Beyond the Atmosphere:
Early Years of Space Science
- APPENDIX K - GLOSSARY
-  This glossary
contains terms used in the narrative that may not be familiar to
some readers. For terms not in the glossary, the reader may find
the following helpful: William H. Allen, ed., Dictionary of
Technical Terms for Aerospace Use, NASA SP-7 (Washington,
- absorption coefficient.
- A numerical quantity that indicates the
relative effectiveness of a material substance such as a gas in
absorbing electromagnetic radiation.
- The quasi-steady radiant emission from
the upper atmosphere as distinguished from the sporadic
emission of the auroras. See discussion p. 66-67.
- alpha particle.
- The nucleus of the helium atom. The
alpha particle has a double positive charge.
- Varying with direction. Radiation that
varies in intensity or nature with direction is said to be
- anomalous propagation of sound.
- Propagation of sound waves that takes
appreciably longer than the expected time to reach an observer,
presumably because the sound did not follow a direct path from
the origin to the observer.
- applied science.
- Scientific research that is intended to
furnish information and data that will aid in achieving
specific practical applications or in developing a desired
- The point in the orbit of a satellite
at which the satellite is at its greatest distance from the
center of the earth.
- artificial satellite.
- A man-made satellite of the earth,
moon, or planet, as contrasted with a natural satellite like
the earth's moon.
- atmosphere of pressure.
- Roughly the pressure of the earth's
atmosphere at sea level. By definition, exactly 1.01325 x
105 newtons per square meter.
- The northern and southern lights-aurora
borealis and aurora australis-which are faint radiations that
at times are seen at high latitudes illuminating the night sky.
The aurora becomes especially pronounced at times of high solar
and magnetic activity.
- bands in a spectrum.
- Emission bands of molecules,
combinations of two or more atoms radiating in characteristic
groups of lines. In contrast, radiating atoms emit discrete
wavelengths, called emission lines of the atom.
- basic science.
- The effort to define basic science
almost invariably comes to grief. The first question to decide
is basic to what ? If basic to some ultimate applications, then
pure, applied, and mission-oriented science can all come under
the heading of basic. But, if basic to science itself is the
intended meaning, then it becomes a matter of what the
scientist himself perceives to be most fundamental, and indeed,
the phrase fundamental science is often used to convey this
- black body.
- A body that absorbs all wavelengths of
electromagnetic radiation. Conversely, when heated a black body
emits in all wavelengths.
- chromosphere of the
- A thin layer of relatively transparent
gases above the photosphere of the sun. See p. 364.
- collision frequency.
- The number of times per second a gas
particle collides with other particles of gas.
- control (of a vehicle).
- A means of orienting, steering, or
otherwise modifying the movement of a vehicle.
-  core of the earth.
- The central region of the earth,
extending to about 3400 kilometers from the center. The core is
very dense, consisting primarily of iron and iron sulfide. Its
outer portions are molten.
- Corona of the sun.
- The outer visible envelope of the sun,
lying above the chromosphere. See p.
- cosmic rays.
- Streams of high-energy subatomic
particles that travel the solar system and bombard the earth
from all directions. See pp. 67-69.
- A step-by-step process leading to a
climactic event such as the firing of a space launch
- crust of the earth.
- The outermost layer of the earth,
consisting of the continents and the floor of the ocean basins.
Beneath the crust is a mantle surrounding a dense core. While
the central part of the core appears to be solid, its outermost
portion underlying the mantle is molten.
- diffusive separation.
- Separation into individual component
parts as in an isothermal mixture of gases in a gravitational
field, where the lighter parts come to predominate at the top
and the heavier at the bottom-as cream separates from
- A system composed of two separated,
equal, electric or magnetic charges of opposite sign.
- Dipole field:
- see chap. 6, pp. 65-66 and fig. 3.
- A scientific discipline is an area of
investigation in which the investigators share a common
paradigm or group of paradigms, embracing a common body of
theory, and techniques and often instrumentation. See
discussion p. 12.
- dissociation of a
- Separation of a molecule into component
parts. If a molecule absorbs enough energy-from heating,
irradiation, or an electrical discharge, for example-it may
split into component parts. The reverse process, in which the
individual parts join to reproduce the original molecule, is
- doppler shift.
- Changes in wavelength caused by the
motion of a radiating source or of the receiver are called
doppler shifts in the radiated wavelengths. When a radiating
source, emitting either sound or electromagnetic waves, moves
either toward or away from an observer, the motion affects the
wavelengths as seen by the observer. If the motion of the
source is toward the observer, the wavelengths are shortened so
that sound is increased in pitch and light shifted toward the
blue end of the spectrum. Motion away from the observer
decreases the pitch of sound and shifts electromagnetic
radiations toward the red.
