55 years ago today, the Space Age began when the Soviet Union launched “Elementary Satellite 1”, better known as Простейший Спутник-1; or, in Latin transliteration, as (Prosteishii) Sputnik-1.
Inadvertently perhaps, but Sputnik-1 also launched what is nowadays called “radio science”: observations that utilize a spacecraft’s radio signal to determine the spacecraft’s position (and thus, the forces that act on the spacecraft) and the properties of the medium through which the signal travels. In the case of Sputnik-1, this meant deducing the density of the upper atmosphere (from the drag force acting on the satellite) and the electromagnetic properties of the ionosphere.
Sputnik-1 spent a total of about three months in orbit (22 days operational) before it fell back to the Earth. By then, the Space Race was running full steam ahead, culminating in the manned Apollo Moon landings in 1969… an accomplishment that, today, seems to be more in the realm of fiction than back in 1957.