Mechanical aspects of the lunar surface magnetometer
ALSEP magnetometer mission and environmental requirements and mechanical design
Nelms, W. L.↗
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Summary of scientific results
The major scientific results of the Apollo 15 flight are summarized. The objectives of the flight are given as: (1) to carry out extensive geological exploration, comprehensive sampling, and photographic documentation of the Apennine Front at Hadley Delta, Hadley Rille, and the mare plain, (2) to emplace the ALSEP near the landing site, and (3) to perform a series of survey experiments with the scientific instrument module (SIM) equipment from lunar orbit and during transearth coast.
Allen, J. P.↗
Cold cathode gage experiment (lunar-atmosphere detector)
A preliminary evaluation of the cold cathode gage experiment which was included in the ALSEP to determine the amount of gas present on the lunar surface is reported. The instrument, electronic circuitry, and deployment are described. The preliminary results are summarized and include temperature history, and variations in gas concentration detected after deployment.
Johnson, F. S.↗
Plasma-sheet ions at lunar distance preceding substorm onset.
During the partial lunar eclipse of August 17, 1970, four intense, transient bursts of kV-energy positive ions were detected at the lunar surface by the Rice University ALSEP Suprathermal Ion Detector Experiment. The eclipse happened to occur during a main-phase geomagnetic storm while the moon was within a few earth radii of the calculated position of the neutral sheet. The two most intense ion bursts were each followed roughly one-half hour later by the sudden onset of a several thousand gamma polar magnetic substorm at the earth's surface. Two smaller ion enhancements were also followed by smaller magnetic disturbances. This observation is interpreted in terms of a downstream escape of plasma-sheet particles associated with the substorm growth phase.
Garrett, H. B.↗
A brief review of ionospheric scintillation fading effects as observed in NASA satellite tracking and data acquisition networks.
Discussion of some results of the effects of ionospheric irregularities on NASA satellite tracking and data acquisition operations. Ionospheric scintillation fading produced by irregularities has been observed at 136 MHz (vhf), 400 MHz (uhf), 1550 MHz (L-band) and 1700 to 2200 MHz (S-band). Details of these observations are presented. Vhf scintillation effects are evident in both auroral and equatorial regions. Fading effects decrease with increasing radio frequency in the auroral region. The same frequency dependence for fading is not observed in the equatorial region. Although there is a seasonal and diurnal character to scintillation in the equatorial region, fading effects are usually more severe than in the auroral region for a given radio frequency. Space diversity measurements indicate that reasonable solutions for vhf telemetry problems are available for either region. Space diversity should provide a solution for microwave frequencies as well. Ionospheric fading amplitude for 1700 MHz is relatively small in the auroral region. In the equatorial region amplitude fading levels for 1550-MHz signals from ATS-5 are often much larger than expected. Observations of the Apollo Lunar Surface Experiment Package (ALSEP) operating at 2300 MHz observed near the geomagnetic equator show fading peaks in excess of 15 dB.
Golden, T. S.↗
Development of an in situ thermal conductivity measurement for the lunar heat flow experiment.
Discussion of the design and calibration of the heat flow experiment of the Apollo Lunar Scientific Experiments Package (ALSEP). The principal objective is to gain evidence on the bulk chemistry of the moon. The heat flow is determined by making independent measurements of the vertical temperature gradient and the thermal conductivity in the inner surface layer (the regolith). Attention is given to the errors associated with the experimental technique. The low thermal conductivity of the regolith layer presents both advantages and disadvantages in heat flow measurement.
Langseth, M. G., Jr.↗
Apollo lunar surface experiments package
Progress in the ALSEP program is reported. Test results are presented for the following areas: Apollo 17 (array E), data subsystem, structural/thermal and crew engineering, and lunar experiments.
Source record↗
The safety and reliability of the S and A mechanism designed for the NASA/LSPE program
Under contract to the Manned Spacecraft Center, NASA/Houston, NOL developed a number of explosive charges for use in studying the surface of the moon during Apollo 17 activities. The charges were part of the Lunar Seismic Profiling Experiment (LSPE). When the Safety and Arming Device used in the previous ALSEP experiments was found unsuitable for use with the new explosive packages, NOL also designed the Safety and Arming Mechanism, and the safety and reliability tests conducted are described. The results of the test program indicate that the detonation transfer probability between the armed explosive components exceeds 0.9999, and is less than 0.0001 when the explosive components are in the safe position.
Montesi, L. J.↗
Water vapor, whence comest thou.
During a 14-hour period on Mar. 7, 1971, the Apollo 14 ALSEP suprathermal ion detector experiment (SIDE) observed an intense, prolonged series of bursts of 48.6-eV ions at the lunar surface. The SIDE mass analyzer showed the mass per unit charge of these ions to be characteristic of water vapor if singly ionized. The event was also observed by the SIDE total ion detectors (TIDs) at the Apollo 14 site and at Apollo 12 (located 183 km to the west). The TID data from SIDE 14 indicate that the energy spectrum was narrower than the 20-eV interval between energy channels. Ion spectra due to the LM exhaust gases are shown to be readily identified by the SIDE and are distinctly different in character from the spectra obtained on March 7. Detailed consideration of other possible sources of water, including the Apollo 14 CSM, leads to the conclusion that the water vapor did not come from a man-made source. Also, it is estimated that the event may have involved a quantity of water much greater than that which has been artificially introduced into the lunar environment. Consequently, it appears to be of lunar origin.
Freeman, J. W., Jr.↗
Direct observation of the lunar photoelectron layer.
