NASA plans to land robot probes on a comet and on a moon of Saturn early next century in new programs that would cost $1.6 billion over the next seven years.

In testimony prepared for a budget hearing before the House committee on science, space and technology, National Aeronautics and Space Administration scientist Lennard A. Fisk said Wednesday that the un manned spacecraft would allow the United States to maintain world leadership in exploration of the solar system.Fisk, the associate NASA administrator for space science and applications, said a mission called Comet Rendezvous Asteroid Flyby, or CRAF, would be launched in 1995 and would streak through space for five years before meeting with the comet Kopff and dropping a probe to its surface.

He said the probe from the spacecraft would penetrate to the core of the comet and study the chemistry of material that may date from the beginning of the solar system.

A second mission, called Cassini, would be launched in 1996 and arrive in an orbit of the planet Saturn in the year 2002.

Once there, Fisk said, the craft would drop a robot lander to the surface of Titan, one of Saturn's moons, and conduct a chemical analysis.

This study, said the scientist, could provide a fundamental understanding about the origins of life.

"The chemistry that gave rise to life in the past is no longer available for us to study (on Earth)," he said. "However, we believe that a chemistry similar to that on the early Earth . . . exists today on Titan."

Both of the missions, said Fisk, will study primordial, pristine matter, "the material from which the solar system formed, the material from which life on Earth formed, and the chemistry which gave rise to that life."

Launch delayed

The launch of Discovery and its five astronauts has been delayed at least two days until March 11 because of a crushed electrical part on a main engine, officials said.