Observatory phase in flyby mission operations encounter period.
Oberon
(NASA SP-7, 1965)
A satellite of Uranus orbiting at a mean
distance of 587,000 kilometers.
object glass
(NASA SP-7, 1965)
= objective.
object-oriented programming
(NASA Thesaurus)
The use of a programming language consisting of a sequence of commands
directed at objects.
objective
(NASA SP-7, 1965)
The lens or combination of lenses which receives light rays from an object
and refracts them to form an image in the focal plane of the eyepiece of an
optical instrument, such as a telescope. Also called object glass.
oblate spheroid
(NASA Thesaurus / NASA SP-7, 1965)
An ellipsoid of revolution,
the shorter axis of which is the axis of revolution. An ellipsoid of revolution, the longer axis of which is the axis of revolution,
is called a prolate spheroid. The earth is approximately an oblate spheroid.
oblique
(Global Land Information System Glossary - USGS)
An image taken with a camera or sensor with the axis intentionally directed
between the vertical and horizontal planes. A high oblique image includes
the horizon in the field of view, while a low oblique shows only the Earth's
surface.
oblique
(NASA SP-7, 1965)
Pertaining to, or measured on, an oblique projection, as oblique equator,
oblique pole, oblique latitude.
oblique coordinates
(NASA Thesaurus / NASA SP-7, 1965)
Magnitudes defining a point relative to
two intersecting nonperpendicular lines, called axes. See Cartesian
coordinates. The magnitude indicate the distance from each axis, measured along a parallel
to the other side. The horizontal distance is called the abscissa and the
other distance, the ordinate.
oblique projection
(NASA SP-7, 1965)
A map projection with an axis
inclined at an oblique angle to the plane of the equator.
oblique shock
(NASA SP-7, 1965)
= oblique shock wave.
oblique shock wave
(NASA SP-7, 1965)
A shock wave inclined at an oblique angle
to the direction of flow in a supersonic
flow field. Sometimes shortened to oblique shock. Compare normal
shock.
oblique shock waves
(NASA Thesaurus)
Shock waves attached to the bow and tail of an aerodynamic vehicle moving
faster than the speed of sound. The sides of the oblique shock waves form
the Mach cone.
obliqueness
(NASA Thesaurus)
The state of being neither perpendicular nor horizontal.
obliquity
(Solar System Dynamics Glossary - JPL)
The angle between the equatorial and orbital planes (or the rotational
and orbital poles) of a body. The obliquity of the ecliptic for the Earth
is the angle between the equatorial and ecliptic planes.
obliquity of the ecliptic
(NASA SP-7, 1965)
(symbol )
The angle between the plane of the ecliptic
(the plane of the earth's orbit) and the plane of the celestial
equator. The obliquity of the ecliptic is computed from the following formula:
23 degrees 27 minutes 08.26 seconds - 0.4684 (t - 1900) seconds, where t is
the year for which the obliquity is desired.
observability (systems)
(NASA Thesaurus)
The property of a system for which observations of the output variables
always is sufficient to determine the initial values of all state variables.
observed
(NASA SP-7, 1965)
In astronomy and navigation, pertaining to a value which has been measured
in contrast to one which is computed.
observed altitude
(NASA SP-7, 1965)
= true altitude.
observed magnitude
(Comet Glossary - JPL)
The observed magnitude of the comet represents the integrated brightness
of the comet's coma or head as seen from Earth. This is normally obtained
by comparing the comet's average surface brightness with that of defocused
stars (matching the comet's size) of known brightness. Because comets have
size (in contrast to stars which are pinpoints of light), a comet of a given
brightness will appear less obvious than a star of the same brightness.
obsidian
(Photoglossary of Volcanic Terms - USGS)
A dense volcanic glass, usually rhyolite in composition and typically black
in color. Compared with window glass, obsidian is rich in iron and magnesium;
tiny (<.005 mm) crystals of iron oxide within the glass cause its dark color.
Obsidian is often formed in rhyolite lava flows where the lava cools so fast
that crystals do not have time to grow. Glass, unlike crystals, has no regular
structure and therefore fractures in smooth conchoidal (curved) shapes. The
intersections of these fractures can form edges sharper than the finest steel
blades.
obstacle avoidance
(NASA Thesaurus)
The use of sensors utilizing laser triangulation as means of preventing
collisions, especially in the operation of roving vehicles on planetary surfaces.
occlusion
(NASA Thesaurus / NASA SP-7, 1965)
Specifically, the trapping of undisolved gas in
a solid during solidification.
occultation
(NASA Thesaurus / NASA SP-7, 1965)
The disappearance of a body behind another body of larger apparent size.