The Charged-Particle Lunar Environment Experiment (CPLEE), a part of the Apollo 14 ALSEP, is an ion-electron spectrometer capable of measuring ions and electrons with energies between 40 eV and 50 keV. Accordingly, the instrument, with apertures 26 cm above the surface, has detected a layer of photoelectrons, or photoelectron gas above the sunlit lunar surface with energies ranging up to 200 eV. The experimental data for periods when the moon was in the earth's magnetotail for electron energies between 40 and 200 eV follows a defined power-law spectrum. The implications of this measurement are two-fold in that the lunar surface potential can be immediately determined to be at least 200 V, and a value of the photoelectron yield of the lunar surface material for photon energies above 40 eV may be computed.
Reasoner, D. L.↗
Lunar thermal measurements in conjunction with Project Apollo
Problems related to the feasibility of measuring lunar heat flow at the lunar surface are analyzed, and the findings which required that a drill be developed for lunar use are discussed. Numerical simulations were made of the in situ measurement of lunar thermal conductivity using a circular ring source of heat. The results of these simulations formed the basis for the criteria used in designing a subsurface thermal probe for ALSEP. Preliminary analyses are presented on the data obtained from the Apollo 15 and 17 missions.
Clark, S. P., Jr.↗
HNS/Teflon, a new heat resistant explosive
HNS/Teflon (90/10) is a new pressed explosive developed for use in the Apollo program. The major advantages of HNS/Teflon are (1) excellent thermal stability at elevated temperatures, (2) superior resistance to sublimation at high temperatures and low pressures and (3) ease of molding powder preparation, pressing and machining. The impact sensitivity of HNS/Teflon is between that of Comp B and Comp A-3 while its explosive performance is about the same as TNT. Under the severe environmental conditions of the moon's surface, this explosive successfully performed its intended function of generating seismic waves in the Apollo ALSEP and LSPE experiments. (Modified author abstract)
Heller, H.↗
Lunar atmospheric composition experiment
On the Apollo 17 mission, a miniature mass spectrometer, called the lunar atmospheric composition experiment (LACE), was carried to the moon as part of the Apollo lunar surface experiments package (ALSEP) to study the composition of and variation in the lunar atmosphere. The instrument was successfully deployed in the Taurus-Littrow valley with its entrance aperture oriented upward to intercept and measure the downward flux of gases at the lunar surface. Initial activation of the LACE instrument occurred on December 27, 1972, approximately 50 hr after sunset, and operation continued throughout the first lunar night. Sunrise brought a high background gas level and necessitated discontinuing operation during lunar daytime except for a brief check near noon. Near sunset, operation was resumed and continued throughout the night. This sequence was repeated for the second and third lunations.
J. H. Hoffman↗
Selenographic control
Evaluation of selenographic data obtained with use of different observational means requires the formulation of rigorous algorithms connecting the systems of coordinates, which the various methods have been referred to. The lunar principal axes of inertia are suggested as most appropriate for reference in lunar mapping and selenographic coordinate catalogues. The connection between the instantaneous axis of lunar rotation (involved in laser ranging, radar studies, astronomical observations from the surface of the moon and VLBI observations of ALSEPs), the ecliptic system of coordinates (which in reductions of observations was considered as fixed in space), the 'Cassini' mean selenographic coordinates (to which physical libration measures were referred), the lunar principal axes of inertia, and the invariable plane of the solar system is discussed.
Moutsoulas, M. D.↗
Observations of electrons at the lunar surface
Observations of electrons at the Apollo 12 and 15 sites by the ALSEP Solar Wind Spectrometer experiments showed qualitative differences. Measurements of photoelectron currents are compared to earlier predictions and calculations. A model describing the interaction of the solar wind and the lunar photoelectron layer is then developed. The observations at the Apollo 15 site are compared to the model. Then, Apollo 12 data are examined to determine the effects of the local lunar magnetic fields. Finally, it is predicted that electron pressure decreases upstream of the moon and in certain circumstances should cause an increase in proton density.
Goldstein, B. E.↗
Surface brightness temperatures at the Apollo 17 heat flow site - Thermal conductivity of the upper 15 cm of regolith
Lunar surface brightness temperatures derived as part of the Apollo 17 heat flow experiment are reported. Nighttime surface temperatures, calculated from the data provided by two thermocouples suspended about 15 cm above the lunar surface, are used to determine the conductivity profile of the upper 15 cm of regolith at the ALSEP site. The surface reaches a maximum temperature of 384 (plus or minus 6) K at lunar noon and cools to a minimum temperature of 102 (plus or minus 1.5 K) at the end of the lunar night. Conductivities of the order of .000015 W/cm-deg K are postulated for a 2-cm porous surface layer overlying more compact regolith material with conductivities in the range of .0001 to .00015 W/cm-deg K between 2 and 15 cm. A mean surface temperature of 216 (plus or minus 5) K is deduced from the thermocouple data. The 256 K temperature measured by the probe sensors at 130 cm thus indicates that a large mean temperature gradient exists at the Apollo 17 site.
Keihm, S. J.↗
The electric potential of the lunar surface
Acceleration and detection of the lunar thermal ionosphere in the presence of the lunar electric field yields a value of at least +10 V for the lunar electric potential for solar zenith angles between approximately 20 and 45 deg and in the magnetosheath or solar wind. An enhanced positive ion flux is observed with the ALSEP Suprathermal Ion Detector when a pre-acceleration voltage attains certain values. This enhancement is greater when the moon is in the solar wind as opposed to the magnetosheath.
Fenner, M. A.↗