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ON 4 October 1957, the space race was born when the Soviet Union launched Sputnik 1-the world鈥檚 first artificial satellite. The satellite even carried out a few scientific experiments while it was circling the Earth more than 224 kilometres up.

The first days of the space race were dominated by the Soviet Union. After Sputnik, the Soviets put a man in space. In 1961, Yuri Gagarin circled the Earth once in his cramped Vostok 1 capsule before descending to Earth.

The Americans missed their chance with these landmarks, but on 20 July 1969 the US became the first nation to put men on the Moon with the Apollo 11 mission. To date, it is the only one to manage this feat.

Since then, the space business has changed out of all recognition. The projects that put men into space and on the Moon were adapted from military research programmes. These days, most of the companies building and launching satellites are commercial concerns: the race is for customers rather than for a place in history.

Big competition

Fresh challenges

ARIANESPACE, a European company, owned by firms in 12 countries dominates the $35 billion commercial launch market. Nearly 60 per cent of the satellites put into orbit during 1996 were launched using the Ariane rocket-a launcher developed by the European Space Agency (ESA). In 1996, Arianespace launched 15 satellites on 10 rockets.

While Arianespace flies satellites, the ESA carries out scientific missions on behalf of its 14 members. Arianespace is hoping that the second flight of its heavy-lift Ariane 5 rocket is less troublesome than its maiden voyage. On 4 June 1996, a software error made the craft explode just 40 seconds after takeoff.

Competition for customers comes from China and Japan, both of which are increasing the number of rockets that they launch each year. Japan is planning 10 launches per year from 1997 onwards and has signed a multimillion-dollar deal with the American aerospace giant Hughes to put 10 satellites into orbit. It also wants to go to the Moon.

The Chinese intend to match the Japanese launch rate once they have proved that their rockets can launch reliably. A series of failed launches in 1995 and 1996 has led to China losing a contract with Intelsat. Other nations such as Brazil, India and Israel are all developing their own rockets-as are several new, private launch firms. The number of small satellites in a low orbit is set to grow by at least 75 per cent and these companies want to cash in.

One of the few constants since the early days of the space age has been the US鈥檚 National Aeronautics and Space Administration. Since its early success with the Apollo missions, NASA has developed the space shuttle-a reusable space plane that can lift satellites and astronauts into orbit.

The development of the shuttle suffered a setback in 1986 when the Challenger model blew up, killing all seven astronauts on board. Now the shuttle is used primarily for scientific missions. NASA leaves it to other aerospace firms such as Lockheed Martin and McDonnell Douglas to launch communications satellites for television and telephone companies.

While NASA has prospered, Russia is a shadow of its former self. The break-up of the Soviet Union has virtually bankrupted the country, leaving little money for expensive rocket science. Russia鈥檚 answer to the shuttle, a reusable space plane called Buran, has been turned into a caf茅 in Moscow鈥檚 Gorky Park.

Even Mir, Russia鈥檚 space station, is dependent on the Americans to keep it supplied with spare parts, fresh astronauts and fuel. The core of the station was put into an orbit 330 000 metres up in 1986.

Russia is building some parts for a much bigger orbiting craft called the International Space Station (ISS). But the financial crisis has already delayed the first launch by 11 months.

Russia has signed launch deals with Arianespace and a consortium of US firms called International Launch Services. Its big card is Proton, because these Russian rockets are among the most reliable in the world. As the number of satellites needing launch slots is likely to boom over the next five years, this deal could help the Russians to bolster their ailing space programme.

While Russia has problems raising the money to support a solo programme, through cooperative agreements with NASA and ESA it is contributing to many science missions. This collaboration may even result in a joint US-Russian manned mission to Mars in 2010. But only if Russia can get its finances in order.

Currently there are more than 300 satellites orbiting the Earth. Some of them are carrying out experiments but the majority are used for communications. Many relay television pictures around the world, convey radio and telephone messages and let the military spy on what is happening at ground level.

