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Active Seismic

NSSDCA ID: 1971-008C-05

Mission Name: Apollo 14 Lunar Module /ALSEP
Principal Investigator:Dr. Robert L. Kovach

Description

The purpose of the active seismic experiment was to generate and monitor seismic waves in the Moon near the surface in order to study the internal structure to a depth of 460 m. The seismic energy source used was the 'thumper' device, which contained 21 small explosive charges. The mortar package containing four high-explosive grenades was planted 91 m from the LM, but its deployment from Earth was postponed and eventually cancelled when it was decided that the back blast from firing the grenades could damage the central station and other experiments. The thumper equipment consisted of a staff held and triggered by an astronaut with the charge initiators mounted on the lower end of its base, a cable connecting the staff (thumper) to the central station, geophones (miniature seismometers) for recording the waves, and a three-channel amplifier with log compressor for telemetering to the earth.

The thumper shots were fired over the period from 18:10:38 to 18:37:07 UT on 5 February 1971. Eight of the 21 shot attempts (shots 5, 6, 8, 9, 10, 14, 15, and 16) were misfires. The thumper device provided data that indicated that two P-wave velocites were measured at the Fra Mauro site. The near surface has a seismic wave velocity of 104 m/s, and a sublayer starting at a depth of 8.5 m has a velocity of 299 m/s. Estimates of the thickness of this substratum range from 38 to 76 m, which is probably indicative of the depth of the Fra Mauro formation.

The Active Seismic also had a passive (listening) mode. The numbers listed for power (6.8 W) and data rate (10.6 kilobits/second) only apply to the active mode. After this, the seismometer was occasionally used in listening mode, which required 5.3 W and had a much lower data rate. During the active modes other experiments would be turned off to support the high data rate.

Alternate Names

  • Apollo14ALSEP/ActiveSeismic
  • S033

Facts in Brief

Mass: 11.2 kg
Power (avg): 6.8 W
Bit rate (avg): 10.6 kbps

Funding Agency

  • NASA-Office of Space Science (United States)

Discipline

  • Planetary Science: Geology and Geophysics

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Prof. Joel S. WatkinsOther InvestigatorUniversity of Texas, Galveston
Dr. Robert L. KovachPrincipal InvestigatorStanford Universitykov@pangea.stanford.edu

Selected References

  • Nunn, Ceri, et al., Lunar Seismology: A Data and Instrumentation Review, Space Science Reviews (2020) Vol. 216, number 89, pages 1-39.
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