Countdown is on in US-Europe battle of the satellite launchers

The next couple of weeks could be crucial in the battle between the United States and Western Europe in the prestigious business of putting satellites into outer space.

While the US relies on the reusable space shuttle, developed at a cost of $10 billion, a consortium of West European nations uses Ariane, a conventional ''throwaway'' rocket built for one-tenth of the shuttle's cost.

Next week, both vehicles are due for launching within a 48-hour period. On June 16, an Ariane rocket is to take off from the French government's launch site in Kourou, French Guiana, laden with a satellite to carry television broadcasts and telephone calls between European countries.

On June 18, the space shuttle Challenger is due to leave Kennedy Space Center , its cargo bay crammed with no fewer than four payloads. These include communications satellites for Indonesia and Canada, a prototype space platform built by West German engineers, and a package of scientific experiments.

These flights should give potential customers for Ariane and the shuttle a golden opportunity to assess the performance of the two craft. At present, the shuttle is winning on terms of reliability, but some firms are skeptical about the cost of launching satellites via the shuttle.

The stakes in the space-launching business are high. According to estimates, between 1985 and 1991 the world will want to put into space about 200 satellites for communications, either for ordinary telephone calls and data or for direct-broadcast TV.

Ariane and the space shuttle are virtually the only contenders for the job. The United States is gradually ''retiring'' its conventional, expendable launchers such as Delta. (However, the Reagan administration wants to allow private companies to buy such rockets and lease National Aeronautics and Space Administration facilities for launching them. Several companies are interested in getting into the launch business.)

The competition was out in the open at the recent Paris Air Show, where the US space shuttle Enterprise was on display. Although it is a prototype that has never been into space, Enterprise drew large crowds.

Only a short distance away officials of a company called Arianespace Inc. were doing their best to draw attention to a life-sized mock-up of Ariane. Beginning next year, Arianespace will market the European rocket. Until then the government-dominated European Space Agency, which has financed Ariane's development, is in charge of launches.

By contrast, Arianespace is vigorously commercial in its outlook. It bills itself as ''the world's first commercial space carrier.'' French electronics firms, banks, and government institutions own 60 percent of the shares in the company.

The next flight of Ariane is crucial for executives at the company. The rocket's track record is spotty. Out of five launches, only three have succeeded.

On the other two occasions, the vehicle crashed into the Atlantic only minutes after leaving its Kourou launch pad. But European space engineers say the failures were only teething problems of the kind that crop up at the start of any new technical development. They point to an impressive order book that suggests five Ariane launches next year and eight in 1985.

By contrast, all the six US space shuttle flights so far have been at least partial successes. On the last mission, in April, the vehicle failed to put its cargo, a government-owned tracking and data relay satellite, into the right orbit. But the fault lay mainly in the special booster rocket developed for this purpose by the US Air Force.

Of greater concern to shuttle managers is the vehicle's brimming flight schedule. In July 1981, NASA was planning a total of 62 flights by the end of 1986. This has been reduced to 51. The figure is important, since the one way NASA hopes to reduce costs is through increasing the number of flights each shuttle vehicle makes per year.

By 1985, NASA will operate four shuttles - Discovery and Atlantis, in addition to Columbia and Challenger, which constitute the current fleet. Eventually, space engineers plan to launch each vehicle every two weeks, making a total of some 100 flights per year. But the latest NASA plans put the number of shuttle missions even by 1987 at only 24, divided roughly equally among the four orbiters.

According to the current price schedule, launching a 1.2 ton communications satellite with the shuttle costs about $16 million. With Ariane it is $25 million to $30 million.

But by government decree, NASA will double its prices in October 1985, bringing the shuttle more in line with Arianespace's charges. What happens after that depends on whether the shuttle operators can increase the flight rate to reduce costs.

Significantly, by this time NASA may no longer be in charge of shuttle launches. James Beggs, the NASA administrator, says he wants his organization to leave that role to a private company. This would free NASA to get on with research and development into new space concepts, such as a permanent space station.

For organizations that plan to operate satellites over the next few years, the next couple of weeks will be highly important as they decide which vehicle to select.

Among the American companies planning communications satellites, Satellite Business Systems, RCA Corporation, American Telephone & Telegraph Co., US Satellite Systems, and American Satellite Company have all indicated they will place their craft on the shuttle.

On the other hand, Southern Pacific Satellite Company and General Telephone & Electronics Corp. have both announced they are backing Ariane, at least for some of their satellites. Both companies have signed deals with Arianespace to launch two satellites next year.

Intelsat, the international satellite communications organization, is showing an evenhanded approach, dividing up launches between the two craft. A consortium of Arab nations called Arabsat is showing a similar approach. It has booked Ariane and the shuttle for two communications craft it plans to launch next year.

The most extraordinary approach is by Western Union. It wants to launch one of its satellites, Westar 6, early in 1984 and has signed up both the shuttle and Ariane for the job.

Western Union, which under the terms of its agreement has already started its launch payments to Arianespace and NASA, explains that it wanted an insurance policy on either vehicle not being available. The company will decide on the issue after evaluating the next flights of both contenders.