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Freeman, J. W., Jr.

Publications and source records attributed to Freeman, J. W., Jr..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

The Apollo lunar surface water vapor event revisited

On March 7, 1971, the first sunrise following the Apollo 14 mission, the Suprathermal Ion Detector Experiment (SIDE) deployed at the Apollo 14 site reported an intense flux of ions whose mass per charge was consistent with water vapor. The amount of water is examined, and the various acceleration processes, responsible for accelerating ions into the SIDE, are discussed. It is concluded that during most of the event the observed water vapor ions were accelerated by the negative lunar surface electric potential and, secondly, that this event was probably the result of mission associated water vapor, either from the LM ascent and descent stage rockets or from residual water in the descent stage tanks.

Freeman, J. W., Jr.↗
NASA NTRS1975

Dawn-dusk magnetosheath plasma asymmetries at 60 earth radii

A study of data from the Apollo lunar surface suprathermal ion detector experiment (Side) package shows that plasma flow and energy parameters in the dusk magnetosheath are much better correlated with geomagnetic activity than those in the dawn magnetosheath. This result is in agreement with a dawn-dusk asymmetry in the magnetosheath magnetic field and in the bow shock configuration. The different orientations between the mean interplanetary magnetic field direction and the shock normal for the magnetosheaths suggest an explanation of the difference in the plasma parameters on the two sides.

Fenner, M. A.↗
NASA NTRS1974

Observation of a driver gas-tangential discontinuity

A complete analysis of an interplanetary disturbance of Nov. 19, 1970 using the Apollo 12-SIDE (Suprathermal Ion Detector Experiment) is presented. The SIDE detectors were pointing at 26.3 degrees from the normal solar-wind direction during the observations. The data were least-squares fitted (using a parabolic hypersurface approximation) to a convected Maxwell-Boltzmann distribution function. The results of the fit combined with two other experiments showed a drastic change in the wind speed (from an steady 352 km/sec down to 219 km/sec), direction, and temperature. Except for a delta-function increase at the onset, the density remained constant. There was a considerable enhancement in the abundance of He and probably of heavier elements. The interplanetary magnetic field exhibited a jump of 21 gamma with a change in latitude from -56 to -76 degrees in solar ecliptic coordinates. It is concluded that the disturbance was due to the driver gas-tangential discontinuity of a solar flare-induced shock wave. The characteristic of the tangential discontinuity fit well with theoretical prediction.

Medrano, R. A.↗
NASA NTRS1973

Electric potential of the moon in the solar wind.

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 Apollo Lunar Surface Experiments Package Suprathermal Ion Detector Experiment when a preacceleration voltage attains certain values. This enhancement is greater when the moon is in the solar wind as opposed to the magnetosheath.

Freeman, J. W., Jr.↗
NASA NTRS1973

Observations of water vapor ions at the lunar surface.

The Apollo 14 Suprathermal Ion Detector Experiment observed a series of bursts of 48.6 eV water vapor ions at the lunar surface during a 14-hr period on Mar. 7, 1971. The maximum flux observed was 100 million ions per sq cm per sec per sr. These ions were also observed at Apollo 12, 183 km to the west. Evaluation of specific artificial sources including the Apollo missions and the Russian Lunokhod leads to the conclusion that the water vapor did not come from a man-made source. Natural sources exogenous to the moon such as comets and the solar wind are also found to be inadequate to explain the observed fluxes. Consequently, these water vapor ions appear to be of lunar origin.-

Freeman, J. W., Jr.↗
NASA NTRS1973

The electric potential of the moon in the solar wind

Acceleration and detection of the lunar thermal ionosphere in the presence of the lunar electric field yields a value of approximately +10 V for the lunar electric potential for solar zenith angles between 20 and 45 deg and in the magnetosheath or solar wind. The ion number density of the thermal ionosphere observed is compatible with a surface neutral number density of about 100,000 atoms/cu cm.

Freeman, J. W., Jr.↗
NASA NTRS1973

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.↗
NASA NTRS1973

Ions from the lunar atmosphere

The ionization of neutral atoms in the lunar atmosphere produces an ionosphere around the moon. These ions are accelerated by the interplanetary electric field and local surface fields to energies of 10 to 500 eV. The Suprathermal Ion Detector Experiment (SIDE) has been observing these ions from the lunar atmosphere. The observations have been divided into four categories based on the acceleration mechanism.

Lindeman, R.↗
NASA NTRS1972

Suprathermal ion detector results from Apollo missions.

This paper reviews briefly the knowledge of the ion environment of the moon as obtained from the Apollo Lunar Surface Experiments Package, Suprathermal Ion Detector Experiment. Topics to be discussed include: an interplanetary shock as seen from the lunar surface; bow shock and magnetosheath ions; magnetotail plasma seen during a magnetic disturbance; suprathermal ions seen during passage of the sunset and sunrise terminators; and ions associated with neutral gas clouds in the vicinity of the moon, and in particular the low energy mono-energetic spectrum of these ions. It is believed that these low energy spectra and some terminator ions can be explained by ion acceleration by the interplanetary electric field. This paper serves as catalog to references to these and other related phenomena.

Freeman, J. W., Jr.↗
NASA NTRS1972

Suprathermal ions near the moon.

This paper reports some preliminary results from the suprathermal ion detectors deployed on the lunar surface by the Apollo 12 and 14 astronauts. Salient features of these results include: the possible observation of sporadic venting of gas from the lunar surface; evidence for a prompt ionization and acceleration mechanism operating in the lunar exosphere; and a preliminary measurement yielding approximately 1 month for the e-folding decay time for the heavier components of the exhaust gases from the Apollo lunar landing systems. Prominent phenomena from which these results have been derived are: (1) ion bursts of low to moderate energy seen in conjunction with lunar sunrise and sunset; (2) solar wind energy ions detected on the night side of the moon; (3) ions of several keV energy seen during the lunar sunset to midnight quadrant of the moon's orbit; (4) magnetosheath ion flux enhancements; (5) ion bursts generated by the lunar impact of the Apollo 13 Saturn upper stage; and (6) geomagnetic storm associated ion flux variations in the earth's magnetotail.

Freeman, J. W., Jr.↗
NASA NTRS1972

Suprathermal ion detector experiment (lunar ionosphere detector)

The highly directional flow of energetic ions down the magnetosheath is described using three different look directions of the three Apollo 15 SIDE instruments. The effects of the interaction of the LM ascent-engine exhaust with the magnetosheath ions observed at the Apollo 15 site are discussed, and a preliminary analysis of the SIDE data for Apollo 12 and 14 is included.

Hills, H. K.↗
NASA NTRS1972

Energetic ion bursts on the nightside of the moon.

Recurrent bursts of positive ions are a persistent feature of the data from the Apollo 12 and Apollo 14 Alsep suprathermal ion detectors. Most remarkable is the occasional occurrence of these events when the Alsep is deep in the lunar night. One such series of bursts seen during December 1969 starting approximately 4.7 days before sunrise at the Apollo 12 Alsep site is reported. These bursts have durations ranging up to 14 min and recur with a highly variable frequency. The ions have differential energy spectra with narrow peaks. The peak energies range from 10 to 1250 eV but are found most frequently in the vicinity of 250 to 500 eV. They can be seen when the field of view of the detector looks as close as 16 deg to the antisolar direction. Data from the ion-mass analyzer indicate that, unlike some similar events seen on other occasions, these ions have mass per unit charge less than 10 amu/q, and hence, are probably of solar-wind origin.

Freeman, J. W., Jr.↗
NASA NTRS1972

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.↗
NASA NTRS1969

Magnetospheric wind.

Magnetospheric gusts of streaming positive ions in equatorial plane detected by ATS 1 synchronous satellite

Freeman, J. W., Jr.↗