When the moon passes between the observer and a star, the star is said
to be occulted. The three associated terms, occultation, eclipse, and transit,
are exemplified by the motions of the satellites of Jupiter. An eclipse occurs
when a satellite passes into the shadow cast by the planet; an occultation
occurs when a satellite passes directly behind the planet; so that it could
not be seen even if it were illuminated; and a transit occurs when a satellite
passes between the observer and the planet, showing against the disk of the
planet.
ocean color scanner
(NASA Thesaurus)
A multispectral scanning radiometer which is geared to observe ocean features
such as chlorophyll, sediments, and topography in the invisible and thermal
ranges of radiation.
ocean dynamics
(NASA Thesaurus)
The study of the controlling forces in different ocean phenomena.
ocean temperature
(NASA Thesaurus)
Surface or subsurface temperature of an entire or specific region of an
ocean.
oceanography
(NASA Thesaurus)
The science that deals with the study and exploration of seas and oceans.
oceans
(NASA Thesaurus)
The continuous salt water bodies that surround the continents and fill
the Earth's great depressions.
Oct, Octn
(NASA SP-7, 1965)
International Astronomical Union abbreviations for Octans. See
constellation.
octal notation
(NASA SP-7, 1965)
Notation of numbers in the scale of eight.
The octal digits can be represented by the eight possible combinations of
three binarydigits.
The interval between any two frequencies
having the ratio of 1:2. The interval in octaves between any two frequencies is the logarithm to
the base 2 (or 3.322 times the logarithm to the base 10) of the frequency
ratio.
Octn
(NASA SP-7, 1965)
International Astronomical Union abbreviations for Octans. See
constellation.
ocular
(NASA SP-7, 1965)
Pertaining to or in relation with the eye.
oculogravic illusion
(NASA SP-7, 1965)
= agravic illusion.
oculogyral illusion
(NASA SP-7, 1965)
The apparent movement of an image in space in the same direction as that
in which one seems to be turning when the semicircular
canals are stimulated.
Flicker control, especially as applied to rockets. Used for bang-bang control.
offgassing
(NASA Thesaurus)
The relative high mass loss characteristic of many nonmetallic materials
upon initial vacuum exposure.
ogive
(NASA Thesaurus / NASA SP-7, 1965)
A body of revolution formed by rotating a circular arc about an axis that
intersects the arc; the shape of this body; also, a nose of a projectile or
the like so shaped. Typically, an ogive has the outline of a Gothic arch, although by definition
it may be rounded rather than pointed. See tangent
ogive.
ohm
(NASA SP-7, 1965)
(abbr )
The unit of electrical resistance; the resistance between two points of a
conductor when a constant difference of potential of 1 volt,
applied between these two points, produces in the conductor a current of 1
ampere (the conductor not being the source of
any electromotive force).
ohmic heating
(Plasma Physics and Fusion Energy Glossary)
Heating that results from the flow of current through a medium with electrical
resistance. In plasmas subjected to ohmic heating, ions are heated almost
entirely by transfer of energy from the hotter, more mobile electrons.
ohmic heating
(NASA SP-7, 1965)
In plasma physics, the energy
imparted to charged particles as they respond to an electric field and make
collisions with other particles. The name was chosen for its similarity to the heat generated in an ohmic
resistance due to the collisions of the charge carriers in their medium.
ohmmeters
(NASA Thesaurus)
Direct-reading instruments for measuring electrical resistance. They are
provided with a scale, usually graduated in either ohms, megohms, or both.
If the scale is graduated in megohms, the instrument is usually called a megohmmeter.
Ohms law
(NASA Thesaurus)
The current in an electric circuit is inversely proportional to the resistance
of the circuit and is directly proportional to the electromotive force in
the circuit. Ohm's law applies, strictly speaking, only to linear constant-current
circuits.
oil fields
(NASA Thesaurus)
Surface boundary of an area from which petroleum is obtained; may correspond
to an oil pool or may be circumscribed by political or legal limits.
oilcan
(NASA SP-7, 1965)
Of a sheet-metal skin or of other covering, to snap in and out between
rows of rivets or between other places of support in a fashion like that of
the bottom of an oilcan.
