Lunar Surface Gravimeter

Last updated

Lunar Surface Gravimeter
ALSEP AS17-134-20501.jpg
The Apollo 17 Lunar Surface Gravimeter on the Moon with ALSEP central station in background.
AcronymLSG
UsesGravitational wave detection, Seismology
Notable experimentsApollo 17
Inventor Lucien LaCoste and Arnold Romberg
Manufacturer Bendix Corporation, LaCoste Romberg, Arthur D. Little

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. The LSG was conceived by its principal investigator Joseph Weber. Weber proposed a number of experimental methods for the detection of gravitational waves, and would go on to be described as the "founding father" of gravitational wave detection. The experiment aimed to measure changes in the local gravitational strength on the Moon's surface through the use of a gravimeter. 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.

Contents

The instrument as a whole was built by Bendix Corporation, who were also responsible for providing operational support for all packages of the Apollo Lunar Surface Experiments Package (ALSEP) flying as part of the Apollo Program. The instrument's primary sensor was built by LaCoste Romberg, a notable producer of gravimeters. The sensor was based on a modified LaCoste and Romberg D-meter and consisted of an adjustable mass on a sprung lever attached to the instrument's measurement electronics. It was capable of measuring gravity to 1 part in 105.

The gravimeter unit that was deployed on Apollo 17 was not properly calibrated and could not be properly zeroed as the instruments balance weights were too light for use in the Moon's gravity. Whilst the experiment continued to be used as a one-axis seismometer, the data received back was noisy and required more modern analysis techniques before the experiments data was proven valuable. The instrument continued to operate until September 30, 1977 when operations support for ALSEP was terminated due to budgetary constraints. Later understanding of gravitational waves showed that even if experiment worked as intended, it would not have been sensitive enough to detect them. Two conceptually similar experiments, the Lunar Gravitational-wave Antenna and Lunar Seismic and Gravitational Antenna, were proposed in 2020 as the Artemis program looks to return to human exploration of the moon.

Background

Gravitational waves are waves of the intensity of gravity that are generated by the accelerated masses of binary stars and other motions of gravitating masses, and propagate as waves outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1893 and then later by Henri Poincaré in 1905 as the gravitational equivalent of electromagnetic waves. [1] In 1916 [2] [3] Albert Einstein demonstrated that gravitational waves result from his general theory of relativity as ripples in spacetime. [4] [5] By the time of the development of the Apollo program, it was believed only the largest objects in the universe such as stars and galaxies would generate gravitational waves of sufficient magnitude to be detectable. [6] : 1 

Following his attendance a general relativity conference at Chapel Hill in 1957, Joseph Weber started work on designing and building detectors that could experimentally prove the existence of gravitational waves. In 1960, he published his proposal for a mechanical detector that would consist of a suspended metal cylinder that would interact with gravitational waves and produce induced vibrations that could be detected. [7] Weber and other members of the scientific community were also exploring other experimental mechanisms to prove the existence of gravitational waves. In 1961, Weber theorised that gravitational waves could induce a resonant dilation in planetary bodies. [8] He suggested that that the Earth and Moon could both be leveraged to examine their interactions with gravitational waves. The Brans–Dicke theory, established by Robert H. Dicke and Carl H. Brans, supported this. The theory suggested that changes in space-time caused by gravitational waves would result in a disturbance of the isostatic equilibrium of a planetary body as the waves propagated through it. [9] Weber presented at a National Aeronautics and Space Administration (NASA) organised conference on relativity in 1961, highlighting that using the Moon to detect gravitational waves was an attractive option due to being seismically quieter than the Earth. [10] These events occurred in parallel to the early feasibility studies of the Apollo program and NASA had already identified a desire to send a gravimeter to the Moon as early as February 1960. [11]

