Editing Luna 3 (section)

== Mission ==
[[File:1959 CPA 2367.jpg|thumb|Luna 3 mission on a Soviet stamp]]
After launching on a [[Luna (rocket)|Luna 8K72]] (number I1-8) rocket over the [[North Pole]], the Blok-E escape stage was shut down by radio control to put Luna 3 on its course to the Moon. Initial radio contact showed that the signal from the space probe was only about one-half as strong as expected, and the internal temperature was rising. The spacecraft spin axis was reoriented and some equipment was shut down, resulting in a temperature drop from 40&nbsp;°C to about 30&nbsp;°C.<ref name=Harvey37>{{cite book |last=Harvey |first=Brian |date=2007 |title=Soviet and Russian Lunar Exploration |publisher=Springer-Praxis |page=37 |isbn=978-0387218960}}</ref> At a distance of 60,000 to 70,000&nbsp;km from the Moon, the orientation system was turned on and the spacecraft rotation was stopped. The lower end of the craft was pointed at the Sun, which was shining on the far side of the Moon.

The space probe passed within 6,200&nbsp;km of the Moon near its south pole at the closest lunar approach at 14:16 UT on 6 October 1959, and continued over the far side. On 7 October, the photocell on the upper end of the space probe detected the sunlit far side of the Moon, and the photography sequence was started.<ref name=Harvey38>{{cite book |last=Harvey |first=Brian |date=2007 |title=Soviet and Russian Lunar Exploration |publisher=Springer-Praxis |page=38 |isbn=978-0387218960}}</ref> The first picture was taken at 03:30 UT at a distance of 63,500&nbsp;km from the Moon, and the last picture was taken 40 minutes later from a distance of 66,700&nbsp;km.

A total of 29 pictures were taken,<ref>{{cite web |url=http://www.jb.man.ac.uk/history/tracking/part1.html |title=Jodrell Bank's role in early space tracking activities – Part 1 |last=Grahn |first=Sven |publisher=University of Manchester |work=Jodrell Bank |access-date=21 July 2019}}</ref> covering 70% of the far side. After the photography was complete the spacecraft resumed spinning, passed over the north pole of the Moon and returned towards the Earth. Attempts to transmit the pictures to the Soviet Union began on 8 October but the early attempts were unsuccessful due to the low signal strength. As Luna 3 drew closer to the Earth, a total of about 17 photographs were transmitted by 18 October. All contact with the probe was lost on 22 October 1959. The space probe was believed to have burned up in the Earth's atmosphere in March or April 1960. Another possibility was that it survived in orbit until 1962 or later.

It was launched initially in an orbit with the perigee outside the upper boundary of the Earth's atmosphere. After the mission was accomplished, and the probe made several orbits around the Earth, the secular rise in the eccentricity resulted in a decrease of the perigee because the semimajor axis is conserved. After eleven orbital revolutions Luna-3 entered the atmosphere of the Earth. It is the first instance of a "man-made [[Kozai mechanism|Lidov-Kozai effect]]".<ref>{{cite book |last1=Shevchenko |first1=Ivan |title=The Lidov-Kozai effect - applications in exoplanet research and dynamical astronomy |date=2017 |publisher=Springer |location=Switzerland |isbn=9783319435206}}</ref>

===First gravity assist===
[[File:Luna3-trajectory-eng.svg|thumb|left|Luna 3 trajectory and the [[gravity assist]] maneuver]]

{{main|Gravity assist#Historical origins of the method}}
The [[gravity assist]] maneuver was first used in 1959 when Luna 3 photographed the far side of Earth's Moon. After launch from the [[Baikonur Cosmodrome]], Luna 3 passed behind the Moon from south to north and headed back to Earth. The gravity of the Moon changed the spacecraft's orbit; also, because of the Moon's own orbital motion, the spacecraft's orbital plane was also changed. The return orbit was calculated so that the spacecraft passed again over the Northern hemisphere where the Soviet ground stations were located. The maneuver relied on research performed under the direction of [[Mstislav Keldysh]] at the [[Steklov Institute of Mathematics]].<ref>{{cite web|url=http://www.keldysh.ru/events/fly|title=Mstislav Keldysh. Mechanics of the space flight|author=T. Eneev, E. Akim|website=Keldysh Institute of Applied Mathematics|language=ru}}</ref><ref>Egorov, Vsevolod Alexandrovich (1957) "Specific problems of a flight to the Moon", ''Physics – Uspekhi'', Vol. 63, No. 1a, pp. 73–117.

Egorov’s work is mentioned in:  Boris V. Rauschenbakh, Michael Yu. Ovchinnikov, and [[Susan McKenna-Lawlor|Susan M. P. McKenna-Lawlor]], ''Essential Spaceflight Dynamics and Magnetospherics'' (Dordrecht, Netherlands:  Kluwer Academic Publishers, 2002), pp. 146–147.   (The latter reference is available on-line at [https://books.google.com/books?id=s8FRVu0blhgC&pg=PA146 Google Books].)</ref><ref>{{cite web |last1=Berger |first1=Eric |title=All hail Luna 3, rightful king of 1950s space missions |url=https://arstechnica.com/science/2019/10/all-hail-luna-3-rightful-king-of-1950s-space-missions/ |website=Ars Technica |date=4 October 2019 |access-date=13 October 2023}}</ref>
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