Omega Navigation System
(NASA Thesaurus)
A very long distance navigation system operating at approximately 10 kHz
(kilohertz), in which hyperbolic lines of position are determined by measurement
of the difference in travel time of continuous wave signals from two transmitters
separated by 5000 nmi (nautical miles) to 6000 nmi (9000 km {kilometers} to
11000 km) or in which changes in distances from the transmitters are measured
by counting RF (radio frequency) wavelengths in the space of lanes as the
vehicle moves from a known position, the lanes being counted by phase comparison
with a stable oscillator aboard the vehicle.
omni
(NASA SP-7, 1965)
1. A prefix meaning all , as in omnidirectional.
2. Short for omnirange.
omnidirectional range
(NASA SP-7, 1965)
= omnirange.
omnirange
(NASA SP-7, 1965)
A radio navigation system providing a direct indication of the bearing
of the omnirange facility from the vehicle. Usually used in combination with
distance measuring equipment.
Also called omnidirectional range.
on-line systems
(NASA Thesaurus)
Systems where the input data enters the computer directly from the point
of origin and/or in which output data is transmitted directly to where it
is used.
onboard data processing
(NASA Thesaurus)
Processing of acquired data aboard an aircraft, satellite, etc., rather
than transmission to ground stations for processing.
one-way
(Space Flight Glossary - JPL)
Communications mode consisting only of downlink received from a spacecraft.
Oort cloud
(NASA Thesaurus)
A region of millions of comets between 30,000 and 100,000 A.U. from the
sun. Comets are perturbed out of the Oort cloud by passing stars and fall
into the inner solar system. The Oort cloud was named after the Dutch astronomer,
Jan Hendrik Oort.
opacity
(Imagine the Universe Dictionary - NASA GSFC)
A property of matter that prevents light from passing through it; non-transparent.
The opacity or opaqueness of something depends on the frequency of the light.
A plasma through which an electromagnetic
wave cannot propagate and is either absorbed or reflected. In general, a plasma is opaque for frequencies below the plasma frequency.
The fact that a plasma is opaque over a certain frequency range will change
the radiation properties within that frequency range. Any radiation emitted
within the volume of the plasma is quickly absorbed. In this opaque region,
therefore, the plasma can only radiate from its surface.
OPCT
(Space Flight Glossary - JPL)
Operations Planning and Control Team, "OPSCON."
open circuit voltage
(NASA Thesaurus)
The steady state or equilibrium potential of an electrode in absence of
external current flow to or from the electrode.
A former NASA project now absorbed by the International Solar Terrestrial
Physics Project. It proposed a simultaneous study of plasmas in the Earth's
magnetosphere and neighborhood using the following four instrumented spacecraft:
interplanetary physics laboratory (IPL), geomagnetic tail laboratory (GTL),
polar plasma laboratory (PPL), and equatorial magnetosphere laboratory (EML).
Used for Origin of Plasmas in Earth Neighborhood.
open system
(NASA SP-7, 1965)
A system that provides for the body's metabolism in an aircraft or spacecraft
cabin by removal of respiratory products and of waste from the cabin and by
use of stored food and oxygen. Compare closed
system.
In computer operations, a word on which an
operation is to be performed.
operating costs
(NASA Thesaurus)
The price for operating a system exclusive of the cost of the system itself.
operating ratio
(NASA SP-7, 1965)
= computing efficiency.
operating systems (computers)
(NASA Thesaurus)
Computer programs for expediting, controlling and/or recording computer
use by other programs. Used for executive systems (computers).
operative temperature
(NASA SP-7, 1965)
In the study of human bioclimatology, one of several parameters devised
to measure the air's cooling effect upon a human body. It is equal to the
temperature at which a specified hypothetical environment would support the
same heat loss from an unclothed, reclining human body as the actual environment.
In the hypothetical environment, the wall and air temperatures are equal and
the air movement is 7.6 centimeters per second. From experiment it has been
found that the operative temperature
where tr is the mean radiant temperature; ta
is the mean air temperature; ts is the mean skin temperature
(all in degrees C); and v is the airspeed in centimeters per second.
Oph, Ophi
(NASA SP-7, 1965)
International Astronomical Union abbreviations for Ophiuchus.
See constellation.
Ophiuchi clouds
(NASA Thesaurus)
Dense concentrations of interstellar gas near the stars Rho Ophiuchi and
Zeta Ophiuchi.
