CAPE CANAVERAL, Fla. (AP) _ Space shuttle Columbia moved to the launch pad Saturday as workers got set to celebrate the 20th anniversary of the liftoff of another spaceship with the same name, the one that carried the first men to the moon.

The shuttle completed a seven-hour trip to launch pad 39B shortly before 5 a.m., and engineers and technicians began readying it for an early August flight with five astronauts who are to release a secret military spy satellite. Meanwhile, others made preparations for Sunday's commemoration of the flight of the first Columbia.

It was July 16, 1969, that an Apollo command module Columbia blasted away from the Kennedy Space Center here with astronauts Neil Armstrong, Edwin ''Buzz'' Aldrin and Michael Collins. Four days later, Armstrong and Aldrin climbed into the lunar landing vehicle Eagle and descended to the moon.

After an historic 22 hours on the surface, the moonwalkers rejoined Collins in mother ship Columbia for the three-day trip home.

The three were at the Marshall Space Flight Center in Huntsville, Ala., on Saturday for a ceremony there before coming here here to join with thousands Sunday in remembering the launch of the Apollo 11 mission.

Outside the giant shuttle assembly building, where Apollo's Saturn 5 rockets once were put together, the former astronauts will make brief remarks and listen to a tape recording of the final minutes of their countdown.

The ''taped liftoff'' will occur at 9:32 a.m. Sunday, precisely the time they left Earth.

As the shuttle Columbia moved to the pad, shuttle launch director Bob Sieck looked back at its namesake.

''Twenty years ago there was another spaceship, also called Columbia, and it was out at the pad,'' he said. ''It had an important mission and an important payload. This parallels it. Shuttle Columbia also has an important mission and an important payload.

''It also will prove we have three orbiters, and that is significant,'' Sieck said.

Columbia will be making its first flight since the Challenger explosion 3 1/2 years ago. The other two shuttles, Discovery and Atlantis, each have been launched twice since flights resumed last September.

After the ceremony here Sunday morning, Armstrong, Aldrin and Collins will ride 20 miles in a motorcade to Cocoa Beach, where they will be honored at a luncheon. On Thursday, the 20th anniversary of the moon landing, the trio will join President Bush for a ceremony at the National Air and Space Museum in Washington.

NASA earlier had set July 31 as the date for launching shuttle Columbia. But agency officials said Thursday that preparations were behind schedule and that a liftoff now is expected during the first week in August. A firm launch date will be set July 26 following a two-day meeting called a flight readiness review.

Columbia's all-military crew is to deploy a classified Defense Department payload believed to be an advanced reconnaissance satellite.

While the counterparts from 1969 are being honored, the shuttle astronauts will fly here Sunday from Houston, in preparation for some practice sessions Monday and Tuesday.

The crew is commanded by Air Force Col. Brewster H. Shaw Jr. The others are Navy Cmdr. Richard N. Richards, Navy Cmdr. David C. Leestma, Air Force Lt. Col. James C. Adamson and Air Force Maj. Mark N. Brown.