THE BIG NOISE in Baltimore this weekend will be a spectacular homecoming celebration for the USS Constellation. The 22-gun sloop, the last all-sail warship built by the U.S. Navy, will head a 25-vessel flotilla and receive a 19-gun salute as she returns to her old Inner Harbor berth this Friday forenoon. The party, combined with Crabtown's Fourth of July festivities, will go on all weekend.

Constellation will leave her restoration dock and round Locust Point about 9 a.m. Fireboat water cannons and Navy warship cannons will salute as Constellation comes into view of the Inner Harbor promenade and pavilions about 10. The vessel and her escorts will pass in review for an hour or more before she's warped into her berth by about 11:30. At noon the official welcoming committee, including Maryland Gov. Parris Glendening, Baltimore Mayor Kurt Schmoke (credited as the spark plug of the restoration project) and Navy Secretary Richard Danzig, will try to make themselves heard above the Naval Academy Band and a flyover of fighter planes.

Many old friends may not recognize the vessel because Constellation, launched in 1854, has been restored to her original configuration. In her previous refitting, after she came to Baltimore in 1955, Constellation's stern had been squared off and a second gun deck added. This had converted her into a frigate, an imitation of the Revolutionary War vessel after which she was named.

Constellation's now a sloop-of-war again, with a rounded stern and a single gun deck. Dismasted and in a sinking condition when she was towed from Pier One to the Fort McHenry Shipyard in 1996, she's now restored, stabilized and sound enough to support her spars, although she'll probably never sail again (she's coming home under tow). Poor old girl.

Moreover, because of an innovative solution by master shipwright G. Peter Boudreau, overseer of the $9 million project, the three-master retains some three-quarters of her original structure. Tearing the vessel down to replace her rotting planks, knees and timbers, as was done in the recent restoration of the USS Constitution ("Old Ironsides"), would have cost $25 million or more. And so much of the deteriorated historic material would have had to be replaced that the end result would have amounted to a replica; so little of the original USS Constitution remains that she's often called New Ironsides.

Boudreau sheathed Constellation's crumbling hull in an immensely strong laminate of ancient fir and epoxy that's not only watertight but is virtually impervious to saltwater, marine borers and other hazards of the cruel sea. The ongoing project is sponsored by the nonprofit Constellation Foundation, with donations so far of about $3 million each from the city, the state and private organizations and individuals.

Constellation spent from 1859 to 1861 on antislavery patrol off the West Coast of Africa, capturing three slave ships and freeing about 700 men, women and children. Her last capture, the Triton, was the first vessel taken by the U.S. Navy in the Civil War. After Appomattox, Constellation carried relief supplies to famine-wracked Ireland. She carried American art treasures to the 1878 International Exhibition in Paris and served as a training ship for the generations of Annapolis midshipmen who led the Navy in the Spanish-American War and World War I. In World War II she served as ceremonial flagship of the Atlantic Fleet.

The ceremonies and concert will conclude about 1. From 2 to 7 the vessel will be open to the public for free touring, this day only, courtesy of Provident Bank, which is sponsoring the celebration. Thereafter admission will be $6 adults, $4.50 seniors over 59, and $3.50 children under 15.

USS CONSTELLATION -- Pier 1, Inner Harbor, Baltimore. 410/837-4636 or 888/225-8466. Web sites: www. bop.org or www. constellation.org. Open for tours, free of charge, Friday from 2 to 7 p.m. Thereafter, it will be open daily 10 a.m. to 8 p.m. with $6 admission for adults, $4.50 seniors over 59 and $3.50 children under 15.

Other events scheduled in Baltimore this weekend:

Friday, 7 to 11 p.m. at Harborplace Amphitheater: A six-foot, Constellation- shaped cake will be served, followed by a concert by the Mahoney Brothers' "Jukebox Review."

Saturday, 11 to 5 at the Amphitheater: street performers. 7 at the Amphitheater: U.S. Navy Concert Band and Sea Chanters.

Sunday, 11 to 5 at Sam Smith parking lot (Light Street, on west shore of harbor): classic car and street rod rally. 11 to 6 at Amphitheater: street performers. 8 to 9:30 at Amphitheater: U.S. Air Force Band "High Flight." 9:30 at Inner Harbor: fireworks.

CAPTION: The USS Constellation, shown here being towed away to the shipyard for repairs in 1996, will return to her Inner Harbor berth in Baltimore on Friday.