Teams from University of California, Los Angeles, Princeton University and University of Maryland (led by Weber) would for several years attempt to measure the Earth's responses to gravitational waves. This would be achieved by using a gravimeter to measure how the Earth would expand and contract, inwards and outwards from its center, effectively turning the entirety of the Earth into a gravitational wave antenna. [9] The devices used for these explorations included various prototype LaCoste and Romberg type gravimeters, that allowed extremely precise measurements. [9] These sensors proved difficult to use for detecting gravity waves due to thermal noise. [9] While teams did try to eliminate sources of noise in their devices, [12] it was eventually found that due to the Earth being a seismically and geomorphically active body, the Earth's background noise for these type of devices could not be overcome at the time. [6] : 3  [13] Despite the setback, by 1964 plans for the development of an Apollo surface gravimetry experiment were underway leveraging the same technologies. [14] : 1  In addition to seeking evidence for gravitational waves, the gravimeter would aim to provide precise information on the tidal deformation of the Moon due to its interaction with the gravitational fields of the Earth and Sun. [14] : 8  [15] Whilst LaCoste and Romberg gravimeters were not designed for operation in the harsher lunar environment, there was confidence in being able to adapt the device with the biggest expected challenge to overcome being the thermal sensitivity of the device. [14] : 9 

Weber had continued developing his bar detectors through the early 1960s iterating on their design and implementation to also reduce the amount of seismic and thermal noise the detector was exposed to, and by 1967 he believed his detectors were picking up signals indicative of gravitational waves. [16] In 1969 Weber published a paper formally declaring his detection of gravitational waves, [17] followed in 1970 with the claim that regular gravitational waves were being detected from the Galactic Center. [18] Whilst there was almost immediate doubt about the scientific validity of these observations, [16] it was intended that the Lunar Surface Gravimeter instrument would work in conjunction with the Weber bar instruments on Earth to better categorise the claimed observations recorded by the instruments. [6] : 3 

Experiment history

Schematic diagram of the Lunar Surface Gravimeter ALSEP Lunar Surface Gravimeter.gif
Schematic diagram of the Lunar Surface Gravimeter

In 1964, the Director of the Office of Manned Space Science, Willis Foster, proposed four geophysics teams for the Apollo lunar surface exploration program. [19] One of the teams was dedicated to gravimetry and consisted of Joseph Weber and Gordon J. F. MacDonald, who was at that time at the University of California, Los Angeles. [19] The team evaluated a number of proposed gravimetry experiments but despite Weber's own work on LSG prototypes starting in 1964, [14] NASA's approval of the Lunar Surface Gravimeter only came late on in the planning process for Apollo 17. [19]

Bendix Corporation was the prime contractor for the Apollo Lunar Surface Experiments Package and were responsible for managing the design, manufacture and testing of all experiments and their integration with the Apollo Lunar Surface Experiments Package (ALSEP) central station. [20] Other experiments that flew as part of ALSEP included the Heat Flow Experiment, Lunar Ejecta and Meteorites Experiment, Lunar Atmospheric Composition Experiment, and Lunar Seismic Profiling Experiment. [21] : 2-1 

Each ALSEP experiment had their own prime contractor allocated, and for the LSG the experiment's flight versions were also manufactured by Bendix. In addition to having primary responsibility for the overall manufacturer of the instrument, Bendix were also responsible for the flight hardware's electronics, due to LaCoste Romberg, a notable producer of gravimeters, not having previous experience building gravimeters for use in the environment of space. [19] [21] : 12-4  The LSG's sensor was developed and built by LaCoste Romberg, and the instrument's thermal control was provided by the Arthur D. Little company. [21] : 12-4 

Concerns were raised by Marshall Space Flight Center about whether the experiment could be delivered by July 1972 in time. To alleviate some of the time pressures, rather than being integrated at Bendix with the rest of the ALSEP experiments in preparation for flight on board Apollo, integration of the experiment was done at Kennedy Space Center. [19]

