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Flashcards
Which is teh standard horizontal coverage are of teh MLS
+/- 40 degrees
Radar: 2 categorien
1. primary radar system: uses their own, reflected signals 2. Secondary radar systems => based on the interrogator/transponder principle
Radar: Primary radar for WX-radar and SR
Pulse modulation or Continuous wave frequency modulation ==> Basiert auf reflected Echos
Radar: secondary radar
they are supplemented by the transponder => Data transport ===> Reply the pulses!! for SR and DME !
Vorteile und Nachteile Primary and secondary radar
vgl. Bild
two aspects concerning max. range
a) physical factors b) signal travel time and pulse repetition frequency
Radar: radar equation => Zum Range verdoppeln power ouput?
all relevant physicals depends apart from propagation (Ausbreitung) path loss and influence of terrain => Power output muss 16x grösser werden, wenn man die range verdoppeln will
Ducting, super-refraction and sub-refraction
When not standard atmosphere => temperature gradient (Inversion)
super-refraction: higher refraction of teh radio waves towards the surface of the Earth
Ducting: radio waves may even be refracted back and forth between the inversion layer
Sub refraction: opposite effect when refraction (brechung) index is negative => wave is refracted away from the Earth's surface and teh range may decrease
Unambiguous range
a distant target return to the transmitter after the transmitter has already sent another pulse the computing and indicator block will interpret this return as a wrong distance
Radar: Minimum detected range
R min = r/2 * C => for continuous wave frequency modulated radar system the min. detectable range
Radar: capacity to separate between targets in the azimuthal plane => angular resolution
distance greater than the beam width separates two identical => 2 separate target ==> if the target are closer, the radar system merges them in into a single target angular resolution: distance between the targets
Radar: Range resolution
to differentiate between two targets at the same bearing (Lage) but at different ranges (slant distance)
bearing
die Lage
hits per second
corresponds to the antenna beam width, the rotating speed of the antenna system and the pulse repetition interval time
Radar: Increasing teh range of a radar system, in general?
reduces the pulse repetition frequency and increase the puls length
Radar: Which factor determines the minimum detectable range?
pulse length
Radar: Which factor determines teh ability to discriminate between targets in azimuth?
Antenna beam width
Radar: Which factor determines teh ability to discriminate between targets in slant range?
pulse length
Primary Surveillance Radar: 2 Radars
is used by air traffic control (ATC) 1. primary radar: Range (Slant distance) 2. secondary radar: bearing (Lage) of the traffic=> provides further data => able to detect aircraft without transponder
Primary Surveillance Radar: are used for ?
1. en route ( RSR = 200--300 NM) 2. Airport (ASR) around 60 NM 3. Airport surface movement
Primary Surveillance Radar: High ranges ==> wie macht man das?
long pulse repetition interval times, low transmitting frequencies and slo rotating antennas
Primary Surveillance Radar: MTI
Moving Target Indication ==> non-moving targets like houses => the indicator blocks all echo with constant travel time ==> Windsock => special filter
The two main design functions of Secondary Surveillance Radar (SSR) Mode S...
air to ground and ground to air data link communications and improved ATC aircraft surveillance
Which one of the following is an advantage of a secondary radar system when compared to a primary radar system?
The required power of transmission from the ground equipment is reduced and also na advantage is their ability to transfer data between aircraft and ground station
Select the correct shape of an SSR aerial/reflector :
Long and flat
The code transmitted by a SSR transponder consists of:
pulses
In which mode of operation does the aircraft weather radar use a cosecant radiation pattern?
mapping
The ISO-ECHO facility of an airborne weather radar is provided in order to
detect areas of possible severe turbulence in cloud
The theoretical maximum range for an Airborne Weather Radar is determined by ...
pulse recurrence frequency
A frequency of airborne weather radar is ...
9375 MHZ ==> SHF
A frequency of 10 GHz is considered to be the optimum for use in an airborne weather radar system because
the larger water droplets will give good echoes and the antenna can be kept relatively small
In general the operation of airborne weather radar equipment on the ground is...
only permitted with certain precautions, to safeguard health of personnel and to protect equipment
In weather radar the use of a cosecant beam in 'Mapping' mode enables
scanning of a large ground zone producing echoes whose signals are practically independent of distance
On which of the following radar displays is it possible to get an indication of the shape, and to some extent the type, of the aircraft generating the return?
Aerodrome Surface Movement Radar (ASMR)
Which of the following types of radar systems is most suited for short-range operation?
primary continuous wave
Weather Radar wavelength
wavelength about 3 cm with a beam width of 3 -5 degrees => frequency 9-10 GHZ ==> guarantees the best results for weather radar systems
Increasing the wavelength increases
Increasing the wavelength increases the range but decreases the radar cross section
Was wird am besten vom Wetterradar reflektiert
wet hail 2. rain 3. wet snow 4. dry hail 5. ice crystals 6. dry snow
Weather radar: STC
STC = sensitivity Timing Control => to compensate for range dependent attenuation. This allow to present similar targets in a similar color independent from target distant
Weather radar: How you can detect turbulent areas or even wind shear
NO CAT!!!!! with the doppler shift => the speed of the target ca be derived from the speed of the aircraft ==> NO CAT because a reflective target is still needed
