Luna Ye-6S

Ye-6S (Cruise)

Ye-6S (Lunar orbit)

The Ye-6S series of lunar probes were the first soviet spacecraft designed to enter lunar orbit. Luna 10 became the first artificial satellite of the moon.

The Ye-6S spacecraft, consisting of a Ye-6 bus with a fueled mass of about 1350 kg attached to a cylindrical pressurized 245 kg lunar orbiter module. It was 1.5 meters tall and 75 cm in diameter at the base. The main propulsion systems for lunar orbit insertion were on the bus, and the science payload was carried on the orbiter module.

The payload comprised seven instruments:

• a gamma-ray spectrometer for energies between 0.3--3 MeV,
• a triaxial magnetometer (on the end of a 1.5 meter boom),
• a piezoelectric micrometeoroid detector,
• gas discharge counters,
• devices for measuring infrared emissions from the Moon,
• low energy X-ray detectors, and
• a bank of charged particle detectors.

Additionally, the radio system was used for gravitational and radio occultation studies. Ye-6S was battery powered and communications were via 183 MHz and 922 MHz aerials.

The first mission was launched on 1 March 1966 but the Blok-L upper stage lost roll control and failed to fire the spacecraft into a lunar trajectory. It was therefore designated Kosmos 111 instead of a Luna designation.

The back-up spacecraft was successfully launched 31 March 1966 and received the designation Luna 10. It was injected into a 200 km × 250 km, 52° Earth orbit and launched towards the Moon by the launch vehicles upper stage. Following a mid-course correction on 1 April, Luna 10 turned around at a distance of 8000 km from the Moon and fired its rockets, slowing by 0.64 km/sec. It entered lunar orbit at 18:44 UT on 3 April 1966 and separated from the bus 20 seconds later. The initial orbit was 349 km × 1015 km with a period of 2 hours 58 minutes and an inclination of 71.9°.

The data returned showed a weak to non-existent magnetic field, cosmic radiation of 5 particles/cm2/sec, 198 micrometeoroid impacts, no discernable atmosphere, and a highly distorted gravity field, suggesting a non-uniform mass distribution. The gamma-ray spectrometer gave compositional information on the Moon'ssurface, showing it to be similar to terrestrial basalt. Luna 10 operated for 56 days, covering 460 lunar orbits and 219 active data transmissions before the batteries were depleted and radio signals were discontinued on 30 May 1966. The orbit at that time was 378 km × 985 km with an inclination of 72.2°.

Also it broadcasted the "Internationale", which was played to the delegates of the Communist Party Congress. Although claimed to be a live broadcast at the time, it was later revealed, that a recording from an earlier communication session was played.