Slowly but surely, tiny Orion Network Systems of Rockville is moving toward its goal of creating a private satellite communications network for businesses in the United States and Europe.

After 18 months of salesmanship and negotiation, Orion said yesterday it had raised $90 million in cash from an international group of seven investors to help fund the $500 million communications project.

The $90 million will be supported by $408 million in loans arranged by Chase Investment Bank Ltd. in London.

The announcement follows seven years of campaigning for permission to enter the international satellite business. Orion won a key victory in July 1989 when the Intelsat communications consortium -- which has veto power over such proposals -- declined to block the Orion application.

The first of Orion's two planned satellites is expected to be launched from Cape Canaveral in late 1993 and the other would go up a year later.

John G. Puente, chairman of the privately owned company, said he saw the completion of the financial arrangements as a major milestone. "We are on the threshold of a new era in satellite telecommunication... ." Puente declared.

The Orion satellite network could communicate with relatively small rooftop antennas costing between $10,000 and $25,000. Businesses could use the Orion network for voice, data and video communications.

Puente said that corporate use of private satellite-based networks for internal communications is growing rapidly. One example, he said, was a network being created to link Chrysler Corp.'s 6,000 dealers.

Orion's idea, however, is to go beyond domestic services and offer networks that connect the United States and Europe.

A similar transatlantic service already is being offered by Pan American Satellite, a small Connecticut company.

Orion vice chairman Christopher Vizas, who founded the company in 1983, said that raising the $90 million involved new concepts in the field of telecommunications, dealing with partners in several countries and even differences in the meaning of business terms from one country to another.

Vizas, Puente and their colleagues at Orion, which has only about 20 employees, traveled back and forth to Europe many times as they sought to wrap up the deal.

Before Orion can proceed with its satellite system, it must get approval for its financing from the Federal Communications Commission.

The company said it anticipated a favorable ruling during the next several weeks.

Orion said it would not disclose the names of the investors who put up the $90 million until FCC approval is granted.

The funds will be administered through a limited partnership called International Private Satellite Partners L.P.

The Orion satellites will be built by British Aerospace Ltd., which also will test and insure the satellites and make sure they work once they are in stationary orbits 22,300 miles above the Atlantic Ocean.

The launch will be handled by General Dynamics Commercial Launch Services of San Diego, which will use Atlas rockets.