Science: Someday I'll talk upon a star: By the year 2000 hand-held satellite telephones will enable us to make calls from anywhere in the world, says Peter Bond

Were ET to return to Earth a few years from now, he would have much less difficulty phoning home. By the end of the century, people will be able to communicate by telephone whether they are climbing Everest, sailing down the Amazon or camel-riding in the Sahara - all courtesy of satellite constellations.

Mobile cellular phones are beginning to catch on - there are now 40 million users worldwide - but they are limited in range and performance. For those who wish to bridge the international divide, satellite telephones have shrunk to briefcase size, but are still unwieldy and relatively expensive. Now, several international consortia, most of them based in the US, aim to bring hand-held portable satellite phones on to the market by the year 2000. The first step was taken last year when the World Administrative Radio Conference allocated a section of the high-frequency radio spectrum to these new services.

First into the sky will be the American Orbcomm and Starsys projects, each involving investment of more than dollars 135m ( pounds 90m). The first two Orbcomm spacecraft are due to be launched early in 1994, with the remaining 24 launches scheduled during 1995. Starsys will follow a year later.

These will not provide direct telephony, but a two-way electronic messaging system. Orbcomm has unveiled two types of communicators, designed in Japan. One full-

feature unit has a seven-line screen and alphanumeric keypad and can send and receive messages in a similar way to electronic mail. The other model has a computer-interface port and can be used for data acquisition and monitoring. Prices will range from dollars 50 to dollars 400, but the cost of sending a short message will be only a few cents.

The companies believe potential applications include keeping track of moving industrial containers and vehicles, accessing data from remote locations around the world, and E-mail links between computers. Both are optimistic that their products will catch on. Starsys predicts that 1 million ground terminals will be tapping into such services in North America alone by 1997.

A different approach has been taken by the American Mobile Satellite Corporation and its Canadian partner, Telesat Mobile. They have already been selected as sole providers of voice and high-speed data communications for all North American mobile users. During 1994, they expect to launch two satellites into orbit 22,350 miles above the equator.

Although they will have the advantage of being the pioneers of the new technology, their system will suffer from the same disadvantages as existing Satcom networks. Larger, more powerful user terminals will be required to transmit and receive the signals, and there will be an annoying time delay of about a quarter of a second as the message travels through space.

The London-based maritime communications organisation, Inmarsat, is looking instead at alternatives for its Project 21. Inmarsat's hand-held phones will communicate via satellites to stations on Earth, known as gateways. Messages will then be routed through existing public communications networks.

Project 21 will enable customers to place or receive voice, fax, data and paging transmissions anywhere in the world. Phones will be able to search for a local cellular phone circuit. If this is unavailable, the call will be routed via space. One or more satellites will always be above the horizon to handle the calls.

Other groups have opted for multi-satellite systems in low Earth orbits. The best known is Motorola's Iridium system, a dollars 3.4bn project that has attracted investment from around the world. Lockheed, the US aerospace giant, has a contract to build 66 operational satellites and 14 spares by 1998. China and Russia are among those queueing up to launch this.

Iridium is the most hi-tech of the new systems, and will be one of the most expensive to use. A hand-held phone will probably cost around dollars 3,000 - double the price of dual-

mode Inmarsat-P terminals. However, unlike the Inmarsat-P sets, which must be operated near windows or away from signal 'shadows' caused by tall buildings, it will be possible to use the Iridium phones anywhere, even inside buildings.

One of Iridium's unique features is its ability to link the satellites in a network, passing messages between them until they access the required public telephone system.

Iridium's approach has been criticised as unnecessarily complex and expensive by Motorola's rivals such as Loral-Qualcomm, whose dollars 1.5bn Globalstar system will use 48 satellites carrying simple repeaters which do the minimum of on-board signal processing. With higher orbits and wider beams, messages will be bounced off the nearest satellite to one of numerous ground stations, so there will be no need to pass calls between satellites. Motorola argues that links between satellites are essential because many countries' telephone systems, particularly in the developing world, are not up to the job.

The various consortia predict a potential market for around 2 million hand-held portable phones by 2002. As the Wall Street Journal commented, they hope to 'attract enough initial users for whom cost isn't a concern - affluent businessmen, government bureaucrats, military personnel and the like'.

The US Federal Communications Commission is expected to award two or three licences for the US portion of the spectrum early next year, but winning regulatory approval in Europe could prove a costly and time-consuming exercise. In this uncertain situation, the attitude of the European Space Agency (ESA) is worthy of note. According to its spokesman, Claus Habfast: 'ESA prefers Inmarsat above the others. It is better to have an operator that is international and under public control.' He went on: 'There is no place for more than one operator.'

Motorola seems to fear that this may well be the case. Last July, the company vice-president, Leonard Kolsky, wrote to several US government agencies complaining that Motorola could not compete on a fair basis with Inmarsat, and asking them to prevent the American Comsat Corp from investing in Inmarsat's Project 21. It appears that there is neither enough money around nor a sufficiently large market to support even the proposed small number of satellite telephone operators.

(Photograph omitted)