A configuration in which a celestial body is in the opposite direction
(180 degrees) from the sun as seen from another body located along the line
between them. (e.g. when Mars, Earth and the Sun are located along a straight
line, Mars is in opposition as seen from Earth.)
opposition
(NASA SP-7, 1965)
1. The situation of two celestial bodies
having either celestial longitudes
or sidereal hour angles differing
by 180 degrees. The term is usually used only in relation to the position
of a planet or the moon from the sun. Compare conjunction.
2. The situation of two periodic quantities differing by half a cycle.
opposition surge
(Galileo Project Glossary - JPL)
An increase in brightness as an observer approaches the line between the
sun and a target. The strength of the surge is an indicator of small-scale
surface texture.
optical activity
(NASA Thesaurus)
Ability to rotate the plane of vibration of polarized light to the right
or left.
optical air mass
(NASA SP-7, 1965)
(symbol m)
A measure of the length of the path through the atmosphere to seal level traversed
by light rays from a celestial body, expressed as a multiple of the path length
for a light source at the zenith. Originally called, simply, air mass.
Also called airpath.
optical axis
(NASA SP-7, 1965)
Of an antenna, a line parallel to, but offset from, the electrical axis
of an antenna. This axis is offset by the distance necessary to have the optical sighting
device removed from the electrical center of the antenna.
optical bistability
(NASA Thesaurus)
A property of certain materials in which a nonlinear response is exhibited
when under the influence of an external driving coherent light, thereby allowing
these materials to behave like optical switches.
optical computers
(NASA Thesaurus)
Computers which use light rather than electricity for all or part of their
operation. They perform multiple tasks in parallel as opposed to electronic
computers which would perform those tasks sequentially. Such increased processing
capability makes them suited for aerospace problems which involve systems
that have a large number of degrees of freedom, i.e., large space structures,
pattern recognition activity, and robotics.
optical control
(NASA Thesaurus)
The control of light sensitive devices by means optical radiation.
optical countermeasures
(NASA Thesaurus)
Equipment for exploiting the vulnerability of laser guided weapon systems.
optical density
(NASA Thesaurus)
The image intensity or density in terms of, or measured by, a reflectance
densitometer.
optical density
(NASA SP-7, 1965)
= photographic transmission density.
optical depth
(Planetary Rings Glossary - ARC)
Optical depth is a measure of the transparency of a ring system. When a
ring is "optically thick" (i.e., the optical depth is large), the ring is
nearly opaque and very little light passes through. When a ring is "optically
thin" (i.e., the optical depth is small), very little material is present
and most of the light passes through.
optical depth
(NASA SP-7, 1965)
= optical thickness.
optical double star
(NASA SP-7, 1965)
Two stars in nearly the same line of sight but differing greatly in distance
from the observer, as distinguished from a physical
double star.
optical haze
(NASA SP-7, 1965)
= terrestrial scintillation.
optical line of sight
(NASA SP-7, 1965)
The generally curved path of visible light through the atmosphere. Often used erroneously for geometrical line of sight.
optical mass
(NASA SP-7, 1965)
= laser.
optical path
(NASA SP-7, 1965)
1. = line of sight.
2. The path followed by a ray of light through an optical system.
optical pumping
(Plasma Physics and Fusion Energy Glossary)
In laser physics, this denotes the process in which absorbed light is stored
in the laser medium. If the absorption & storage process creates a population
inversion, laser action can occur (and extract the energy stored by optical
pumping in the form of laser emission).
optical pyrometer
(NASA SP-7, 1965)
A device for measuring the temperature
of an incandescent radiating body by comparing its brightness
for a selected wavelength interval within the visible
spectrum with that of a standard source; a monochromatic radiation pyrometer.
Temperatures measured by optical pyrometers are known as brightness temperatures
and except for black bodies are less than the true temperatures.
optical relay systems
(NASA Thesaurus)
Systems using photocouplers in which the output device is a light sensitive
switch that provides the same on and off operations as the contacts of a relay.
optical scanners
(NASA Thesaurus)
A light source and phototube combined as a single unit for scanning moving
strips of paper or other materials in photoelectric side-register control
systems.
optical slant range
(NASA Thesaurus / NASA SP-7, 1965)
The horizontal distance in a homogeneous
atmosphere for which the attenuation
is the same as that actually encountered along the true oblique path.
