters,” Nelson said. 

During its short lifetime, Deep Space 1 successfully flew past two other solar system objects, the asteroid Braille in 1999 and, more recently, the comet Borrelly on Sept. 22. 

On Thursday, scientists gave reporters at the fall meeting of the American Geophysical Union in San Francisco an update on what they learned from the Borrelly encounter, which marked only the second time a spacecraft was able to photograph the dark nucleus of a comet. 

During the flyby, the spacecraft flew within 1,360 miles of Borrelly, snapping images of the shoe-shaped comet, mapping its topography and making other scientific measurements. 

The images showed the surface of Borrelly is nearly as dark as the almost pure carbon used as toner in photocopiers, Nelson said. On average, the surface absorbs as much as 97 percent of the sunlight that fall onto it. 

The spacecraft’s cameras also captured bright jets of dust and gas shooting in tight columns from the comet. 

“They cross each other like a bunch of searchlights coming off a city at night,” said Larry Soderblom of the U.S. Geological Survey and head of the mission’s imaging team. 

Comets grow active when their orbits take them on close approaches toward the sun, which can bake them with its warming rays. Scientists said they were able to measure temperatures as high as 162 degrees Fahrenheit on the surface of Borrelly. 

That heat boils off the frozen mix of water and dust that make up the interior of comets, sending it spewing into space. That material represents the frozen remnants of the stuff from which our solar system coalesced some 4.5 billion years ago. 

Soderblom called that mix the “most primitive materials from which we, the solar system and life arose.” 

Although cometary nuclei are typically jet black, the luminous glow of the cloud of gas and dust that envelops the frozen snow balls can be among the brightest objects visible in the night sky. 

“It is one of the great and fun curiosities of science,” Nelson said. 

Scientists are still unsure if Borrelly is the absolute darkest known object in the solar system. The only known rival is Iapetus, one of the moons of Saturn. 

NASA designed Deep Space 1 to test a dozen innovative technologies in space. Mission members consider its afterlife as a science mission as a bonus.