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Words begining with "E"
Earth Observing System (EOS)
A series of small - to intermediate-sized spacecraft that is the
centerpiece of NASAs Mission to Planet Earth (MTPE). Planned for
launch beginning in 1998, each of the EOS spacecraft will carry a
suite of instruments desiqned to study global climate change. MTPE
will use space-, aircraft-, and ground-based measurements to study
our environment as an integrated system. Designing and implementing
the MTPE is, of necessity, an international effort. The MTPE program
involves the cooperation of the U.S., the European Space Agency
(ESA), and the Japanese National Space Development Agency (NASDA).
The MTPE program is part of the U.S. interagency effort, the Global
Change Research Program.
EOS Research
Spacecraft Research purpose
EOS-AM1 Characterization of land and ocean surfaces
(1998) sea-surface temperature
terrestrial and ocean productivity
clouds, aerosols, and radiative balance
EOS-COLOR ocean color and productivity
(1998)
EOS-AERO1 atmospheric aerosols and ozone
(2000)
EOS-PM1 clouds, precipitation, radiative balance,
(2000) terrestrial snow, and sea ice
sea surface temperature
terrestrial and ocean productivity
atmospheric temperature and moisture
EOS-ALT1 ocean circulation, ice sheet mass balance
(2002) and land-surtace topography
EOS-CHEM1 atmospheric chemical species and their
(2002) transformations
solar radiation
Projected year of launch shown in parentheses
Earth Observing System Data & Information System
(EOSDIS)
The system that will manage a dataset of Earth science
observations to be collected over a 15-year period. Existing data
indicates that the Earth is changing, and that human activity
increasingly contributes to this change. To monitor these changes, a
baseline of "normal" performance characteristics must be obtained.
For the Earth, these baseline characteristics must cover a global
scale and a long enough period that the variation caused by seasonal
changes and other cyclical or periodic events (e.g., El
Nino and the solar cycle)
may be included in the analyses. The baseline characteristics also
must enable scientists to quantify processes that govern the Earth's
system. Functionally, EOSDIS will provide computing and networking
facilities supporting EOS research activities, including data
interpretation and modeling; processing, distribution, and archiving
of EOS data: and command and control of EOS observatories.
Earth Probes
Discipline specific satellites and instruments that will be used
by NASA to obtain observations before the launch of EOS
spacecraft. Generally smaller than the EOS satellites and
instruments, Earth Probes are planned to complement the broad
environmental measurements from EOS with highly focused studies in
areas such as tropical rainfall (TRMM),
ocean productivity (SeaWiFS), atmospheric ozone (TOMS),
and ocean surface winds (NSCAT).
Earth Radiation Budget Experiment (ERBE)
An experiment to obtain data to study the average radiation
budget of the Earth and determine the energy transport gradient
from the equator to the poles. Three satellites were flown in
different orbits to obtain the data: the Earth Radiation Budget
Satellite, ERBS (launched in October 1984), NOAA-9 (launched in
December 1984), and NOAA-I0 (launched in September 1986). See
Television and Infrared Observation Satellite (TIROS)
Earth station (aka Ground Station)
Hardware necessary to acquire data directly from environmental
satellites. The WEFAX Earth station
diagram illustrates a basic ground station configuration for
obtaining direct readout data from geostationary environmental
(weather) satellites.
Earth System
The Earth regarded as a unified system of interacting components,
including geosphere (land),
atmosphere (air), hydrosphere
(water and ice), and biosphere
(life).
Earth's Interacting Componets
Geosphere Physical elements of the Earth's
surface, crust, and interior.
Processes in the geosphere include
continental drift, volcanic eruptions
and earthquakes.
Atmosphere Thin layer of gas or air that
surrounds the Earth. Processes in
the atmosphere include winds,
weather, and the exchange of gases
with living organisms.
Hydrosphere Water and ice on or near the surface
of the Earth. Includes water vapor in
clouds; ice caps and glaciers, and
water in the oceans, rivers, lakes, and
aquifers. Processes in the
hydrosphere include the flow of
rivers, evaporation. and rain.