Instrument description

The instrument was a gravimeter, based on the LaCoste and Romberg D-meter, [22] that primarily consists of an adjustable mass on a sprung lever attached to the instrument's measurement electronics. [6] : 4  [22] The experiment had a total mass of 12.7 kg, a volume of 26,970 cm3, and utilised a maximum of 9.3 W of power. [23] [24] : 2-9  It was capable of measuring gravity to 1 part in 105. [24] : 2-9  The mass was adjustable through the addition or removal of weights which would allow the experiment to both be tested in Earth gravity to prove out its functionality, and also be operated in lunar gravity without modification to the device. [6] : 5  [25] The measurement electronics were primarily driven by a trio of capacitor plates. Two plates were affixed to the experiment's frame in parallel with a third plate between them attached to the sprung lever. [6] : 4  The gravimeter was designed to measure seismic responses in a range between 0 and 16 Hz. [6] : 4  The experiment required its operational temperature to be maintained at 323 K (50 °C; 122 °F) to within 1 millidegree. [23] To regulate the instrument temperature a static sunshield was attached to reduce excess heat buildup, a hole on the top of the instrument allowed the radiation of heat into space, insulation on the bottom of the instrument prevented the transfer of heat from the lunar surface and an internal electric heater prevented the device from cooling. [23] [24] Power and communications with the experiment was provided via a ribbon cable connected to the ALSEP central station, through which all other active ALSEP experiments were provided with power. [23]

Surface operations

The experiment was deployed on the Moon's surface by Apollo 17 astronauts Gene Cernan and Harrison Schmitt on December 12, 1972. [23] Deployment consisted of levelling the instrument, deploying the sunshield and attaching the power and communications cable to the ALSEP central station. [23]

Following the deployment of the LSG, it was discovered that the instrument's calibration weights were not heavy enough to allow the sprung level to be properly balanced. Apollo 17 astronauts made several attempts to debug the issue on the Moon. [25] This included releveling the instrument, rocking the instrument side to side, tapping "sharply" with increasing force and sending a variety of commands to the device. [6] : 7  Eventually it was accepted the LSG was no longer able to operate as a gravimeter. Adjustments were made to the sensor via remote commands by placing the weight mechanism in contact with the sprung level, applying a small amount of force. [25] The hope was that it could be used as a low-fidelity seismograph which is how it functioned for the remainder of its operational life. [25]

The instrument experienced large deviations from its desired operational temperatures in both March 1974 and July 1975, when the instrument's internal heater became stuck in a mode which kept the heater active. [24] : 2:9 – 2:10  In both instances, the heater was manually commanded to cycle in order to reset it and allow the instrument to return to its operational temperature and continued to return data. [24] : 2:9 – 2:10  The instrument continued to operate until September 30, 1977 when operations support for ALSEP was terminated due to budgetary constraints. [19] : 144  [23] [25]

Failure cause

It is agreed that the instruments balance weights were too light for use in the Moon's gravity and unable to provide the necessary adjustments to the instrument's sensor that would allow the sprung lever to balance freely and move unhindered. [6] [19] [22] [25]

The experiment's researchers from University of Maryland claimed that this was due to an arithmetic error, [6] [25] [19] and claimed this was an error known by the manufacturers LaCoste Romberg. [6] LaCoste Romberg addressed the device's failure nearly 30 years later. The challenge the company described is that the weights of the masses for use on the Moon could not simply be assumed to be 1/6th the mass of those for testing on Earth. Due to the need to factor in the mechanical properties of the sprung lever and its center of gravity, no two devices were perfectly alike. [22] Each instrument would normally be assessed by comparing read-outs against known gravity values at test locations, and the device's weights adjusted to account for the variations inherent to each instrument. This was done for the test article, but wasn't done for the flight article to speed up the manufacturing process to meet the tight deadlines. [22] Mass values that had been calculated for the flight-like test article were used for the weights on the actual flight hardware, and subsequently only found to be incorrect after deployment during the mission. [22]

This problem was compounded by that the fact that when modifying the D-meter design for use on the Moon, a decision was taken to reduce the extent with which fine adjustments could be made since the instrument was going to be static. The result was an instrument that had half of the fine-adjustment capability. If this change had not been made, then the wrong mass values could have been accounted for and the device operated normally. [22] Apollo 17's Schmitt claimed that Weber's team had refused to test the device on a slope in a way that would emulate lunar gravity, in order to protect the proprietary nature of the instrument. [26] [27]

