Telstar was roughly spherical – about 88cm in diameter and weighting 77kg). Its dimensions were limited by what would fit the Delta rocket. Its surface was covered with solar cells that could generate 14W.
It featured what's said to be an innovative transponder, which could relay data, a TV channel or telephone calls.
Because it span, an array of cavity antennas was needed in order to maintain uninterrupted communications. The uplink was at 6GHz. Signals were down converted to 4GHz and amplified using a travelling wave tube, then retransmitted.
While the first data was transmitted the next day, the major event took place on 23 July, with a live TV transmission. Part of the technology required was a system to convert the images from the NTSC's 525 lines to the 405 lines used by UK TVs. This, apparently, required a room full of equipment.
Telstar was a short lived success; transistor failure saw it go out of service in February 1963.