optical thickness
(NASA Thesaurus)
A measure of the cumulative attenuation of electromagnetic radiation in
transit through a medium. In calculations of the transfer of radiant energy,
the mass of a given absorbing or emitting material lying in a vertical column
of unit cross sectional area and extending between two specific levels. Used
for optical depth.
optical thickness
(NASA SP-7, 1965)
Specifically, in calculations of the transfer of radiant
energy, the mass of a given absorbing or emitting material lying in a
vertical column of unit cross-sectional area and extending between two specific
levels. Also called optical depth. If z1 and z2 are the lower and upper limits, respectively,
of a layer in which the variation of a density
of some absorbing or emitting substance is given as a function of height z,
then the quantity
is called the optical thickness of that substance within that particular layer.
optical turbulence
(NASA SP-7, 1965)
Irregular and fluctuating gradients of optical refractive
index in the atmosphere. Optical turbulence is caused mainly by mixing of air of different temperatures,
and particularly by thermal gradients which are sufficient to reverse the
normal decrease in density with altitude, so that convection occurs.
optical waveguides
(NASA Thesaurus)
Any device or component that guides optical energy.
optically effective
atmosphere
(NASA SP-7, 1965)
That portion of the atmosphere lying below
the altitude from which scattered light at twilight still reaches the observer
with sufficient intensity to be discerned. Also called effective atmosphere.
The top of this region lies between 50 and 60 kilometers.
optics
(NASA Thesaurus)
Branch of physical science concerned with the transmission, generation,
manipulation, and detection of electromagnetic radiation in the wavelength
range from vacuum ultraviolet to the far infrared.
Pertaining to a trajectory, path, or control
motion, one that minimizes or maximizes some quantity or combination of quantities
such as fuel, time, energy, distance, heat transfer, etc. This optimum condition,
or path, is commonly calculated by a type of mathematics known as calculus
of variations.
optimization
(NASA Thesaurus)
The procedure used in the design of a system to maximize or minimize some
performance index. May entail the selection of a component, a principle of
operation, or a technique.
optoelectronic devices
(NASA Thesaurus)
Electronic devices combining optic and electric ports.
optogalvanic spectroscopy
(NASA Thesaurus)
A method of obtaining absorption spectra of atomic and molecular species
in flames and electrical discharges by measuring voltage and current changes
upon laser irradiation.
OR
(NASA SP-7, 1965)
1. The logical operator which has the property that A or B is true if either
A is true or B is true.
2. In Boolean algebra, the operation
of union.
OR-circuit
(NASA SP-7, 1965)
= OR-gate.
OR-gate
(NASA SP-7, 1965)
A gate whose output is energized when any one
or more of the inputs is in its prescribed state. An OR-gate performs the
function of the logical inclusive-OR , of Boolean
algebra.
orbit
(NASA SP-7, 1965)
1. The path of a body or particle under the influence of a gravitational
or other force. For instance, the orbit of a celestial
body is its path relative to another body around which it revolves. Orbit is commonly used to designate a closed path and trajectory to denote
a path which is not closed. Thus, the trajectory of a sounding rocket, the
orbit of a satellite.
2. To go around the earth or other body in an orbit, sense 1.
orbit insertion
(NASA Thesaurus)
The process by which a spacecraft enters into a desired orbit around a
celestial body.
orbit spectrum utilization
(NASA Thesaurus)
Telecommunication techniques in spectrum conservation for reducing user
costs.
orbit transfer vehicles
(NASA Thesaurus)
Concept of propulsive (velocity producing) rockets or stages for use with
crew transfer modules, manned sortie modules, or other payloads. Used for
OTV.
orbital
(NASA SP-7, 1965)
Taking place in orbit, as orbital refueling , orbital launch
, or pertaining to an orbit as orbital plane.
orbital elements
(NASA Thesaurus / NASA SP-7, 1965)
A set of seven parameters defining the orbit of a
body attracted by a central, inverse-square force. Several different sets of parameters have been used. For artificial satellites
the elements usually given are: longitude of the ascending node, ;
inclination of the orbit plane, i; argument of perigee, ;
eccentricity, e; semimajor axis, a; mean anomaly, M; and epoch, t0
.
The predicted lifetime of a satellite in orbit, usually based on such criteria
as solar flux density, atmospheric density, the lessening of the eccentricity
of elliptical orbits, or the gravitational effects of the sun or the moon.
orbital motion
(NASA SP-7, 1965)
Continuous motion in a closed path such as a circle or an ellipse.
orbital period
(Solar System Dynamics Glossary - JPL)
The time required for an object to make a complete revolution along its
orbit. For example, the orbital period for a typical main-belt asteroid is
about 4 years.