Science

Gravimetry

Due to the instrument's failure, the LSG did not manage to achieve two of its primary objectives, to identify any gravitational wave–induced oscillations in the Moon and to measure the isostatic response to tidal forces from the Sun and Earth. [24] [28] : 4–5  Since the deployment of the instrument, it has become known that Weber bars were not capable of detecting gravitational waves nor was the LSG sensitive enough to detect gravitational waves. [29]

Seismography

To get the instrument to operate as a seismograph, there was a need to use the weight caging mechanism to apply a force to the sprung lever in order to balance it. This had significant negative effects on the instrument. It set up substantial new harmonic resonances in the instrument, reduced its sensitivity to some frequencies and increased its sensitivity to frequencies now occupied by the device's own resonance. [6] : 7–8 

The data received from ALSEP experiments would typically be sent as tapes to the principal investigator of each experiment for analysis. It was then expected the principal investigator would forward on the tapes to be archived by the National Space Science Data Center. [25] Weber's team did not transfer any of the measurements taken between 1972 and 1976 to the National Space Science Data Center, [30] release any of the data themselves and no examination of the instrument's operation as a seismometer occurred. [25] One PhD was completed by Russell Tobias based on this experiment. [28] In the instrument's final report, it was stated that the computers used for analysing the experiment's data were taken back by NASA, [6] although this applied to many lunar science experiments. [25]

Even though the data between 1972 and 1976 remains unavailable, from March 1976 there were operational changes in how data was received and processed from the ALSEP station, with all data being sent to the University of Texas. Data was stored in a raw form and required decoding for each instrument. [25] In 2015, an evaluation of this data found that the instrument detected deep and shallow moonquakes, and impact events. [25] The investigation suggested that combining the LSG and other Apollo seismograph data might increase the resolution and understanding of the Moon's internal structure. [25]

Future experiments

Whilst the LSG failed in its original objectives, the potential for the Moon as an environment conducive to the study of gravitational waves remains. The Moon in a general sense exhibits very little seismic activity but particularly in the frequency bands suited to the study of gravitational waves, the moon exhibits a noise level orders of magnitude lower than found on Earth. [31] [32] [33] Areas on the Moon's surface that are in permanent shadow, such as at the lunar poles, are thermally stable. This reduces any instrument noise caused by thermal variability. [34] As well as being thermally stable, these locations have been measured to have the coldest known temperatures in the solar system. [35] Cool temperatures reduce sensor noise caused by the thermal motion of particles. [36] With NASA and the European Space Agency (ESA) working towards a new period of human exploration on the Moon, both agencies have sought input on science goals. [37] [38] Two lunar surface experiments to study the theorised responses of a planetary body to gravitational waves were put forward in response to a call for proposals from ESA in 2020, with the Italian Gran Sasso Science Institute proposing the Lunar Gravitational-Wave Antenna [39] and the French Astroparticle and Cosmology Laboratory proposing the Lunar Seismic and Gravitational Antenna. [40] The Lunar Gravitational-Wave Antenna would leverage an array of highly sensitive seismometers on the surface of the Moon, to measure the response of the Moon to gravitational waves and to distinguish this signal from a seismic background. [39]

Related Research Articles

<span class="mw-page-title-main">Apollo 12</span> Second crewed Moon landing

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.

<span class="mw-page-title-main">Apollo 14</span> Third crewed Moon landing

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.

<span class="mw-page-title-main">Apollo 17</span> Sixth and latest crewed Moon landing

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.

<span class="mw-page-title-main">Geophysics</span> Physics of the Earth and its vicinity

Geophysics is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. Geophysicists, who usually study geophysics, physics, or one of the Earth sciences at the graduate level, complete investigations across a wide range of scientific disciplines. The term geophysics classically refers to solid earth applications: Earth's shape; its gravitational, magnetic fields, and electromagnetic fields ; its internal structure and composition; its dynamics and their surface expression in plate tectonics, the generation of magmas, volcanism and rock formation. However, modern geophysics organizations and pure scientists use a broader definition that includes the water cycle including snow and ice; fluid dynamics of the oceans and the atmosphere; electricity and magnetism in the ionosphere and magnetosphere and solar-terrestrial physics; and analogous problems associated with the Moon and other planets.

