Passive Seismic Experiment Package: Difference between revisions
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==Deployment and operation== |
==Deployment and operation== |
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The PSEP was placed {{Convert|16.8|m}} from the Apollo 11 [[Lunar Module Eagle|Lunar Module]] at [[Tranquility Base]] on July 21, 1969.<ref name=":0" /> |
The PSEP was placed {{Convert|16.8|m}} from the Apollo 11 [[Lunar Module Eagle|Lunar Module]] at [[Tranquility Base]] on July 21, 1969.<ref name=":0" /> of the on the and .<ref name=":0" /> |
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The instrument temperature reached a maximum of {{Convert|190|F|C}} which was {{Convert|50|F|C}} greater than the expected maximum of {{Convert|150|F|C}}. This higher than expected temperature did result in minor effects such as intermittent transient signals on the low frequency seismometers, but this did not impact instrument performance in any significant way.<ref name=":0" /> The low frequency seismometers drifted out of their operating range on the last two days and could not be recalibrated due to an inability of the package to receive commands. <ref name=":0" /> |
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| ⚫ | The seismometers were particularly impacted by the amount of seismic noise that emanated from the Lunar Module, cause by venting, fluid circulation, and the Lunar Module's response to changes in temperature. The resulted in a recommendation for future missions to deploy seismometers at the furthest possible distance from the Lunar Module.<ref name=":0" /> |
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| ⚫ | The seismometers were particularly impacted by the amount of seismic noise that emanated from the Lunar Module, cause by venting, fluid circulation, and the Lunar Module's response to changes in temperature. The resulted in a recommendation for future missions to deploy seismometers at the furthest possible distance from the Lunar Module.<ref name=":0" /> |
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==Science== |
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==Measurements and science== |
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The background seismic levels on the moon were found to be very low, far lower than that measured by any known Earth instrument at the time. Whilst there are large thermal variations due to the diurnal cycle, this does not result in a high background noise. A different hypothesis suggested that the moon would have a continuous level of asteroid impacts that would result in a high background noise, this was similarly disproven. <ref name=":2">{{Cite journal |last=Latham |first=Gary V. |last2=Ewing |first2=Maurice |last3=Press |first3=Frank |last4=Sutton |first4=George |last5=Dorman |first5=James |last6=Nakamura |first6=Yosio |last7=Toksöz |first7=Nafi |last8=Wiggins |first8=Ralph |last9=Derr |first9=John |last10=Duennebier |first10=Frederick |date=1970-01-30 |title=Passive Seismic Experiment |url=https://www.science.org/doi/10.1126/science.167.3918.455 |journal=Science |language=en |volume=167 |issue=3918 |pages=455–457 |doi=10.1126/science.167.3918.455 |issn=0036-8075}}</ref> |
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Six types of signals were identified by the instrument package. ''L-events'' were the only signal classification with a hypothesised natural origin, and with their main characteristics being described as having a long duration (<1-hour) and an emergent initiation. These events would produce a signal that would build up slowly to its peak and then slowly fade to the background level. There was great variability in their character and occurrence, being detected by both the long-period and short-period seismometers. This time of signal was detected 83 times during the Apollo 11 missions at an average of 4 per day. <ref name=":1" /> The origins of these signals were suggested to be either meteroid impacts or shallow moon-quakes and the frequency matched predictions previously made.<ref name=":2" /> |
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Whilst the Apollo 11 astronauts were present on the moon, the PSEP detected many seismic signals in relation to their activities, mainly on the short period/high frequency vertical seismograph. This included the astronauts footfall's on the lunar surface, or when in direct physical contact with the Lunar Module. <ref name=":2" /> |
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==Instrument failure== |
==Instrument failure== |
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Revision as of 00:38, 17 April 2023
 The Passive Seismic Experiment Package on the Moon | |
| Acronym | PSEP |
|---|---|
| Notable experiments | Apollo 11 mission |
| Inventor | Dr. Gary Latham Lamont-Doherty Geological Observatory;
Dr. Maurice Ewing, Lamont-Doherty Geological Observatory; Dr. Frank Press, Massachusetts Institute of Technology; Dr. George Sutton, University of Hawaii. |
