Surveyor 6
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Surveyor 6 was the sixth lunar lander of the
American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...
uncrewed
Surveyor program The Surveyor program was a NASA program that, from June 1966 through January 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. The Surveyor craft ...
that reached the surface of the
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
. Surveyor 6 landed on the
Sinus Medii Sinus Medii (Latin ''sinus mediī'' "Middle Bay") is a small lunar mare. It takes its name from its location at the intersection of the Moon's equator and prime meridian; as seen from the Earth, this feature is located in the central part of the ...
. A total of 30,027 images were transmitted to Earth. This spacecraft was the fourth of the Surveyor series to successfully achieve a soft landing on the Moon, obtain post landing television pictures, determine the abundance of the chemical elements in the lunar soil, obtain touchdown dynamics data, obtain thermal and radar reflectivity data, and conduct a Vernier engine erosion experiment. Virtually identical to Surveyor 5, this spacecraft carried a television camera, a small bar magnet attached to one footpad, and an alpha-scattering instrument as well as the necessary engineering equipment. It landed on November 10, 1967, in Sinus Medii, 0.49 deg in latitude and 1.40 deg w longitude (
selenographic coordinates The selenographic coordinate system is 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. ...
)–the center of the Moon's visible hemisphere. The spacecraft accomplished all planned objectives. The successful completion of this mission satisfied the Surveyor program's obligation to the Apollo project. On November 24, 1967, the spacecraft was shut down for the two-week lunar night. Contact was made on December 14, 1967, but no useful data was obtained. Lunar soil surveys were completed using photographic and
alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produce ...
backscattering methods. A similar instrument, the APXS, was used onboard several Mars missions. In a further test of space technology, Surveyor 6's engines were restarted and burned for 2.5 seconds in the first lunar liftoff on November 17 at 10:32 UTC. This created 150 lbf (700 N) of thrust and lifted the vehicle 12 feet (4 m) from the lunar surface. After moving west eight feet, (2.5 m) the spacecraft once again successfully soft landed and continued functioning as designed. Surveyor 6 landed near the crash site of
Surveyor 4 Surveyor 4 was the fourth lunar lander in the American uncrewed Surveyor program sent to explore the surface of the Moon. This spacecraft crashed after an otherwise flawless mission; telemetry contact was lost 2.5 minutes before touchdown. The ...
, which malfunctioned a few months earlier in July 1967.


Science experiments


Television

The TV camera consisted of a
vidicon Video camera tubes were devices based on the cathode ray tube that were used in television cameras to capture television images, prior to the introduction of charge-coupled device (CCD) image sensors in the 1980s. Several different types of tubes ...
tube, 25 and 100 mm
focal length The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power. A positive focal length indicates that a system converges light, while a negative foca ...
lenses, shutters,
polarizing filter A polarizer or polariser is an optical filter that lets light waves of a specific polarization pass through while blocking light waves of other polarizations. It can filter a beam of light of undefined or mixed polarization into a beam of well ...
s (as opposed to
color filter Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associa ...
s used on the previous Surveyor cameras), and iris mounted nearly vertically and surmounted by a mirror that could be adjusted by stepping motors to move in both
azimuth An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematicall ...
and elevation. The polarizing filters served as analyzers for the detection of measurement of the linearly polarized component of light scattered from the lunar surface. An auxiliary mirror was used for viewing the lunar surface beneath the spacecraft. The frame by frame coverage of the lunar surface provided a 360 deg azimuth view and an elevation view from approximately +90 deg above the plane normal to the camera z axis to −60 deg below this same plane. Both 600 line and 200 line modes of operation were used. The 200 line mode transmitted over an
omnidirectional antenna In radio communication, an omnidirectional antenna is a class of antenna which radiates equal radio power in all directions perpendicular to an axis (azimuthal directions), with power varying with angle to the axis (elevation angle), declining t ...
and scanned one frame each 61.8 seconds. A complete video transmission of each 200 line picture required 20 seconds and utilized a
bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...
of 1.2 kHz. Most transmissions consisted of the 600 line pictures, which were telemetered by a
directional antenna A directional antenna or beam antenna is an antenna which radiates or receives greater power in specific directions allowing increased performance and reduced interference from unwanted sources. Directional antennas provide increased performance ...
. The frames were scanned each 3.6 seconds. Each frame required nominally one second to be read from the vidicon and utilized a 220 kHz bandwidth for transmission. The optical surfaces were the cleanest of any mission because of a redesigned mirror hood. The television images were displayed on a slow scan monitor coated with a long persistence
phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or vi ...
. The persistence was selected to optimally match the nominal maximum frame rate. One frame of TV identification was received for each incoming TV frame and was displayed in real time at a rate compatible with that of the incoming image. These data were recorded on a video magnetic
tape recorder An audio tape recorder, also known as a tape deck, tape player or tape machine or simply a tape recorder, is a sound recording and reproduction device that records and plays back sounds usually using magnetic tape for storage. In its present- ...
and on 70 mm film. The camera performance was excellent in terms of both the quantity and quality of pictures. Between lunar landing, lunar 'second' landing, and the lunar first day sunset on November 24, 1967, 29,914 pictures were taken and transmitted. File:Surveyor 6 Fig 7-41d1.jpg, The mare surface File:Surveyor 6 Fig 7-41d2.jpg, Another view of the mare surface


