FADED documents in archaic script, long overlooked in a Spanish archive, are giving scholars the first clear and authoritative picture of the ships that carried Columbus to the New World. These caravels, sturdy and highly maneuverable vessels, were the major advance in seafaring technology that launched the Age of Discovery.

A careful analysis of the documents, made by Eugene Lyon for the University of Florida, reveals for the first time the dimensions, armament and rigging of one of Columbus's ships - his favorite, Nina. She was about 67 feet long, with a beam of 21 feet and a draft of just under 7 feet. On her third voyage to America, in 1498, she had four masts, instead of two or three as had been thought.

Some of the shipboard ambience and aroma also emerges from the new-found accounts. Crowded among the sailors on Nina were farmers and stockmen, a miner and a priest, crossbowmen and several convicted murderers, including two gypsy women. Already, six years after discovery, America was a lure to those wishing to start life anew. They were armed to conquer and hoping to settle.

Under square sails on the fore and main masts and smaller triangular sails on the mizzen and counter mizzen masts, the crew and passengers ate biscuits, fatback and beans seasoned heavily with garlic. They cooked in large copper kettles over fires kindled with vine shoots and fed with olive wood. Stowed below deck were tons of wheat, casks of wine and olive oil, cheese, vinegar, salt pork and sardines.

While other recent findings are reviving debate over where Columbus - Admiral Don Christoval de Colon - first landed in the New World on Oct. 12, 1492, the discovery and analysis of shipping documents in the Archive of the Indies in Seville are expected to contribute more to the understanding of those early voyages of exploration. How the ships were repaired and outfitted, how they were rigged, what cargoes they hauled and how various contractual arrangements shaped early commerce with the New World are among the many fascinating details the documents contain.

Of more immediate importance, the knowledge of Nina's dimensions and rigging is expected to influence the many replicas of Columbus's ships that are being planned for the quincentennial celebration of the 1492 voyage to the New World. Until now, as the historian Samuel Eliot Morison once wrote no one really knew what the Nina, Pinta and Santa Maria really looked like and every picture of them ''is about 50 percent fancy.''

The most striking insights, says Dr. Lyon, who is an adjunct professor of history at the University of Florida, relate to how the entire economy of Spain was being mobilized in the late 1490's to support the New World fleets and how the Spanish had ''a very clear intent to settle'' America sooner than had been generally thought. Historians, he said, have ''understressed'' the settlement motives of the early Spanish voyages.

Dr. Lyon, who is also research director of the St. Augustine Foundation, which supervises the restoration of the oldest city in the United States, came upon the 400-page bundle of documents, called the Libro de Armadas, while conducting other research in Seville in 1979. References to ''Nina, also known as Santa Clara'' caught his eye, and in time he realized that these pages of contracts, bills of lading and receipts for ship supplies held valuable, if prosaic, clues to heroic undertakings.

Dr. Lyon is an expert in old Spanish script and is completing a translation of the documents, a project sponsored by the University of Florida's Center for Early Contact Studies and financed through a grant from the National Endowment for the Humanities. The full translation will be published by the University of Florida Press. Dr. Lyon wrote a brief description of the new findings about Nina for the November issue of the National Geographic magazine and reviewed the many other contents of the documents in the course of several interviews.

''As far as I could tell, and I asked many Columbus scholars in Seville, nobody had ever read these documents,'' Dr. Lyon said. Detailed Accounts for 2 Caravels

The contracts and long lists of ship supplies covered the outfitting of Spanish fleets from 1495 to 1500. Accounts for Nina and her sister ship, Santa Cruz, were especially detailed because the two caravels belonged to Ferdinand and Isabella in partnership with Columbus.

Nina brought Columbus home from his first voyage, and a caravel by that name, presumably the same ship, was in the large fleet for his second voyage, in 1493. Aboard Nina off the coast of Cuba, Columbus made the fleet's crewmen swear that they also believed they had reached the mainland of Asia. After barely surviving a hurricane and other adventures, Nina had to be completely overhauled and refitted before she could embark in the vanguard of Columbus's third expedition.

Dr. Lyon said the documents showed that the third expedition was underwritten by two Italian traders who were in debt to the Spanish crown. Columbus's own finances were apparently straitened. To pay his seamen in 1498, he used funds he was to have taken to the New World colony, hoping to balance the books with gold to be found there.

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Before Nina set sail, her master, Pedro Frances of Palos, acknowledged receipt of the caravel's hull, masts, yards, rigging and other equipment, the list of which runs pages and affords the first detailed description of the ship. The master was illiterate and others had to sign the receipt for him.

