MINIMUM DETECTABLE SIGNALA received
signal whose power is just above the noise level of
MSLMean sea level. a suffix used after altitude
NADIRThe position directly under a satellite on the
earths surface at a specific point in time. Also,
NESDISNational Environmental Satellite, Data,
and Information Service, adivision of NOAA.
NEXRADAcronym for NEXt generation RADar
(WSR-88D Doppler radar).
NIPRNETUnclassified Internet Protocol Routing
NOAANational Oceanic and Atmospheric
Administration. NOAA is an agency of the U.S.
Department of Commerce.
NODAL INCREMENTThe longitude, in degrees,
between successive northbound equatorial
crossings of a polar-orbiting satellite.
NODAL PERIODThe period, in minutes. between
successive northbound equatorial crossings of a
NODDSNavy Oceanographic Data Distribution
NOISEAny unwanted, usually random, fluctuation
of a signal.
NON-ASSOCIATED PRINCIPAL USERA
principal user with access to a WSR-88D system
through means of dial-in telecommunications.
NWRNNational Weather Radar Network.
NWSNational Weather Service, a division of
NYQUIST VELOCITYThe maximum unambig-
uous velocity that can be measured by a Doppler
OKTASEighths of the sky.
ORBITThe path that a satellite follows in its motion
through space, relative to the earth.
OUTFLOW BOUNDARYThe leading edge of
horizontal airflow resulting from cooler, denser air
sinking and spreading out at the surface. Often
caused by the downdraft of thunderstorms.
PERIGEEThe lowest point (shortest distance from
the surface) in a satellite orbit.
PERIODA general term for the time required for
one orbit around the earth.
PHASEA particular angular stage or point of
advancement in a cycle; the fractional part of the
angular period, through which the wave has
advanced, measured from the phase reference.
PIXELThe individual component of an image scan
line defined by a single video sample in a digital
image system. The greater the number of pixels in
a line, the greater the displays resolution.
POESPolar Orbiting Environmental Satellite.
POLAR ORBITINGSatellites with high orbital
angles, crossing over the polar regions of the earth.
PRINCIPAL USERPrincipal users of the WSR-
88D are the National Weather Service (NWS), the
Air Force Weather Agency (AFWA), the Naval
Meteorology and Oceanography Command,
Marine Corps Weather Service Units, and the
Federal Aviation Administration.
energy as waves through or along a medium.
PULSEA single short duration transmission of
PULSE DURATIONTime occupied by a burst of
transmitted radio energy. This may also be
expressed in units of range (pulse length).
PULSE REPETITION FREQUENCY (PRF)The
number of radar pulses transmitted per second.
PULSE REPETITION TIME (PRT)The time
interval from the beginning of one pulse to the
beginning of the next succeeding pulse.
PULSED RADARA type of radar designed to
facilitate range measurement in which transmitted
energy is emitted in periodic, brieftransmissions.