Luna 10

• 1. Introduction

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  Luna 10, also known as Lunik 10, became the first artificial satellite of the Moon in 1966. It was also the first human-made satellite of any body other than Earth and the Sun. The Soviet Union flew it as a robotic mission in the Luna program. Once in lunar orbit, it would measure the Moon's magnetism, radiation and rocks from above. What could one battery-powered spacecraft learn about a world it never touched? What was hiding beneath the lunar surface? And what was played for a Communist Party congress back on Earth?

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• 2. Instruments And Batteries

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  Luna 10 belonged to the E-6S series and drew its power from batteries. Its dry mass in orbit was 540 kilograms.

  The gamma-ray spectrometer covered energies between 0.3 and 3 MeV, a range the source also gives as 50 to 500 picojoules. A triaxial magnetometer measured the Moon's magnetic field, and a meteorite detector counted impacts. Other instruments studied the solar plasma and measured infrared emissions from the Moon. More devices tracked radiation conditions in the lunar environment, and the craft carried out gravitational studies as well.

  Every one of these instruments depended on a successful entry into lunar orbit, which came in the first days of April 1966.

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• 3. Orbit Around The Moon

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  At 10:48 GMT on the 31st of March 1966, Luna 10 launched toward the Moon. A midcourse correction followed on the 1st of April. On the 3rd of April the spacecraft entered lunar orbit and finished its first circuit three hours later. By Moscow time, that moment fell on the 4th of April.

  A 245-kilogram instrument compartment then separated from the main bus. The bus itself occupied an orbit of 218 by 621 miles, inclined at 71.9 degrees to the lunar equator.

  Across 460 lunar orbits, Luna 10 made 219 active data transmissions. Radio signals were discontinued on the 30th of May 1966. The spacecraft later crashed on the Moon, although the date of that impact is unknown. Those 219 transmissions carried measurements that researchers would publish before the year was out.

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• 4. Rocks And Radioactivity

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  On the 8th of November 1966, Alexander Vinogradov and colleagues at the USSR Academy of Sciences published what the gamma-ray spectrometer had found. It had detected radiation from uranium, thorium and potassium on the Moon's surface. Potassium here means the radioactive isotope potassium-40.

  These readings let scientists compare lunar rock with rock on Earth. The rock of the dark lunar mare resembled Earth's basalts. The lunar highlands corresponded instead to Earth's ultramafic rocks.

  Natural nuclear reactions accounted for 10% of the gamma radiation coming from the lunar surface. Cosmic rays caused the other 90%. The rock was only one layer of the story, because the craft's orbit also felt something heavy beneath the surface.

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• 5. Mascons And Meteoroids

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  The word "mascons" is short for mass concentrations. These are areas of denser material below the lunar surface, and they distort the paths of craft orbiting the Moon. Luna 10 supplied the first evidence that they exist, and the source calls this perhaps its most important finding.

  Near the spacecraft, the density of meteoroids was 100 times higher than in interplanetary space. The same orbital laboratory gathered data on the strength of the Moon's magnetic field, its radiation belts and cosmic radiation.

  The mission's best-remembered moment, however, happened far from the Moon, at a Communist Party congress.

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• 6. The Internationale

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  The 23rd Congress of the Communist Party of the Soviet Union was meant to hear a live broadcast from Luna 10. The spacecraft carried solid-state oscillators programmed to reproduce the notes of "The Internationale".

  On the night of the 3rd of April, controllers held a rehearsal, and the playback went well. The next morning, they discovered that a note was missing. They played the previous night's tape to the assembled gathering instead. They claimed it was a live broadcast from the Moon.

  Meanwhile, the real work continued in orbit around the Moon, where the spacecraft still had many weeks of measurements ahead.

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