Test 1

Question 1

What is angular resolution

Answer 1

The ability to distinguish between targets that are close in azimuth and elevation. Function of beam width and range

Question 2

Relationship between antenna and beamwidth

Answer 2

The bigger the antenna the more focused the beam

Question 3

What is range resolution based on?

Answer 3

Range resolution is based on Pulse Width.

Question 4

What is range resolution?

Answer 4

Pulse length divided by 2

Question 5

**Advantages of pulse radar (Need to know 2)

Answer 5

Only one antenna required, good range accuracy, simple electronics, good ground mapping and weather detection

Question 6

**Disadvantages of pulse radar (Need to Know 2)

Answer 6

Lower AOP limits detection range (low PRF), cannot filter out ground clutter without increased processing, not very accurate in velocity measurements

Question 7

**CW/Doppler radar advantages (Need to know 2)

Answer 7

Can filter out ground clutter, high AOP increases detection range, very accurate velocity measurements, good against high aspect angle targets, simple

Question 8

**CW/Doppler radar disadvantages (Need to know 2)

Answer 8

Two antennas required (more weight and space), no range information, susceptible to doppler notch, degraded capabilities against beam and stern targets

Question 9

**Pulse Doppler radar advantages (Need to know 2)

Answer 9

Only one antenna required, filters out ground clutter, high output power, good all aspect capability

Question 10

**Pulse Doppler radar disadvantages (Need to know 2)

Answer 10

Complicated electronics, susceptible to doppler notch, range measurement difficult with a HPRF PD Radar.

Question 11

Describe active aircraft signature reduction

Answer 11

Observable emissions:
RF Signals
Acoustic
IR

Question 12

Describe passive aircraft signature reduction

Answer 12

All observable signal resulting from external illumination:
EO/Visual
Electro-magnetic/Radar

Question 13

** What is the most critical signature for most aircraft?

Answer 13

RCS is the most cricital signature for most aircraft because radar provides an all weather, long range detection capability (early warning) and also provides target range, azimuth, and velocity data (target tracking.

Question 14

What dominates radar signature?

Answer 14

Shape which determines how much incident RF power is captured and sent back

Question 15

What factors affect RCS signature?

Answer 15

Azimuth and Elevation (Target)

Frequency and Polarization (Radar)

Question 16

**What four methods make an aircraft stealthy?

Answer 16

Shaping - Reflect energy another direction (MOST IMPORTANT)
Absorption - Turn radar into heat
Cancellation - Active/Passive cancelling out
Transparencies - Allow radar to pass thru material

Question 17

List primary shaping techniques

Answer 17

Compound curve, Faceted shaping, Planform alignment

Question 18

Describe compound curve

Answer 18

Replace straight edges with curved to reflect less

Question 19

Describe faceted shaping

Answer 19

Orient flat surfaces to deflect radar

Question 20

Describe planform edge alignment

Answer 20

Align edges to limited set of angles

Question 21

Describe how surface roughness effects RCS

Answer 21

Fastener to panel interface increases RCS.

Reflections more significant at higher frequencies and low graze angles

Question 22

See LO slides 58-62…..

Answer 22

DO IT or DON’T

Question 23

What are some fundamental characteristics of IR?

Answer 23

All objects (above absolute zero) emit IR radiation

- 0 K/-273 oC
- Heated externally (e.g., the Sun) or internally (e.g., engine)

Question 24

Define Watts and Lumens.

Answer 24

• The watt is a unit of power or heat (thermal)

- The lumen is a unit of light output (brightness) or the ability to see with the eye (photometric)

Question 25

** What are the three forms of interaction that can take place when energy strikes or is incident upon a surface?

Answer 25

- Absorption (a) - Reflection (f) - Transmission (t) - Total must add up to one (100%): a + r + t = 1

Question 26

Define Absorption

Answer 26

Incident energy not refelcted or transmitted. Transformed into another form such as heat

Question 27

Define Reflection

Answer 27

Incident energy not absorbed or transmitted.

Question 28

Define Transmission

Answer 28

When energy propagates through a medium, the energy not absorbed or reflected will be transmitted.

Question 29

**List applications of the optical/IR detection systems.

Answer 29

- EO/IR imaging systems - Detectors - Terminal homing seekers - Video trackers - Automatic target recognizers - IRCM systems - Laser systems - Space imaging systems

Question 30

Why should you avoid the 5-8u region?

Answer 30

Atmospheric attenuation.

Question 31

**Angular (azimuth and elevation) resolution is a function of blank and blank

Answer 31

Beamwidth and Range

Question 32

**Range resolution is based on which paramater

Answer 32

Pulse width

Question 33

** All objects (blank) temperature emit radaition

Answer 33

0K -273C*

Question 34

** Thermal radiation measures (blank) in terms of (blank) (units) whereas photometic radiation measures (blank) in terms of (blank)

Answer 34

Power/Heat in terms of watts | Light in terms of lumens

Question 35

** When planning for the use of optical/IR sensors, detectors or employment of EO weapons, there are several considerations which must be taken into consideration with regards to source heating and source viewing

Answer 35

- Orientation - Season - Sun angle - Weather (rain, wind) - Thermal crossover - Approach axis - Background - Distance - IR decoys

Question 36

** Describe the basic passive aircraft signature reduction concepts, and list the four passive signatures

Answer 36

Passive signature reduction concepts counter threat detectors and trackers with aircraft design and configration. Passive aircraft signatures are the acoustic signature, the visual signature, the IR signature, and the RCS

Question 37

**** State the goal of radar absorbent material in aircraft design?

Answer 37

The goal of RAM in aircraft to design is to reduce spectacular reflections and multi bounce reflections. AND to reduce energy diffracted from trailing edges or discontinuities by absorbing energy as the wave travels along the surface.

Question 38

** List three radar systems techniques that may be used to counter stealth aircraft

Answer 38

Low frequency radar, high frequency radar, bistatic or multistatic radar, or ultra-wide band radar.