<span class="mw-page-title-main">Lunar Laser Ranging experiments</span> Measuring the distance between the Earth and the Moon with laser light

Lunar Laser Ranging (LLR) is the practice of measuring the distance between the surfaces of the Earth and the Moon using laser ranging. The distance can be calculated from the round-trip time of laser light pulses travelling at the speed of light, which are reflected back to Earth by the Moon's surface or by one of several retroreflectors installed on the Moon. Three were placed by the United States' Apollo program, two by the Soviet Lunokhod 1 and 2 missions, and one by India's Chandrayaan-3 mission.

<span class="mw-page-title-main">Apache Point Observatory Lunar Laser-ranging Operation</span>

The Apache Point Observatory Lunar Laser-ranging Operation, or APOLLO, is a project at the Apache Point Observatory in New Mexico. It is an extension and advancement of previous Lunar Laser Ranging experiments, which use retroreflectors on the Moon to track changes in lunar orbital distance and motion.

<span class="mw-page-title-main">Gravimetry</span> Measurement of the strength of a gravitational field

Gravimetry is the measurement of the strength of a gravitational field. Gravimetry may be used when either the magnitude of a gravitational field or the properties of matter responsible for its creation are of interest. The study of gravity changes belongs to geodynamics.

The Hollow Moon and the closely related Spaceship Moon are pseudoscientific hypotheses that propose that Earth's Moon is either wholly hollow or otherwise contains a substantial interior space. No scientific evidence exists to support the idea; seismic observations and other data collected since spacecraft began to orbit or land on the Moon indicate that it has a thin crust, extensive mantle and small, dense core. Overall it is much less dense than Earth.

<span class="mw-page-title-main">Spacecraft magnetometer</span> Widely used scientific instrument aboard satellites and probes

Spacecraft magnetometers are magnetometers used aboard spacecraft and satellites, mostly for scientific investigations, plus attitude sensing. Magnetometers are among the most widely used scientific instruments in exploratory and observation satellites. These instruments were instrumental in mapping the Van Allen radiation belts around Earth after its discovery by Explorer 1, and have detailed the magnetic fields of the Earth, Moon, Sun, Mars, Venus and other planets and moons. There are ongoing missions using magnetometers, including attempts to define the shape and activity of Saturn's core.

<span class="mw-page-title-main">Lunar seismology</span> Study of ground motions of the Moon

Lunar seismology is the study of ground motions of the Moon and the events, typically impacts or moonquakes, that excite them.

<span class="mw-page-title-main">Apollo Lunar Surface Experiments Package</span> Scientific instruments left by the Apollo astronauts on the Moon

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.

<span class="mw-page-title-main">Apollo 12 Passive Seismic Experiment</span>

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.

<span class="mw-page-title-main">Apollo 14 Passive Seismic Experiment</span>

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.

<span class="mw-page-title-main">Jean-Paul Richard</span> Canadian physicist

Jean-Paul Richard was a Canadian physicist, academic and researcher. He was a Professor of Physics at the University of Maryland.

<span class="mw-page-title-main">Passive Seismic Experiment Package</span> 1969 American experiment on the Moon

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.

<span class="mw-page-title-main">Laser Ranging Retroreflector</span> 1969 American experiment on the Moon

The Laser Ranging Retroreflector (LRRR) was the first ever deployable lunar laser ranging experiment. It was carried on Apollo 11 as part of the Early Apollo Scientific Experiments Package, and on Apollo 14 and Apollo 15 as part of the Apollo Lunar Surface Experiments Package (ALSEP). The LRRR consists of a series of corner reflectors set within a panel. Laser beams sent from Earth are bounced off the retroreflector and the timing of the return signal can be used to measure the distance from the signal source to the reflector. The reflector was conceived by James E. Faller in 1961. The experiment's principal investigator was initially Carroll Alley of the University of Maryland who was eventually succeeded by Faller.

