Surveyor 7
Encyclopedia
Surveyor 7 was the seventh and last lunar lander of the American
unmanned Surveyor program
sent to explore the surface of the Moon
.
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. The objectives for this mission were to: (1) 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); (2) obtain postlanding TV pictures; (3) determine the relative abundances of chemical elements; (4) manipulate the lunar material; (5) obtain touchdown dynamics data; and, (6) 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 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 Jan. 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.
The spacecraft landed near the large lunar crater Tycho
, named for the famous astronomer. This crater is visible to the naked eye from Earth with luminous rays of impact ejected material emanating radially from it.
Surveyor 7 was the final spacecraft in the Surveyor program. It landed perfectly, less than two miles (3 km) from the navigational target. 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. Battery damage was suffered in the first lunar night and transmission contact was subsequently sporadic. The spacecraft was last in contact on 20 February 1968.
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.
tube, 25 and 100 mm focal length
lenses, shutters, polarizing filter
s, and iris mounted nearly vertically and surmounted by a mirror that could be adjusted by stepping motors to move in both azimuth 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
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
. 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 dynamic range
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
. 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
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.
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 of the alpha particle
s scattered from the lunar surface, and the other, containing four sensors, detected energy spectra of the proton
s produced via reaction (alpha and proton) in the surface material. Each detector assembly was connected to a pulse height analyzer
. 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
. 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 January 1968, and February 13 to 20 February 1968.
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
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
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 deg to -72 deg 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.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
unmanned Surveyor program
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...
sent to explore the surface of 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...
.
- Launched January 7, 1968; landed January 10, 1968
- Weight on landing: 305.7 kg (674.0 lb)
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. The objectives for this mission were to: (1) 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); (2) obtain postlanding TV pictures; (3) determine the relative abundances of chemical elements; (4) manipulate the lunar material; (5) obtain touchdown dynamics data; and, (6) 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 on January 10, 1968, on the outer rim of the crater Tycho
Tycho (crater)
Tycho is a prominent lunar impact crater located in the southern lunar highlands, named after the Danish astronomer Tycho Brahe . To the south is the crater Street; to the east is Pictet, and to the north-northeast is Sasserides. The surface around Tycho is replete with craters of various sizes,...
. Operations of the spacecraft began shortly after the soft landing and were terminated on January 26, 1968, 80 hours after sunset. On Jan. 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.
The spacecraft landed near the large lunar crater Tycho
Tycho (crater)
Tycho is a prominent lunar impact crater located in the southern lunar highlands, named after the Danish astronomer Tycho Brahe . To the south is the crater Street; to the east is Pictet, and to the north-northeast is Sasserides. The surface around Tycho is replete with craters of various sizes,...
, named for the famous astronomer. This crater is visible to the naked eye from Earth with luminous rays of impact ejected material emanating radially from it.
Surveyor 7 was the final spacecraft in the Surveyor program. It landed perfectly, less than two miles (3 km) from the navigational target. 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. Battery damage was suffered in the first lunar night and transmission contact was subsequently sporadic. The spacecraft was last in contact on 20 February 1968.
Television
The TV camera consisted of a vidiconVideo camera tube
In older video cameras, before the mid to late 1980s, a video camera tube or pickup tube was used instead of a charge-coupled device for converting an optical image into an electrical signal. Several types were in use from the 1930s to the 1980s...
tube, 25 and 100 mm focal length
Focal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus...
lenses, shutters, polarizing filter
Polarizing filter (Photography)
The polarizing filter used with most modern cameras is a circular polarizer. The first stage of the polarizer is a linear filter which filters out light that is linearly polarized in a specific direction...
s, and iris mounted nearly vertically and surmounted by a mirror that could be adjusted by stepping motors to move in both azimuth 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
Omnidirectional antenna
In radio communication, an omnidirectional antenna is an antenna which radiates radio wave power uniformly in all directions in one plane, with the radiated power decreasing with elevation angle above or below the plane, dropping to zero on the antenna's axis. This radiation pattern is often...
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
Directional antenna
A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive and reduced interference from unwanted sources....
. 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 dynamic range
Dynamic range
Dynamic range, abbreviated DR or DNR, is the ratio between the largest and smallest possible values of a changeable quantity, such as in sound and light. It is measured as a ratio, or as a base-10 or base-2 logarithmic value.-Dynamic range and human perception:The human senses of sight and...
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
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
. 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
Tape recorder
An audio tape recorder, tape deck, reel-to-reel tape deck, cassette deck or tape machine is an audio storage device that records and plays back sounds, including articulated voices, usually using magnetic tape, either wound on a reel or in a cassette, for storage...
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.
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 (curiumCurium
Curium is a synthetic chemical element with the symbol Cm and atomic number 96. This radioactive transuranic element of the actinide series was named after Marie Skłodowska-Curie and her husband Pierre Curie. Curium was first intentionally produced and identified in summer 1944 by the group of...
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 of the alpha particle
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...
s scattered from the lunar surface, and the other, containing four sensors, detected energy spectra of the proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
s produced via reaction (alpha and proton) in the surface material. Each detector assembly was connected to a pulse height analyzer
Pulse height analyzer
A Pulse Height Analyzer is an instrument used in nuclear and elementary particle physics research which 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 for later...
. 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
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
, helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
, and lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
. 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 January 1968, and February 13 to 20 February 1968.
Soil Mechanics Surface Sampler
The soil mechanicsSoil mechanics
Soil mechanics is a branch of engineering 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 and particles but soil may also contain organic solids, liquids, and gasses and other...
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
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
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
Pantograph
A pantograph is a mechanical linkage connected in a special manner based on parallelograms so that the movement of one pen, in tracing an image, produces identical movements in a second pen...
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 deg to -72 deg 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.