India’s Moon Odyssey » The Moon
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The Moon

The Moon is Earth's only natural satellite and the fifth-largest natural satellite in the Solar System.

The average centre-to-centre distance from the Earth to the Moon is 3,84,403 km, about thirty times the diameter of the Earth.

The Moon's diameter is 3,474 km, a little more than a quarter of that of the Earth. This means that the Moon's volume is about 2 per cent that of Earth and the pull of gravity at its surface about 17 per cent that of the Earth.

The Moon makes a complete orbit around the Earth every 27.3 days (the orbital period), and the periodic variations in the geometry of the Earth-Moon-Sun system are responsible for the lunar phases that repeat every 29.5 days.

The Moon is the only celestial body to which humans have travelled and upon which humans have landed. The first artificial object to escape Earth's gravity and pass near the Moon was the Soviet Union's Luna 1. The first artificial object to impact the lunar surface was Luna 2. And the first photographs of the normally-occluded far side of the Moon were made by Luna 3, all in 1959.

The first spacecraft to perform a successful lunar soft landing was Luna 9, and the first unmanned vehicle to orbit the Moon was Luna 10, both in 1966. The United States' Apollo programme has achieved the only manned missions to date, resulting in six landings between 1969 and 1972.

Human exploration of the Moon ceased with the conclusion of the Apollo program, although several countries have announced plans to send people or robotic spacecraft to the Moon.

Journeys to the Moon

The race to the Moon started with the Soviet's unmanned Luna 2 making a hard landing on the lunar surface on September 14, 1959.

This was soon followed by the landing of the first humans on the Moon in 1969, widely seen around the world as one of the pivotal events of the 20th century.

Neil Armstrong July 21, 1969 Apollo 11
Buzz Aldrin July 21, 1969 Apollo 11
Pete Conrad November 19-20, 1969 Apollo 12
Alan Bean November 19-20, 1969 Apollo 12
Alan Shepard February 5-6, 1971 Apollo 14
Edgar Mitchell February 5-6, 1971 Apollo 14
David Scott July 31–August 2, 1971 Apollo 15
James Irwin July 31–August 2, 1971 Apollo 15
John W. Young April 21-23, 1972 Apollo 16
Charles Duke April 21-23, 1972 Apollo 16
Eugene Cernan December 11-14, 1972 Apollo 17
Harrison Schmitt December 11-14, 1972 Apollo 17

The far side of the Moon was first photographed on October 7, 1959 by Soviet probe Luna 3. In an effort to compete with these Soviet successes, the then U.S. president John F. Kennedy proposed the national goal of landing a man on the Moon.

However, the Soviets remained in the lead for some time, the Luna 9 being the first probe to soft land on the Moon and transmit pictures from the Lunar surface on February 3, 1966. It was proven that a lunar-lander would not sink into a thick layer of dust, as had been feared.

The first artificial satellite of the Moon was the Soviet probe Luna 10 (launched on March 31, 1966). One of the main impediments to human exploration of the Moon was development of adequate heat shield technology to permit atmospheric re-entry without completely burning up a manned spacecraft. The U.S. gained early supremacy in this field through NASA research in thermogravimetric experiments in hypersonic wind tunnels.

On December 24, 1968, the crew of Apollo 8, Frank Borman, James Lovell and William Anders became the first human beings to see the far side of the Moon with their own eyes (as opposed to seeing it on a photograph).

Humans first landed on the Moon on July 20, 1969. The first man to walk on the lunar surface was Neil Armstrong, commander of the U.S. mission Apollo 11.

The first robot lunar rover to land on the Moon was the Soviet vessel Lunokhod 1 on November 17, 1970 as part of the Lunokhod program. The last man to stand on the Moon was Eugene Cernan, who as part of the mission Apollo 17 walked on the Moon in December 1972.

Moon rock samples were brought back to Earth by three Luna missions (Luna 16, 20, and 24) and the Apollo missions 11 to 17 (except Apollo 13, which aborted its planned lunar landing).

From the mid-1960s to the mid-1970s there were 65 moon landings (with 10 in 1971 alone), but after Luna 24 in 1976 they suddenly stopped. The Soviet Union started focusing on Venus and space stations and the U.S. on Mars and beyond.

In 1990, Japan visited the Moon with the Hiten spacecraft, becoming the third country to orbit the Moon. The spacecraft released the Hagormo probe into lunar orbit, but the transmitter failed, thereby preventing further scientific use of the mission.

In September 2007, the SELENE spacecraft was launched, with the objectives to obtain scientific data of the lunar origin and evolution and to develop the technology for the future lunar exploration.

NASA launched the Clementine mission in 1994, and Lunar Prospector in 1998.

In 1998, HGS-1, a commercial satellite from Hong Kong performed two flybys of the Moon in order to change orbital inclination.

The European Space Agency launched a small, low-cost lunar orbital probe called SMART 1 on September 27, 2003. SMART 1's primary goal was to take three-dimensional X-ray and infrared imagery of the lunar surface. SMART 1 entered lunar orbit on November 15, 2004 and continued to make observations until September 3, 2006, when it was intentionally crashed into the lunar surface in order to study the impact plume.

China has begun the Chang'e programme for exploring the Moon and is investigating the prospect of lunar mining, specifically looking for the isotope helium-3 for use as an energy source on Earth. China launched the Chang'e 1 robotic lunar orbiter on October 24, 2007.

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