Luna 2

Luna 1 and the three spacecraft of Luna programme before it were part of the Ye-1 series of spacecraft with a mass of 156 kilograms (344 lb).[8] Luna missions that failed to successfully launch or achieve good results remained unnamed and were not publicly acknowledged.[9][10] The first unnamed probe exploded on launch on 23 September 1958. Two more launches were unsuccessfully attempted on 11 October 1958 and 4 December 1958.[11] Luna 1 was the fourth launch attempt and the first partial success of the program.[12] It launched on 2 January 1959 and missed the Moon by 5,965 kilometres (3,706 mi).[13]

One mission separated Luna 1 and Luna 2, a launch failure that occurred with an unnamed probe on 18 June 1959.[14] Luna 2 would be the Soviet Union's sixth attempt to impact the Moon.[15] It was the second of the Ye-1a series, modified to carry a heavier payload of 156 kilograms (344 lb)[16] and had a combined mass of 390.2 kilograms (860 lb).[17] Luna 2 was similar in design to Luna 1,[18] a spherical space probe with protruding antennas and instrumentation.[19] The instrumentation was also similar to Luna 1,[18] which included a triaxial fluxgate magnetometer,[20] a piezoelectric detector, a scintillation counter, ion traps and two gas-discharge counters, while the Luna 2 included six gas-discharge counters.[21] There were no propulsion systems on Luna 2 itself.[22]

Upper stage of Luna rocket

Luna 2 carried five different types of instruments to conduct various tests while it was on its way to the Moon.[23] The scintillation counters were used to measure any ionizing radiation and the Cherenkov radiation detectors to measure electromagnetic radiation caused by charged particles.[24] The primary scientific purpose of the Geiger Counter carried on Luna 2 was to determine the electron spectrum of the Van Allen radiation belt. It consisted of three STS-5 gas-discharge counters mounted on the outside of an airtight container.[25] The last instrument on Luna 2 was a three component fluxgate magnetometer. It was similar to that used on Luna 1 but its dynamic range was reduced by a factor of 4 to ±750 gammas (nT) so that the quantisation uncertainty was ±12 gammas.[26] The probe's instrumentation was powered by silver-zinc and mercury-oxide batteries.[24][27]

A copy of the Soviet pennant sent on the Luna 2 probe to the Moon, at the Kansas Cosmosphere.

The spacecraft also carried Soviet pennants which were located on the probe and on the Luna 2 rocket.[28] The two sphere-shaped pennants in the probe had surfaces covered by 72 pentagonal elements in a pattern similar to that later used by association footballs.[29][30] In the centre was an explosive charge designed to shatter the sphere, sending the pentagonal shields in all directions.[30] Each pentagonal element was made of titanium alloy; the centre regular pentagon had the State Emblem of the Soviet Union with the Cyrillic letters СССР ("USSR") engraved below and was surrounded by five non-regular pentagons which were each engraved with СССР СЕНТЯБРЬ 1959 ("USSR SEPTEMBER 1959").[29][31] The third pennant was similar engravings on aluminium strips which were embossed on the last stage of the Luna 2 rocket.[28]

The scientists took extra, unspecified precautions in preventing biological contamination of the Moon.[32]

The radiation detectors and magnetometer were searching for lunar magnetic and radiation fields similar to the Van Allen radiation belt around Earth, sending information about once every minute[26] until its last transmission which came about 55 km away from the lunar surface.[40] Although it did prove previous measurements of the Van Allen radiation belts that were taken from Luna 1 around the Earth,[40] it was not able to detect any type of radiation belts around the Moon[41] at or beyond the limits of its magnetometer's sensitivity (2–3x10⁻⁴ G).[42]

Luna 2 showed time variations in the electron flux and energy spectrum in the Van Allen radiation belt.[43] Using ion traps on board, the satellite made the first direct measurement of solar wind flux from outside the Earth's magnetosphere.[44] On its approach to the lunar surface, the probe did not detect any notable magnetic field to within 55 kilometres (34 mi) from the Moon.[23][40] It also did not detect a radiation belt around the Moon, but the four ion traps measured an increase in the ion particle flux at an altitude of 8,000 kilometres (5,000 mi), which suggested the presence of an ionosphere. The probe generated scientific data that was printed on 14 kilometres (8.7 mi) of teletype, which were analysed and published in spring 1960.[41]

According to Donald William Cox, Americans were starting to believe that they were making progress in the Space Race and that although the Soviet Union might have had larger rockets, the United States had better guidance systems, but these beliefs were questioned when the Soviets were able to impact Luna 2 on the Moon.[45][46] At that time the closest Americans had come to the Moon was about 37,000 kilometres (23,000 mi) with Pioneer 4.[46] Soviet Premier Nikita Khrushchev, on his only visit to the United States, gave President Dwight D. Eisenhower a replica of the Soviet pennants that Luna 2 had just placed onto the lunar surface.[46][47] Luna 2 and its predecessors all came to be used throughout the USSR and around the world as pro-communist propaganda. Donald W. Cox wrote in his 1962 book The Space Race:

Although the Sputniks and Luniks did not themselves provide better cars, refrigerators, color TV sets, and homes for the peasants and laborers of the Soviet Union and her satellite states, they did evoke added inspiration for the earthbound followers of the communist way of life helping to take their minds off shortages of consumer goods. The people were spurred on to work just a little harder for the glorious motherland and to outstrip the west in the less dramatic and more basic things of life, like coal and steel production.[45]

Luna 2 was a success for the Soviets, and was the first in a series of missions (lunar impactors) that were intentionally crashed on the Moon. The later U.S.-made Ranger missions ended in similar impacts. Such controlled crashes have remained useful even after the technique of soft landing was mastered.[48] NASA used hard spacecraft impacts to test whether shadowed Moon craters contain ice by analyzing the debris that got thrown out.[49]

The pennant presented to Eisenhower is kept at the Eisenhower Presidential Library and Museum in Abilene, Kansas, U.S.[50] A copy of the spherical pennant is located at the Kansas Cosmosphere in Hutchinson, Kansas.[51]

On 1 November 1959, the Soviet Union released two stamps commemorating the spacecraft. They depict the trajectory of the mission.[52]

• Soviet space program
• Sinus Lunicus
• List of artificial objects on the Moon