What influence did Arthur C. Clarke have on early satellite development?

Question

Partially inspired by this uhoh question on SciFi.SE

In writing up my answer, I came across this interview Clarke gave to NPR in 2008 where this quote is made

While Clarke came up with the idea of the communications satellite, it was John Pierce of Bell Labs who was instrumental in developing the first communications satellites, Echo I and Telstar, in the 1950s. Clarke had interacted with Pierce during that period.

And

Das: Do you consider the paper on geostationary orbits your most important contribution?

Clarke: It’s definitely my most important contribution. And maybe in a generation or so the space elevator will be considered equally important.

The article implies Clarke played some important role but never focuses on that role enough to paint a complete picture. How much of a role did Clarke's ideas play in helping to make modern satellites what they are today?

Answer 1

Clarke proposed geostationary communications satellites in a letter to Wireless World magazine in early 1945. Later in the same year he expanded on this idea in two more papers, one of which was published as Extra-Terrestrial Relays in Wireless World in late '45.

The article mentions the orbital altitude needed for a 24-hour orbital period (42000 km orbital radius), suggests a solar-thermal power source (photovoltaic technology being in its infancy, and possibly unknown to Clarke), and provides some figures for useful radio signal strength. Clarke was envisioning crewed science stations in geosynch orbit, with communication relays as an afterthought, which obviously isn't how things played out.

While this is probably the first time the idea was exposed to a broad popular audience, it isn't truly the first time it was conceived. The basic concept was presented (without details) in a 1942 science fiction story. The concept of geostationary satellites was described by Hermann Oberth in a 1923 book, and expanded upon by Herman Potočnik in 1928.