Roger Emery, a space scientist with the Rutherford-Appleton Laboratory
in England, and who helped build the Infrared Space Observatory (ISO)
satellite for the European Space Agency (ESA), responded.

Satellites are made of lots of materials.
Each has to be tested to make sure it does not change in the high
vacuum of space and can withstand the temperatures which can be very cold.
Space agencies keep long lists of materials and
components which they have tested for use in space, to help the engineers.
These are often materials which combine strength with lightness, such as
aluminium alloys or carbon fibre for the structure, since the cost of
launching the satellite is mainly determined by its weight.

Apart from the structure of the satellite, there are many other parts, much
of which involve electronics and the use of semiconductors, like silicon.
These are needed for the satellite to receive command signals from the Earth
and to send signals back, all controlled by a computer. This electronics
looks much like the insides you find in a radio or television, but made
using components selected for space, and specifically components that are
not easily affected by the radiation in space. To provide the power for all
this, photocells are used in the form of large panels to convert sunlight
into electricity, and batteries are also used to store this power.

With these basic parts of the satellite sorted out, it also needs to include
instruments so that it can perform its special jobs. Examples are cameras
to look down at the Earth for weather satellites (Meteosat) or telescopes to
look up for astronomy (Hubble Space Telescope). Some of these need the
satellite to be controlled very carefully in position. For this, small gas
jets are used, often with the actual position being measured by a camera
designed to look at the stars.

So you can see, metals, special plastics and glasses are used to make
satellites - with great care being taken in their selection and testing -
and sometimes even gas or liquids in special containers.