Alpha-Scattering Surface Analyzer

The alpha-scattering surface analyzer was designed to measure directly the abundances of the major elements of the lunar surface. The instrumentation consisted of an alpha source (curium 242) collimated to irradiate a 100 mm (3.94 in) diameter opening in the bottom of the instrument where the sample was located and two parallel but independent charged particle detector systems. One system, containing two sensors, detected the energy spectra of the alpha particles scattered from the lunar surface, and the other, containing four sensors, detected energy spectra of the protons produced via reactions (alpha and protons) in the surface material. Each detector assembly was connected to a
pulse height analyzer A pulse-height analyzer (PHA) is an instrument that accepts electronic pulses of varying heights from particle and event detectors, digitizes the pulse heights, and saves the number of pulses of each height in registers or channels, thus recording ...
. A digital electronics package, located in a compartment on the spacecraft, continuously telemetered signals to Earth whenever the experiment was operating. The spectra contained quantitative information on all major elements in the samples except for hydrogen, helium, and lithium. Curium collected on the collimator films and was scattered by the gold plating on the inside bottom of the sensor head. This resulted in a gradually increasing background and reduction of the sensitivity technique for heavy elements. One proton detector was turned off during the second day of operation because of noise. A total of 43 hours of data was obtained from November 11 to 24, 1967. The final data was obtained 4 hours after local sunset. However, after the spacecraft 'hopping' maneuver on November 17, 1967, the sensor head was upside down. Measurements were continued in order to obtain information on solar protons and cosmic rays. Therefore, data for the purpose of the chemical analysis of lunar surface material were obtained only during the first 30 hours of operation. During this period, 27 hours and 44 min of data were known to be noise free.


Accomplishments

Surveyor 6 was the first spacecraft to lift off from another celestial body. It was monitored by the Jet Propulsion Laboratory in Pasadena. It used its liquid-fueled vernier engines to lift itself from its original landing site to a position some 10 feet away."1967 Year In Review, UPI.com"
/ref> This was later noted by the Mars Geyser Hopper mission as a post-soft landing propulsive hop that pre-dated its proposal.


See also

*
List of artificial objects on the Moon This is a partial list of artificial materials left on the Moon, many during the missions of the Apollo program. The table below does not include lesser Apollo mission artificial objects, such as a hammer and other tools, retroreflectors, Apollo ...


References

{{Use American English, date=January 2014 6 Spacecraft launched in 1967 Missions to the Moon Spacecraft launched by Atlas-Centaur rockets Soft landings on the Moon Hopping spacecraft 1967 on the Moon