The Genesis space capsule that crashed into the Utah desert last month failed because four pencil stub-size gravity switches designed to trigger the release of the spacecraft's parachutes were installed backward, NASA officials said yesterday.

Michael G. Ryschkewitsch, chairman of NASA's Mishap Investigation Board, said engineers assembling the Genesis probe more than four years ago were misled by errors in designs prepared by Bethesda-based Lockheed Martin Corp. "The drawings are not correct," Ryschkewitsch said.

The Genesis setback came five years after the Mars Climate Orbiter apparently vanished into space or burned up in the Martian atmosphere after Lockheed Martin engineers incorrectly programmed it with English rather than metric units.

The latest mishap focused attention on NASA's preflight review process, which was modified after the Climate Orbiter fiasco. "We try to put many tests and many reviews into the system," Ryschkewitsch said. "One of the questions we have to ask is, 'How did we miss this?' "

Lockheed Martin declined to comment yesterday.

The $264 million Genesis probe was launched three years ago to collect particles of solar wind on more than 200 ceramic tiles. On its return, the parachutes were supposed to allow it to drift gently toward Earth until a helicopter could pluck it out of the sky.

Instead, neither the first drogue parachute nor a larger parafoil opened, and the 450-pound capsule smacked into Utah's high desert at the U.S. Army's Dugway Proving Ground at 193 mph.

The capsule broke open, and many of the tiles shattered. Scientists at Dugway packed the remnants into 3,000 separate containers and sent them to Houston's Johnson Space Center, where they will eventually be opened in a special clean room.

"Scientists are talking with the scientific community now," NASA spokesman William Jeffs said in a telephone interview from Houston. "They need to understand what the impact would be from cleaning techniques and technology for decontamination."

Despite the damage, scientists have expressed optimism that they will find a way to clean the tile fragments to researchers' satisfaction and enable samples to be sent out for study.

The atoms embedded in the tiles make up all the elements and isotopes that existed in the solar system when it was formed about 4.5 billion years ago, and scientists believe they can provide important baseline information for the study of the solar system today.

Ryschkewitsch cautioned that the Genesis findings were "only a preliminary release of information," but added that "we have confidence in the information." The board expects to finish its investigation of the Genesis affair by the end of November, he said.

Ryschkewitsch described the suspect switches as cylindrical sensors three-quarters of an inch long and about the diameter of a pencil. The capsule had two pairs so that if one pair malfunctioned, the other pair would take over.

When Genesis decelerated entering Earth's atmosphere, a plunger inside the switch was supposed to compress with the rising G-forces, closing a circuit, Ryschkewitsch explained. As the craft descended further and slowed, the pressure would relax, breaking the circuit and activating a trigger to deploy the drogue parachute.

Because the design drawings called for the switches to be installed backward, Ryschkewitsch said, neither the primary set nor the backups could do their jobs. Ryschkewitsch said the switches are so small that investigators needed to X-ray the part to verify they were improperly installed.

Scientists were also studying design drawings of NASA's Stardust probe, which will bring comet particles back to Earth in 2006 with a parachute reentry system using the same switches as Genesis.

Ryschkewitsch said different investigators were examining the Stardust design drawings, but "while the switches are the same, the installation . . . is quite different." He said preliminary analysis suggested the Stardust switches are in the correct position.

A Genesis team member looks at the capsule, which collected solar wind particles, after it fell to Earth last month without deploying its parachute at Dugway Proving Ground in Utah.