| Manufacturer | Lamont-Doherty Geological Observatory, Columbia University and the California Institute of Technology's Seismological Laboratory |
The Passive Seismic Experiment Package (PSEP) was deployed on the lunar surface to establish the structure, tectonic activity, physical nature, and composition of the Moon.[1] The first seismometer to be deployed on a planetary body other the Earth, it was set up by the astronauts of Apollo 11 as part of the Early Apollo Surface Experiments Package (EASEP). [1]
Background
There had been multiple prior attempts by the California Institute of Technology at measuring the moons seismic activity through seismometers provided on Ranger 3, Ranger 4 and Ranger 5; but all three landers on these missions failed to reach their destination successfully. [2] The research group at the Lamont-Doherty Geological Observatory had developed a seismometer to fly on landers that were part of the Surveyor program. This did not occur due to reduced payload capacities and the prioritisation of experiments that would provide transferable knowledge related to crewed landings on the moon. [2]
Instrument
Power to this experiment was provided by EASEP via solar cell panels. On later Apollo missions as part of ALSEP, power was provided to their passive seismic experiments via a radioisotope thermoelectric generator. Due to power being provided by solar cells, operation of the experiment was limited to the lunar day.[2]
The experiments sensor system was made of two parts. The first consisted of three low-frequency seismometers in an orthogonal triaxial arrangement to capture horizontal movement and vertical movement. The second consisted of a single axis high-frequency seismometer that only measured vertical motion.[2]
Deployment and operation
The PSEP was placed 16.8 metres (55 ft) from the Apollo 11 Lunar Module at Tranquility Base on July 21, 1969.[1] A set of 15 commands could be sent to the experiment package from a mission control on Earth to control the instruments levelling and calibration motors.[1]
The instrument temperature reached a maximum of 190 °F (88 °C) which was 50 °F (10 °C) greater than the expected maximum of 150 °F (66 °C). This higher than expected temperature did result in minor effects such as intermittent transient signals on the low frequency seismometers, but this did not impact instrument performance in any significant way.[1] The low frequency seismometers drifted out of their operating range on the last two days and could not be recalibrated due to an inability of the package to receive commands. [1]
The seismometers were particularly impacted by the amount of seismic noise that emanated from the Lunar Module, cause by venting, fluid circulation, and the Lunar Module's response to changes in temperature. The resulted in a recommendation for future missions to deploy seismometers at the furthest possible distance from the Lunar Module.[1]
Measurements and science
The background seismic levels on the moon were found to be very low, far lower than that measured by any known Earth instrument at the time. Whilst there are large thermal variations due to the diurnal cycle, this does not result in a high background noise. A different hypothesis suggested that the moon would have a continuous level of asteroid impacts that would result in a high background noise, this was similarly disproven. [3]
Six types of signals were identified by the instrument package. L-events were the only signal classification with a hypothesised natural origin, and with their main characteristics being described as having a long duration (<1-hour) and an emergent initiation. These events would produce a signal that would build up slowly to its peak and then slowly fade to the background level. There was great variability in their character and occurrence, being detected by both the long-period and short-period seismometers. This time of signal was detected 83 times during the Apollo 11 missions at an average of 4 per day. [2] The origins of these signals were suggested to be either meteroid impacts or shallow moon-quakes and the frequency matched predictions previously made.[3]
Whilst the Apollo 11 astronauts were present on the moon, the PSEP detected many seismic signals in relation to their activities, mainly on the short period/high frequency vertical seismograph. This included the astronauts footfall's on the lunar surface, or when in direct physical contact with the Lunar Module. [3]
Instrument failure
The experiment was terminated on August 27, 1969 when the experiment package failed to receive and execute commands from earth. [1]
References
- ^ a b c d e f g h "Apollo 11: Preliminary Science Report. NASA SP-214". NASA Special Publication. 214. 1969-01-01.
- ^ a b c d e Latham, G; Ewing, M; Press, F; Sutton, G (1969). "The Apollo Passive Seismic Experiment". Science. 165: 241–250.
- ^ a b c Latham, Gary V.; Ewing, Maurice; Press, Frank; Sutton, George; Dorman, James; Nakamura, Yosio; Toksöz, Nafi; Wiggins, Ralph; Derr, John; Duennebier, Frederick (1970-01-30). "Passive Seismic Experiment". Science. 167 (3918): 455–457. doi:10.1126/science.167.3918.455. ISSN 0036-8075.