<span class="mw-page-title-main">Lunar Surface Magnetometer</span> Apollo lunar science experiment

The Lunar Surface Magnetometer (LSM) was a lunar science experiment with the aim of providing insights into the interior of the Moon and how its latent magnetic field interacts with the solar wind. It was deployed on the Moon as part of Apollo 12, Apollo 14 and Apollo 16 missions.

<span class="mw-page-title-main">Heat Flow Experiment</span> American moon mission experiment

The Heat Flow Experiment was a United States NASA lunar science experiment that aimed to measure the rate of heat loss from the surface of the Moon. Four experiments were carried out on board Apollo missions. Two experiments were successfully deployed as part of Apollo 15 and Apollo 17. The instrument on Apollo 16 was deployed but the cable from it to the ALSEP central station was broken and the experiment was rendered inoperable. A heat flow experiment was carried onboard Apollo 13 but the mission was aborted in-flight and the instrument never reached the surface.

<span class="mw-page-title-main">Lunar Seismic Profiling Experiment</span>

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.

<span class="mw-page-title-main">Lunar Traverse Gravimeter</span> Experiment on Apollo 17

The Lunar Traverse Gravimeter was a lunar science experiment, deployed by astronauts on the lunar surface in 1972 as part of Apollo 17. The goal of the experiment was to use relative gravity measurements to infer potential attributes about the geological substrata near the Apollo 17 landing site.