- The study of the gravitational field of
the earth and its relationship to the solid structure of the
planet. Also called physical geodesy. See p. 186.
- A fundamental particle of matter
carrying a single negative electric charge and having a mass 1/
1840 that of a proton.
- electron volt.
- The energy equivalent to that acquired
by an electron in falling through an electric potential of I
volt. It is equal to 1.60210 x 10-19
- An atom or molecule is said to be
excited when it has absorbed sufficient energy to raise it
above the normal or ground-level state, but not enough to
- The search for and study of
extraterrestrial life. See pp. 274, 352-53.
- exponential atmosphere.
- An atmosphere in which an increase in
altitude by a fixed height H always decreases the pressure and
density by a constant factor. See p. 60.
- forbidden line.
- An emission line corresponding to a
less probable wavelength than any given by the usual selection
rules. In emitting light a radiating atom obeys the laws of
quantum theory, in which certain rules, called selection rules, give the wavelengths an atom is most likely to
emit. Under certain conditions, however, an atom may emit a
less likely wavelength.
- The self-contained aggregate of stars,
nebulas, gases, and dust of which the sun and its planets are
members. The galaxy is one of billions of such systems, also
called galaxies, which collectively compose the
- Magnetic flux density of
10-5 gauss or 10-9 tesla.
-  geodesy.
- The science that deals mathematically
with the size and shape of the earth, the earth's external
gravity field, and surveys so precise that size and shape of
the earth must be taken into consideration. See pp.
- The figure of the earth as defined by
the level surface that over the oceans coincides with mean sea
level. See pp. 189-96.
- geomagnetic equator.
- The great circle of the earth lying
midway between the north and south poles of the earth's dipole
- geomagnetic latitude and
- Analogous to geographic latitude and
longitude, but referred to the dipole magnetic poles and
geomagnetic equator instead of to the geographic poles and
- geometrical geodesy.
- Study, by geometrical and astronomical
measurements, of the precise size and shape of the earth and
accurate location of points on the surface of the earth. See
- geopotential function.
- That function which at each point is
equal to an arbitrary constant minus the energy that would be
acquired by a unit mass in failing from rest at infinity to the
point in question. The gradient of the geopotential function,
which can be obtained by vector calculus, yields the earth's
- Layers of rocks that have been tilted
from their original horizontal stratification to form a huge
basin which then fills with sediments.
- The rate of change of a quantity with
distance in a specified direction is the gradient
of the quantity in that direction. When the term
gradient is used without specifying the direction, it is taken
to mean the rate of change of the quantity in question in the
direction of greatest rate of change.
- The process of directing the movements
of an aircraft, spacecraft, missile, or other vehicle. In
general such vehicles are equipped so that they can be
controlled to follow the guidance supplied to them.
- hydrated compound.
- A compound in which the molecules
contain water (H2O) or hydroxyl
radicals and protons (OH and H).
- A mathematical process used in the
calculus for deriving a function from its slope. The reverse
process, which yields the slope of a given function, is
- International Geophysical Year
- An internationally agreed on period,
July 1957 through December 1958, during which observation of
worldwide geophysical phenomena was greatly increased by
cooperative effort of participating nations. Activities were
continued through December 1959 as International Geophysical
Cooperation. See pp. 50-51.
- A charged atom or molecularly bound
group of atoms; sometimes also a free electron or other charged
subatomic particle. In the normal state atoms and molecules are
electrically neutral. An atom or molecule that acquires one or
more electrons becomes negatively charged and is called a
negative ion. If the particle loses one or more electrons it
becomes positively charged and is called a positive ion.
- ionization gauge.
- A gauge in which the effect of an
ambient gas on the electric current flow from a hot filament is
used to measure a property of the gas, such as charge
- Upper levels of the earth's atmosphere,
extending outward from about 70 kilometers altitude and
containing free electronically charged particles that reflect
radio waves. See pp. 64-65.
- Of constant temperature.
- isotropic radiation.
- Radiation that is of equal intensity in
- law of sines.
- In trigonometry, the law which states
that in a triangle the lengths of the sides are in proportion
to the sines of the opposite angles. Thus, if a, b, c are the
three sides of a triangle, and [Greek letters] alpha, beta,
gamma are the angles opposite to a, b, and
respectively, then a/sin alpha = b/sin beta = c/sin
- level surface.
- A surface to which the force of gravity
is everywhere perpendicular. pp
-  liftoff.
- The rising of a space launch vehicle
from its launching stand immediately after firing.
- The distance light travels in one year,
equal to 9.46055 x 1015
- line in a spectrum.
- Light emitted or absorbed at a discrete
wavelength by a radiating or absorbing atom.
