When did Arthur C. Clark first begin working on the invention of the satellite?

Answer 1

Clarke wasn't an engineer, he didn't actually sit down, design, and build a satellite. Instead, he was a scientist and science fiction author, who wrote visionary works from the 1940's and on. It was he who first wrote about the idea of using manned space stations as television relay studios for global broadcast around the world. He rightly claimed the value of placing any such relay devices in a "geostationary orbit", one that stays fixed above a set point over the Earth's equator. Placing three of these stations equidistant around the equator would allow nearly total global coverage, nearly up to the poles. Satellite companies later took his ideas and actually designed and built the satellites to do the work he first envisioned. He first wrote about this around 1945. The first actual communications satellites went up in the 1960's.

However, Clarke's vision of what a communications satellite would look like was vastly different from today's reality. His vision was restricted by the fact that at that time, the transistor was not yet invented. Electronic equipment used vacuum tubes requiring enormous power supplies. Such equipment was notoriously unreliable with MTBF (mean time between failure) measured in only hundreds of hours and would require constant repair & maintenance. He suggested that a communications satellite would be very large, perhaps as big as medium sized office block, and would house a significant technical staff who would live on the satellite. It would probably have to be constructed in space and boosted into the geosynchronous orbit when completed.

Today's communications satellites are generally just a few metres in length and width and weigh just a few tons. Their electronics are based on VLSI (very large scale integration) that allows millions of transistors on a microchip, and giving an MTBF measured in hundreds of thousands of hours.