Systems of two or more satellites (including planets) that orbit the same
primary and whose orbital mean motions are in a ratio of small whole numbers.
orbital servicing
(NASA Thesaurus)
The replenishing of propellants, pressurants, coolants, and the replacement
of modules and experiments, during some phase of a spacecraft flight to extend
the mission and lifetime, or change the payloads.
orbital velocity
(NASA Thesaurus / NASA SP-7, 1965)
1. The average velocity at which an earth satellite
or other orbiting body travels around its primary.
Compare separation velocity.
2. The velocity of such a body at any given point in its orbit, as in
its orbital velocity at the apogee is less than at the perigee.
3. = circular velocity.
orbiting
(NASA SP-7, 1965)
Of a spacecraft, in orbit about the earth
or other spatial body, as in an orbiting astronomical laboratory.
orbits
(NASA Thesaurus)
The paths of bodies or particles under the influence of a gravitational
or other force. Used for orbital motion and periodic orbits.
order of magnitude
(NASA SP-7, 1965)
A factor of 10. Compare octave, magnitude.
Two quantities of the same kind which differ by less than a factor of
10 are said to be of the same order of magnitude. Order of magnitude is used
loosely by many writers to mean a pronounced difference in quantity but the
difference may be much less or much more than a factor of 10.
order of reflection
(NASA SP-7, 1965)
The number of hops, or trips, to the ionsphere and back to earth, that
a radio wave makes in traveling from one
point to another.
ordinary ray
(NASA SP-7, 1965)
That magnetoionic wave component deviating the least, in most of its propagation
characteristics, relative to those expected for a wave
in the absence of the earth's magnetic field. More exactly, if at fixed electron
density, the direction of the earth's magnetic field were rotated until its
direction is transverse to the direction of phase propagation, the wave component
whose propagation is then independent of the magnitude of the earth's magnetic
field. Also called ordinary-wave component. See magnetic
double refraction, magnetoionic theory.
ordinary wave component
(NASA SP-7, 1965)
= ordinary ray.
organ
(NASA SP-7, 1965)
A portion or subassembly of a computer which
constitutes the means of accomplishing some inclusive operation or function
(e.g., arithmetic organ).
organic charge transfer
salts
(NASA Thesaurus)
Organic compounds exhibiting temperature-dependent electrical, magnetic,
and heat transfer properties.
organic chemistry
(NASA Thesaurus)
The study of the composition, properties, structure, and reactions of carbon-based
compounds, specifically hydrocarbons and their derivatives, and normally excluding
carbon oxides, metallic carbonates, carbides, and carbon-sulfur and carbon-nitrogen
compounds.
organic compounds
(Galileo Project Glossary - JPL)
Complex chemical compounds that contain carbon
organic peroxides
(NASA Thesaurus)
Organic compounds containing radical groups combined with oxides in which
two atoms of oxygen are linked together, e.g., diethyl peroxide.
organic solids
(NASA Thesaurus)
Solid materials composed of organic materials.
Ori, Orio
(NASA SP-7, 1965)
International Astronomical Union abbreviations for Orion. See
constellation.
origin
(NASA SP-7, 1965)
The reference from which measurement begins.
Orio
(NASA SP-7, 1965)
International Astronomical Union abbreviations for Orion. See
constellation
Originally, at right angles; later generalized to mean the vanishing of
a sum (or integral) of products. The cosine of the angle between two vectors V1 and V2
with the respective components x1, y1, z1,
and x2, y2, z2 is proportional to the sum
of products x1x2 + y1y2 + z1z2.
Hence, if the vectors are perpendicular, the latter sum equals zero. For this
reason any two series of numbers (x1, x2, ... Xn)
and (y1, y2, ...yn) is said to be orthogonal
if
.
orthogonal antennas
(NASA SP-7, 1965)
In radar, a pair of transmitting and receiving antennas,
or a single transmitting-receiving antenna, designed for the detection of
a difference in polarization between the
transmitted energy and the energy returned from the target.
A set of functions, any two of which, by analogy to orthogonal vectors,
vanish if their product is summed by integration over a specified interval.
