 Diagram of a charge from the Lunar Seismic Profiling Experiment | |
| Acronym | LSPE |
|---|---|
| Notable experiments | Apollo 17 |
The Lunar Seismic Profiling Experiment (LSPE) was a lunar science experiment, deployed by astronauts on the lunar surface in 1972 as part of Apollo 17. The goal of the LSPE was to record the seismic response generated by a variety of sources including the detonation of eight explosive charges, the ascent propulsion system on the lunar module and any natural sources. [1]
The Active Seismic Experiment (ASE) had flown on both Apollo 14 and 16 providing information both about near-surface structures through the use of mortars, and information about deep lunar structures by measuring the impacts of previous lunar modules and Saturn V third stages. However, between these two sub-surface levels, little was known about the upper 10 km of the Moon's surface. The LSPE was specifically designed to reduce this knowledge gap. It would record the seismic response generated by a variety of sources including the detonation of eight explosive charges and the ascent propulsion system on the Apollo Lunar Module, to provide information on the upper levels of the lunar crust at depths of several kilometers. [2]
The LSPE differed from the Active Seismic Experiment by having larger explosive packages that could be deployed further away allowing for the greater exploration at depth. The Active Seismic Experiment's explosive charges were based on a rocket-propelled mortar, whereas the explosives used with the LSPE were placed directly onto the Moon's surface at distance from the geophones. This necessitated an active transmitter as part of the LSPE package in order to trigger the explosive packages whereas the ASE only had a receiver that would trigger the firing of the charges rocket and would detonate upon impact with the lunar surface. The geophone array for the LSPE had a triangular configuration plus a central geophone whereas the ASE had a linear geophone array. [3]
The experiment's components primarily consisted of an array of four geophones and eight explosive charges of mixed yield. The four geophones were in effect miniaturised moving coil-magnet seismometers. Each explosive charge consisted of molded Hexanitrostilbene and Teflon in a 90:10 ratio and were similar in composition to those that flew as part of Apollo 14. [4] The set of eight explosive charges consisted of two pairs of 1⁄8-pound (57 g) and 1⁄4-pound (113 g) charges and another four charges each weighing 1⁄2 lb (227 g), 1 lb (454 g), 3 lb (1,361 g), and 6 lb (2,722 g). [4] All charges were cylindrical except the 6-pound charge which was cubic in shape. [4] Triggering of explosives would be done remotely after the safe departure of the Apollo 17 astronauts from the surface of the Moon. [1]
The explosives had a number of fail-safe mechanisms to prevent premature detonation. The explosive safe/arm plate was held in place by a pull pin and a timed release mechanism, itself only initiated with the removal of an independent pull ring. A secondary firing timer along with a firing pin mechanism both had pull pins that had to be removed as part of deployment. If either timers started prematurely, they would lock the pull rings into place so that they could not be removed. If the safe arm timed mechanism released early the safe/arm pull ring would be locked into place and could not be removed. [5] The safe/arm timed mechanism would not retract until at least 90 hours after deployment and each explosive package had its own distinct arming time. [5] Each explosive package had its own thermal battery that would power a receiver. Each explosive package would only detonate upon successfully receiving an ignition signal from the experiment package. [5]
During the first EVA, the LSP experiment's 4 geophones were deployed as part of the ALSEP package. Geophones 1 and 2 would be placed to run in sequence aligned with the Sun either side of the ALSEP package. The other two geophones were then placed in a sequence running perpendicular to geophones 1 and 2, creating a triangle with three geophones with one geophone located in the middle. [5] The experiment's antenna was erected and the explosive transport modules were placed into sunlight. [5] This was because the thermal timers and arming mechanisms were not permitted below a temperature of 40 °F (4 °C). [5] The mission's second and third EVA were used to place the explosive packages at a variety of locations, with varying distances and directions from the Apollo 17 landing site. These packages were deployed up to a maximum distance of 2.7 km (1.7 mi). [1] [5] Once deployment was completed, the experiment package would transmit firing signals to the explosive packages. [5] Triggering of explosives would be done remotely after the safe departure of the Apollo 17 astronauts from the surface of the Moon. [1] As part of the deployment process, the astronaut would remove three pull rings from each explosive package, which would in total remove four safety pins. [5]
