Spacecraft above Moon.

Artist's concept of Lunar Orbiter at the Moon.

Goals: As the first in the series dedicated to scientific investigation of the Moon, Lunar Orbiter 4 was to conduct a broad, systematic, photographic survey to increase understanding of lunar surface features and to serve as a basis for selecting sites for more-detailed study by subsequent orbital and landing missions.

Accomplishments: Lunar Orbiter 4 was the first spacecraft to fly a polar orbit around the Moon. As the Moon rotated beneath its flight path, It imaged almost all of the Moon's near side and three-quarters of the far side, and took the first photo of the lunar south pole. It also gathered gravitational data in preparation for Lunar Orbiter 5.

4 May 1967: Launch
17 Jul 1967: Lunar Impact


Mission Type: Orbiter
Launch Vehicle: Atlas-Agena D (no. 22 / Atlas D no. 5804 / Agena D no. AD131 / 6633)
Launch Site: Eastern Test Region / launch complex 13, Cape Canaveral, USA
NASA Center: Langley Research Center
Spacecraft Mass: 385.6 kg at launch
Spacecraft Instruments: 1) imaging system; 2) micrometeoroid detectors; and 3) radiation dosimeters
Spacecraft Dimensions: 2 m high, 5.2 m across with dish and omnidirectional antenna deployed
Spacecraft Power: Four solar panels; nickel-cadmium batteries for use in Moon's shadow
Maximum Power: 375 W
Antenna Diameter: 1 meter (high-gain antenna)
Total Cost: $163 million (total for all 5 spacecraft in Lunar Orbiter program)
References:
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

National Space Science Data Center, http://nssdc.gsfc.nasa.gov/

Solar System Log by Andrew Wilson, published 1987 by Jane's Publishing Co. Ltd.


Lunar Orbiter 4 was the first in the series dedicated to scientific surveys of the Moon. After a burn at 21:54 UT on 8 May 1967, the spacecraft entered a 2,705 x 6,034-kilometer orbit inclined at 85.48 degrees, becoming the first vehicle to enter polar orbit around the Moon.

Controllers successfully overcame a problem with the Thermal Camera Door, and subsequently, during its two-month mission, the orbiter took pictures of 99 percent of the near side and 75 percent of the far side of the Moon in a total of 193 frames. The images had a resolution of up to 60 meters.

In early June, controllers lowered the spacecraft's orbit to match that of Lunar Orbiter 5 so scientists could collect gravitational data in support of the latter mission. Before losing contact on 17 July, Lunar Orbiter 4 took the first photos of the lunar south pole and discovered a 240-kilometer-long crustal fault on the far side.

Since contact was lost before controlled impact, the spacecraft naturally crashed onto the Moon on 6 October 1967 due to gravitational anomalies.

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