For example, f(x) and g(x) are orthogonal in the interval x = a to x =
b if the integral of a to b f of x g of x d x equals zero
The functions are also said to be normal if
The most familiar examples of such functions, many of which have great importance
in mathematical physics, are the sine and cosine functions between zero and
2.
orthogonic
(NASA SP-7, 1965)
Pertaining to a state in which the spatial variations of a quantity have
two planes of symmetry at right angles to each other.
osciducer
(NASA SP-7, 1965)
A transducer in which information pertaining
to the stimulus is provided in the form of deviation from the center frequency
of an oscillator.
oscillation
(NASA Thesaurus / NASA SP-7, 1965)
1. Fluctuation or vibration on each side of a mean value or position.
2. Half an oscillatory cycle, consisting of a fluctuation or vibration in
one direction; half a vibration.
3. The variation, usually with time, of the magnitude of a quantity with respect
to a specified reference when the magnitude is alternately greater and smaller
than the reference.
oscillator
(NASA Thesaurus / NASA SP-7, 1965)
A nonrotating device for producing alternating current.
oscillator strengths
(NASA Thesaurus)
A quantum mechanical analog of the number of dispersion electrons having
a given natural frequency in an atom, used in an equation for the absorption
coefficient of a spectral line.
oscillatory wave
(NASA SP-7, 1965)
A wave in which only the form advances, the individual
particles moving in closed orbits, as ocean waves in deep water.
oscilloscope
(NASA Thesaurus / NASA SP-7, 1965)
1. An instrument for producing a visual representation of oscillations
or changes in an electric current.
2. Specifically, a cathode-ray oscilloscope. The face of the cathode-ray tube used for this representation is called
a scope or screen.
The ellipse that a satellite would follow
after a specific time t (the epoch of
osculation) if all forces other than central inverse-square forces ceased
to act from time t on. An osculating orbit is tangent to the real, perturbed, orbit and has the
same velocity at the point of tangency.
OSO
(AS&T Dictionary)
Orbiting Solar Observatories-- A series of eight Sun observing satellites
launched from 1962 to 1975.
OSO-8
(NASA Thesaurus)
One of a series of NASA orbiting solar observatories developed mainly for
solar research. Used for OSO-J.
OSR
(Space Flight Glossary - JPL)
Optical Solar Reflector, thermal control component onboard a spacecraft.
OSS-1 payload
(NASA Thesaurus)
Experiment package flown aboard the Space Shuttle STS-3 in 1982 which was
sponsored by the NASA Office of Space Sciences from which the acronym is derived.
OSSA
(Space Flight Glossary - JPL)
Office Of Space Science and Applications, NASA.
OSTA-1 payload
(NASA Thesaurus)
Spaceborne experiments flown aboard the Space Shuttle STS-2 in 1981 which
was sponsored by the NASA Office of Space & Terrestrial Applications from
which the acronym is derived. Used for Office of Space & Terrestr Applic Payloads.
OSTA-3 payload
(NASA Thesaurus)
Spaceborne systems flown aboard the Space Shuttle STS-17, sponsored by
the NASA Office of Space & Terrestrial Applications from which the acronym
is derived. The systems included the feature identification and location experiment-1
(FILE-1), the measurement of atmospheric pollution from satellite (MAPS),
the imaging camera-B, and the large format camera/attitude reference system
(LFC/ARS). Used for Office of Space & Terrestr Applic Payloads.
osteoporosis
(NASA Thesaurus)
A medical condition whose chief symptom is the loss of internal bone mass.
otitic barotrauma
(NASA SP-7, 1965)
= aero-otitis media.
OTM
(Space Flight Glossary - JPL)
Orbit Trim Maneuver, spacecraft propulsive maneuver.
otolith
(NASA SP-7, 1965)
A small calcareous concretion located in the inner ear which plays a part
in the mechanism or orientation.
otolith organs
(NASA Thesaurus / NASA SP-7, 1965)
Structures of the inner ear (utricle and saccule) which responds to linear
acceleration and tilting.
out of phase
(NASA SP-7, 1965)
The condition of two or more cyclic motions
which are not at the same part of their cycles at the same instant. Also called
out of step. Compare in phase. Two or more cycles motions which are at the same part of their cycles
at the same instant are said to be in phase or in step.
out of step
(NASA SP-7, 1965)
= out of phase.
outer atmosphere
(NASA SP-7, 1965)
Very generally, the atmosphere at a great distance from the earth's surface;
an approximate synonym for exosphere.
outer planets
(NASA SP-7, 1965)
The planets with orbits larger than that of Mars: Jupiter, Saturn, Uranus,
Neptune, and Pluto.
