Lunar Orbiter 1
Encyclopedia
The Lunar Orbiter 1 robotic (unmanned) spacecraft
, part of the Lunar Orbiter Program
, 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.
The spacecraft was placed in an Earth
parking orbit
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 1866.8 km (117.5 by 1,160 ) and had a period of 3 hours 37 minutes and an inclination of 12.2 degrees. On August 21 perilune was dropped to 58 kilometres (36 mi) and on August 25 to 40.5 kilometres (25.2 mi). The spacecraft acquired photographic data from August 18–29, 1966, and readout occurred through September 14, 1966.
A total of 42 high resolution and 187 medium resolution frames were taken and transmitted to Earth covering over 5 million square km of the Moon's surface, accomplishing about 75% of the intended mission, although a number of the early high-res photos showed severe smearing. It also took the first two pictures of the Earth ever from the distance of the Moon. Accurate data were acquired from all other experiments throughout the mission.
Orbit tracking showed a slight "pear-shape" to 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 N latitude, 161 degrees E longitude (selenographic coordinates
) on the Moon's far side on October 29, 1966 on its 577th orbit. The early end to the nominal one year mission was due to the small amount of remaining attitude control gas and other deteriorating conditions and was planned to avoid transmission interference with Lunar Orbiter 2
.
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
, part of the Lunar Orbiter Program
Lunar Orbiter program
The Lunar Orbiter program was a series of five unmanned lunar orbiter missions launched by the United States from 1966 through 1967. Intended to help select Apollo landing sites by mapping the Moon's surface, they provided the first photographs from lunar orbit.All five missions were successful,...
, was designed primarily to photograph smooth areas of the lunar
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
surface for selection and verification of safe landing sites for the Surveyor
Surveyor program
The Surveyor Program was a NASA program that, from 1966 through 1968, sent seven robotic spacecraft to the surface of the Moon. Its primary goal was to demonstrate the feasibility of soft landings on the Moon...
and Apollo missions. It was also equipped to collect selenodetic, radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
intensity, and micrometeoroid
Micrometeoroid
A micrometeoroid is a tiny meteoroid; a small particle of rock in space, usually weighing less than a gram. A micrometeor or micrometeorite is such a particle that enters the Earth's atmosphere or falls to Earth.-Scientific interest:...
impact data.
The spacecraft was placed in an Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
parking orbit
Parking orbit
A parking orbit is a temporary orbit used during the launch of a satellite or other space probe. A launch vehicle boosts into the parking orbit, then coasts for a while, then fires again to enter the final desired trajectory...
on August 10, 1966 at 19:31 (UTC). The Trans lunar injection
Trans Lunar Injection
A Trans Lunar Injection is a propulsive maneuver used to set a spacecraft on a trajectory which will arrive at the Moon.Typical lunar transfer trajectories approximate Hohmann transfers, although low energy transfers have also been used in some cases, as with the Hiten probe...
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
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
. 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 1866.8 km (117.5 by 1,160 ) and had a period of 3 hours 37 minutes and an inclination of 12.2 degrees. On August 21 perilune was dropped to 58 kilometres (36 mi) and on August 25 to 40.5 kilometres (25.2 mi). The spacecraft acquired photographic data from August 18–29, 1966, and readout occurred through September 14, 1966.
A total of 42 high resolution and 187 medium resolution frames were taken and transmitted to Earth covering over 5 million square km of the Moon's surface, accomplishing about 75% of the intended mission, although a number of the early high-res photos showed severe smearing. It also took the first two pictures of the Earth ever from the distance of the Moon. Accurate data were acquired from all other experiments throughout the mission.
Orbit tracking showed a slight "pear-shape" to 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 N latitude, 161 degrees E longitude (selenographic coordinates
Selenographic coordinates
Selenographic coordinates are used to refer to locations on the surface of Earth's moon. Any position on the lunar surface can be referenced by specifying two numerical values, which are comparable to the latitude and longitude of Earth...
) on the Moon's far side on October 29, 1966 on its 577th orbit. The early end to the nominal one year mission was due to the small amount of remaining attitude control gas and other deteriorating conditions and was planned to avoid transmission interference with Lunar Orbiter 2
Lunar Orbiter 2
The Lunar Orbiter 2 spacecraft 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...
.
| 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 |