Satellites communicate with the Earth using microwaves. Early satellites used a section of the electromagnetic spectrum known as the C-band which involved frequencies between 4 and 6 gigahertz or a billion cycles per second. Receiving these signals requires a 3.5-metre satellite dish and they can be blocked by heavy rain or thunderstorms.

Sensing satellites

Separate orbits

TO get around these problems new sections of the spectrum are being used. Ku-band microwaves at frequencies of between 11 and 14 gigahertz are already used, and even higher frequencies, the Ka-band between 18 and 31 gigahertz, will soon come into service.

Higher frequencies means shorter wavelengths and smaller reception dishes. Signals from Ka-band satellites can be picked up on dishes only 18 inches across.

Satellites use antennas for receiving and sending the microwave signals. Because microwaves become attenuated as they travel back and forth, satellites use transponders to boost signals so that they can be received back on Earth.

The specific job that a satellites does determines which orbit around the Earth it will use. One of the most popular orbits is called the geostationary orbit, some 35 900 kilometres above the Earth鈥檚 surface. This idea was first proposed by science-fiction author Arthur C. Clarke in 1945 in an article for the British magazine Wireless World. A company or government placing three satellites in geostationary orbits 120 degrees apart can beam signals to any part of the Earth.

To avoid overcrowding in geostationary orbits, the International Telecommunications Union (ITU) decides who gets which slots. The orbit is divided into slices two or three degrees apart. Any closer and signals to and from satellites would interfere with each other. As a result, there are only a few hundred possible slots and those positioned over countries are heavily contested.

The growing interest in satellite communications has meant that many companies are claiming slots even though they have no intention of building and flying satellites themselves. Instead, they auction the slot to someone who does want it, often making huge profits in the process.

The tiny island nation of Tonga, for example, owns seven orbital slots even though it has no aerospace industry. The slots, over the Pacific Ocean between Japan and the US, are expected to be heavily used in the near future. To generate money, Tonga leases the slots to communications firms for their satellites.

Other slots in the Pacific Rim area are getting heavily overbooked. Currently, there are seven times more applications for slots in this region than available airspace. In mid-1997, the ITU is holding a conference to try to sort out the mess. Soon any firm wishing to reserve a satellite parking space will have to prove that it has the money and technical ability to build and launch the spacecraft.

Phoning home

New rockets

ANOTHER orbit likely to get crowded by the turn of the century is the Low Earth Orbit (LEO). Satellites in this orbit circle the Earth at heights of between 200 and 3000 kilometres, taking about an hour and a half to complete a circuit. The satellites fly at lower altitudes so it takes between 50 and 70 LEO spacecraft to cover the Earth. The plan is to build global phone networks. Once such networks are in place, it will be possible to make a phone call from the middle of the Sahara to New York. Permission to place satellites in LEO have only recently become available, as have the radio and microwave frequencies they will use. With the cost of building satellites falling, it is now cost-effective to consider putting many spacecraft in orbit.

Currently, 11 firms are planning to put satellites into these low orbits. Many have yet to find the money they need to launch their spacecraft. To date, only Motorola with its 66-satellite Iridium system and Globalstar with its 48-strong network have the money they need. Iridium is due to launch its first satellite later this year.

Putting a satellite in a LEO is not without its problems. Atmospheric drag and gravity gradually make the orbits degrade. The satellites being used in LEO-based mobile phone networks will periodically have to be replaced when they run out of fuel and can no longer be repositioned.

Because of Russia鈥檚 place on the globe, it has to put its satellites into a different orbit to ensure they cover the whole country. This Molniya orbit, is inclined 65 degrees away from the equatorial plane. A spacecraft following it traces a highly elliptical path around the Earth, at its perigee (point nearest the Earth) it is 500 kilometres high and at its apogee (farthest point) 40 000 kilometres. A craft taking this route takes eight hours to circle the planet so three are needed to give round-the-clock coverage.

And as the number of satellites circling the Earth increases, the greater the threat they face from space junk. This debris is generated when a rocket blows up in orbit or when it discards a stage or fuel tank en route to its destination.

