What does a satellite look like?

Compared to a rocket and a space shuttle, a satellite looks a little flimsy on the outside. Its body is covered all over with thin metal foil, and its "limbs" look thin enough to snap off at any time. Its shape comes in all sorts of variations depending on use. Some are shaped like an old flashlight, some like a screwdriver, some like a Rubik's cube, and some like a giant aspirin tablet.

No matter what the shape, satellites are usually about as big as a car in size.

Just what uses do satellites have?

As broad as the imagination of man. People use satellites today to send messages on car telephones, and a similar service was offered to airline passengers two or three years ago.

Besides communications, of course, satellites can also be used for observing the weather, for locating mineral deposits or schools of fish, for scientific experiments, and for military intelligence.

Taiwan's satellites would be used mainly for communications and meteorology.

How did satellites come about?

Actually, the idea of a communications satellite was raised as early as 1945 by the British author Arthur C. Clarke.

But the key role in bringing satellites to the world was played not by scientists but by the moon.

In 1946 the U.S. Navy accidentally discovered that a radar signal wasreflected off the moon and back, and in 1959 they used the moon to sendsignals between Washington and Hawaii. Echo, a giant balloon covered inaluminum for better reflection, was launched into space in 1960.

How long do most satellites last?

The chief limitation on the life of satellite is not how long it can stay in orbit but how long the supply of electricity it needs to operate can last.

The electricity for most satellites is supplied by either solar cells or storage cell batteries. The main problem is that solar cells can collect only a limited amount of electricity from the sun. The U.S. satellite Hyperion, for example, has 3,600 solar cells on its surface but generates no more than 15 watts of power, and when it enters the earth's umbra, it loses generating power completely and has to rely on storage cells to maintain normal operations. And the number of storage cells on a satellite is limited by considerations of weight.

Scientists from the U.S. and the U.S.S.R. may develop a way to refuel satellites in the future to extend their longevity almost indefinitely.

What can be done with satellites that have "died a natural death"?

Satellites that have "died a natural death" --along with the rockets that carried them into space and boosters discarded along the way--become space rubbish that is difficult to deal with and highly dangerous.

Most of this space rubbish can't be controlled or collected and, what's worse, may have the potential to explode. In 1965 an abandoned booster exploded into 460-some fragments that are still roaming about in space. Fortunately, there have been no reports to date of them damaging another satellite.

How many satellites are there in orbit now,and could space be getting "full up"?

It is estimated that around 10,000 objects had been sent into space by 1977 and that 1,228 satellites were still functioning by 1983.

It would seem that space is still a long way from being full up. So why are people so anxious to "grab turf"?

It's because stronger and stronger signals have been used in recent years to simplify surface reception equipment.

With stronger signals, satellites must be farther apart be to avoid mutual interference, and fewer satellites can stay together in the same orbit.

So even though space is not yet full up, a "first come, first served" mentality still seems rather prevalent.

[Picture Caption]

The space shuttle is one of the tools used to carry satellites aloft. (photo courtesy of Newton magazine)