References

  1. ↑ Poincaré, H. (1905). "Sur la dynamique de l'électron - Note de Henri Poincaré publiée dans les Comptes rendus de l'Académie des sciences de la séance du 5 juin 1905 - Membres de l'Académie des sciences depuis sa création" [On the dynamics of the electron - Note by Henri Poincaré published in the Reports of the Academy of Sciences of the session of June 5, 1905 - Members of the Academy of Sciences since its creation](PDF). www.academie-sciences.fr (in French). Retrieved 3 November 2023.
  2. ↑ Einstein, A (June 1916). "Näherungsweise Integration der Feldgleichungen der Gravitation". Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften Berlin . part 1: 688–696. Bibcode:1916SPAW.......688E. Archived from the original on 2016-01-15. Retrieved 2014-11-15.
  3. ↑ Einstein, A (1918). "Über Gravitationswellen". Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften Berlin. part 1: 154–167. Bibcode:1918SPAW.......154E. Archived from the original on 2016-01-15. Retrieved 2014-11-15.
  4. ↑ Finley, D (2013). "Einstein's gravity theory passes toughest test yet: Bizarre binary star system pushes study of relativity to new limits". Phys.Org. Retrieved April 8, 2024.
  5. ↑ Barish, Barry C.; Weiss, Rainer (1999-10-01). "LIGO and the Detection of Gravitational Waves". Physics Today. 52 (10): 44–50. doi:10.1063/1.882861. ISSN   0031-9228.
  6. 1 2 3 4 5 6 7 8 9 10 11 12 13 Giganti, John J.; Larson, J.V.; Richard, J.V.; Tobias, R.L.; Weber, J (January 1977). "Lunar Surface Gravimeter Experiment - Final Report to the National Aeronautics and Space Administration" (PDF). NASA Technical Reports Server. Archived (PDF) from the original on December 23, 2023. Retrieved January 3, 2024.
  7. ↑ Weber, J. (1960-01-01). "Detection and Generation of Gravitational Waves". Physical Review. 117 (1): 306–313. Bibcode:1960PhRv..117..306W. doi:10.1103/PhysRev.117.306.
  8. ↑ Weber, J. (1961). General relativity and gravitational waves. New York: Interscience Publishers, Inc. p. 187.
  9. 1 2 3 4 Weiss, R; Block, B (1965-11-15). "A gravimeter to monitor the 0 S 0 dilational mode of the Earth". Journal of Geophysical Research. 70 (22): 5615–5627. doi:10.1029/JZ070i022p05615.
  10. ↑ Drew, H; Barskey, C.; Tinling, C; Thomasson, N; Ogata, S; Zyskowski, J; Schiff, L (1961). "Proceedings of the Conference on Experimental Tests of Theories of Relativity" (PDF). Gravity Probe B, Stanford University. NASA. p. 114.
  11. ↑ "A Lunar Exploration Program Based upon Saturn-boosted Systems". 1960-02-01.
  12. ↑ Block, B; Moore, R. D. (1966-09-15). "Measurements in the Earth mode frequency range by an electrostatic sensing and feedback gravimeter". Journal of Geophysical Research. 71 (18): 4361–4375. doi:10.1029/JZ071i018p04361.
  13. ↑ Weber, J (1968-04-01). "Gravitational waves". Physics Today. 21 (4): 34–39. doi:10.1063/1.3034919. ISSN   0031-9228.
  14. 1 2 3 4 Weber, J; MacDonald, G (1964). "Section VII - Lunar Gravity Measurements". Apollo Lunar Science Program, Report of Planning Teams. Part II Appendix. NASA Technical Memorandum. National Aeronautics and Space Administration.
  15. ↑ Simmons, G (1972). On the Moon with Apollo 17: A Guidebook to Taurus-Littrow. National Aeronautics and Space Administration.
  16. 1 2 Cervantes-Cota, Jorge L.; Galindo-Uribarri, Salvador; Smoot, George F. (2016). "A Brief History of Gravitational Waves". Universe. 2 (3): 22. arXiv: 1609.09400 . Bibcode:2016Univ....2...22C. doi: 10.3390/universe2030022 . ISSN   2218-1997.
  17. ↑ Weber, J. (1969-06-16). "Evidence for Discovery of Gravitational Radiation". Physical Review Letters. 22 (24): 1320–1324. Bibcode:1969PhRvL..22.1320W. doi:10.1103/PhysRevLett.22.1320.
  18. ↑ Weber, J. (1970-07-20). "Anisotropy and Polarization in the Gravitational-Radiation Experiments". Physical Review Letters. 25 (3): 180–184. Bibcode:1970PhRvL..25..180W. doi:10.1103/PhysRevLett.25.180.
  19. 1 2 3 4 5 6 7 8 Beattie, D. A. (2001). Taking science to the moon: lunar experiments and the Apollo Program. New series in NASA history. Baltimore: Johns Hopkins University Press. ISBN   978-0-8018-6599-2.
  20. ↑ Langseth, M. G. (1977-09-01). "Lunar heat-flow experiment". NASA Technical Reports Server. Lamont-Doherty Geological Observatory of Colombia University.