Last year, a French satellite called Cerise collided with a piece of an old Ariane rocket and was nearly knocked off course. NASA constantly tracks the position of 6000 large pieces of space debris, but as some of them follow eccentric orbits it is often difficult to predict where they will go next.

The space shuttle is more than 15 years old, and has yet to fulfil its promise to lower the cost and complexity of getting off the planet. At present the most expensive way to put a satellite in orbit is to use the shuttle. NASA wants to replace the craft by 2000 to make it easier and cheaper to get into space. Last year, NASA signed a $941 million contract with Lockheed Martin for the development of a reusable spaceplane called the X-33.

This wedge-shaped plane may lift off vertically like existing rockets, but it will glide back to Earth like the shuttle. It is due to make its first flight in March 1999. There are many hurdles to overcome if this deadline is to be met. The engines of the X-33 will need to be of a novel design known as an aerospike. In existing rockets, exhaust gases directed against the side of the engine鈥檚 nozzle create thrust. In an aerospike, the exhaust plays over the outer surface of the nozzle. The push of hot gases against the spike generates thrust. Manoeuvring is done by varying thrust over the spike鈥檚 sides instead of swivelling the nozzle. The temperature in the exhaust plume can reach 3000 掳C and Lockheed Martin is looking at ways to keep the central spike cool. If it can solve this, aerospike technology could cut launch costs to $15 million. A satellite launch with the shuttle now costs $500 million.

Cheap ride

First flights

THE aerospike engines will form part of the superstructure of the X-33, known as a lifting body. This means it does not have wings as the shape of the plane is sufficiently aerodynamic to provide lift.

While NASA is preparing its new generation of launch vehicles, Arianespace is trying to correct problems revealed during the maiden flight of its Ariane 5 heavy-lift rocket, when a software error caused the rocket to blow up 40 seconds after launch. The same software worked fine on the smaller Ariane 4 rocket, but Ariane 5 is heavier and has a different flight pattern. Sadly, no one thought to see if this different faster ascent would cause software problems. A second Ariane 5 flight is scheduled for September this year. If all the bugs have been ironed out, the rocket will go into commercial service in 1998.

But the big players-Arianespace, Lockheed Martin and McDonnell Douglas-all face competition from new launchers being developed by private companies. One of the biggest is the Sea Launch system. This is a joint venture between Boeing, the Norwegian shipmaker Kvaerner and Russian and Ukrainian aerospace firms RSC-Energia and NPO-Yuzhnoye. This company is turning an old oil rig into a launch platform. A separate ship will dock with the rig and unload a pre-prepared Russian Zenit rocket for launch. The first flight of a Sea Launch rocket is due in June 1998.

A clutch of small launch firms in the US is also attempting to capture a share of the market for LEO satellites. Kelly Space, for example, is planning to launch satellites from San Bernadino airport using converted F-106 jet fighters. The ageing planes will be converted into crewless drones which will be towed behind a 747 to a height of 14 kilometres. Then they power themselves to a LEO by means of an internal rocket engine, release their payload and finally glide back to Earth.

Kelly Space has signed a deal with Motorola to launch replacement satellites for its Iridium network. The first commercial Kelly flight is due in 1999-and the company claims to be able to slash the cost of launching satellites to less than $300 per 453 grams compared with the shuttle鈥檚 costs of $10 000 for the same weight.

Building in space

Human orbits

SCORPIUS is another firm, with plans for its first commercial launch next year. The Scorpius launcher uses lots of small, liquid-fuelled rockets to generate enough thrust to lift a LEO payload. Test flights of Scorpius rockets are already taking place, and its launch costs will be less than $1000 per 453 grams.

Kistler Aerospace and the Pioneer Rocket-plane Corporation are also developing new launchers but are reluctant to release details of projected launch costs. Pioneer has yet to find all the money it needs to develop its concept of a piloted spaceplane called Pathfinder. To encourage more human exploration of space, a group of astronauts and aerospace enthusiasts announced the X Prize in May 1996. This $10 million cash purse will be given to the first company to build and fly a reusable spaceship capable of carrying three people -not necessarily astronauts-on a sub-orbital flight. No one has made a serious attempt at completing the task.

