Over federal prosecutors' objections that he may flee to a foreign country, U.S. naval intelligence analyst Samuel Loring Morison was freed today on $100,000 bond.

Morison is charged with leaking classified photos of Soviet shipbuilding operations to a private British military magazine.

With his girlfriend and four members of his family looking on in federal court here, Morison sighed with relief when U.S. Magistrate Paul M. Rosenberg accepted a signed pledge by Morison's mother, Judith Day Morison, turning over her prospective $100,000 retirement fund if Morison should fail to appear for his trial in December.

Morison, 39, the scholarly looking grandson of the U.S. Navy's foremost historian, the late Samuel Eliot Morison, has been in jail on $500,000 bond since Oct. 1 after his arrest by FBI agents at Dulles International Airport, where he was about to board a flight to England.

He was charged under the U.S. espionage statute with unauthorized disclosure of three satellite photographs of a nuclear-powered Soviet aircraft carrier under construction at a shipyard on the Black Sea.

The pictures appeared in the Aug. 7 issue of Jane's Defence Weekly, one of several periodicals of Jane's Publishing Co., highly regarded for its authoritative publications on military hardware.

Morison, a $30,000-a-year analyst for the Naval Intelligence Support System in Suitland, from which the satellite photos allegedly were stolen, also moonlighted as a $5,000-a-year editor for Jane's.

At today's bond hearing before Rosenberg, Morison's attorney, Jacob A. Stein, did not dispute that Morison leaked the satellite pictures to the magazine, but suggested that little or no harm to U.S. security was caused by it.

Besides, he said, classified information is almost routinely leaked to news media by government employes without criminal prosecution. There is no prosecution, he argued, because there is no evidence that the "leakers" had reason to believe that the information could be used to harm the United States.

In addition, Stein waved a copy of an official Pentagon periodical called "Soviet Military Power 1984," published three months before the Jane's photos, that contained a full-color artist's rendering of the same Black Sea shipyard.

Prosecutor Michael Schatzow countered that the artist's drawing was "general" with "not very much detail." In contrast, he said, the photos in Jane's could be of vital importance to the Soviets, not because of the pictures themselves, but because of the information-gathering capabilities they demonstrated.

Further, Schatzow argued, FBI agents searching Morison's bachelor apartment in Crofton found "a great amount of government material . . . much of it secret."

With his government intelligence career now effectively ended, Schatzow said, Morison is "subject to being approached and exploited by some foreign government" and could be tempted to flee.

Rosenberg turned down Schatzow's request that Morison put up $250,000 bond secured by property and agreed to the $100,000 pledge by Morison's mother.