The eight explosive charges provided detectable seismic two-way traveltime signal down to depths of 2.7 km. The impact of the Apollo 17 lunar module ascent stage provided a detectable two-way signal from a depth of 5 km of the Moon's surface. The instrument identified that beneath the Apollo 17 landing site there were three layers in the upper 5 km, with distinctive seismic velocity properties. The first was a surface layer 248 m thick with a seismic velocity of 250 ms−1. This surface layer lay atop a ~927 m thick layer with a faster seismic velocity of 1200 ms−1. Explosive package #1, the furthest from the geophone array, generated slower travel times than was expected. This was explained by the presence of the Camelot crater either through interaction with the crater structure itself or that the crater resulted in slower material being present at depth. [2] The impact of the Apollo 17 lunar module suggested that at depth there was material with a seismic velocity of 4000 ms−1. Data from this impact required normalisation due the impact site being elevated 1.4 km above the Apollo 17 landing site. [2]
Interpretation of the seismic velocities with other geological relationships led to two primary structural inferences. The first was that the top two layers of seismically distinct materials were likely composed of basaltic lava flows. The seismically fastest and likely deepest layer, has been interpreted to consist primarily of breccias that primarily composes the highland material that surrounded the Apollo 17 valley landing site. A breccia sample taken by Apollo 15 was found through laboratory measurements to have a similar seismic velocity to the 4000 ms−1. [2] The experiment package provided passive observation of lunar seismic events between August 15, 1976, and April 25, 1977. [6]
Apollo 12 was the sixth crewed flight in the United States Apollo program and the second to land on the Moon. It was launched on November 14, 1969, by NASA from the Kennedy Space Center, Florida. Commander Charles "Pete" Conrad and Lunar Module Pilot Alan L. Bean performed just over one day and seven hours of lunar surface activity while Command Module Pilot Richard F. Gordon remained in lunar orbit.
Apollo 14 was the eighth crewed mission in the United States Apollo program, the third to land on the Moon, and the first to land in the lunar highlands. It was the last of the "H missions", landings at specific sites of scientific interest on the Moon for two-day stays with two lunar extravehicular activities.
Apollo 16 was the tenth crewed mission in the United States Apollo space program, administered by NASA, and the fifth and penultimate to land on the Moon. It was the second of Apollo's "J missions", with an extended stay on the lunar surface, a focus on science, and the use of the Lunar Roving Vehicle (LRV). The landing and exploration were in the Descartes Highlands, a site chosen because some scientists expected it to be an area formed by volcanic action, though this proved not to be the case.
Apollo 17 was the eleventh and final mission of NASA's Apollo program, the sixth and 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 the Moon, while Command Module Pilot Ronald Evans orbited above. Schmitt was the only professional geologist to land on the Moon; he was selected in place of Joe Engle, as NASA had been under pressure to send a scientist to the Moon. The mission's heavy emphasis on science meant the inclusion of a number of new experiments, including a biological experiment containing five mice that was carried in the command module.
The Apollo spacecraft was composed of three parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth. The expendable (single-use) spacecraft consisted of a combined command and service module (CSM) and an Apollo Lunar Module (LM). Two additional components complemented the spacecraft stack for space vehicle assembly: a spacecraft–LM adapter (SLA) designed to shield the LM from the aerodynamic stress of launch and to connect the CSM to the Saturn launch vehicle and a launch escape system (LES) to carry the crew in the command module safely away from the launch vehicle in the event of a launch emergency.
A geophone is a device that converts ground movement (velocity) into voltage, which may be recorded at a recording station. The deviation of this measured voltage from the base line is called the seismic response and is analyzed for structure of the Earth.
Apollo 15 lunar surface operations were conducted from July 30 to August 2, 1971, by Apollo 15 Commander David Scott and Apollo Lunar Module Pilot James Irwin, who used the first Lunar Roving Vehicle to make three exploratory trips away from their landing site at the base of the Apennine Mountains, near Hadley Rille.
The ALSE (Apollo Lunar Sounder Experiment) (also known as Scientific Experiment S-209, according to NASA designations) was a ground-penetrating radar (subsurface sounder) experiment that flew on the Apollo 17 mission.
Lunar seismology is the study of ground motions of the Moon and the events, typically impacts or moonquakes, that excite them.
The Apollo Lunar Surface Experiments Package (ALSEP) comprised a set of scientific instruments placed by the astronauts at the landing site of each of the five Apollo missions to land on the Moon following Apollo 11. Apollo 11 left a smaller package called the Early Apollo Scientific Experiments Package, or EASEP.
