Surveyor 7 was the seventh and last 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 ...

sent to explore 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 ...

. A total of 21,091 pictures were transmitted to Earth. Surveyor 7 was the fifth and final spacecraft of the Surveyor series to achieve a lunar

soft landing Soft landing may refer to: *Soft landing (aeronautics) A soft landing is any type of aircraft, rocket or spacecraft landing that does not result in significant damage to or destruction of the vehicle or its payload, as opposed to a hard la ...

. The objectives for this mission were to perform a lunar soft landing (in an area well removed from the maria to provide a type of terrain photography and lunar sample significantly different from those of other Surveyor missions); obtain postlanding TV pictures; determine the relative abundances of chemical elements; manipulate the lunar material; obtain touchdown dynamics data; and obtain thermal and radar reflectivity data. This spacecraft was similar in design to the previous Surveyors, but it carried more scientific equipment including a television camera with polarizing filters, a surface sampler, bar magnets on two footpads, two horseshoe magnets on the surface scoop, and auxiliary mirrors. Of the auxiliary mirrors, three were used to observe areas below the spacecraft, one to provide stereoscopic views of the surface sampler area, and seven to show lunar material deposited on the spacecraft. The spacecraft landed on the

lunar surface The geology of the Moon (sometimes called selenology, although the latter term can refer more generally to " lunar science") is quite different from that of Earth. The Moon lacks a true atmosphere, which eliminates erosion due to weather. It does ...

on January 10, 1968, on the outer rim of the crater Tycho. Operations of the spacecraft began shortly after the soft landing and were terminated on January 26, 1968, 80 hours after sunset. On January 20, while the craft was still in daylight, the TV camera clearly saw two laser beams aimed at it from the night side of the crescent Earth, one from Kitt Peak National Observatory, Tucson, Arizona, and the other at Table Mountain at Wrightwood, California. Operations on the second lunar day occurred from February 12 to 21, 1968. The mission objectives were fully satisfied by the spacecraft operations. Battery damage was suffered during the first lunar night and transmission contact was subsequently sporadic. Contact with Surveyor 7 was lost on February 21, 1968. NASA and Bellcom mission planners considered the Surveyor 7 site as a potential target for a crewed late Apollo mission, perhaps Apollo 20, though a combination of operational constraints, including the high latitude of the site and its rough terrain, and the early cancellation of post-

Apollo 17 Apollo 17 (December 7–19, 1972) was the final mission of NASA's Apollo program, the most recent time humans have set foot on the Moon or traveled beyond low Earth orbit. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on ...

lunar missions, contributed to the site's elimination. Surveyor 7 Fig 7-41e2

Surveyor 7 was the first probe to detect the faint glow on the lunar horizon after dark that is now thought to be light reflected from electrostatically levitated

Moon dust Lunar soil is the fine fraction of the regolith found on the surface of the Moon. Its properties can differ significantly from those of terrestrial soil. The physical properties of lunar soil are primarily the result of mechanical disintegra ...

.Strange Things Happen at Full Moon , LiveScience
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Science instruments

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, 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 elevations. The polarizing filters served as analyzers for the detection of measurements of the linearly polarized component of light scattered from the lunar surface. 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 A 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 of 1.2 kHz. Most transmissions consisted of 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 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 ...

for transmission. The

dynamic range Dynamic range (abbreviated DR, DNR, or DYR) is the ratio between the largest and smallest values that a certain quantity can assume. It is often used in the context of signals, like sound and light. It is measured either as a ratio or as a base-1 ...

and sensitivity of this camera were slightly less than those on the Surveyor 6 camera. Resolution and quality were excellent. The television images were displayed on a slow scan monitor coated with a long persistency

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 persistency 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 transmitted 20,961 pictures during the first lunar day, January 10 to January 22, 1968. From February 12 to February 14, the camera was operated in the 200 line mode because of loss of horizontal sweep in the 600 line mode. During the second lunar day, 45 pictures were transmitted before loss of power caused suspension of camera operation. File:Surveyor 7 Fig 7-41e1.jpg, Panorama of the surface File:Surveyor 7 Fig 3-43.jpg, An area 350 meters northeast of the spacecraft showing a large block about 5 meters across and 2 meters high File:Surveyor 7 Fig 3-57.jpg, Spotted rock 25 cm across, about 2 meters from Surveyor 7 File:Surveyor 7 Fig 3-62.jpg, Vesicular fragment about 35 cm across, about 7 meters from Surveyor 7

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 Curium is a transuranic, radioactive chemical element with the symbol Cm and atomic number 96. This actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first inte ...

242) collimated to irradiate a 10 mm 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 A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a Continuum (measurement), continuum. The word was first used scientifically in optics to describ ...

of the

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 ...

s scattered from the lunar surface, and the other, containing four sensors, detected energy spectra of the

proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

s produced via reaction (alpha and proton) 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 Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

, and

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...

. The experiment provided 46 hours of data accumulated from three lunar surface sample measurements. These measurements were of a portion of undisturbed local lunar surface, a lunar rock, and an extensively trenched area of the lunar surface. Data were obtained during the first and second lunar days, January 12 to 23, 1968, and February 13 to 21, 1968. The alpha backscattering instrument failed to deploy properly. Mission controllers successfully used the surface soil sampler claw to push the alpha backscattering instrument into the proper position to conduct its experiments.

Soil Mechanics Surface Sampler

The

soil mechanics Soil mechanics is a branch of soil physics and applied mechanics that describes the behavior of soils. It differs from fluid mechanics and solid mechanics in the sense that soils consist of a heterogeneous mixture of fluids (usually air and wat ...

surface sampler was designed to pick up, dig, scrape, and trench the lunar surface, and transport lunar surface material while being photographed so that the properties of the lunar surface could be determined. The sampler consisted primarily of a scoop with a container, a sharpened blade, and an

electric motor An electric motor is an Electric machine, electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a Electromagneti ...

to open and close the container. The flat foot of the scoop incorporated two embedded rectangular horseshoe magnets. The scoop was mounted on a

pantograph A pantograph (, from their original use for copying writing) is a mechanical linkage connected in a manner based on parallelograms so that the movement of one pen, in tracing an image, produces identical movements in a second pen. If a line dr ...

arm that could be extended about 1.5 m or retracted close to the spacecraft motor drive. The arm could also be moved from an azimuth of +40° to -72° or be elevated 130 mm by motor drives. It could also be dropped onto the lunar surface under force provided by gravity and a spring. The scoop was mounted below the television camera in a position that allowed it to reach the alpha-scattering instrument in its deployed position and redeploy it to another selected location. The instrument performed 16 bearing tests, seven trenching tests, and two impact tests. It also freed the alpha-scattering instrument when it failed to deploy on the lunar surface, shaded this instrument, and moved this instrument for evaluation of other samples. Performance was flawless during 36 hours of operation between January 11 and January 23, 1968. The instrument responded to commands on February 14, 1968, which verified that it had survived the lunar night. The power system, however, was unable to support any operations.

References

External links

Surveyor 7 panorama
reprocessed
Surveyor Program Results (PDF) 1969Surveyor Program Results (Good Quality Color PDF) 1969
{{Use American English, date=January 2014 7 Spacecraft launched in 1968 Missions to the Moon Spacecraft launched by Atlas-Centaur rockets Soft landings on the Moon 1968 on the Moon