- Lyman alpha line.
- The hydrogen atom is capable of
emitting (or absorbing) electromagnetic radiation in several
different series of lines. One of these is known as the Lyman
series. The longest wavelength of the Lyman series is at 1216
Å in the ultraviolet region, and is known as
Lyman alpha. The next longest wavelength of the series is
Lyman beta, then Lyman gamma, etc.
- magnetic storm.
- A disturbance in the earth's magnetic
field assumed to be caused by streams of particles and magnetic
fields from the sun.
- The region of space surrounding the
earth where the magnetic field plays a prominent, often
controlling, role relative to particle radiations found there.
- main stage.
- That stage of a launch vehicle-usually
the largest stage-that is used to lift the launch vehicle and
its payload to a high enough altitude that the remaining stages
of the vehicle can project the payload into orbit or into a
- man-machine relations.
- Relations between man and a
machine-such as an aircraft or spacecraft. The matching of
human characteristics to a machine so as to obtain maximum
efficiency or optimum conditions for operation is called
The integrated combination of
man and machine in an operating unit is called a
- mantle of the earth.
- The interior of the earth between about
3400 kilometers-the outer boundary of the core-and the
- mare (pl. maria).
- The maria are the dark regions of the
moon, once thought to be seas, hence the term mare from the
Latin for sea. The term is also applied to dark regions on
- mean free path.
- The average distance a gas particle
travels between successive collisions with other
- An elementary particle of mass
intermediate between the masses of the electron and
- Sometimes used to denote the middle
atmosphere, between the stratosphere and the ionosphere.
- The system of all galaxies. The
- A fast moving mass from space
traversing the atmosphere.
- A meteor that survived passage through
the atmosphere to strike the ground.
- A meteor or meteorite that is a few
hundreds of micrometers or less in diameter.
- Applied science carried out in support
of a specifically stated mission, such as providing the
necessary weaponry for naval warfare, maintaining adequate air
power, improving agriculture, developing natural resources, or
predicting the weather.
- monochromatic beam.
- A beam of radiation of a single
- A huge cloud of gas and dust in
- An electrically neutral particle of
mass essentially equal to that of the proton. A free neutron is
unstable, decaying (with a half life of about 12 minutes) to an
electron and a proton. (To say that the half life of a neutron
is 12 minutes means that of a group of N neutrons, N/2 of them
will decay before 12 minutes, and N/2 of them after 12
- oblate ellipsoid of revolution.
- The surface (or solid) obtained by
revolving an ellipse about its minor axis. Revolving the
ellipse about its major axis produces a prolate ellipsoid of
-  orbit.
- The closed path of a moving body or
particle around another object. See also trajectory.
- The gas whose molecules consist of
three oxygen atoms combined: O3.
- The region of the atmosphere in the
upper stratosphere and lower mesosphere where there are
appreciable quantities of ozone. See pp. 61, 63, fig. 1.
- For a satellite orbit, the nearest
point to the center of the earth.
- photosphere of the sun.
- The visible disk of the sun. See pp.
- The study of the gravitational field of
the earth and its relationship to the solid structure of the
planet. Also called dynamical geodesy. See p. 186.
- Pirani gauge.
- A pressure gauge in which the rate of
cooling of a heated filament by the ambient gas is used to
measure the pressure of the gas.
- A hot gas consisting of equal numbers
of positive and negative ions.
- polarized light.
- The wave theory of light pictures light
as electromagnetic vibrations in space, with electric and
magnetic vectors vibrating perpendicularly to each other.
Normally in a beam of light the orientations of the electric
and magnetic vectors are random. But if the electric (or
magnetic) vectors all vibrate parallel to a common plane, the
light in the beam is said to be plane polarized.
- programmatic science.
- Science carried out as part of a
specific program say, the atomic energy program, or the NASA
space science program as illustrations-and constrained (loosely
perhaps, but constrained nevertheless) to fit within the
general confines of the program.
- The nucleus of the hydrogen atom. The
proton carries a single positive electric charge, and has a
mass of 1.673 x 10-27
- A star that emits radiation in equally
- pure science.
- See uncommitted science.
- quantum theory.
- The theory that all electromagnetic
radiation is emitted and absorbed in quanta of energy equal to
hv, where h
is a constant called the Planck
constant after the propounder of quantum theory, and
v , is the frequency of the radiation.
- An exceedingly remote astronomical
object which appears like a blue star but which because of the
prodigious quantities of energy it radiates may turn out to be
- radiation belt.
- The portion of a planetary
magnetosphere that contains charged particle radiations unable
to escape because of the ambient magnetic field.
- radio galaxy.
- A galactic system that emits
prominently in radio wavelengths.
