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aerobraking
- the use of atmospheric drag to slow a spacecraft
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albedo
- a measure of the ability of a body to reflect light
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aphelion
- the point in the orbit of a planet where it is farthest from the sun
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astronomical unit (A.U.)
- a measure for distances within the solar system, equal to the mean
ditance of the Earth from the sun, which is about 93,000,000 miles
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atmosphere
- the gaseous envelope surrounding a celestial body
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axis of rotation
- the straight line, real or imaginary, passing through a rotating body
and is the line about which that body rotates
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azimuth
- the distance in degrees along the horizon, westward from the south
point of the horizon, to the place where a vertical circle through the
star or other object intersects the horizon
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backscattering
- the deflection of particles or radiation by scattering processes through
angles greater than 90 degrees with respect to the original direction
of motion
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- an ideal or imaginary body that is absolutely black when cold, but
is a perfect absorber of radiation and at the same time a perfect radiator.
Black body temperatures are used to work out the theoretical laws of
radiation and to calculate the temperature of the sun.
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carbon dioxide
- a gas used by all green plants and recycled by them to form wood and
the oxygen we breathe. In very large quantities it can be poisonous
to animal life.
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CCD
- charge coupled device
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celestial equator
- the great circle of the celestial sphere all points of which are 90
degrees from the poles. It is the plane of the Earth's equator projected
onto the celestial sphere.
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climatology
- the scientific study of climate
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convection
- transmission of heat by moving heated gases. In a hot-air furnace
the heated air rises and cooler, heavier air falls.
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density
- the amount of matter in a unit volume of a substance; usually the
mass per unit of volume
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diameter
- the distance from one side of a body to the other, measured through
the center
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diurnal motion
- the apparent daily rotation of the heavens from east to west; an effect
of Earth's rotation about its axis
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eccentricity
- the degree of flattening of an ellipse and how much it deviates from
a circular shape. With reference to the orbit of a planet, the distance
between the center of its orbit and the center of the
primary about which it revolves.
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escape velocity
- the speed that any object must acquire in order to escape from a planet's
gravitation
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fluorescence
- the emission of electromagnetic radiation as the result of exposure
to some other radiation, which emission ceases when the stimulus that
produces it ceases to act on the emitting substance. Thus light passing
through a gas, may change the energy state of the atoms and cause them
to emit light of a different wavelength.
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geodetic
- the study of the size and shape of Earth, the measurement of terrestrial
gravitational forces, and the location of fixed points on Earth's surface
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- the phase when more than half (but not all) of the planet's side facing
Earth is illuminated by the sun.
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- a great circle of the celestial sphere passing through the celestial
poles and a celestial body or the vernal equinox. An hour circle moves
with the body as the celestial sphere rotates, unlike the celestial
meridian of a point that remains fixed.
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interference fringes
- the alternate light and dark bands that are seen when two beams of
homogenous light enter into interference with each other, i.e., when
they overlap and illuminate an identical area
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interferometer
- any instrument designed for producing and studying interference of
two or more trains of waves or beams of electromagnetic radiation of
the same range of wavelengths. Usually denotes an optical interferometer
that separates a beam of light into two or more parts that travel in
different paths and are then combined together to produce interference
fringes.
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joule
- the S.I. unit of energy, work, or quantity of heat. It is the force
of one newton acting over a distance of a meter.
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Kepler's laws of planetary motions and orbits
- Laws governing the motions of planets in their orbits:
1. The orbits of the planets are ellipses with the sun at a common
focus.
2. The line joining a planet and the sun sweeps over equal areas
during equal intervals of time.
3. The squares of the periods of revolution of any two planets are
proportional to the cubes of their mean distances from the sun.
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landing rocket
- a "secondary rocket" intended to be used for descending to the surface
of the moon or another planet while the major vehicle remains in an
orbit around the destination body
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mass
- the amount of matter in a body, which should not be confused with
weight. The same object will have different weights in space and Earth
but the mass remains constant.
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nadir
- the point on the celestial sphere that is diametrically opposite the
zenith, so that the zenith, nadir and center of Earth are in one straight
line. It is always 90 degrees below the horizon.
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- the hiding of one heavenly body by another, as when the moon passes
between Earth and a star, or when one of the moons of Jupiter or Saturn
passes behind the planet
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- the point in a planet's orbit in which it is closest to Earth. When
viewing a planet it will appear on the opposite side of the sky as the
sun. Two bodies are in opposition when the difference in celestial longitude
is 180 degrees.
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payload
- anything that a flight vehicle carries beyond what is required for
its operation during flight
-
- (1) A sun with respect to its planets, or a planet with respect to
its satellites; (2) the brighter member of a double star system
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perihelion
- the point in the orbit of a planet where it is nearest to the Sun
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quadrature
- two bodies are in quadrature when their difference in celestial longitude
is 90 degrees. This is the position of a superior planet when its elongation
is 90 degrees, east or west, depending on the direction of the planet
from the Sun
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retrograde motion
- backward (westward) motion of the planet among the stars, resulting
from the fact that it is viewed from the moving Earth. It is the motion
that a planet has when its right ascension is decreasing.
Each year, when Earth passes a superior planet, such as Mars, the
planet appears to move backward for a short time. It is the same effect
you see when two trains are running in the same direction on side
by side tracks. The slower train appears to be moving backward.
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right ascension
- a celestial coordinate; it is the angular distance measured from the
vernal equinox eastward along the celestial equator to the hour circle of a given star or other celestial body. It can be
defined also as the arc of the celestial equator or the angle at the
celestial pole between the hour circle of the vernal equinox and the
hour circle of the body.
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spatial resolution
- a measure of a system's ability to control a robot's tool tip
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telemeter
- 1. an instrument that provides its data readout to a location remote
from the sensing device;
2. to transmit data to a remote point
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telemetry
- the use of telemeters for measuring and transmitting data
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teleoperation
- the remote operation of a device. In the field of telerobotics, robotics
and teleoperations are merged to produce a remotely operated robot.
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- transforming a hostile environment into one able to sustain human
life; this includes a source of oxygen, water, plant life, and correct
air pressure and temperature.
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tetrahedral
- a solid with four plane faces
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topography
- the configuration of a land surface, including its relief
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ultraviolet radiation
- the invisible electromagnetic radiation beyond the violet end of the
spectrum of visible light, of wavelengths ranging, roughly, from 4000
down to 400 angstroms
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vernal equinox
- the position on the celestial sphere occupied by the sun on or about
March 21 when its path on the ecliptic crosses the celestial equator
going from south to north. This point is also called the March equinox
and the First Point of Aries.
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winter solstice
- the position on the ecliptic occupied by the sun about December 22
when it reaches its greatest southerly declination
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x-rays
- very short wavelength radiations beyond the ultraviolet in the spectrum,
which are about one ten-thousandth as long as the visible violet and
are extremely penetrating
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ylem
- the hypothetical primordial matter, proposed by George Gamow, from
which the chemical elements may have been formed
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zenith
- the point of the celestial sphere directly overhead, 90 degrees above
the horizon, for any point on Earth; it is the point where a plumb line
extended upward would intersect the celestial sphere