Biosphere The wealth and diversity of living
organisms on the Earth. Processes in
the biosphere include life and death
evolution, and extinction.
Earth System Science
An integrated approach to the study of the Earth that stresses
investigations of the interactions among the Earths components in
order to explain Earth dynamics, evolution, and global change.
Eccentricity (aka ecce or E0 or e)
One of six Keplerian
elements, it describes the shape of an orbit. In the Keplerian
orbit model, the satellite orbit is an ellipse, with eccentricity
defining the "shape" of the ellipse. When e = 0, the ellipse is a
circle. When e is very near 1, the ellipse is very long and
skinny.
Eccentricity
- e = O = circular orbit
- O < e < 1 = elliptical orbit
- e = 1 = parabolic orbit
- e > 1 = hyperbolic orbit
Eclipse
The partial or total apparent darkening of the sun when the moon
comes between the sun and the Earth (solar eclipse), or the darkening
of the moon when the full moon is in the Earths shadow (lunar
eclipse).
Eclipse Blindness
Focus-point type of vision loss caused by looking at the sun for
too long a time, which can burn a hole in the retina of the eye.
Ecology
Science dealing with the interrelationships between livinq
orqanisms and their environments.
Ecosystem
Any natural unit or entity including living and non-living parts
that interact to produce a stable system through cyclic exchange of
materials.
Electromagnetic Radiation
Energy propagated as time-varying electric and magnetic fields.
These two fields are inextricably linked as a single entity since
time-varying electric fields produce time-varying magnetic fields and
vice versa. Light and radar are
examples of electromagnetic radiation differing only in their
wavelenghts (or frequency).
Electric and magnetic fields propaqate throuqh space at the speed of
liqht.
Electromagnetic Spectrum
The entire range of radiant energies or wave frequencies from the
longest to the shortest wavelengths - the categorization of solar
radiation. Satellite sensors collect this energy, but what the
detectors capture is only a small portion of the entire
electromagnetic spectrum. The spectrum usually is divided into seven
sections: radio, microwave,
infrared, visible,
ultraviolet,
x-ray, and gamma-ray radiation.
Electromagnetic Wave
Method of travel for radiant energy (all energy is both particles
and waves), so called because radiant energy has both magnetic and
electrical properties. Electromagnetic waves are produced when
electric charges change their motion. Whether the frequency is high
or low, all electromagnetic waves travel at 300,000,000 meters per
second.
Electromotive
Producing an electric current through differences in potential.
Electromotive Force
The force that can alter the motion of electricity, measured in
terms of the energy per unit charge imparted to electricity passing
through the source of this force. Electromotive force causes current
flow in a circuit.
Element Set (aka Keplerian
elements, classical elements, satellite elements)
Specific information used to define and locate a particular
satellite. The set includes the catalog number; epoch year, day, and
fraction of day; period decay rate; argument of perigee; inclination;
eccentricity; right ascension of the ascending node; mean anomaly;
mean motion; revolution number at epoch; and element set number. This
data is contained in the two-line orbital elements provided by NASA
in the NASA Prediction Bulletin. See Keplerian
elements.
Elevation
The angle at which an antenna must be pointed above the horizon
for optimal reception from a spacecraft.
Elliptical Orbits
Bodies in space orbit in elliptical rather than circular orbits
because of factors such as gravity and drag. The point where the
orbiting satellite is closest to Earth is the perigee,
sometimes called peri-apsis or perifocus. The point where the
satellite is farthest from Earth is called apogee,
apoapsis, or apifocus. A line drawn from perigee to apogee is the
line-of-apsides, sometimes called the major-axis of the ellipse. It's
simply a line drawn through the ellipse the long way.
