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Words begining with "M"
Magnetosphere
Region surrounding a celestial body where its magnetic field
controls the motions of charged particles. The Earths magnetic field
is dipolar in nature. That is, it behaves as if produced by a giant
bar magnet located near the center of the planet with its north pole
tilted several degrees from Earth's geographic north pole.
The Earth's magnetic field presents an obstacle to the solar wind,
as a rock in a running stream of water. This obstacle is called a bow
shock. The bow shock slows down, heats, and compresses the solar
wind, which then flows around the rest of Earths magnetic field. See
Van Allen belts.
MAPS-NET
Maryland Pilot Earth Science and Technology Education NETwork.
NASA sponsored education project designed to complement NASAs
Mission to Planet Earth. MAPS-NET has been
developed to enrich math and science curricula and enhance teacher
preparation in Earth system science.
Middle and high school teachers learn about Earth sciences and
satellite direct readout at
graduate-level summer workshops; academia, federal agencies, and the
private sector form the support network.
MSFC (Marshall Space Flight Center)
See NASA Centers.
Mean Anomaly (aka MO or MA or phase)
Specifies the mean location (true anomaly
specifies the exact location) of a satellite on an orbit ellipse at a
particular time, assuming a constant mean
motion throughout the orbit . Epoch specifies the particular time
at which the satellites position is defined, while mean anomaly
specifies the location of the satellite at epoch.
Mean anomaly is measured from 0 degrees to 360 degrees during one
revolution. It is defined as 0 degrees at perigee,
and hence is 180 degrees at apogee.
See Keplerian elements.
Mean Motion (aka NO)
Averaged speed of a satellite in a non-circular orbit (i.e.
eccentricity>0).
Satellites in circular orbits travel at a constant speed. Satellites
in non-circular orbits move faster when closer to the Earth, and
slower when farther away. Common practice is to compute the mean
motion (average the speed), which is measured in revolutions per day.
Measurement System Integrity
The tracking and documentation over the long term of all causes of
error or uncertainty in a final data-analysis product. These include
instrument calibration, adequacy of measurement
validation, data coverage and sampling density, availability and
quality of ancillary data, procedures for data analysis and
reduction, the results of checks against independent measurement, and
quantitative error analysis.
Measurement Validation
The establishment of confidence in the numerical relationship
between the calibrated sensor output and the actual variable being
measured.
Mercator Projection
A method of making maps in which the Earths surface is shown as a
rectangle with the meridians as parallel straight lines spaced at
equal intervals and the parallels of latitude as parallel straight
lines intersecting the meridians at right angles. Areas away from the
equator appear larger than they are, with the qreatest distortion
near the poles.
Mesopause
The upper boundary of the mesosphere where the temperature of the
atmosphere reaches its lowest
point
Mesophere
The atmospheric layer above the stratosphere,
extending from about 50 to 85 kilometers altitude. The temperature
generally decreases with altitude.
Metadata
Information describing the content or utility of a data set. For
example, the dates on which data were procured are metadata.
Meteor
The former Soviet Union's series of polar-orbiting weather
satellites. The Meteor satellites transmit images in a system
compatible with the NOAA polar-orbitinq satellites.
Meteorology
Study of the atmosphere and
its phenomena.
METEOSAT
METEOrological SATellite. Europe's geostationary weather
satellite, launched by the European Space Agency and now operated by
an organization called Eumetsat. METEOSAT transmits at 1691 and
1694.5 MHz.
Metsat
Generic term for meteorological ( weather
satellites).
MHz (megahertz)
1,000,000 hertz.
Micrometer (um, aka micron)
One millionth of a meter, used to measure wavelengths
in the electromagnetic
spectrum.
Microprocessor
Controlling unit of a microcomputer, laid out on a tiny silicon
chip and containing the logical elements for handling data,
performing calculations, carrying out stored instructions, etc.
Microwave
Electromagnetic radiation with wavelengths between about 1000
micrometers and one meter
Middle Infrared
Electromagnetic radiation between the near
infrared and the thermal
infrared, about 2-5 micrometers.
Millibar (mb)
One thousandth of a bar, a unit of atmospheric pressure. The
average atmospheric
pressure at sea level is ) .01325 bars or 1013.25 mb. See
pascal (Pa).
Mission to Planet Earth (MTPE)
International research program to understand our planet's
environment as a system. A
major challenge of MTPE is to observe, understand, model, assess, and
eventually predict global change. Meeting this challenge will help to
evaluate the impact that human activity (e.g., clearing forests and
burning fossil fuels) has on our environment, and to distinguish
human-induced changes from the effects of natural events (e.g.
volcanic eruptions, erosion).