The biggest space project of the next decade will without doubt be the creation of the International Space Station. Once finished, the station will allow humans to maintain a permanent presence in space. It will boast seven laboratories in which scientists will study the effects of zero gravity on the formation of protein crystals to improve our understanding of biological processes.

Protein crystals and plants grown in zero gravity are very different from their Earth-bound counterparts. By studying the differences researchers hope to be able to understand more about the important forces controlling development. Once they know what governs the way something develops, they may be able to manipulate it for their own ends.

Many of the proteins being studied in space are implicated in diseases such as cystic fibrosis. Insights gained by studying them off planet may lead to new cures. Also, many industrial processes benefit by being carried out in zero gravity. NASA is investigating the feasibility of making semiconductors in space because crystals grown in zero gravity are purer.

Last month, NASA announced an 11-month delay to the first launch of Space Station modules because of Russian financial problems. When the programme restarts, the plan is to make 35 assembly flights using the space shuttle as well as European and Russian rockets, and for the station to be fully operational in 2002. Then a six-strong crew will start work in its home-cum-lab-320 kilometres above the Earth.

Europe will use the Ariane 5 rocket to put pieces of the station into orbit. European space scientists are developing the atmospheric re-entry vehicle-a splash-down capsule that will be used to evacuate the station in an emergency. ESA is also developing a space ferry that will ship supplies to the station when they are needed. Eventually the ferry will take fresh crew to the station.

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Through dark clouds clearly

WHILE most satellites are simply passing on television, data or voice signals, the rest are involved in remote sensing-either looking out at the Universe or down onto Earth. Recent innovations in technology have meant that more information than ever is being gathered about climatic conditions on our planet and the effect we are having on them.

Many of the satellites looking down on Earth are watching cloud patterns. These are used by meteorological organisations to plot global weather patterns and make predictions.

These satellites use a variety of instruments to plot cloud movements. Often these are simply cameras that record visible light, but sometimes infrared detectors are brought in to pick up invisible wind movements.

The picture a satellite takes has been likened to a flash photograph. The light from a flash bulb illuminates a scene, catching on film what is reflected. Weather and other remote-sensing satellites do the same, but instead of light, they bounce radio and microwaves off the Earth or clouds to pick out details.

Some satellites now use a monitoring instrument called a synthetic aperture radar (SAR). This works in the following way. The amount of detail that any particular radio imaging system (radar) can pick up is determined by the length of its antenna. A SAR creates a huge virtual antenna by combining echoes received as it travels along its orbit.

Once echoes are corrected for the distance the satellite has travelled, they are combined to give a more detailed picture than was possible before. This gives SARs the ability to look through dusty and cloudy conditions to what is underneath.

Increasingly, satellites are being used to monitor the effects of global warming. Many are circling the Earth around the North and South poles looking at ice floes. Many of these spacecraft have only recently been launched, so it is too early to say how serious the greenhouse effect is.

The European Space Agency will be launching Envisat, a highly sophisticated environmental monitoring satellite in July 1999. During its six-year lifetime, it will keep an eye on the polar icecaps as well as monitoring ozone depletion.

While some satellites watch the Earth, others are peering out into space. The most well-known is the Hubble Space Telescope. Soon after its launch in April 1990, Hubble had to be repaired because some of its instruments were faulty. Once the myopic telescope was fixed, the satellite began sending back astonishing pictures of events in distant galaxies.

In February 1997, Hubble had a second servicing mission in which some of its instruments were replaced and its insulation patched and repaired. The shuttle was used to carry out the repair mission and the instruments were replaced during a series of space walks.

A new instrument called the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) was fitted. This enables Hubble to peer with even greater accuracy far into the Universe, and to look at the light that is scattered by clouds of gas and dust in order to see newly forming stars and check whether planets that could support life are present. Hubble cannot see individual planets so it has to look for perturbations caused by them in the light from stars.