El Nino
A warming of the surface waters of the eastern equatorial Pacific
that occurs at irregular intervals of 2-7 years, usually lasting 1-2
years. Along the west coast of South America, southerly winds promote
the upwelling of cold, nutrient-rich water that sustains large fish
populations, that sustain abundant sea birds, whose droppings support
the fertilizer industry Near the end of each calendar year, a warm
current of nutrient-poor tropical water replaces the cold,
nutrient-rich surface water. Because this condition often occurs
around Christmas, it was named El Nino (Spanish for boy child,
referring to the Christ child). In most years the warming lasts only
a few weeks or a month, after which the weather patterns return to
normal and fishing improves. However, when El Nino conditions last
for many months, more extensive ocean warming occurs and economic
results can be disastrous. El Nino has been linked to wetter, colder
winters in the United States; drier, hotter summers in South America
and Europe; and drought in Africa. See ENSO.
ELT
Emergency Locator Transmitter. See Search
and Rescue.
Energy Budget
A quantitative description of the energy exchange for a physical
or ecological system. The budget includes terms for radiation,
conduction, convection, latent heat, and for sources and sinks of
energy
ENSO (El Nino-Southern Oscillation)
Interacting parts of a single global system of climate
fluctuations. ENSO is the most prominent known source of interannual
variability in weather and climate around the world, though not all
areas are affected. The Southern Oscillation (SO) is a global-scale
seesaw in atmospheric pressure between Indonesia /North Australia,
and the southeast Pacific. In major warm events El Nino warming
extends over much of the tropical Pacific and becomes clearly linked
to the SO pattern. Many of the countries most affected by ENSO events
are developing countries with economies that are largely dependent
upon their agricultural and fishery sectors as a major source of food
supply, employment, and foreign exchange. New capabilities to predict
the onset of ENSO events can have a global impact. While ENSO is a
natural part of the Earth's climate, whether its intensity or
frequency may change as a result of global warming is an important
concern.
Environment
The complex of physical, chemical, and biological factors in which
a living organism or community exists.
EOS
See Earth Observing System.
EOSDIS
See Earth Observing System Data and Information
System.
EPA (Environmental Protection Agency)
U.S. agency that ensures: Federal environmental laws are
implemented and enforced effectively; U.S. policy - both foreign and
domestic - fosters the integration of economic development and
environmental protection so that economic growth can be sustained
over the long term; public and private decisions affecting energy,
transportation, agriculture, industry, international trade, and
natural resources fully integrate considerations of environmental
quality; national efforts to reduce environmental risk are based on
the best available scientific information communicated clearly to the
public; everyone in our society recognizes the value of preventing
pollution before it is created; people have the information and
incentives they need to make environmentally-responsible choices in
their daily lives; and schools and community institutions promote
environmental stewardship as a national ethic.
Ephemeris
A tabulation of a series of points that define the position and
motion of a satellite. See Keplerian
elements.
EPIRB
Emergency Position Indicating Radio Beacon See Search
and Rescue.
Epoch (aka Epoch Time or TO)
Epoch specifies the time of a particular description of a
satellite orbit. See Keplerian
elements.
Equator
An imaginary circle around the Earth that is everywhere equally
distant (90 degrees from the North Pole and the South Pole. The
equator is a qreat circle and defines latitude 0 degrees.
ERBE
See Earth Radiation Budget Experiment.
ESA
European Space Agency
Eutrophication
The process whereby a body of water becomes rich in dissolved
nutrients through natural or man-made processes. This often results
in a deficiency of dissolved oxygen, producing an environment that
favors plant over animal life.
Evaporation
Change from a liquid (more dense) to a vapor or gas (less dense)
form. When water is heated it becomes a vapor that increases humidity
Evaporation is the opposite of condensation.
Exosphere
The uppermost layer of the atmosphere,
its lower boundary is estimated at 500 km to 1000 km above the
Earth's surface. It is only from the exosphere that atmospheric gases
can, to any appreciable extent, escape into outer space.
External Forcing
Influence on the Earth system (or one of its components) by an
external agent such as solar radiation or the impact of
extraterrestrial bodies such as meteorites.
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