NASA's MTPE uses space-, aircraft-, and ground-based measurements
to provide the scientific basis for understanding global change. The
program will produce longterm global maps of clouds, land and ocean
vegetation, atmospheric ozone,
sea-surface temperature, and other global processes necessary to
understand the state of the Earth and to detect any patterns of
change. This information will be available to scientists and policy
makers through the Earth Observing System Data and Information System
(EOSDIS).
The centerpiece of NASA's MTPE will be the Earth Observing System
(EOS), a series of satellites planned
for launch beginning in 1998. Measurements from EOS will be
complemented by the Earth Probes, a series of discipline-specific
satellites and instruments designed to observe Earth processes where
smaller platforms and/or different orbits from EOS are required.
Planned Earth Probes will measure tropical
rainfall, ocean productivity, ozone,
and ocean surface winds. In addition, MTPE includes current NASA
Earth science missions collecting important data on the global
environment, such as the Upper Atmosphere Research Satellite (
UARS) and the Ocean Topography
Experiment ( TOPEX/POSEIDON),
Space Shuttle experiments such as ATLAS,
and aircraft campaiqns.
Model (noun)
A mathematical representation of a process, system, or object
developed to understand its behavior or to make predictions. The
representation always involves certain simplifications and
assumptions.
Modem (modulator/demodulator)
Device that allows two computers (which use binary
data in the form of bits) to communicate using a telephone line
(which uses tones). When the computer is transmitting data, the modem
is needed to modulate binary data into tones. When receiving data,
the device is needed to demodulate the tones to obtain the binary
data required by the computer. Since the computer must be both a
transmitter and receiver of data, the modem must be able to modulate
and demodulate data.
Modulation
Variation in the frequency of a radio wave in accordance with some
other impulse. Modulation is essential to communication systems in
which a number of different signals must all share the same medium.
One way this sharing can be accomplished is to place each signal in
its own band of frequencies in
the medium. Amplitude modulation and
frequency modulation are two ways in
which signals can be moved within the frequency domain to accomplish
placement and sharing.
The combining of a number of signals to share a communication
medium by dividing it into different frequency bands for each signal
is called
frequency-division multiplexing.
Amplitude modulation (AM) is technologically quite simple, and the
bandwidth of the amplitude-modulated carrier is at most twice the
bandwidth of the modulating
signal. However, an amplitude-modulated carrier is very prone to the
effects of additive noise.
Frequency modulation (FM) is more complicated than amplitude
modulation, and the bandwidth of the frequency-modulated carrier can
be many times that of the modulating signal. However, the process of
demodulating a frequency-modulated carrier eliminates much of the
deleterious effects of additive noise. This trade-off between
bandwidth and noise reduction characterizes most communication
situations.
Monsoon
Heavy winds characterized by a pronounced seasonal change in
direction. Winds usually blow from land to sea in the winter, while
in the summer, the flow reverses and precipitation is more common.
Monsoons are most typical in India and southern Asia.
Montreal Protocol
An international agreement to drastically reduce
CFC production, the Protocol was
adopted in Montreal in 1987. It was significantly strengthened at a
subsequent meeting in London in 1990 that called for a complete
elimination of CFCs by the year 2000. The agreement was again amended
by a Meeting of the Parties in Copenhagen in November 1992.
Consumption of controlled substances - such as CFCs and halons - was
greatly reduced or eliminated, and many accountability dates were
moved forward. often from January 2000 to 1 January 1996
Mosaic
A composite picture built up from a number of image segments. An
example of a mosaic is the WEFAX
transmission, which includes both polar and mercator mosaics derived
from TIROS-N/NOAA polar orbit
image data.
Mountain and Valley Breezes
System of winds that blow downhill during the night (mountain
breeze) and uphill during the day (valley breeze).
MTPE
See Mission to Planet Earth
Multiplexer
A device that combines several separate communications signals
into one and outputs them on a sinqle line.
Multispectral Scanner (MSS)
A line-scanning instrument flown on Landsat
satellites that continually scans the Earth in a 185 km (100 nautical
miles) swath. On Landsats 1, 2,4, and 5,
the MSS had four spectral bands in the visible
and near-infrared with an
IFOV of 80 meters. Landsat-3 had a
fifth band in the thermal
infrared with an IFOV of 240
meters.
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