Lunar Orbiter 1

Lunar Orbiter 1

Mission type	Lunar orbiter
Operator	NASA
COSPAR ID	1966-073A
SATCAT №	2394
Mission duration
Spacecraft properties
Manufacturer	The Boeing Co.
Launch mass	385.6 kg (850 lb)
Start of mission
Launch date	August 10, 1966, 19:31 (1966-08-10UTC19:31) UTC
Rocket	Atlas SLV-3 Agena-D
Launch site	Cape Canaveral LC-13
End of mission
Disposal	Deorbited
Decay date	October 29, 1966 (1966-10-30) "about 13:29 GMT"
Orbital parameters
Reference system	Selenocentric
Semi-major axis	2,694 km (1,674 mi)
Eccentricity	0.33
Periselene	189.1 to 40.5 km (117.5 to 25.2 mi)
Aposelene	1,866.8 km (1,160.0 mi)
Inclination	12 degrees
Period	208.1 minutes
Lunar orbiter
Orbital insertion	August 14, 1966
Impact site
Orbits	577
---- Lunar Orbiter program ← None Lunar Orbiter 2 →

The Lunar Orbiter 1 robotic spacecraft, part of NASA's Lunar Orbiter program, was the first American spacecraft to orbit the Moon. It was designed primarily to photograph smooth areas of the lunar surface for selection and verification of safe landing sites for the Surveyor and Apollo missions. It was also equipped to collect selenodetic, radiation intensity, and micrometeoroid impact data.

Mission controllers injected the spacecraft into a parking orbit around Earth on August 10, 1966, at 19:31 UTC. The trans-lunar injection burn occurred at 20:04 UTC. The spacecraft experienced a temporary failure of the Canopus star tracker (probably due to stray sunlight) and overheating during its cruise to the Moon. The star tracker problem was resolved by navigating using the Moon as a reference, and the overheating was abated by orienting the spacecraft 36 degrees off-Sun to lower the temperature.

Lunar Orbiter 1 was injected into an elliptical near-equatorial lunar orbit 92.1 hours after launch. The initial orbit was 189.1 by 1,866.8 kilometers (117.5 mi × 1,160.0 mi) and had a period of 3 hours 37 minutes and an inclination of 12.2 degrees. On August 21, perilune was dropped to 58 km (36 mi) and on August 25 to 40.5 km (25.2 mi). The spacecraft acquired photographic data from August 18 to 29, 1966, and readout occurred through September 14, 1966.

Spacecraft orbit and photographic coverage on the near side (left) and far side (right)

It took some pictures of the Moon and the Earth. The reported number of pictures varies. Accurate data were acquired from all other experiments throughout the mission.

Orbit tracking showed a slight "pear-shape" of the Moon based on the gravity field, and no micrometeorite impacts were detected. The spacecraft was tracked until it impacted the lunar surface on command at 7 degrees north latitude, 161 degrees east longitude (selenographic coordinates) on the Moon's far side on October 29, 1966, on its 577th orbit. The early end of the nominal one-year mission resulted from a shortage of remaining attitude control gas and other deteriorating conditions and was planned to avoid transmission interference with Lunar Orbiter 2.

Notable achievements

• Lunar Orbiter 1 took the first two pictures of Earth from the distance of the Moon.
• First American spacecraft to orbit the Moon

Photographs

A number of the early high-resolution photos showed severe smearing. There are major discrepancies in the reported number of photographs returned by Lunar Orbiter 1, as well as for the entire Lunar Orbiter program. Reported numbers for the series of 5 orbiters range from 1654 to 2180, and up to 2600.

According to the Wikipedia article for Lunar Orbiter 1,

A total of 42 high-resolution and 187 medium-resolution frames were taken and transmitted to Earth, covering more than 5 million square kilometers of the Moon's surface, accomplishing about 75% of the intended mission,

According to https://www.lpi.usra.edu/resources/lunarorbiter ,

Lunar Orbiter I was designed to be a photographic survey program for Apollo landing sites within ±5 degrees latitude (i.e., along the equator) and ±45 degrees longitude (i.e., on the lunar near side). The spacecraft was launched August 10, 1966. Between August 18 and 29 it produced 413 high- and moderate-resolution photographs, covering 262,000 square kilometers of the nearside of the Moon and over 3 million square kilometers of the farside of the Moon.

NASA's 1970 Guide to Lunar Orbiter Photographs

In 1970, NASA published its Guide to Lunar Orbiter Photographs. According to this document, during the conversion process from magnetic tape to film, the video signal was intentionally distorted.

P8. Table. Mission totals for all lunar Orbiters:

• 1012 Exposures. (Each exposure has one each High and Medium resolution picture.)
• 898 Medium Resolution Complete Frames Useful for Interpretation.
• 695 High Resolution Complete Frames Useful for Interpretation.

Pictures for Lunar Orbiter I called out in the table:

• Apollo: 136 exposures, all of the high-resolution (telephoto) frames were deemed "Not useful for interpretation or not read out"
• General interest; near side: 57 exposures, 51 of the high-resolution frames were deemed "Not useful for interpretation or not read out"

The total number of useful frames from this table is 207 medium-resolution frames and 15 high-resolution frames, or a total of 222 useful pictures.

Instruments and data

Instruments

Lunar Photographic Studies	Evaluation of Apollo and Surveyor landing sites
Meteoroid Detectors	Detection of micrometeoroids in the lunar environment
Caesium Iodide Dosimeters	Radiation environment en route to and near the Moon
Selenodesy	Gravitational field and physical properties of the Moon

• 

  The first ever image of Earth from the distance of the Moon, August 23, 1966. This probe took a second such image on August 25.

• 

  Part of the photo to the left as reprocessed by LOIRP in 2008.

See also

• Lunar Orbiter Image Recovery Project
• Exploration of the Moon
• Lunar Orbiter 2
• Lunar Orbiter 3
• Lunar Orbiter 4
• Lunar Orbiter 5

External links

• Destination Moon: A History of the Lunar Orbiter Program (1976) by the NASA History Office
• Lunar Orbiter Photo Gallery - Mission 1 by the Lunar and Planetary Institute