The Lunar Flag Assembly (LFA) was a kit containing a flag of the United States designed to be erected on the Moon during the Apollo program. Six such flag assemblies were planted on the Moon. The nylon flags were hung on telescoping staffs and horizontal bars constructed of one-inch anodized aluminum tubes. The flags were carried on the outside of the Apollo Lunar Module (LM), most of them on the descent ladder inside a thermally insulated tubular case to protect them from exhaust gas temperatures calculated to reach 2,000 °F (1,090 °C). The assembly was designed and supervised by Jack Kinzler, head of technical services at the Manned Spacecraft Center (MSC) in Houston, Texas. Six of the flags were ordered from a government supply catalog and measured 3 by 5 feet ; the last one planted on the Moon was the slightly larger, 6-foot (1.8 m)-wide flag which had hung in the MSC Mission Operations Control Room for most of the Apollo program.
The Apollo 12 Passive Seismic Experiment (PSE) was placed on the lunar surface by the Apollo 12 mission as part of the Apollo Lunar Surface Experiments Package (ALSEP). The PSE was designed to detect vibrations and tilting of the lunar surface and measure changes in gravity at the instrument location. The vibrations are due to internal seismic sources (moonquakes) and external. The primary objective of the experiment was to use these data to determine the internal structure, physical state, and tectonic activity of the Moon. The secondary objectives were to determine the number and mass of meteoroids that strike the Moon and record tidal deformations of the lunar surface.
The Apollo 14 Passive Seismic Experiment (PSE) was placed on the lunar surface on February 5, 1971, as part of the Apollo 14 ALSEP package. The PSE was designed to detect vibrations and tilting of the lunar surface and measure changes in gravity at the instrument location. The vibrations are due to internal seismic sources (moonquakes) and external. The primary objective of the experiment was to use these data to determine the internal structure, physical state, and tectonic activity of the Moon. The secondary objectives were to determine the number and mass of meteoroids that strike the Moon and record tidal deformations of the lunar surface.
Active Seismic Experiment (ASE) was carried on Apollo 14 and Apollo 16 as part of the Apollo Lunar Surface Experiments Package (ALSEP). ASE used a thumper device and a mortar with explosive charges to explore subsurface lunar structure and elastic properties. The experiment's principal investigator was Robert Kovach of Stanford University. The experiment was succeeded on Apollo 17 by the Lunar Seismic Profiling experiment.
The Cold Cathode Gauge Experiment, also known as the Lunar Atmosphere Detector, was a scientific package that flew on board Apollo 12, Apollo 13, Apollo 14, and Apollo 15. The goal of the experiment was to measure the density of the Moon's tenuous atmosphere, but not its composition.
The Suprathermal Ion Detector Experiment (SIDE) was a lunar science experiment, first deployed by astronauts on the lunar surface in 1969 as part of Apollo 12, and later flying on Apollo 14 and Apollo 15. The goal of SIDE was to study any potential lunar ionosphere and the solar wind.
The Lunar Atmospheric Composition Experiment (LACE) was a miniature magnetic deflection mass spectrometer. The experiment's aim was to study the composition and variations of the lunar atmosphere. The only deployment of LACE was as part of the Apollo Lunar Surface Experiments Package (ALSEP) on Apollo 17 within the Taurus–Littrow valley.
The Passive Seismic Experiment Package (PSEP) was a scientific experiment deployed on the lunar surface by the astronauts of Apollo 11 as part of the Early Apollo Surface Experiments Package (EASEP). The experiment's goal was to determine the structure, tectonic activity, physical nature, and composition of the Moon. PSEP was the first seismometer to be deployed on a planetary body other than Earth.
The Solar Wind Spectrometer was a scientific package that flew on the Apollo 12 and Apollo 15 missions to the surface of the Moon. The goal was to characterise the solar wind near the Moon's surface and to explore its interactions with the lunar environment. The experiments' principal investigator was Dr Conway W. Snyder of the Jet Propulsion Laboratory.
The Lunar Surface Gravimeter (LSG) was a lunar science experiment that was deployed on the surface of the Moon by the astronauts of Apollo 17 on December 12, 1972. Conceived and led by Joseph Weber as principal investigator, the experiment aimed to measure changes in the local gravitational strength on the Moon's surface. These measurements were intended to provide insight into the internal structures of the Moon as it tidally deformed due interaction with the gravitational fields of the Earth and Sun. In addition the experiment hoped to contribute experimental evidence of the existence of gravitational waves.
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