ECHO
Satellite Communications Glossary
Satellite Communications — Echo
Information on Echo
On 12 August 1960, in conjunction with Bell Telephone Laboratories
and the Jet Propulsion Laboratory, NASA launched a passive reflector,
Echo I: a 30-m plastic balloon (weighing 61.2 kg)
with an aluminium coating. The balloon had 82 panels that
were folded before launch and inflated in orbit. A second
satellite, Echo II, was launched on 25 January 1964
but inflated too rapidly and the balloon exploded.
Echo was
used principally for FM voice, facsimile and data transmission, but
was also used on 19 August 1960 to test picture
transmission. Although a passive reflector, Echo contained two tracking
beacons transmitting with a power of 10 mW at a
frequency of 107.9 MHz.
Although Echo was simple and
reliable, it was severely limited by being a passive reflector—despite
the sphere having a reflectivity of 98%, Earth stations required
extremely high-power transmitters (approximately 10 kW). Even with these high
powers, useable receive powers were only possible because the satellite
operated at a low height of 1 500 km. At
that height, however, the periods of rotation were very small
(118.3 minutes) so that the satellite was only accessible to
ground stations for a short time.
Other topics in our resources on Satellite Communications related to Echo include:
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