According to the list, Nina had a bowsprit and two boomlets, one fore and one aft. The sails for the four masts were described as ''worn'' or ''old,'' though she carried an extra set of new sails for the fore and main masts. She had six shrouds, or lines, on each side of the main mast; four on each side to support the foremast, and three on each side for the mizzen. In all, Nina carried 2,517 pounds of new hemp rigging line for cables, sheet-ropes, tie-runners, bowlines and lifts. She had rope ladders and 68 pullies and blocks of varying sizes. Bread, Wine and Raisins

On deck was a small boat with six oars. Nina also carried a new 200-pound anchor as well as two smaller anchors. She was equipped with an ax, adze, saw and caulking iron.

For weaponry Nina carried 10 bombardas, breach-loaded guns that were probably fitted on the gunwales. There were 80 lead balls for the guns, 54 long and 20 short lances and 100 pounds of gunpowder.

As the day of departure approached, Nina's hold was packed with cargo: 18 tons of wheat, 34 barrels of wine, some seven tons of sea biscuit or unleavened bread, almost two tons of flour, more than a ton of cheese, a ton of salt pork, barrels of water, jars of olive oil and stores of sardines, raisins and garlic. To keep them from rolling and bumping, the barrels and jars were cushioned with vine shoots and olive wood, which also served as firewood.

''I learned more about fatback than I ever wanted to know,'' Dr. Lyon remarked, looking up from a page of the document. The pork was obtained throughout southern Spain and washed with heated lye from the Triana soap works. The pieces of fatback were then rubbed with red clay and bran to create a protective crust, marked with an iron and packed in baskets to load aboard the caravels.

Estimates of Nina's dimensions were derived from calculations of the number of barrels required to hold the listed cargo, which Dr. Lyon said came to 52 tons. The ship's overall carrying capacity was probably 58 to 60 tons. By the measurements of that time, two barrels equaled one Spanish tonelada. The ship's length, beam and draft were thus inferred by multiplying the rows of barrels in the hold. Jose Maria Martinez-Hidalgo, a Columbus scholar and former director of the Maritime Museum in Barcelona, assisted in this analysis. Two Wrecks From the Era

Knowledge of the caravels is sparse because no architectural plans of them exist and contemporary drawings were more fanciful than accurate. For example, Bruce F. Thompson, a nautical archeologist at Texas A & M University, expressed surprise at learning that Nina had four masts, not three.

Divers from the Institute of Nautical Archeology at Texas A & M have recently identified two wrecks of ships as being caravels of the Columbus era. No confirmed caravel wrecks had ever been found before. The badly damaged remains are submerged at Highbourne Island in the Bahamas and at Molasses Reef in the Turks and Caicos Islands. Mr. Thompson said the two wrecks and the Seville documents should answer many questions about the construction and operation of caravels.

For the 1498 expedition, Nina and Santa Cruz carried more than 90 people on the royal payroll, according to Dr. Lyon. These included 18 farmers or stockmen, 50 crossbowmen, a priest, a locksmith, a miner and a surgeon. The documents list among the passengers 10 convicted murderers freed on condition that they emigrate to the New World. Two of them were the gypsy women, Catalina and Maria.

Another section of the documents contains what Dr. Lyon said was the first formal contract issued by the Spanish crown to a miner sent to ''dig and sluice'' for gold in the New World. The miner was Pablo Beluis, citizen of Valencia, who embarked with four assistants in caravels that sailed to America in 1495 under the command of Juan Aguado. 'Trying to Reproduce Spain'

Among the tools consigned to Pablo were three hammers, three chisels, two pairs of tongs, four adzes, four saws and a large supply of iron nails. It was agreed that Pablo would receive one-tenth of the gold he found, with the rest belonging to the King and Queen.

On the same Aguado expedition, the documents show, the ships carried cattle and horses with a supply of bridles and saddles. The ships picked up sheep in the Canary Islands.

''They were trying to reproduce Spain in the New World,'' Dr. Lyon observed.

A list of medicines supplied to some of the caravels provides an insight into pharmaceuticals of the day. The 113 items on one list included a prune laxative, quince juice, violet conserve, rum, lard, rose water, lemon juice, lily root, arsenic, a compound of honey and opium and a reddish resin of the dragon tree for the painful swellings of gout.

Another list gives the Christian names of Indian slaves brought back in 1499. ''The list ends abruptly, as if there's more,'' Dr. Lyon said. Sale May Have Been 'Forced'

A note in the margin of the Libro de Armadas discloses that on Oct. 9, 1499, Columbus ordered Pedro Frances to turn Nina and its equipment over to Diego Ortiz, her new owner.

''This may have been a forced sale,'' Dr. Lyon said. ''Things had been going badly for Columbus. Two weeks earlier, colonists in Santo Domingo had revolted against his leadership and forced him to sign a humiliating settlement with Francisco Roldan, leader of the rebellion.

Columbus returned to Spain in chains in 1500, having proved himself less a leader of men than a visionary explorer. Nina, his favorite caravel, sailed out of history's sight.

By Eugene Lyon (NYT/Gary Guisinger)