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Acronym | PSE |
---|---|
Uses | To detect vibrations and tilting of the lunar surface and measure changes in gravity |
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 (meteoroids and impacts from the spent S-IVB and LM ascent stages). 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 PSE unit was constructed principally of beryllium and had a mass of 11.5 kg, including the electronics module and thermal insulation. It was housed in a drum-shaped enclosure 23 cm in diameter and 29 cm in height. The enclosure was rounded on the bottom and rested on a leveling stool. The PSE consisted of two main subsystems, a sensor unit and an electronics module. The sensor unit contained three matched long-period (LP) seismometers aligned orthogonally in a triaxial set to measure one vertical and two horizontal components of surface motion. The horizontal component seismometers were very sensitive to tilt and were leveled to high accuracy by means of a two-axis motor-driven gimbal operated by ground command. A third motor adjusted the vertical component seismometer in the vertical direction. A fourth, short-period (SP) seismometer with a resonant period of 1 second measured vertical motion at a peak sensitivity of 8 Hz and a response range from 0.05 to 20 Hz. A thermal shroud and 6-W heater for thermal control comprised the rest of the experiment package. The thermal shroud was aluminized mylar which covered the instrument and the ground surrounding the base out to about 75 cm radially. A gnomon and level sensor were mounted on the top center of the shroud. The shroud was modified slightly from the one used on Apollo 12. Total power drain varied from 4.3 to 7.4 W.
The seismometers consisted of an inertial mass on a sensor boom suspended by springs and hinges, a capacitor plate and a damping magnet. The LP seismometers could function in a flat-response mode and in a peaked response mode. In the flat response mode, the LP seismometers had a natural period of 15 s. In the peaked-response mode, they acted as underdamped pendulums with a natural period of 2.2 s. Sensitivity to ground motion peaked sharply at 0.45 Hz in peaked response mode with a useful frequency range of 0.004 to 2 Hz. Maximum sensitivity was enhanced by a factor of 6 in the peaked response mode, but sensitivity to low-frequency signals was reduced. All seismometers could detect ground motions as small as 0.3 nm. At tidal frequencies, gravitational acceleration was measured by monitoring the feedback current used to center the seismometer mass. The sensitivity of the instruments was 0.008 mgal. The lunar surface impacts of the spent S-IVB and LM ascent stages were used as external calibration sources for the seismometers. The known mass and velocity of these stages at surface impact and the lunar impact point coordinates enabled the computation of energy generated at impact and the point of energy application. (The calibration characteristics were determined by measuring seismometer response to these energy sources.)
The seismometers were deployed on February 5, 1971, and operated at reduced gain while the astronauts were on the lunar surface and turned to maximum sensitivity for most of the time after that. The ALSEP central station was located at 3°38′38″S17°28′39″W / 3.6440°S 17.4775°W . The passive seismic experiment was deployed 3 meters north of the central station. At deployment, the LP vertical seismometer was unstable in the flat response mode, so all three LP seismometers were operated in peaked-response mode until 17 November 1976 when the problem was rectified. The gimbal motor operating the leveling for the LP horizontal Y seismometer showed intermittent malfunction. The Apollo 14 ALSEP suffered several periods of loss of signal, in one case for over two months. All data were lost for these periods and commanding of the instruments was not possible. Seismic disturbances were noted throughout the lunar day, but particularly near sunrise and sunset, these were believed to be due to expansion and contraction of the mylar shroud and/or the cable to the central station. The instrument was configured to standby mode on 30 September 1977 as part of the ALSEP station shutdown.
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.
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A seismometer is an instrument that responds to ground noises and shaking such as caused by quakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The output of such a device—formerly recorded on paper or film, now recorded and processed digitally—is a seismogram. Such data is used to locate and characterize earthquakes, and to study the Earth's internal structure.
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.
The Pegasus Project was a NASA initiative to study the frequency of micrometeoroid impacts on spacecraft by means of a constellation of three satellites launched in 1965. All three Pegasus satellites were launched by Saturn I rockets, and remained connected with their upper stages.
The Fast Auroral SnapshoT Explorer was a NASA plasma physics satellite, and was the second spacecraft in the Small Explorer program (SMEX). It was launched on 21 August 1996, from Vandenberg Air Force Base aboard a Pegasus XL launch vehicle. The spacecraft was designed and built by NASA's Goddard Space Flight Center (GSFC). Flight operations were handled by GSFC for the first three years, and thereafter were transferred to the University of California, Berkeley's Space Sciences Laboratory.
Passive seismic is the detection of natural low frequency earth movements, usually with the purpose of discerning geological structure and locate underground oil, gas, or other resources. Usually the data listening is done in multiple measurement points that are separated by several hundred meters, over periods of several hours to several days, using portable seismometers. The conclusions about the geological structure are based on the spectral analysis or on the mathematical reconstruction of the propagation and possible sources of the observed seismic waves. If the latter is planned, data are usually acquired in multiple points simultaneously, using so called synchronized lines. Reliability of the time reverse modelling can be further increased using results of reflection seismology about the distribution of the sound speed in the underground volume.
Lunar seismology is the study of ground motions of the Moon and the events, typically impacts or moonquakes, that excite them.
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The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission was a robotic lander designed to study the deep interior of the planet Mars. It was manufactured by Lockheed Martin Space, was managed by NASA's Jet Propulsion Laboratory (JPL), and two of its three scientific instruments were built by European agencies. The mission launched on 5 May 2018 at 11:05:01 UTC aboard an Atlas V-401 launch vehicle and successfully landed at Elysium Planitia on Mars on 26 November 2018 at 19:52:59 UTC. InSight was active on Mars for 1440 sols.
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 Charged Particle Lunar Environment Experiment (CPLEE), placed on the lunar surface by the Apollo 14 mission as part of the Apollo Lunar Surface Experiments Package (ALSEP), was designed to measure the energy spectra of low-energy charged particles striking the lunar surface. It measured the fluxes of electrons and ions with energies from 40 eV to 20 keV. The primary purpose of the experiment was to examine plasma particles originating from the Sun and the low-energy particle flux in the Earth's magnetic tail.
The Seismic Experiment for Interior Structure (SEIS) is a seismometer and the primary scientific instrument on board the InSight Mars lander launched on 5 May 2018 for a landing on 26 November 2018; the instrument was deployed to the surface of Mars on 19 December. SEIS is expected to provide seismic measurements of marsquakes, enabling researchers to develop 3D structure maps of the deep interior. Better understanding the internal structure of Mars will lead to better understanding of the Earth, Moon, and rocky planetary bodies in general.
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.
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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.
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