Luna 1

Luna 1 (E-1 series), first known as First Cosmic Ship, then known as Mechta (Russian: Мечта, lit.: Dream) was the first spacecraft to reach the vicinity of the Moon and the first of the Luna program of Soviet automatic interplanetary stations successfully launched in the direction of the Moon.

While traveling through the outer Van Allen radiation belt, the spacecraft's scintillator made observations indicating that a small number of high energy particles exist in the outer belt. The measurements obtained during this mission provided new data on the Earth's radiation belt and outer space. The Moon was found to have no detectable magnetic field. The first ever direct observations and measurements of the solar wind, a strong flow of ionized plasma emanating from the Sun and streaming through interplanetary space, were performed. That ionized plasma concentration was measured to be some 700 particles per cm3 at altitudes 20-25 thousand km and 300 to 400 particles per cm3 at altitudes 100-150 thousand km. The spacecraft also marked the first instance of radio communication at the half-million-kilometer distance.

A malfunction in the ground-based control system caused an error in the rocket's burntime, and the spacecraft missed the target and flew by the Moon at a distance of 5,900 km at the closest point. Luna 1 then became the first man-made object to reach heliocentric orbit and was then dubbed a "new planet" and renamed Mechta ("Dream"). Its orbit lies between those of Earth and Mars. The name "Luna-1" was applied retroactively years later. Luna-1 was originally referred to as the "First Cosmic Rocket", in reference to its achievement of escape velocity.