- The reverse of dissociation, with the
separated parts of a molecule rejoining to reproduce the
original molecule from which they came. For example, an
electron may recombine with a positive ion to form a neutral
atom or molecule; a positive ion may join with a negative ion
to form a neutral molecule; or two neutral atoms might
recombine to form a molecule.
- A quantitative measure of the affinity
of particles for recombining.
- reflection coefficient.
- A numerical quantity that gives the
proportions and manner in which a medium reflects incident
- The bending of electromagnetic rays by
properties of the medium traversed.
- relativistic particle.
- A particle moving sufficiently close to
the speed of light that effects of relativity, such as an
increase in mass or a slowing of time, become
- resonance line.
- The longest Wavelength that an atom can
emit or absorb.
- A rocket so mounted on a vehicle or
spacecraft that it fires in the direction opposite to the
motion of the vehicle or spacecraft. Retrorockets are used to
slow down the vehicles on which they are mounted.
- rocket stage.
- A self-propelled separable element of a
rocket vehicle. In a multistage rocket, each rocket unit fires
after the one behind it has used up its propellant and
(normally) been discarded. See page. p. 135.
-  satellite.
- An attendant body that revolves around
another body called the satellite's primary. By
custom, the bodies revolving around the sun are called
planets, not satellites, of the sun.
- scientific discipline.
- An area of scientific investigation in
which the investigators share a
common paradigm or group of
paradigms-embracing a common body of theory-and techniques and
often instrumentation that stem from the underlying theoretical
basis of the discipline.
- sectorial harmonic.
- One of a series of terms representing
the gravitational potential of the earth, in which the terms
exhibit pronounced variation with longitude. See
harmonic and p. 192.
- Seyfert galaxy.
- A spiral galaxy with a very compact,
highly luminous nucleus.
- solar wind.
- A continuous wind of charged particles
from the sun, blowing through interplanetary space.
- Devices, manned or unmanned, that are
intended to be placed in an orbit about the earth in space, or
on a trajectory to another celestial body.
- space launch vehicle.
- A combination of rocket stages, with
the necessary guidance and control equipment, used to project a
spacecraft into space.
- space probe.
- Spacecraft sent away from earth into
space. See. p. 153.
- space science.
- Scientific investigations made possible
or significantly aided by rockets, satellites, and space
probes. See chap. 1, especially, pp. 11-15.
- Electromagnetic radiation displayed or
visualized as a function of wavelength. Thus, the rainbow is
part of the spectrum of sunlight.
- spherical harmonic.
- One of a series of terms expressing the
geopotential function in sines and cosines of latitude and
longitude. See pp.
- See rocket stage.
- The layer of the earth's atmosphere
between about 16 and 50-55 kilometers altitude, lying above the
troposphere and extending to the stratopause; temperature
generally increases with altitude in the stratosphere. See
- sunspot cycle.
- A cycle of variation in the total
number and area of spots on the sun's surface, from a maximum
to a minimum with an average period of 11 years. Since magnetic
fields on the sun reverse with each such cycle, the period of a
complete cycle of spottedness-plus-magnetic-condition is 22
- superconducting cavity.
- When certain materials are brought
sufficiently close to absolute zero temperature, they become
perfect electrical conductors capable of sustaining circulating
electrical currents indefinitely without resistance losses. A
cavity in which such conditions of superconductivity are
maintained is a superconducting cavity. The resonance
properties of such superconducting cavities permit the
construction of highly accurate oscillators, or clocks.
- synchronous orbit.
- The orbit over the earth's equator at
an altitude of 36,000 km, in which the rate of revolution of
the satellite around the earth equals the rate of rotation of
the earth, so that the satellite always stays over the same
spot on the ground.
- Technical know-how; the knowledge and
ability to do things of a technical or engineering nature,
including the field of industrial arts.
- Measuring an object or phenomenon at a
distance. Radio is often used to transmit the measured data
from the point of measurement to a remote observer.
- In general, the path in three
dimensions (i.e. space) of a moving body. The word trajectory
is often used to mean flight
path. If the trajectory is a
closed path around another object like the earth, the
trajectory is called an orbit. When the path is
not closed, the word trajectory is usually used.
- The lowest portion of the atmosphere,
extending from the ground to the base of the
-  uncommitted or pure science.
- Science carried out simply to pursue
what the researcher considers to be important problems, the
solutions to which show promise of revealing significant
information about nature and the universe. Uncommitted or pure
science is not constrained by programmatic, applications, or
- The amount of rotational motion
possessed by it fluid is called its vorticity.
- zonal harmonic.
- One of a series of terms representing
the gravitational potential of the earth. Zonal harmonics
correspond to coefficients Jnm. for which
m = 0 and which depend only on latitude. See
harmonic and also