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Words begining with "R"
Research and Development.
- In optics, the point or object from which light proceeds.
- In geometry, a straight line proceeding from a given point, or
fixed pole, about which it is conceived to revolve.
- In astronomy, the point in the heavens from which a shower of
meteors seems to proceed.
Energy transfer in the form of electromagnetic waves or particles
that release energy when absorbed by an object.
A measure of all the inputs and outputs of radiative energy
relative to a system, such as Earth. See
Earth Radiation Budget Experiment.
Cooling process of the Earths surface and adjacent air, which
occurs when infrared (heat) energy
radiates from the surface of the Earth upward through the atmosphere
into space. Air near the surface transfers its thermal energy to the
nearby ground through conduction, so that radiative cooling lowers
the temperature of both the surface and the lowest part of the
Theory dealing with the propagation of electromagnetic radiation
throuqh a medium.
Giving off or capable of giving off radiant energy in the form of
particles or rays, as in alpha, beta, and gamma rays.
An instrument that quantitatively measures electromagnetic
radiation. Weather satellites carry radiometers to measure radiation
from snow, ice, clouds, bodies of water, the Earth's surface, and the
Radio Frequency (RF)
A frequency that is useful for radio transmission, usually between
10 kHz and 300,000 MHz.
A balloon-borne instrument that measures meteorological parameters
from the Earth's surface up to 20 miles in the atmosphere.
The radiosonde measures temperature, pressure, and humidity, and
transmits or "radios" these data back to Earth. Upper air winds also
are determined through tracking of the balloon ascent.
Radiosonde observations generally are taken twice a day (0000 and
1200 UTC) around the globe. NOAA's
National Weather Service (NWS)
operates a network of about 90 radiosonde observing sites in the U.S.
and its territories. When the balloons burst, radiosondes return to
Earth on a parachute. Approximately 25 percent are recovered and
returned to NWS for reconditioning and reuse.
The complete range of frequencies or wave lengths of
electromagnetic waves, specifically those used in radio and
An electrical impulse sent through the atmosphere at radio
An evergreen woodland of the tropics distinguished by a continuous
leaf canopy and an average rainfall of about 100 inches per year.
Rain forests play an important role in the global environment. The
Earth sustains life because of critical balances and interactions
among many factors. Were there not processes at work that limit the
effects of other essential processes, Earth would become
uninhabitable. Destruction of tropical rain forests reduces the
amount of leaf area in the tropics, and consequently the amount of
carbon dioxide absorbed, causing increases in levels of carbon
dioxide and other atmospheric gases. It is estimated that cutting
and burning of tropical forests contributes about 20 percent of the
carbon dioxide added to the atmosphere each year. The World Resources
Institute and the International Institute for Environment and
Development have reported that the worlds tropical forests are being
destroyed at the rate of fifty-four acres per minute, or twenty-eight
million acres lost annually Rain forest destruction also means the
loss of a wide spectrum of biological life, erosion of soil, and
Calibrated container that measures the amount of rainfall durinq a
specific period of time.
Random Access Memory Computers use two types of memory, RAM and
ROM. RAM is the computers working area, the
primary location where the microprocessor stores the information it
needs. The designation "random access stems from the microprocessors
ability to access information In memory randomly by knowing its
location, or address, rather than hunting through memory sequentially
from beginning to end. Because information in RAM is stored
electronically, accessing data stored in RAM is much faster than
getting that data from a mechanical storage device such as a disk
drive. But because it is stored electronically, all information in
RAM is temporary (which is why you must store it on a more permanent
storage capability, such as a disk).
As it happens.
The ability of a receiver to detect weak signals through the noise
level of the receiving system, which includes the antenna
and internal thermal noise of the receiver. See signal-to-noise
The return of light or sound waves from a surface. If a reflecting
surface is plane, the angle of reflection of a light ray is the same
as the angle of incidence.
Flattening the Earth into a standard map projection. When the
spherical Earth is photographed by satellites, areas lying near the
outer edge of the picture are distorted. Remappinq rectifies the
The technology of acquiring data and information about an object
or phenomena by a device that is not in physical contact with it. In
other words, remote sensing refers to gathering information about the
Earth and its environment from a distance, a critical capability of
the Earth Observing System.
For example, spacecraft in low-Earth orbit pass through the outer
thermosphere, enabling direct sampling of chemical species there.
These samples have been used extensively to develop an understanding
of thermospheric properties. Explorer - 17, launched in 1963, was the
first satellite to return quantitative measurements of gaseous
stratification in the thermosphere. However, the mesosphere and lower
layers cannot be probed directly in this way - global observations
from space require remote sensing from a spacecraft at an altitude
well above the mesopause. The formidable technological challenges of
atmospheric remote sensing, many of which are now being overcome,
have delayed detailed study of the stratosphere and mesosphere by
comparison with thermospheric research advances.
Some remote-sensing systems encountered in everyday life include
the human eye and brain, and photoqraphic and video cameras.
A measure of the ability to separate observable quantities. In the
case of imagery, it describes the area represented by each pixel
of an image. The smaller the area represented by a pixel, the more
accurate and detailed the image. APT has
a resolution of 4 km, i.e., each pixel represents a square, 4 km on
each side. HRPT has a resolution of
1.1 km at nadir (4 km at edge of
scan), and WEFAX of 8 km. See
The smallest unit of area in an image of discrete elements. The
area represented by a pixel.
An east-to-west orbit of Earth (Earth spins west to east). See
Process of the Earth circling the sun in its orbit. Revolution
determines the seasons, and the length of the year. In addition,
differences in seasons occur because of Earth's inclination
(tilt on its axis) of about 23.5 degrees as it revolves around the
sun. Compare with rotation.
See radio frequency.
Right Ascension of Ascending Node (aka Omega, RAAN or RA of
One of six Keplerian
elements, it indicates the rotation of the orbit plane from some
reference point. Two numbers orient an orbital plane in space;
inclination is the first, this
is the second. After specifying inclination, an infinite number of
orbital planes are possible. The intersection of the equatorial plane
and the orbital plane must
be specified by a location on the equator
that fully defines the orbital plane. The line
of nodes occurs in two places. However, by convention, only the
ascending node (where the
satellite crosses the equator going from south to north) is
specified. The descending
node (where the satellite crosses the equator going from north to
south) is not.
Because the Earth spins, conventional latitude and longitude
points are not used to separate where the lines of node occur.
Instead, an astronomical coordinate system is used, known as the
right-ascension/declination coordinate system, which does not spin
with the Earth. Right ascension of ascending node is an angle,
measured at the center of the Earth, from the vernal
equinox to the ascending node. For example, draw a line from the
center of the Earth to the point where the satellite crossed the
equator (going from south to north). If this line points directly at
the vernal equinox, then RAAN = 0 degrees.
Read Only Memory. Refers to the computer memory chips that contain
information the computer uses (along with system files) throughout
the system, including the information it needs to get itself started.
Information in ROM is permanent; it doesn't vanish when the power is
turned off. Compare with RAM.
Process of the Earth turning on its axis. Rotation determines day
and night, and the length of the day. Compare with revolution.
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