Lunar Orbiter program

Lunar Orbiter is the name of five American lunar probes, the moon orbited 1966-1968 as Orbiter in a close orbit to measure it and analyze the gravitational field.

All five spacecraft, launched by NASA on August 10, 1966 at precise intervals of 88 to 90 days, were successful, only the third orbiter had small losses. The photographs and measured data were the basis for an accurate lunar atlas, which was created in 1968 and captured the moon back.

Mission

The main task of the Lunar Orbiter was to map the surface of the moon exactly photographically. Should be selected based on the images then landing sites for the manned lunar landings of the Apollo space flights. Next the first attempts were made to Selenodäsie, the measurement of the Moon (Greek Selene ) and its gravity field. Also, the internal structure of the moon and the so-called mascons under the lunar crust presented represents a research topic

The Lunar Orbiter missions 1 to 5 were the continuation of the Ranger explorations 1964/65 of three lunar regions ( 17,000 shots from Ranger 7 to 9, including extreme close-up before impact ) and arrive without any failure. They found approximately simultaneously with the Surveyor missions 1-7 and their gentle landings. First missile tests to reach the moon orbits found in 1960 by two Pioneer probes and in 1964 in the Ranger program.

The probes were launched with a two-stage Atlas - Agena D rocket and pivoted into a highly elliptical orbit around the moon one whose perilune ( moon next point) was approximately 200 kilometers above the surface. Compared to the lunar orbit speed evaded the web speeds from a few percent.

For Lunar Orbiter 1 to 3 orbits were chosen with low orbital inclination, which led exclusively on areas near the equator. Lunar Orbiter 4 and 5, however, were brought to polar orbits, which allowed mapping of the entire lunar surface.

Technical Equipment

The probes had a height of 1.68 meters and a width of 5.65 m, measured over the spread antennas. The take-off mass varied according to the Orbiter 386-391 kilograms. The multi- path correction reignitable engine worked with Aerozin 50 and nitrogen tetroxide and delivered a thrust of about 450 Newtons.

There were two cameras used with a wide angle and a telephoto lens. Recordings were made ​​each adjacent pairs, the framing of the telephoto lens was always in the center of the wide angle shot. During the exposure, the film was moved to compensate for the speed of the spacecraft. As a film unperforated 70 mm film from Kodak Special High Definition Aerial film (SO -368 ) was used by the 79 meters were included. This film is automatically developed and fixed by contact with a so-called Bimat Kodak film. After completion of the photographic images of the negative film could then be electronically scanned from end to beginning and returned to Earth. These scanned a 0,005 mm measuring light beam from the film in the transverse strips ( framelets ) of 2.68 mm width with 17,000 rows. Thereafter, the film was further conveyed by 2.54 mm and the next framelet scanned. The scan of a complete image pair took 43 minutes to complete.

On Earth, the received image signals were stored on data tapes and each framelet was exposed by a cathode ray tube on 35mm film from which you anfertigte by joining replicas of the original recordings. Thus, the strips that run through each Lunar Orbiter Photography explain.

Course of the five missions

• Lunar Orbiter 1 was launched on August 10, 1966, came after four days in a lunar orbit. From the 26th lunar orbit on August 18, he started with the recordings and sent to the crash on October 29, 1966 a total of 229 images. ( Take off weight: 386 kg, orbital inclination: 12.14 ° )
• Lunar Orbiter 2 launched on 6 November 1966 reached four days later a lunar orbit and transferred to the charge on October 11, 1967 817 images. ( Take off weight: 391 kg, orbital inclination: 11.97 ° )
• Lunar Orbiter 3 on 5 February 1967 and came into the lunar orbit three days later and sent to the crash on October 10, 1967 626 images. Due to some malfunction Lunar Orbiter 3 is considered to be not quite so successful. ( Take off weight: 386 kg, orbital inclination: 21.00 ° )
• Lunar Orbiter 4 launched on May 4, 1967, and reached four days later the moon. The orbit was in contrast to the earlier missions much higher and nearly polar. The probe took 546 pictures in a crash on October 31, 1967. Thereby, the moon front and the back was almost completely recorded at about 3/4. ( Take off weight: 390 kg, orbital inclination: 88.80 ° )
• Lunar Orbiter 5 launched on August 1, 1967, and waved on August 4, also in a polar, but more elliptical lunar orbit, which led closer to the surface. As of August 6, 1967 844 images were transmitted, including from the moon back not quite captured. Lunar Orbiter 5 crashed on January 31, 1968 the moon. ( Take off weight: 390 kg, orbital inclination: 85.00 ° )

Results

The Lunar Orbiter probes mapped the moon with an accuracy of 60 meters. The resulting therefrom Moon Atlas is still one of the standard lunar research. The potential Apollo landing sites were particularly well photographed, with resolutions of up to 2 meters. In particular, the oblique views with telephoto optics were among the most respected photos of their time. Especially the recorded on August 23, 1966 image of a rising Earth over the lunar surface has gone down in history. Lunar Orbiter was also the first U.S. probe program in which there were no serious failure.

In addition to program gaining precise orbit data for the analysis of the lunar gravitational field was successful. From these data, one could prove mascons, strong mass concentrations in the subsurface of the moon for the first time.

Similarly, the fact of the eccentric center of gravity of the moon, the source of a bound rotation, derived from perturbations of lunar satellite was. With some success, NASA has also sought a kind of triangulation to the moon back. The photos of the spacecraft from the lunar surface were used to their paths over the - to calculate back to the type of photographic resection - invisible from the Earth. Last but not least we also gained experience over the space flight navigation close to the Moon.

Digitizing

Currently, all data tapes of the five Lunar Orbiter missions in the wake of the Lunar Orbiter Image Recovery Project ( LOIRP ) are digitized. Head of the project is Dennis Wingo, who leads a small team of engineers. Overall, it is 1,500 rolls of film to digitize. The high resolution and detail of the recovered photos to surpass today (as of 2010 ), all other images that are there from the moon. This high quality of the recovered photos, it will now be possible, a comparison with other photos of the moon - about those whom the Lunar Reconnaissance Orbiter has recorded since 2009 - to conduct and document changes on the lunar surface (eg by intervening meteorite impacts ) to be able to. The U.S. space agency financed most of the LOIRP research. It also provides the accommodation in which the team has found his home: A former McDonald's restaurant on the grounds of NASA Ames Research Center in Mountain View, jokingly it is therefore called mcmoon 's.