On 10 July 1962, AT&T launched Telstar I, which
was the first satellite to provide repeated transmission without delay.
Telstar was launched into an orbit between 956 km
and 5 633 km with 44.8º inclination. The 87.6-cm sphere
weighed 80 kg and was powered by solar cells. Unfortunately,
Telstar I’s electronic equipment was damaged by radiation from
the Van Allen belts and only lasted until 21 February
1963. A more radiation-resistant Telstar II was launched on
7 May 1963 and was used for telephone, television, facsimile
and data transmission.
Telstar was a simple repeater that
received signals at 6.390 GHz, amplified them and retransmitted them
at 4.170 GHz. These C-band frequencies were chosen because of
the ready availability of existing terrestrial microwave radio-relay equipment. The
satellite power amplifier used a specially developed 50-MHz, 2-W broadband
travelling-wave tube allowing colour television signals to be relayed across
the Atlantic for the first time.
Other topics in our resources on Satellite Communications related to Telstar include: