ALBEDO - Relative brightness. It is the ratio of the amount of electromagnetic radiation reflected by a body to the amount of incident radiation.
ALPHA PARTICLE - A positive particle consisting of 2 protons and 2 neutrons. It is the nucleus of a helium atom.
ANGSTROM UNIT - A unit of length equal to 10-10 meters or 10-4 microns. It is approximately fourbillionths of an inch. In solids, such as salt, iron, aluminum, the distance between atoms is usually a few Angstroms.
APERTURE - A small opening such as a camera shutter through which light rays pass to expose film when the shutter is open.
ATTENUATION - Decrease in intensity usually of such wave phenomena as light or sound.
BASALT - A type of dark gray rock formed by solidification of molten material. The rocks of Hawaii are basalts.
BISTATIC RADAR - The electrical properties of the Moon's surface can be measured by studying the characteristics of radio waves reflected from the Moon. If the radio transmitter and receiver are located at the same place, the term monostatic radar is used. If they are located at different places, then bistatic is used. In the study of the Moon with bistatic radar, the transmitter is aboard the CSM and the receiver is on the Earth.
BRECCIA - A coarse-grained rock composed of angular fragments of pre-existing rocks.
BOUNDARY LAYER - The interaction layer between the solar wind bow shock and the magnetopause. (See text and figure 76.)
BOW SHOCK - The shock wave produced by the interaction of the solar wind with the Earth's magnetosphere. (See text and figure 76.)
CARTOGRAPHY - The production and science of accurately scaled maps.
CASSETTE - Photographic film container.
CISLUNAR - Pertaining to the space between the Earth and Moon or the Moon's orbit.
COLLIMATOR - A device for producing beams of parallel rays of light or other electromagnetic radiation.
COLORIMETRIC - Pertaining to the measurement of the intensities of different colors as of lunar surface materials.
COSMIC RAYS - Streams of very high energy nuclear particles, commonly protons, that bombard the Earth and Moon from all directions.
COSMOLOGY - Study of the character and origin of the universe.
CRATER - A naturally occurring hole. On Earth, a very few craters are formed by meteorites striking the Earth; most are caused by volcanoes. On the Moon, most craters were caused by meteorites. Some lunar craters were apparently formed by volcanic processes. In the formation of lunar craters, large blocks of rock (perhaps as large as several hundred meters across) are thrown great distances from the crater. These large blocks in turn from craters also-such craters are termed secondary craters.
CROSS-SUN - A direction approximately 90 degrees to the direction to the Sun and related to lunar surface photography.
CROSSTRACK - Perpendicular to the instantaneous direction of a spacecraft's ground track.
CRYSTALLINE ROCKS - Rocks consisting wholly or chiefly of mineral crystals. Such rocks on the Moon are usually formed by cooling from a liquid melt.
DIELECTRIC - A material that is an electrical insulator. Most rocks are dielectrics.
DIURNAL - Recurring daily. Diurnal processes on Earth repeat themselves every 24 hours but on the Moon repeat every 28 Earth days. The length of a lunar day is 28 Earth days.
DOPPLER TRACKING - A system for measuring the trajectory of spacecraft from Earth using continuous radio waves and the Doppler effect. An example of the Doppler effect is the change in pitch of a train's whistle and a car's horn on passing an observer. Because of this effect, the frequency of the radio waves received on Earth is charged slightly by the velocity of the spacecraft in exactly the same way that the pitch of a train's whistle is changed by the velocity of the train.
DOWN-SUN - In the direction that is directly away from the Sun and related to lunar surface photography.
EARTHSHINE - Illumination of the Moon's surface by sunlight reflected from the Earth. The intensity is many times smaller than that of the direct sunlight.
ECLIPTIC PLANE - The plane defined by the Earth's orbit about the Sun.
EFFLUENT - Any liquid or gas discharged from a spacecraft such as waste water, urine, fuel cell purge products, etc.; also any material discharged from volcanoes.
EGRESS - A verb meaning to exit or to leave. The popularization of this word has been attrib-uted to the great showman, P. T. Barnum, who reportedly discovered that a sign marked exit had almost no effect on the large crowds that accumulated in his exhibit area but a sign marked "to egress" led the crowds outdoors. In space terminology it means simply to leave the spacecraft.
EJECTA - Lunar material thrown out (as resulting from meteoroid impact or volcanic action).
ELECTRON - A small fundamental particle with a unit of negative electrical charge, a very small mass, and a very small diameter. Every atom contains one or more electrons. The proton is the corresponding elementary particle with a unit of positive charge and a mass of 1837 times as great as the mass of the electron.
EXOSPHERE - The outermost portion of the Earth's or Moon's atmosphere from which gases can escape into outer space.
FIELD - A region in which each point has a definite value such as a magnetic field.
FIELD OF VIEW - The region "seen" by the camera lens and recorded on the film. The same phrase is applied to such other equipment as radar and radio antennas.
FILLET - Debris (soil) piled against a rock; several scientists have suggested that the volume of the fillet may be directly proportional to the time the rock has been in its present position and to the rock size.
FLUORESCENCE - Emission of radiation at one wavelength in response to the absorption of energy at a different wavelength. Some lunar materials fluoresce. Most do not. The process is identical to that of the familiar fluorescent lamps.
FLUX - The rate of flow per unit area of some quantity such as the flux of cosmic rays or the flux of particles in the solar wind.
FRONT - The more or less linear outer slope of a mountain range that rises above a plain or plateau. In the U.S., the Colorado Front Range is a good example.
GALACTIC - Pertaining to a galaxy in the universe such as the Milky Way.
GAMMA - A measure of magnetic field strength; the Earth's magnetic field is about 50,000 gamma. The Moon's magnetic field is only a few gamma.
GAMMA-RAY - One of the rays emitted by radioactive substances. Gamma rays are highly penetrat-ing and can traverse several centimeters of lead.
GARDENING - The overturning, reworking, and changing of the lunar surface due to such processes as meteoroid impact, volcanic action, aging and such.
GEGENSCHEIN - A faint light covering a 20-degree field-of-view projected on the celestial sphere about the Sun-Earth vector (as viewed from the dark side of the Earth).
GEOCHEMICAL GROUP - A group of three experiments especially designed to study the chemical composition of the lunar surface remotely from lunar orbit.
GEODESY - Originally, the science of the exact size and shape of the Earth; recently broadened in meaning to include the Moon and other planets.
GEOPHONE - A small device implanted in the lunar surface during the deployment of the ASK to detect vibrations of the Moon from artificial and natural sources.
GEOPHYSICS - Physics of planetary bodies, such as the Earth and Moon, and the surrounding environment; the many branches include gravity, magnetism, heat flow, seismology, space physics, geodesy, meteorology, and sometimes geology.
GNOMON - A rod mounted on a tripod in such a way that it is free to swing in any direction and indicates the local vertical; it gives Sun position and serves as size scale. Color and reflectance scales are provided on the rod and a colorimetric reference is mounted on one leg.
GRADIENT - The rate of change of something with distance. Mathematically, it is the space rate of change of a function. For example, the slope of a mountain is the gradient of the elevation.
IMBRIAN AGE - Two methods of measuring age on the Moon are used. One provides the absolute age, in years, and is based on radioactivity. The other gives only relative ages. A very old event on the Moon is that which produced the Imbrium basin. The age of other geologic features can be determined with respect to the Imbrium event.
INGRESS - A verb meaning to enter. It is used in connection with entering the LM. See also "egress."
IN SITU - Literally, "in place", "in its original position". For example, taking photographs of a lunar surface rock sample "in situ" (as it lies on the surface).
LIMB - The outer edge of the apparent disk of a celestial body, as the Moon or Earth, or a portion of the edge.
LITHOLOGY - The character of a rock formation.
LUNATION - One complete passage of the Moon around its orbit.
MANTLE - An intermediate layer of the Moon between the outer layer and the central core..
MARE - A large dark flat area on the lunar surface (Lunar Sea). May be seen with the unaided eye.
MARIA - Plural of mare.
MASCONS - Large mass concentrations beneath the surface of the Moon. They were discovered only three years ago by changes induced by them in the precise orbits of space-craft about the Moon.
MASS SPECTROMETER - An instrument which distinguishes chemical species in terms of their different isotopic masses.
METEORITE - A solid body that has arrived on the Earth or Moon from outer space. It can range in size from microscopic to many tons. Its composition ranges from that of silicate rocks to metallic iron-nickel. For a thorough discussion see Meteorites by Brian Mason, John Wiley and Sons, 1962.
METRIC PHOTOGRAPHY - Recording of surface topography by means of photography, together with an approp-riate network of coordinates, to form the basis of accurate measurements and reference points for precise photographic mapping.
MICROSCOPIC - Of such a size as to be invisible to the unaided eye but readily visible through a microscope.
MINERALOGY - The science of minerals; deals with the study of their atomic structure and their general physical and chemical properties.
MONOPOLE - All known magnets have two poles, one south pole and one north pole. The existence of a single such pole, termed a monopole, has not yet been established but is believed by many physicists to exist on the basis of theoretical studies. Lunar samples have been carefully searched on Earth for the presence of monopoles.
MORPHOLOGY - The external shape of rocks in relation to the development of erosional forms or topo-graphic features.
MOULTON POINT - A theoretical point along the Sun-Earth line located 940,000 statute miles from the Earth at which the sum of all gravitational forces is zero.
NADIR - That point on the Earth (or Moon) vertically below the observer.
NAUTICAL MILE - It is 6,280 feet-19% larger than a "regular" mile. [sic: a nautical mile is usually defined as 6,076 feet.]
NEUTRON - An uncharged elementary particle that has a mass nearly equal to that of a proton and is present in all known atomic nuclei except hydrogen.
OCCULTATION - The disappearance of a body behind another body of larger apparent size. For example the occultation of the Sun by the Moon as viewed by an Earth observer to create a solar eclipse.
OZONE - Triatomic oxygen (03); found in significant quantities in the Earth's atmosphere.
P-10 - A gas mixture consisting of 90 percent argon, 9.5 percent carbon dioxide, and 0.5 percent helium used to fill the X-ray detectors of the X-Ray Fluorescence Experiment.
PANORAMA - A series of photographs taken from a point to cover 360 degrees around that point.
PENUMBRA - The part of a shadow in which the light (or other rays such as the solar wind) is only partially masked, in contrast to the umbra in which light is completely masked, by the intervening object.
PETROGRAPHY - Systematic description of rocks based on observations in the field (e.g. on the Moon), on returned specimens, and on microscope work.
PHOTOMULTIPLIER TUBE - An electron tube that produces electrical signals in response to light. In the tube, the signal is amplified to produce a measureable output current from very small quantities of light.
PLASMA - A gas composed of ions, electrons, neutral atoms and molecules. The interactions between particles is mainly electromagnetic. Although the individual particles are electrically positive or negative, the gas as a whole is neutral.
POSIGRADE - Lunar orbital motion in the direction of lunar rotation.
PRIMORDIAL - Pertaining to the earliest, or original, lunar rocks that were created during the time between the initial and final formation stages of the Moon.
PROTON - The positively charged constituent of atomic nuclei.
RADON - Isotopes of a radioactive gaseous element with atomic number 86 and atomic masses of 220 and 222 formed by the radioactive decay of radium.
RAY - Bright material that extends radially from many craters on the Moon; believed to have been formed at the same time as the associated craters were formed by impacting objects from space; usually, but not always, arcs of great circles. They may be several hundred kilometers long.
REGOLITH - The unconsolidated residual material that resides on the solid surface of the Moon (or Earth).
RETROGRADE - Lunar orbital motion opposite the direction of lunar rotation.
RILLE/RILL - A long, narrow valley on the Moon's surface.
RIM - Elevated region around craters and rilles.
SAMPLE - Small quantities of lunar soil or rocks that are sufficiently small to return them to Earth. On each mission several different kinds of samples are collected. Contingency sample consists of 1 to 2 pounds of rocks and soil collected very early in the surface operations so that at least some material will have been returned to Earth in the event that the surface activities are halted abruptly and the mission aborted. Documented sample is one that is collected with a full set of photographs to allow positive identification of the sample when returned to Earth with the sample in situ together with a complete verbal description by the astronaut. Comprehensive sample is a documented sample collected over an area of a few yards square.
S-BAND - A range of frequencies used in radar and communications that extends from 1.55 to 5 2 kilomegahertz.
SCARP - A line of cliffs produced by faulting or erosion.
SEISMIC - Related to mechanical vibration within the Earth or Moon resulting from, for example, impact of meteoroids on the surface.
SHOCKED ROCKS - Rocks which have been formed by or subjected to the extremes of temperature and pressure from impacts.
SOLAR WIND - Streams of particles (mostly hydrogen and helium) emanating from and flowing approximately radially outward from the Sun.
SPATIAL - Pertaining to the location of points in three-dimensional space; contrasted with temporal (pertaining to time) locations.
SPECTROMETER - An instrument which separates radiation into energy bands (or, in a mass spectrometer, particles into mass groups) and indicates the relative intensities in each band or group.
SPUR - A ridge of lesser elevation that extends laterally from a mountain or mountain range.
STELLAR - Of or pertaining to stars.
STEREO - A type of photography in which photographs taken of the same area from different angles are combined to produce visible features in three-dimensional relief.
SUPPLEMENTARY SAMPLE STOP - A stop added to a traverse after the stations are numbered. Mission planning continues through launch and the supplementary sample stops are inserted between normal traverse stations.
SUPRATHERMAL - Having energies greater than thermal energy.
SUBSATELLITE - A small unmanned satellite, deployed from the spacecraft while it is in orbit, designed to obtain various types of solar wind, lunar magnetic, and S-band tracking data over an extended period of time.
TALUS - Rock debris accumulated at the base of a cliff by erosion of material from higher elevation.
TEMPORAL - Referring to the passage or measurement of time.
TERMINATOR - The line separating the illuminated and the darkened areas of a body such as the Earth or Moon which is not self-luminous.
TERRA - Those portions of the lunar surface other than the maria; the lighter areas of the Moon. They are visible to the unaided eye.
TIDAL - Referring to the very small movement of the surface of the Moon or the Earth due to the gravitational attraction of other planetary bodies. Similar to the oceanic tides, the solid parts of the Earth's crust rise and fall twice daily about three feet. Lunar tides are somewhat larger. The tides of solid bodies are not felt by people but are easily observed with instruments.
TIMELINE - A detailed schedule of astronaut or mission activities indicating the activity and time at which it occurs within the mission.
TOPOGRAPHIC - Pertaining to the accurate graphical description, usually on maps or charts, of the physical features of an area on the Earth or Moon.
TRANSEARTH - During transit from the Moon to the Earth.
TRANSIENT - A short lived event that does not repeat at regular intervals, often occurring in a system when first turned-on and before reaching operating equilibrium. For example, the initial current surge that occurs when an electrical system is energized.
TRANSLUNAR - During transit from the Earth to the Moon.
TRANSPONDER - A combined receiver and transmitter whose function is to transmit signals automatically when triggered by a suitable signal. Those used in space are sensitive to radio signals.
UMBRA - The dark central portion of the shadow of a large body such as the Earth or Moon. Compare penumbra.
UP-SUN - Into the direction of the Sun and related to lunar surface photography.
URANIUM - One of the heavy metallic elements that are radioactive.
VECTOR - A quantity that requires both magnitude and direction for its specification, as velocity, magnetic force field and gravitational acceleration vectors.
WAVELENGTH - The distance between peaks (or minima) of waves such as ocean waves or electromagnetic waves.
X-RAY - Electromagnetic radiation of non-nuclear origin within the wavelength interval of 0.1 to 100 Angstroms (between gamma-ray and ultra-violet radiation). X-rays are used in medicine to examine teeth, lungs, bones, and other parts of the human body; they also occur naturally.
ZODIACAL LIGHT - A faint glow extending around the entire zodiac but showing most prominently in the neighborhood of the Sun. (It may be seen in the west after twilight and in the east before dawn as a diffuse glow. The glow may be sunlight reflected from a great number of particles of meteoritic size in or near the ecliptic in the planetoid belt).