Luna 10

18:44 UTC, 3 April 1966

At 18:44 UTC on 3 April 1966 — 21:44 Moscow time — Luna 10 fired its braking engine and entered a selenocentric orbit, becoming the Moon's first artificial satellite.

The manoeuvre slowed the spacecraft from approximately 2.1 to 1.25 kilometres per second. A course correction on 1 April had lined up the encounter, but only the Earth-commanded deceleration let lunar gravity take hold.

After insertion, the instrumented satellite section separated from the propulsion section and began radio communication with Earth.

What TASS announced that day

TASS issued the communiqué reporting that Luna 10 had become the first artificial satellite of the Moon. At the Soviet Communist Party congress, delegates heard the spacecraft transmit the notes of "The Internationale" as the achievement was announced.

That first communiqué gave the orbit only approximately — 350 by 1,000 kilometres, a period of about three hours. The figures were subsequently reported more precisely: roughly 350 kilometres above the surface at perilune and 1,017 at apolune, a period of 2 hours 58 minutes 15 seconds, and an inclination of about 71 degrees to the lunar equator.

First to orbit, not first to reach

This was the first spacecraft to orbit the Moon, not the first to reach it. Luna 2 had impacted the surface in 1959.

Even the date gets misreported. The insertion falls on 3 April in both UTC and Moscow civil time, but the first complete orbit ended after midnight Moscow time — which is where the erroneous 4 April comes from.