  21. 1 2 3 Giganti, J. J.; Larson, J. V.; Richard, J. P.; Weber, J. (1973-01-01). "Lunar Surface Gravimeter Experiment". NASA. Johnson Space Center Apollo 17 Prelim. Sci. Rept.
  22. 1 2 3 4 5 6 7 Chapin, D. A. (2000). "Gravity measurements on the moon". The Leading Edge. 19 (1): 88–91. doi:10.1190/1.1438472. ISSN   1070-485X.
  23. 1 2 3 4 5 6 7 "NASA - NSSDCA - Experiment - Details". nssdc.gsfc.nasa.gov. Archived from the original on 2023-08-30. Retrieved 2024-01-04.
  24. 1 2 3 4 5 6 Bates, J.; Lauderdale, W. W.; Kernaghan, H. (1979-04-01). "ALSEP termination report" (PDF). Archived (PDF) from the original on 2019-04-12. Retrieved 2024-01-04.
  25. 1 2 3 4 5 6 7 8 9 10 11 12 13 Kawamura, T; Kobayashi, N; Tanaka, S; Lognonné, P (2015). "Lunar Surface Gravimeter as a lunar seismometer: Investigation of a new source of seismic information on the Moon". Journal of Geophysical Research: Planets. 120 (2): 343–358. Bibcode:2015JGRE..120..343K. doi:10.1002/2014JE004724. ISSN   2169-9097. Archived from the original on 2024-01-04. Retrieved 2024-01-20.
  26. ↑ Schmitt, H. (2017-11-06). "Chapter 4 – 30 Days and Counting". America’s Uncommon Sense. Archived from the original on 2023-12-23. Retrieved 2023-12-23.
  27. ↑ Phinney, William C. (2015-11-01). "Science Training History of the Apollo Astronauts". p. 132.
  28. 1 2 Tobias, R. L. (1978). The lunar surface gravimeter and the search for gravitational radiation (Thesis). OCLC   18232780. ProQuest   302901798.
  29. ↑ Cozzumbo, A; Mestichelli, B; Mirabile, M; Paiella, L; Tissino, J; Harms, J (2023-09-28), Opportunities and limits of lunar gravitational-wave detection, arXiv: 2309.15160
  30. ↑ Eichelman, W. F.; Lauderdale, W. W. (1974-08-01). "Apollo scientific experiments data handbook". NASA Technical Reports Server. Lyndon B. Johnson Space Center.
  31. ↑ Branchesi, M; Falanga, M; Harms, J; Jani, K; Katsanevas, S; Lognonné, P; Badaracco, F; Cacciapuoti, L; Cappellaro, E; Dell’Agnello, S; de Raucourt, S; Frigeri, A; Giardini, D; Jennrich, O; Kawamura, T (2023-10-20). "Lunar Gravitational-Wave Detection". Space Science Reviews. 219 (8): 67. Bibcode:2023SSRv..219...67B. doi:10.1007/s11214-023-01015-4. hdl: 20.500.11850/639001 . ISSN   1572-9672.
  32. ↑ Nakamura, Y; Latham, G. V.; Dorman, H. J.; Harris, J. E. (1981). Passive Seismic Experiment, Long Period Event Catalog, Final Version (1969 Day 202 - 1977 Day 273, ALSEP Stations 11, 12, 13, 14, 15, and 16) (Report). Institute for Geophysics. hdl:2152/65671.
  33. ↑ Lognonné, P; Le Feuvre, M; Johnson, C. L.; Weber, R. C. (December 2009). "Moon meteoritic seismic hum: Steady state prediction". Journal of Geophysical Research: Planets. 114 (E12). Bibcode:2009JGRE..11412003L. doi:10.1029/2008JE003294. ISSN   0148-0227.
  34. ↑ Williams, J. P.; Greenhagen, B. T.; Paige, D. A.; Schorghofer, N.; Sefton-Nash, E.; Hayne, P. O.; Lucey, P. G.; Siegler, M. A.; Aye, K. Michael (October 2019). "Seasonal Polar Temperatures on the Moon". Journal of Geophysical Research: Planets. 124 (10): 2505–2521. Bibcode:2019JGRE..124.2505W. doi:10.1029/2019JE006028. ISSN   2169-9097.
  35. ↑ "Lunar Reconnaissance Orbiter: Temperature Variation on the Moon" (PDF). NASA Science. 2014.
  36. ↑ Hong, T; Yang, H; Gustafson, E. K.; Adhikari, R. X.; Chen, Y (2013-04-02). "Brownian thermal noise in multilayer coated mirrors". Physical Review D. 87 (8): 082001. arXiv: 1207.6145 . Bibcode:2013PhRvD..87h2001H. doi:10.1103/PhysRevD.87.082001.
  37. ↑ Foust, J. (2020-08-24). "NASA seeks input on Artemis science goals". SpaceNews. Retrieved 2024-03-30.
  38. ↑ "Open Space Innovation Platform - OSIP - Campaign: Ideas for exploring the Moon with a large European lander". ideas.esa.int. Retrieved 2024-03-30.
  39. 1 2 Harms, J; et al. (1 March 2021). "Lunar Gravitational-wave Antenna". The Astrophysical Journal. 910 (1): 1. arXiv: 2010.13726 . Bibcode:2021ApJ...910....1H. doi: 10.3847/1538-4357/abe5a7 .
  40. ↑ "Open Space Innovation Platform - OSIP - Idea: LUNAR SEISMIC AND GRAVITATIONAL ANTENNA (LSGA)". ideas.esa.int. Retrieved 2024-04-19.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.