A robot camera floated down the grand staircase of the luxury liner Titanic today 12,500 feet beneath the sea, viewing the grand promenade deck and a nearby room with a large chandelier still hanging from the ceiling.

Explorers from the Woods Hole Oceanographic Institution began diving in a three-man submersible on Sunday, surveying the wreck and preparing for today's attempt to enter the ship for the first time since it sank in the early hours of April 15, 1912.

Robert D. Ballard, leader of the Woods Hole team, radioed back after 6 p.m. today, saying "it was like landing on the moon" as the submarine glided down to the deck of the Titanic, landing before a gaping hole that once was a huge decorated glass dome over a staircase.

He said that after the landing, the 28-inch experimental robotic camera called Jason Jr. was launched from a small platform on the bow of the submarine and flown like a helicopter down the wide stairs.

Ballard said in an interview over a radio telephone from sea that the highlight of today's trip was the robot's easy, picturesque glide down the multideck staircase. The journey ended four decks deep into the ship when, according to Ballard, "we turned Jason around and saw a big wire hanging there . . . . We got spooked and decided going back was the better part of valor. We backed up the staircase."

Ballard said today's dive began with the usual 2 1/2-hour trip from the research ship Atlantis II to the Titanic. The submarine, called Alvin, has a three-man crew: Ballard; Ralph M. Hollis, Alvin's pilot; and Martin Bowen, Jason's pilot.

The Alvin alighted on the ocean bottom about 200 feet astern of the Titanic in a large field of debris left from the break-up of the ship. "The bottom was plowed up like somebody had come through with a great plow," he said, "like the ship had plowed right into the bottom," making a "huge berm of mud" and debris.

The Titanic sits upright in its grave, its forward two-thirds intact, its stern third missing.

Ballard said he was surprised to find that the ship had not settled cleanly, but "had buckled, with its bow plunging down into the bottom, its middle straight and its stern down -- like its back was broken."

The Alvin moved toward the hulk, over mud littered with porcelain cups and dishes, wine bottles and unidentifiable chunks of metal.

As the submersible approached the Titanic, "a big black wall" came into view, extending "as far as you can see off to the left and right and above," Ballard said.

Along the black wall, he said, "beautifully preserved" portholes were visible, "glossed over with a film, like a veil."

As the submarine rose above the topmost deck, Hollis landed it facing the hole that had been the glass dome over the multideck grand staircase.

The submarine then released its experimental robot camera. "We went down through four decks, like through a layer cake," Ballard said, viewing large Ionic pillars and crystal chandeliers on either side as the robot moved.

Jason was piloted into one room where a chandelier hung. "It was very eerie looking into one of those decks," Ballard said. "We came up to one chandelier within a few inches and took pictures" of the crystal and decorations, including a sea creature called a cryanoid that Ballard said resembles "a woman with feathers in a flowered hat."

When the robot was turned around, the crew saw a large hanging wire. Fearing it might become tangled, "we got spooked," Ballard said, and glided the robot, attached with a 200-foot tether, back up the stairway.

One of the strangest sights on the Titanic was the rust, Ballard said, which hung in three- and four-foot-long stalactites in vivid reds, oranges and yellows.

On the decks, the rust ran in rivulets and "was bleeding down the ship," he said.

Jason is equipped with a color video camera capable of surveying 170 degrees of the visual field, allowing it to fully scan the rooms it passes through.

The Titanic exploration is part of an expedition from the Woods Hole institution sponsored by the Navy. The official purpose of the trip is to give Jason its first deep-dive tests.

The researchers on this mission are the same as those on the French-American mission that located the resting place of the Titanic, in the North Atlantic about 500 miles off Nova Scotia, last Sept. 1.

On that mission, only a few camera passes with black-and-white film were made above the Titanic. This trip will include 12 diving days and hundreds of thousands of color video and still pictures from inside and outside the ship.

Ballard said the Titanic is so huge that, in the 25-foot submarine, "we can drive along the boat's deck just as if we were passengers" on a stroll.

Submarine pilot Hollis maneuvered the Alvin along the forward deck Monday, up to the wheelhouse. The wooden parts of the instruments were missing, but "the currents keep the brass polished," Ballard said. "The ship's wheel is all brass and it looks like it was installed yesterday."

The Titanic has lain on the bottom for 74 years after striking an iceberg, which tore a 300-foot gash in its forward hull. Within three hours of its distress signal, the ship dropped beneath the surface, taking more than 1,500 victims. About 800 people were rescued by another ship on the morning of April 15.

The Woods Hole expedition is committed to leaving everything in place on the ocean floor, Ballard said. Just before leaving the dock July 8, Ballard said he might change his mind about bringing up artifacts or raising the ship if the wooden parts of the ship were being eaten away and other structures were being damaged.