Areas or groups of rocks surrounded by rocks of older age. Used for klippen.
outliers (statistics)
(NASA Thesaurus)
In sets of data values so far removed from other values in the distribution
that their presence cannot be attributed to the random combination of change
causes.
output
(NASA Thesaurus / NASA SP-7, 1965)
1. The yield or product of an activity furnished by man, machine, or a
system.
2. Power or energy delivered by an engine, generator, etc.
3. The electrical signal which emanates from a
transducer and which is a function of the
applied stimulus. Compare input. The quantity represented by the signal may be given in terms of electrical
units, frequency, or time.
output unit
(NASA SP-7, 1965)
In computer terminology, a unit which delivers information from the computer
to an external device or from internal storage
to external storage.
overall heat-transfer
coefficient
(NASA SP-7, 1965)
(symbol U ). The value U , in British
thermal units per hour per square foot per degrees F in the equation Q
= UA(t) where Q is
heat flow per unit time; A is area; and t is temperature.
overexpanding nozzle
(NASA SP-7, 1965)
A nozzle in which the fluid
is expanded to a lower pressure than the external pressure. An overexpanding nozzle has an exit area larger than the optimum.
Overhauser effect
(NASA Thesaurus)
In atomic physics, a radio frequency field applied to a substance in an
external magnetic field, whose nuclei have spin 1/2 and which has unpaired
electrons at the electron spin resonance frequency. This results in polarization
of the nuclei as great as if the nuclei had the much larger electron magnetic
moment.
overpressure
(NASA Thesaurus)
(1) The pressure resulting from the blast wave of an explosion. It is referred
to as positive when it exceeds atmospheric pressure and negative during the
passage of the wave when resulting pressures are less than atmospheric pressure.
(2) The transient pressure, usually expressed in pounds per square inch, exceeding
existing atmospheric pressure manifested in the blast wave from an explosion.
During some period of the passage of the wave past a point, the overpressure
is negative.
overshoot
(Global Land Information System Glossary - USGS)
That portion of an arc (line) digitized past its intersection with another
arc.
OWLT
(Space Flight Glossary - JPL)
One-Way Light Time, elapsed time between Earth and spacecraft or solar
system body.
oxazole
(NASA Thesaurus)
Compounds that contain a five-membered heterocyclic ring containing one
nitrogen and one oxygen atom.
oxidant
(NASA SP-7, 1965)
= oxidizer.
oxidation
(NASA Thesaurus)
A reaction in which electrons are removed from a reactant. Sometimes, more
specifically the combination of a reactant with oxygen.
oxidation-reduction
reactions
(NASA Thesaurus)
An oxidizing chemical change, where an element's positive valence is increased
(electron loss), accompanied by a simultaneous reduction of an associated
element (electron gain).
oxidizer
(NASA Thesaurus / NASA SP-7, 1965)
(symbol o, used as subscript). Specifically, a substance (not necessarily
containing oxygen) that supports the combustion of a fuel
or propellant.
oximeter
(NASA SP-7, 1965)
An instrument for measuring the oxygen saturation of the blood.
oxygen 17
(NASA Thesaurus)
An isotope of oxygen.
oxygen bottle
(NASA SP-7, 1965)
A small container for pressurized oxygen used in life-support systems.
See bailout bottle.
oxygen mask
(NASA SP-7, 1965)
A covering for the nose and lower face fitted with special attachments
for breathing oxygen or a mixture of oxygen and other gases. The oxygen mask has provision for separating the expired breath from the
incoming oxygen.
Base for a broad field of nitrogen ceramics utilizing silicon, aluminum,
and other elements to produce high temperature refractory materials.
ozone
(NASA Thesaurus)
A very active form of oxygen that may be produced by the corona, arcing,
or ultra-violet rays.
ozone layer
(NASA SP-7, 1965)
= ozonosphere.
ozonosphere
(NASA Thesaurus / NASA SP-7, 1965)
The general stratum of the upper atmosphere
in which there is an appreciable ozone concentration and in which ozone plays
an important part in the radiation balance of the atmosphere. This region
lies roughly between 10 and 50 kilometers, with maximum ozone concentration
at about 20 to 25 kilometers. Also called ozone layer. See atmospheric
shell.